WETLANDS IN PAKISTAN: WHAT IS HAPPENING TO THEM

WETLANDS IN PAKISTAN: WHAT IS HAPPENING TO THEM

RULES AND REGULATIONS of THE NEW FULTON FISH MARKET COOPERATIVE AT HUNTS POINT, INC.

http://www.newfultonfishmarket.com/RULES-AND-REGULATIONS-NFFM_rev-9_04_07.pdf

Grass Carp Propagation

Grass Carp Propagation by   By Kenneth Williams GRASS CARP, OR white amur, (Ctenopharyngodon idella), were first brought into the United States in 1963 by the U.S. Fish and Wildlife Service Warm Water Fish Experiment Station near Stuttgart, Arkansas. The fish came from Malaysia and were used to study the potential for weed control in ponds and lakes. Grass carp are one of the largest members of the minnow family, (Cyprinidae). They may weigh up to 110 pounds but rarely exceed 35 pounds when stocked in ponds. Their life span is about 12 to 15 years but experience has shown that most ponds must be restocked after 7-8 years because the fish may be killed, captured by anglers, or die of natural causes. Also older grass carp do not remove vegetation as efficiently as younger fish. Although usually classified as an opportunistic feeder, grass carp aggressively feed on vegetation. However, grass carp feeding and growth is greatly reduced when water temperature drops below 57 degrees F. These fish prefer soft vegetation but consume tougher plant species as preferred food supplies are diminished. Grass carp readily consume pelleted fish rations when available. Stocker fingerlings (8-10 inches) can reach a weight of 5-7 lb in a growing season and 15-20 lb after 3 years provided an adequate food supply exists. In natural habitat, adult grass carp are found in back waters of large river systems in Asia. Aquatic vegetation is abundant and provides both food supply and cover from predators. Spawning is determined primarily by photoperiod (day length) and water temperature. The fish begin to spawn when flood waters swell rivers, water temperature reaches 70-75 degrees F. and photoperiod is increasing above eight hours of daylight per day. Mature adults form schools and swim upstream for many miles into the swift flowing waters found in upper reaches of the river. The grass carp spawn and release fertilized, semi-buoyant, non-adhesive eggs down stream. Currents (1-5 feet per second) are required to prevent eggs from lodging on the bottom, silting over and dying. Eggs moving down stream are oxygenated and hatch into fry after an incubation period of 24-28 hours. The larvae receive nourishment from the yolk sac for 1-3 days before active feeding begins. Grass carp fry smaller than 1.25 inches feed on phytoplankton, zooplankton and invertebrates. As they grow larger aquatic insects become more important in the diet. Grass carp 2-4 inches long are large enough to consume multicellular algae and aquatic macrophytes. Grass carp reach sexual maturity in two-three years in Oklahoma. Spawning does not occur in ponds and lakes. Reproductive organs reach an incomplete state of development and become dormant. As water temperature rises above 80 degrees F. eggs and milt are resorbed into the fish. Natural spawning conditions do not exist for grass carp in the United States with the possible exception of the Mississippi river. Successful grass carp spawning and hatching requires a thorough knowledge of the fish, healthy brood stock, gentle handling and an understanding of induced hormonal spawning techniques. Brood Fish Management Brood fish care begins the summer before they will be spawned. Grass carp that are in poor condition going into the winter and early spring make poor spawners. Brood stock should not be of uniform size because the males are smaller than the females. Brood fish four years old are preferred for use as induced spawners. Most of these fish will weigh 15-20 lb. Brood fish are stocked at a rate of 200-1000 lb per acre depending on the number of fry needed. Males and females are stocked in about equal numbers. Stock brood fish in a pond containing a large amount of aquatic vegetation and supplementally feed with a floating, catfish ration at no more than 1-2 percent of body weight. Sinking pelleted feed should not be fed because it is not readily accepted by the grass carp. Add additional forages such as grass clippings or alfalfa if vegetation is eaten before spawning season. Maintain good water quality in the pond. Dissolved oxygen should not drop below 2 mg/L (ppm). Ponds should not be seined if dissolved oxygen is below 4 mg/L. Brood fish must be seined carefully to avoid stress and damage to the fish. Use a knotless mesh seine if possible. Usually 1-2 persons hold up the back of the seine to prevent the fish from jumping over the net. Protective clothing is advised by some workers to avoid blows from large grass carp. A baseball catcher's mask can be worn to protect the face. Brood fish can be seined and placed in round tanks before water temperature reaches the level required for spawning. This technique allows fish to recover from harvest stress before spawning is induced. Fish harvested at water temperatures above 68 degrees F. should be spawned within a day to achieve best results. Grass carp are ready for induced spawning in late May or early June when water temperature has reached 70 degrees F. At water temperatures above 80 degrees F. spawning success declines because resorption of eggs may occur in female fish. Sexes are determined by feeling the pectoral fins. Male grass carp have a rough, sandpaper texture on the pectoral fin and spine, also protuberances on the head and opercles. The male "pearl organ" should protrude. Females have a distended abdomen compared to males and a red area around the egg vent indicating that the fish is ready to spawn. If sex cannot be determined do not use the fish for spawning purposes. Induced Spawning Grass carp can be hormonally induced to spawn in several ways. Originally, carp pituitary alone was used. This method is still used, but ovulation success may vary because hormone strength in the carp pituitary gland is dependent on processing, age and condition of the fish. Carp pituitary can be used fresh or more conveniently as an acetone-dried extract. For example, 0.5 g of the extract is ground dry with a mortar and pestle, then 10 cc of sterile water is added, slowly and thoroughly mixed. The mixture is allowed to stand for about 30 minutes. The hormone dissolves in the water and is drawn off with a syringe. Settled solids are not used. The preparation is ready for immediate use or it can be stored in small vials in the freezer. Grass carp are injected with 3-5 mg of pituitary per lb of female or 0.6- 1.0 cc of the prepared solution per 10 lb of brood fish. Stress on brood fish must be kept to a minimum. Do not remove fish from holding tanks to give injections. Use a knotless mesh cradle or piece of knotless seine to capture the fish, hold it to the side of the tank, cover the fish head with a towel to help prevent movement and inject the hormone intramuscularly with a 20 gauge needle at the base of the last ray of the dorsal fin. Optimum injection volume for grass carp is 2 cc or less. Two injections are used to induce female spawning. The first injection contains 1/10 of the total dosage. This injection is followed by the remaining 9/10 of the dosage in 18-24 hours. Male grass carp are given 1-2 mg per lb of body weight or 0.2-0.4 cc of prepared hormone solution per 10 lb of brood fish. Male fish are injected at the time the female is administered the second injection. Adequate fertilization of spawn requires two males for each female grass carp. Separate the sexes in separate tanks of water. Use fin clips or other means to identify individual fish if necessary. Check female spawning condition beginning one hour before expected spawn. Handle fish gently! Stress will reduce or prevent successful or complete ovulation and result in little or no spawn. Spawning procedures and egg handling should be done in subdued lighting. Direct sunlight can kill or damage eggs. Carefully capture the female in a large, deep, dip net. Use an uncoated nylon net or other material that will not damage the fish. Bring the fish to the side of the tank and lift to the surface of the water. Turn the fish on her back with the belly exposed slightly above water line. Gently stroke the belly towards the vent. Copious egg flow indicates the female is ready to spawn. The female is not ready to spawn if few or no eggs flow freely from the vent. When a few eggs flow, recheck the fish in 30 minutes. If no eggs are observed, check the fish again in one hour. Eggs are in an anoxic condition at ovulation and begin to deteriorate rapidly because they no longer receive a blood supply from the ovary. Dead or deteriorating eggs look cloudy and should be removed. Eggs in good condition are usually grayish-green to brown or orange. Best spawning success occurs when eggs are stripped no later than 30 minutes after ovulation. Cover the vent with a thumb or finger when egg flow indicates the female is ready to spawn. Carefully hold the fish by the caudal peduncle. Another worker should grab the head of the fish and wrap it in a towel, making sure to cover the eyes. Dry the fish to prevent water from dripping into the egg pan. Hold the fish over a clean, dry pan 12 to 18 inches in diameter and about 6 to 8 inches deep. Raise the head slightly above the tail and direct the egg flow into the pan. Females can be anesthetized before egg removal with MS-222 (1 tablespoon per 10 gallons of water). To anesthetize the fish, place it in a 100 gallon horse tank filled with water and anesthetizing agent until it is calm. Each male is dipped from the holding tank and dried with a towel. Milt is stripped from the male by starting behind the pelvic fins and squeezing toward the vent. Milt can be taken prior to actual need and stored in plastic bags in a refrigerator. Avoid cross contamination. Use one bag per individual fish. A small amount of water should be added to stored milt immediately before use. Swirl 5-10 seconds then mix with eggs. Water will kill sperm in about one minute. Swirl the eggs and milt gently, with a finger, paint brush or feather for 2 to 3 minutes. Add a volume of water about equal to the volume of eggs, stir gently for 3 minutes then pour off as much water as possible. Repeat water rinse two times to water harden eggs. Eggs become fully hardened in about 10 minutes. One quart volume contains 225,000 to 250,000 fertilized eggs. Place the eggs in hatching jars. Water flow should be strong enough to keep the eggs suspended but not strong enough to wash them out of the hatching jar. Eggs should hatch after 24 hours incubation in water about 75 degrees. When larvae hatch they rise to the surface and follow the current of the overflow. The overflow water can spill over into an aquarium. The aquarium drain should be screened with 50 mesh per inch net screen. During the first three days larvae will use food energy stored in their yolk sack. Larval stocking densities can be as high as 50,000 per gallon of water at this time. Water flow in the aquarium should remain high enough to suspend larvae from the bottom of the tank. Stock fry into rearing ponds at three to five days old Fill the ponds about a week before fry are to be stocked to reduce predaceous insects and disease. Wells are the best source of water for fry ponds. Unwanted fish and insects can be introduced into ponds filled from streams and reservoirs. Stream or pond water must be filtered. Grass carp fry can be stocked into the rearing ponds at a rate of 100,000 to 500,000 per acre. Fry initially feed on zooplankton. To produce an adequate supply of these microscopic animals it is usually necessary to fertilize the pond. Fertilization puts a green "bloom" on the pond caused by large numbers of phytoplankton or microscopic plants. Zooplankton feed on the phytoplankton. The amount of fertilizer needed and results of fertilization vary with physical features of the pond and nutrient loading. Ammonium polyphosphate has been used successfully at rates of 1-2 gallons per acre foot. Some producers prefer a mix of organic and inorganic fertilizers. Chicken manure has been used along with inorganic fertilizer at a rate of 300-400 pounds per acre per week in 0.1-0.5 acre ponds. Research at Langston University has shown that daily applications of 0.1-0.25 lb ammonium chloride/acre foot provides excellent pond fertilization. Begin supplemental feeding with minnow meal as soon as the fish are stocked. Uneaten meal may fertilize the pond sufficiently to maintain the desired bloom. Feed fish two to four times daily. Avoid over feeding fish. When grass carp have reached a length of three to four inches they should be removed from high density ponds and restocked into ponds at a density of 3,000 to 5,000 fish per acre for growth to a stocking size of eight to ten inches. a survival rate from fry to fingerling of 40%-60% is considered good. It is preferable to stock 3-4 inch fingerlings in growout ponds containing abundant aquatic vegetation. However, the fish should continue to be supplementally fed with minnow meal until they can take a regular catfish pellet. A 28%-32%, 3/16 inch, floating catfish pellet can be fed to the grass carp until they reach harvestable size. Feed no more than 2% of total standing crop body weight per day, less if other foods are present. Grass carp production can range from 2,000 to 4,000 pounds per acre in well fed and managed ponds. References Hatchery Manual For Grass Carp And Other Riverine Cyprinids. R.W. Rottmann and J.V. Shireman. Bulletin 244, University of Florida, Gainesville, Fl. 32611 Propagation Of Grass Carp. Harry K.Dupree, U.S. Fish And Wildlife Service, Fish Farming Experimental Station, Stuttgart, AR 72160 Data is given by:http://www.luresext.edu/aquaculture/grasscarppropogation.htm

SEED PRODUCTION AND HATCHERY MANAGEMENT

SEED PRODUCTION AND HATCHERY MANAGEMENT of fish

Aquarium Fish: Use of MS-222 (Tricaine Methanesulfonate) to Induce Sedation and Anesthesia in Ornamental Fishes By Kenneth Wingerter

Aquarium Fish: Use of MS-222 (Tricaine Methanesulfonate) to Induce Sedation and Anesthesia in Ornamental Fishes By Kenneth Wingerter

EFFECT OF CHEMICAL ANOXIA ON PROTEIN KINASE C AND Na+/K+-ATPase IN HEPATOCYTES OF GOLDFISH (CARASSIUS AURATUS) AND RAINBOW TROUT (ONCORHYNCHUS MYKISS)

EFFECT OF CHEMICAL ANOXIA ON PROTEIN KINASE C AND Na+/K+-ATPase IN HEPATOCYTES OF GOLDFISH (CARASSIUS AURATUS) AND RAINBOW TROUT (ONCORHYNCHUS MYKISS)

Microbiological quality of fish grown in wastewater-fed and non-wastewater-fed fishponds in Hanoi, Vietnam: influence of hygiene practices in local retail markets Nguyen Thi Phong Lan, Anders Dalsgaard, Phung Dac Cam and Duncan Mara

Microbiological quality of fish grown in wastewater-fed
and non-wastewater-fed fishponds in Hanoi, Vietnam:
influence of hygiene practices in local retail markets
Nguyen Thi Phong Lan, Anders Dalsgaard, Phung Dac Cam and Duncan Mara


ABSTRACT
Nguyen Thi Phong Lan
Phung Dac Cam
Department of Microbiology,
National Institute of Hygiene and Epidemiology,
1 Yersin St,10,000, Hanoi,
Viet Nam
Anders Dalsgaard (corresponding author)
Department of Veterinary Pathobiology,
Royal Veterinary and Agricultural University,
Grønnega° rdsvej 15, DK-1870, Frederiksberg C,
Denmark
Tel.:+45 35 282 720
Fax: +45 35 282 757 E-mail: ad@kvl.dk
Duncan Mara
School of Civil Engineering,
University of Leeds,
Leeds LS2 9JT,
UK
Mean water quality in two wastewater-fed ponds and one non-wastewater-fed pond in Hanoi,
Vietnam was ,106 and ,104 presumptive thermotolerant coliforms (pThC) per 100 ml,
respectively. Fish (common carp, silver carp and Nile tilapia) grown in these ponds were sampled
at harvest and in local retail markets. Bacteriological examination of the fish sampled at harvest
from both types of pond showed that they were of very good quality (2 2 3 pThC g21 fresh
muscle weight), despite the skin and gut contents being very contaminated (102 2 103 pThC g21
fresh weight and 104 2 106 pThC g21 fresh weight, respectively). These results indicate that the
WHO guideline quality of #1000 faecal coliforms per 100 ml of pond water in wastewater-fed
aquaculture is quite restrictive and represents a safety factor of ,3 orders of magnitude.
However, when the fish from both types of pond were sampled at the point of retail sale, quality
deteriorated to 102 2 105 pThC g21 of chopped fresh fish (mainly flesh and skin contaminated
with gut contents); this was due to the practice of the local fishmongers in descaling and
chopping up the fish from both types of pond with the same knife and on the same chopping
block. Fishmonger education is required to improve their hygienic practices; this should be
followed by regular hygiene inspections.
Key words | coliforms, fishculture, hygiene, retail markets, Vietnam, wastewater
INTRODUCTION
Fish production in excreta-fertilized fishponds is a very
ancient practice, especially in the Far East and notably
China where the practice is believed to have been initiated
over 3,000 years ago (Zhiwen 1999). In Vietnam wastewaters
are used for aquaculture as a source of both water
and nutrients (Vo 2001). The nutrients supports the growth
of plankton and other micro-organisms which are consumed
by the fish with little additional feeding taking place.
In periurban Hanoi there are ,2,500 ha of aquaculture
ponds, over 99 percent of which are used for fish culture,
mainly carp and tilapia, with a small area (,1 percent) for
shrimp production (Mai et al. 2004). Most of the wastewater-
fed fishponds are located in Thanh Tri district in the
south of the city, where there are ,330 ha of wastewaterfed
fishponds (Vo & Edwards 2005); there is also widespread
wastewater use for rice culture which is often
alternated with fish production (Tran 2001).
In order to assure the microbiological safety of fish
raised in wastewater-fed fishponds the World Health
Organization’s guideline is that the fishpond water should
have a faecal coliform count of #1000 per 100 ml (WHO
1989); this guideline value is expected to be retained in the
new guidelines which are currently being prepared (WHO
2006). Various bodies have made recommendations for the
microbiological quality of fish rather than the fishpond
water. For example, the International Commission on
Microbiological Specifications for Foods (1986) recommended
an ‘m’ value of 11 E. coli g21 and an ‘M’ value
doi: 10.2166/wh.2007.014
209 Q IWA Publishing 2007 Journal of Water and Health | 05.2 | 2007
of 500 E. coli g21 of uncooked fresh and frozen fish flesh,
where m and M are defined as follows: if the E. coli count is
,m the quality is ‘satisfactory’; if it is .M it is ‘unsatisfactory’;
and, if no more than three out of five fish samples
have values between m and M, it is ‘acceptable’. In Vietnam
the national standards are #100 E. coli g21 of uncooked
fresh and frozen fish flesh and #3 E. coli g21 of cooked fish
flesh (Ministry of Health 1998). A comprehensive review of,
and the corresponding rationales for, microbiological
criteria for safe fish are given in Institute of Medicine (2003).
Studies on the microbiological quality of fish raised in
wastewater-fed fishponds are few with some studies
indicating that faecal bacteria may penetrate the fish flesh
when fish is grown in highly polluted water (Buras et al.
1985, 1987; Buras 1990), whereas other studies found no or
little penetration of micro-organisms in aquaculture
environments in which the fish were not stressed (Edwards
1992). Furthermore, the level of microbiological crosscontamination
and quality of wastewater-fed fish sold to
consumers at retail markets are unknown. In this paper we
report the results of an investigation into the microbiological
quality of fish from wastewater-fed and non-wastewater-
fed fishponds in Thanh Tri district of Hanoi, both at
harvest and at the point of sale in local retail markets.
METHODS
Study locations and sampling
Fishponds
The study was carried out in two wastewater-fed ponds and
one nominally non-wastewater-fed (control) pond in Yen
So commune, Thanh Tri district. The areas of the
wastewater-fed ponds were ,3 and ,15 ha and their liquid
depths were ,1.5 2 2m. Both ponds were fed with raw
wastewater directly from the Kim Nguu River through a
pumping station located in the commune; ponds also
received direct discharges of domestic wastewater from
households around the ponds. The Kim Nguu river is
essentially a wastewater canal: CEETIA (1997) found it to be
heavily polluted, with biological oxygen demand (BOD)
and chemical oxygen demand (COD) concentrations some
3 2 7 times higher than the Vietnamese permitted standard
levels (#50mg BOD l21 and #100mg COD l21 for
wastewaters discharged into water bodies used for aquaculture
and crop irrigation). Toan (2004) found thermotolerant
coliform (ThC) numbers of 3 £ 107 per 100 ml in
the inlet of a fishpond in Yen So commune fed with water
from the Kim Nguu river.
The control pond, with an area of ,14 ha and a depth
of ,1.5 2 2m, was located on the alluvial plain adjacent to
the west bank of the Red River beyond a flood-control dyke.
Red River water was used to feed the control pond as
wastewater could not be economically pumped across the
dyke. Before the control pond was selected for the study,
samples of its contents were analysed for ThC numbers
(details in Results section below).
In Yen So commune the most commonly cultured fish
are common carp (Cyprinus carpio), silver carp
(Hypophthalamichthys molitrix), and Nile tilapia (Oreochromis
niloticus). The growing season is ,10 months and
at harvest common carp weigh ,500 2 600 g, silver carp
,200 2 300 g, and tilapia ,150 2 200 g. In this study, five
individual fish of each of these three species were collected
at ,7 a.m. immediately after they had been harvested from
the wastewater-fed and non-wastewater-fed ponds. Each
fish was placed in a sterile plastic bag. At the same time the
fish samples were collected, grab samples of the fishpond
water were collected from 15 2 20 cm below the surface in
sterile 500-ml glass sampling bottles. The fish and fishpond
water samples were then protected against heat and
sunlight and transported to the laboratory within 30
minutes. Samples were kept at 4 2 58C upon arrival at the
laboratory and analyzed within six hours of collection.
Local retail fish markets
There are several retail markets within 4 km of Yen So
commune to which fish are transported in bamboo baskets
on bicycles or motorbikes early in the morning. At the
market the fish are kept alive in small aerated basins filled
with tap water (Figure 1); the same basin is used for fish
from both wastewater-fed and non-wastewater-fed ponds.
The fishmongers, who are usually women, generally sit on
small wooden chairs close to the ground. They gut and
clean the fish on small wooden chopping boards placed on
the ground (Figure 2). Normally the scales are removed and
210 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
the gut removed through a cut in the side of the fish. Carp
are then chopped into pieces, placed in a polythene bag and
sold. Tilapia are de-gutted and sold as whole fish after the
scales have been removed. The same knife is used for all
stages of fish processing. The fishmongers clean the
chopping board only twice a day, generally at the end of
the morning and afternoon trading sessions.
The fish sampled at the markets were ‘tracked’ from the
fishpond at harvesting and accompanied to the market, so
that it was known which fish came from the wastewater-fed
ponds or the non-wastewater pond. At the market whole
fish were purchased and the fishmonger asked to process
each fish in the normal way (i.e., to remove the scales and
gut the fish, then chop it into pieces). Each fish processed in
this way was then placed in a sterile plastic bag and taken
immediately to the laboratory for analysis.
Microbiological examination
Fish sampled at harvest
Samples of the skin, muscle and intestinal tract of the whole
fish samples were collected separately under aseptic
conditions, as follows:
(a) skin samples were taken from a 10-cm2 (2 £ 5 cm)
central area of the fish by marking out, using a sterile
template and scalpel, the outline of the desired area and
then removing, with sterile scalpel and forceps, as thin a
layer of the skin as possible (1 2 2 mm); the skin sample
was then placed in a sterile Petri dish.
(b) flesh (muscle) samples were taken by first sterilizing the
surface with a red-hot knife blade and then removing,
with sterile scalpel and forceps, the flesh immediately
below the singed surface so that a sample could be
taken of the raw flesh below; each sample collected in
this way weighed ,5g.
(c) the whole intestinal tract of each fish was removed
aseptically with sterile scalpel and forceps.
Similar sample types (skin, flesh or intestinal tract) from
each of five fish of a single species (common carp, silver
carp or tilapia) were removed, pooled, placed in a
polyethylene bag to give a five-fish composite sample,
which was then weighed. Nine times this weight of a
solution of 0.1% peptone and 0.85% sodium chloride at pH
7.5 was added and this 1-in-10 dilution was then
homogenized in a BagMixer model VW400 stomacher
(Interscience, St Nom, France) for 30 seconds. This dilution
Figure 1 | A local retail fish market in Yen So commune.
Figure 2 | Processing of a carp at a local retail market in Yen So commune.
211 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
was then used for microbiological analyses directly or
diluted further, as described below.
Fish sampled at markets
A ,10-g sample of fish flesh was taken from one of the
pieces of fish in each of five plastic bags containing the same
fish species (common carp, silver carp or tilapia). These
samples were then pooled in a polyethylene bag to give a
five-fish composite sample which was then weighed. They
were then diluted and homogenized, as described above.
Bacteriological analyses
Serial 1-in-10 dilutions to 1027 were made of each fish or
wastewater sample using the peptone-NaCl diluent. Bacteriological
analyses for presumptive ThC, enterococci and aerobic
standard plate countswere then carried outwithin 30minutes
using the procedures recommended by the Nordic Committee
on Water and Food Analysis (Danish Standards Association
1999, 2001, 2002). Spread plates of membrane lauryl sulphate
agar (MM0615 broth with 15 g L0011agar l21; Oxoid Ltd,
Basingstoke,Hampshire,England) and Slanetz&Bartley agar
(Oxoid CM0377) were used for presumptive ThC and
enterococci, respectively, with incubation at 448C for 24h
(ThC) and 48h (enterococci). Pour-plates of tryptone yeast
extract agar (Oxoid CM1012 water plate count agar) were
used for standard plate counts (SPC) following incubation at
378C for 48 h. After incubation colonies growing on the agar
plates were enumerated and the counts of cell-forming units
(CFU) per g of fish (fresh weight) and CFU per100ml of
fishpond water determined.
Statistical analyses
The student t test was used to compare the geometric mean
results from the wastewater-fed and the non- wastewaterfed
ponds, and ANOVA for those from the three fish
species. The data were analyzed in Excel 2003 (Microsoft
Corp., Seattle, WA).
RESULTS
Fishpond water
The two wastewater-fed fishponds had significantly higher
mean counts of presumptive ThC (p , 0.0001) and enterococci
(p , 0.001) than the nominally non-wastewater-fed
pond: two orders of magnitude higher for presumptive ThC
and one order of magnitude higher for enterococci; there was
no difference in the standard plate counts (Table 1). The ThC
counts inthewastewater-fed pondswere nearly three orders of
magnitude higher than the WHO (1989) guideline value of
#1000 per 100 ml, whereas those in the nominally nonwastewater-
fed pond were less than one order of magnitude
above this guideline value.
Fish sampled at harvest
There was no major significant differences (i.e., those
important froma public health perspective) in bacteriological
Table 1 | Numbers of faecal indicator bacteria and standard plate counts in wastewater-fed and non-wastewater-fed fishponds
Wastewater-fed pondsa Non-wastewater-fed pond
Bacterial group Nc Meand s n Meanc s p (t test)b
Presumptive thermotolerant coliforms 9 5.92 0.91 10 3.79 0.57 0.0001
Enterococci 7 4.41 0.68 10 3.43 0.47 0.001
Standard plate count 8 7.79 1.02 10 7.57 0.79 0.183
aThere was no significant difference in the bacterial counts in the two wastewater-fed ponds (t test: p . 0.05).
bValues in bold indicate significant differences.
cNumber of water samples analysed.
dLog geometric mean bacterial numbers per 100 ml.
212 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
qualities between the skin, gut contents or flesh for the three
fish species when comparing their origin from either wastewater-
fed or non-wastewater-fed ponds (Tables 2–4). Comparison
of bacterial numbers in skin samples from the three
fish species revealed no significant differences, except in one
casewhere skin samples fromwastewater-fed silver carp had a
higher SPC than non-wastewater-fed silver carp.
Fish from both wastewater-fed and non-wastewater-fed
ponds contained similar bacterial numbers in their gut
contents: 105–106 presumptive ThC g21 and 103–105 enterococci
g21 (Table3).Amongst the fishfromthewastewater-fed
ponds common carp contained significantly higher numbers
of presumptive ThC and enterococci than silver carp and
tilapia. Common carp are primarily bottom feeders and thus
will be exposed to high bacterial numbers in pond sediment,
whereas silver carp and tilapia primarily feed in the water
column where bacterial concentrations are lower.
Fish flesh samples collected by the stringently aseptic
technique contained no or very few faecal indicator
bacteria, whereas the SPC were ,103 CFU g21 (Table 4).
No significant differences were found in bacterial
numbers between fish from the wastewater-fed and the
non-wastewater fed ponds. Thus the very limited penetration
of faecal bacteria into the fish flesh came primarily
from the fish gut.
Fish sampled at point of retail sale
The bacteriological qualities of all three fish species from
both types of fishpond were substantially worse after
handling, cleaning and purchase in the local retail markets
than that at harvest: the geometric mean presumptive ThC
and enterococci counts in the fish samples from both the
wastewater-fed and non-wastewater-fed ponds were
Table 2 | Numbers of faecal indicator bacteria and standard plate counts on the skin of fish collected immediately after harvest from wastewater-fed and non-wastewater-fed ponds
Wastewater-fed pondsa
(nb 5 20)
Non-wastewater-fed pond
(n 5 18)
Bacterial group Fish n Meand s N Mean s p (t test)c
Presumptive thermotolerant coliforms Common carp 6 2.53 0.83 6 2.46 0.90 0.44
Silver carp 6 2.30 0.43 6 2.19 1.71 0.44
Tilapia 8 2.95 1.10 6 3.27 1.18 0.69
p (ANOVA) 0.38 0.35
Enterococci Common carp 6 1.93 1.35 6 2.51 0.84 0.80
Silver carp 6 2.07 1.48 6 1.88 1.29 0.40
Tilapia 8 3.10 1.10 6 3.08 0.99 0.48
p (ANOVA) 0.20 0.18
Standard plate counts Common carp 6 5.35 0.82 6 5.01 0.44 0.20
Silver carp 6 5.47 0.69 5 4.29 1.14 0.03
Tilapia 8 5.48 1.15 4 5.50 0.61 0.51
p (ANOVA) 0.96 0.10
aThere was no significant difference in the bacterial counts on the skin of the fish harvested from the two wastewater-fed ponds (t test: p . 0.05).
bNumber of skin samples analysed.
cValues in bold indicate significant differences.
dLog geometric mean bacterial numbers g21.
213 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
102–105 CFU g21 and the SPC ranged from 106–107 CFU
g21 (Table 5). Numbers of presumptive ThC and enterococci
were significant higher in silver carp than in
common carp and tilapia. In general, there was no
significant difference between the bacteriological qualities
of the fish from the wastewater-fed ponds and those from
the non-wastewater-fed ponds.
DISCUSSION
The water in the non-wastewater-fed pond receiving water
from the Red River was faecally contaminated at a level of
just under 104 presumptive ThC per 100 ml, but the quality
of the flesh of fish from this pond at harvest showed little if
any faecal contamination (maximum 2–3 presumptive ThC
g21). The flesh from fish harvested from the much more
contaminated wastewater-fed ponds (just under 106 presumptive
ThC per 100 ml) contained similar levels of
presumptive ThC and was thus of an equally satisfactory
microbial quality. Thus very few faecal indicator bacteria
penetrated into the fish flesh even in the highly faecal
polluted wastewater-fed fish pond. However the SPC of the
fish flesh was 102–104 CFU g21, indicating that bacterial
penetration did occur, but at similar levels in the wastewater-
fed and non-wastewater-fed ponds.
A limited number of other studies have investigated the
association between microbiological qualities of the fishpond
water and the fish in both laboratory environments
and functioning waste-fed aquaculture ponds. A few studies,
mainly conducted in Israel, have suggested a threshold
bacterial concentration in the fishpond water above which
Table 3 | Numbers of faecal indicator bacteria and standard plate count in the gut of fish collected immediately after harvest from wastewater-fed and non-wastewater-fed ponds
Wastewater-fed pondsa
(nb 5 20)
Non-wastewater-fed pond
(n 5 18)
Bacterial group Fish N Meand s n Mean s p (t-test)c
Presumptive thermotolerant coliforms Common carp 6 5.33 1.12 6 6.19 0.85 0.91
Silver carp 6 4.67 0.91 6 4.65 0.95 0.48
Tilapia 8 5.17 1.07 6 4.62 1.47 0.21
p (ANOVA)c 0.53 0.04
Enterococci Common carp 6 3.75 1.01 6 5.11 1.35 0.96
Silver carp 6 3.36 0.64 6 3.25 0.62 0.39
Tilapia 8 3.42 0.60 6 2.57 0.90 0.02
p (ANOVA) 0.63 0.001
Standard plate counts Common carp 6 7.97 0.73 6 8.32 0.21 0.85
Silver carp 6 7.42 0.48 6 7.85 0.75 0.86
Tilapia 8 7.58 0.63 6 7.60 0.85 0.52
p (ANOVA) 0.30 0.20
aThere was no significant difference in the bacterial counts in the gut of the fish harvested from the two wastewater-fed ponds (t test: p . 0.05).
bNumbers of individual fish analysed.
cValues in bold indicate significant differences.
dLog geometric mean bacterial numbers g21.
214 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
bacteria enter the edible muscle tissues of fish and thus
increase the risk of exposure for consumers of the fish.
Buras and co-workers (Buras et al. 1985, 1987; Buras 1990)
reported such a threshold concentration of total culturable
bacteria in fishpond water of 1 2 5 £ 106 per 100 ml, but
this seems to have been due to a major malfunction in the
wastewater treatment plant which introduced such high
organic loadings into the receiving fishpond that the fish
were extremely stressed and only just able to survive (P.
Edwards, personal communication, 2005). A study in
Thailand reported an SPC range in septage-fed fishponds
of 1.8 £ 105–2.0 £ 106 per 100 ml of pond water which
produced fish with minimal bacterial penetration into their
flesh (Edwards et al. 1984). Exposure of 132 healthy tilapia
to fishpond E. coli concentrations of up to 106 cfu per
100 ml from wastewater sources led to little or no detectable
bacterial or bacteriophage penetration into their flesh
(Fattal et al. 1988, 1993). In the United States Hejkal et al.
(1983) found a maximum of 25 faecal streptococci per 100 g
of fish muscle even though the gut contained .105 per
100 g. The fish in the Buras studies were grown under
conditions of high stress which is atypical of normal
aquaculture ponds; thus the penetration of micro-organisms
into the fish flesh in this study may have been an
exceptional case. The results of the current study, together
with other studies on well-managed ‘normal’ wastewaterfed
fishponds (reviewed by Edwards 1992), suggest that the
maximum permissible number of faecal indicator bacteria in
wastewater-fed fishponds should be less than that which
would lead to significant contamination of the fish flesh.
However, further research is needed to assess how many
orders of magnitude are needed to provide a realistic (i.e.,
Table 4 | Numbers of faecal indicator bacteria and standard plate count in the flesh of fish collected immediately after harvest from wastewater-fed and non-wastewater-fed ponds
Wastewater-fed pondsa,b
(nc 5 20)
Non-wastewater-fed pond
(n 5 18)
Bacterial group Fish n Meane s n Meanc s p (t-test)d
Presumptive thermotolerant coliforms Common carp 6 0.41 0.28 6 0.30 0 0.17
Silver carp 6 0.30 0 6 0.30 0 2
Tilapia 8 0.30 0 6 0.41 0.28 0.86
p (ANOVA)d 0.32 0.39
Enterococci Common carp 6 0.41 0.28 6 0.30 0 0.17
Silver carp 6 0.51 0.53 6 0.30 0 0.17
Tilapia 8 0.30 0 6 0.41 0.28 0.86
p (ANOVA) 0.48 0.39
Standard plate count Common carp 6 3.03 0.94 6 3.13 0.97 0.57
Silver carp 6 3.40 1.20 6 2.65 0.55 0.09
Tilapia 8 2.72 0.46 6 3.88 0.78 0.99
p (ANOVA) 0.38 0.03
aThere was no significant difference in the bacterial counts in the flesh of the fish harvested from the two wastewater-fed ponds (t test: p . 0.05).
bOnly three of the 20 fish examined had measurable numbers of presumptive ThC and enterococci per g of flesh (zero colony formation was recorded as ,2g21).
cNumbers of individual fish analysed.
dValues in bold indicate significant differences.
eLog geometric mean bacterial numbers g21.
215 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
not over-restrictive) safety factor for faecal bacterial
indicator numbers in wastewater-fed fishponds.
Our results indicate that these fish flesh qualities were
satisfactory in terms of their faecal bacterial indicator
counts and complied with the recommendations of the
International Commission on Microbiological Specifications
for Foods (1986) and the Vietnamese Ministry of
Health (1998). They are in partial agreement with the fish
quality classification scheme developed by Buras et al.
(1987); this proposed “that in the case of fish grown in
wastewater, the quality of the fish should be determined by
the presence of any bacteria in the muscles” and “that the
indicators should be bacteria that grow on nutrient and
mFC agar, and the bacteriological quality should be
expressed as: 0 2 10 bacteria ml21, very good; 10 2 30
bacteria ml21, medium quality; more than 50 bacteria ml21,
not acceptable” [sic; it is not clear what quality was to be
assigned for 31 2 49 bacteria ml21]. Thus, based on this
scheme, the fish flesh qualities at harvest were ‘very good’
on the basis of their E. coli counts but ‘not acceptable’ on
the basis of their SPC (Table 4). It is difficult to imagine a
wastewater-fed (or river-water-fed) aquaculture situation in
which the “nutrient and mFC agar” counts are the same as
this would imply that all (or essentially all) the bacteria
present were faecal coliforms/E. coli. We thus accept the
classification of Buras et al. (1987) but only in terms of
the E. coli counts g21 of fish flesh and not in terms of the
SPC g21.
Table 5 | Numbers of faecal indicator bacteria and standard plate counts in fish samples (flesh, skin, bone) from wastewater-fed and non-wastewater-fed ponds purchased at local
retail markets
Wastewater-fed pondsa
(nb 5 52)
Non-wastewater-fed pond
(n 5 64)
Bacterial group Fish n Meand s n Mean s p (t test)c
Presumptive thermotolerant coliforms Common carp 10 2.89 0.69 20 3.45 1.80 0.82
Silver carp 20 4.23 1.35 20 4.28 1.28 0.55
Tilapia 22 3.49 0.78 24 3.73 0.95 0.81
p (ANOVA)c 0.004 0.15
Enterococci Common carp 10 2.68 0.92 20 3.23 1.29 0.87
Silver carp 20 4.33 1.26 20 3.70 0.69 0.02
Tilapia 22 3.68 0.63 24 3.54 0.57 0.22
p (ANOVA) 0.0003 0.24
Standard plate count Common carp 10 6.49 0.54 20 6.65 1.31 0.64
Silver carp 19 6.93 0.52 19 6.91 0.93 0.46
Tilapia 22 6.93 0.65 24 6.99 0.95 0.58
p (ANOVA) 0.11 0.57
aThere was no significant difference in the bacterial counts in the fish harvested from the two wastewater-fed ponds (t test: p . 0.05).
bNumbers of individual fish analysed.
cValues in bold indicate significant differences.
dLog geometric mean bacterial numbers g21.
216 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
Surprisingly, the fish from both the wastewater-fed and
the non-wastewater fed ponds contained similar bacterial
concentrations in their gut contents (,105–106 presumptive
ThC g21 and ,103–105 enterococci g21). This may be
partly explained by the relatively high numbers of presumptive
ThC) in the non-wastewater pond (,104 per
100 ml). Our findings of high numbers of faecal bacteria in
the gut content are in agreement with several studies
reviewed by Edwards (1992). Fish samples (muscle, skin,
bone) purchased at retail markets contained from ,1,000
to ,20,000 presumptive ThC g21, irrespective of whether
the fish originated from the wastewater-fed or the nonwastewater
fed ponds. This indicates that significant faecal
cross-contamination occurred at the markets during handling
and processing of the fish for human consumption. As
noted by Buras et al. (1987), “exposure to pathogens can
occur when fish are handled and cleaned. During the
digestive tract removal, the content is usually spilled and
contaminates the intestinal cavity of the fish and the hands
of the handler. Casual rinsing does not prevent contamination”.
Clearly, local environmental health officers/assistants
need to educate local fishmongers so that (a) they are
aware of the risks for faecal contamination of the fish
products and possible occupational health risks of their
unhygienic practices and (b) they are then able to
implement and sustain improved hygiene practices; they
also need to be regularly inspected by the local environmental
health officers/assistants to ensure that their fishhandling
and cleaning practices are always hygienic.
Finally, it should be noted that only the bacteriological
quality of fish from wastewater-fed and non-wastewater-fed
fishponds was investigated by the use of bacterial indicators.
Thus, the possible occurrence and food-safety aspects of
fishborne zoonotic parasites, in particular trematode parasites,
bacterial and viral pathogens, and any bio-accumulation
of toxic chemicals in the wastewater, were not
assessed.
CONCLUSIONS
† Fish grown in both wastewater-fed and nominally nonwastewater-
fed fishponds with presumptive ThC counts
of ,106 and ,104 per 100 ml, respectively, were of very
good quality at harvest (2 2 3 presumptive ThC g21 of
flesh). This indicates that the current WHO guideline
value for wastewater-fed aquaculture (#1000 E. coli per
100 ml of fishpond water) is quite restrictive as it
represents a high factor of safety of three orders of
magnitude.
† Grossly unhygienic fish handling and cleaning practices
at the local retail markets caused significant recontamination
(102 2 105 presumptive ThC g21) of the fish
grown in both wastewater-fed and nominally nonwastewater-
fed ponds.
† The fishmongers in the local retail markets should be
informed about their unhygienic fish handling and
cleaning practices, and how these can be improved to
reduce the faecal cross-contamination of the fish they
sell.


ACKNOWLEDGEMENTS
We are grateful to the Danish International Development
Agency (Danida) which financially supported this research
through its Enhancement of Research Capacity (ENRECA)
programme through the project “Sanitary Aspects of
Drinking Water and Wastewater Reuse in Vietnam” (grant
no. 104.Dan.8.L). The study also received financial support
from the EU INCO-DEV project “Production in Aquatic
Peri-urban Systems in Southeast Asia” (PAPUSSA) (project
no:ICA4-2001-10072).
REFERENCES
Buras, N. 1990 Bacteriological guidelines for sewage-fed fish
culture. In Wastewater-fed Aquaculture. Proceedings of the
International Seminar on Wastewater Reclamation and Reuse
for Aquaculture, Calcutta, India, 6 2 9 December 1988 (ed.
P. Edwards & R. S. V. Pullin), pp. 223–226. Environmental
Sanitation Information Center, Asian Institute of Technology,
Bangkok, Thailand.
Buras, N., Duek, L. & Niv, S. 1985 Reactions of fish to microorganisms
in wastewater. Applied and Environmental
Microbiology 50, 989 2 995.
Buras, N., Duek, L., Niv, S., Hepher, B. & Sandbank, E. 1987
Microbiological aspects of fish grown in treated wastewater.
Water Research 21, 1–10.
217 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007
CEETIA 1997 Investigations into Environmental Pollution Caused
by Industrial Activities in Hanoi. (Report for the Hanoi
People’s Committee). Center for Environmental Engineering
and Technology in Urban and Industrial Areas, Hanoi
University of Civil Engineering, Hanoi, Vietnam.
Danish Standards Association 1999 Environmental Quality –
Enumeration of Enterococci – Colony Count on Solid
Medium. (Danish Standard No. DS 2401:1999). Danish
Standards Association, Charlottenlund, Denmark.
Danish Standards Association 2001 Water Quality – Detection and
Enumeration of Escherichia coli and Coliform bacteria – Part
1: Membrane Filtration Method. (Danish Standard No. DS/EN
ISO 9308-1:2001). Danish Standards Association,
Charlottenlund, Denmark.
Danish Standards Association 2002 Water Quality – Enumeration
of Culturable Micro-organisms – Colony Count by Inoculation
in a Nutrient Agar Culture Medium. (Danish Standard No.
DS/EN ISO 6222/Till.1:2002). Danish Standards Association,
Charlottenlund, Denmark.
Edwards, P. 1992 Reuse of Human Wastes in Aquaculture: A
Technical Review. Water and Sanitation Program, The World
Bank, Washington, DC.
Edwards, P., Pacharaprakiti, C., Kaewpaitoon, K., Rajput, V. S.,
Ruamthaveesub, P., Suthirawut, S., Yomjinda, M. & Chao,
C. H. 1984 Re-use of Cesspool Slurry and Cellulose
Agricultural Residues for Fish Culture. (AIT Research Report
No. 166). Asian Institute of Technology, Bangkok, Thailand.
Fattal, B., Dotan, A., Tchorsh, Y., Parpari, L. & Shuval, H. I. 1988
Penetration of E. coli and F2 bacteriophage into fish tissues.
Schriftenreihe des Vereins fu¨ r Wasser-, Boden- und
Lufthygiene 78, 27–38.
Fattal, B., Dotan, A., Parpari, L., Tchorsh, Y. & Cabelli, V. J. 1993
Microbiological purification of fish grown in fecally
contaminated commercial fish pond. Water, Science and
Technology 27(7 2 8), 303–311.
Hejkal, T. W., Gerba, C. P., Henderson, S. & Freeze, M. 1983
Bacteriological, virological and chemical evaluation of a
wastewater 2 aquaculture system. Water Research 17,
1749–1755.
Institute of Medicine 2003 Scientific Criteria to Ensure Safe Food.
National Academies Press, Washington, DC.
International Commission on Microbiological Specifications for
Foods 1986 Micro-organisms in Foods 2 –Sampling for
Microbiological Analysis: Principles and Specific
Applications, 2nd ed. Blackwell Scientific Publications,
Oxford, England.
Mai, T. P. A., Ali, M., Hoang, L. A. & To, T. T. H. 2004 Urban and
Peri-urban Agriculture in Hanoi: Opportunities and
Constraints for Safe and Sustainable Food Production.
(Technical Bulletin No. 32). AVRDC – The World Vegetable
Center, Tainan, Taiwan.
Ministry of Health 1998 Recommended Microbiological Limits for
Food. (Circular No. 91/429). Ministry of Health, Hanoi,
Vietnam.
Toan, T. Q. 2004 A Study of the Efficiency of Wastewater-fed
Fishponds as a Low-cost Wastewater Treatment System.
(internal report). National Institute of Occupational and
Environmental Health, Hanoi, Vietnam.
Tran, V. V. 2001 Sewage water aquaculture in Hanoi: current status
and further development. In Wastewater Reuse in Agriculture
in Vietnam: Water Management, Environment and Human
Health Aspects. IWMI Working Paper No. 30 (ed.
L. Raschid-Sally, W. van der Hoe & M. Ranawaka), pp.
24–25. International Water Management Institute, Colombo,
Sri Lanka.
Vo, Q. H. 2001 Wastewater reuse through aquaculture in Hanoi:
status and prospects. In Wastewater Reuse in Agriculture in
Vietnam: Water Management, Environment and Human
Health Aspects. IWMI Working Paper No. 30 (ed.
L. Raschid-Sally, W. van der Hoe & M. Ranawaka), pp.
20–23. International Water Management Institute, Colombo,
Sri Lanka.
Vo, Q. H. & Edwards, P. 2005 Wastewater reuse through urban
aquaculture in Hanoi: status and prospects. In Urban
Aquaculture (ed. B. Costa-Pierce, A. Desbonnet, P. Edwards &
D. Baker), pp. 103–117. CABI Publishing, Wallingford,
England.
WHO 1989 Health Guidelines for the Use of Wastewater in
Agriculture and Aquaculture. (Technical Report Series No.
778). World Health Organization, Geneva, Switzerland.
WHO 2005 Guidelines for the Safe Use of Wastewater, Excreta and
Greywater. Volume 3: wastewater and excreta use in
aquaculture. World Health Organization, Geneva,
Switzerland.
Zhiwen, S. 1999 Rural Aquaculture in China. (RAP Publication No.
1999/22). Regional Office for Asia and the Pacific, Food and
Agriculture Organization, Bangkok, Thailand.
Available online January 2007
218 Nguyen Thi Phong Lan et al. | Microbiological quality of wastewater-fed fish in Hanoi Journal of Water and Health | 05.2 | 2007

Flesh quality differentiation of wild and cultured Nile tilapia (Oreochromis niloticus) populations

African Journal of Biotechnology Vol. 11(17), pp. 4086-4089, 28 February, 2012
Available online at http://www.academicjournals.org/AJB
DOI: 10.5897/AJB11.3392
ISSN 1684–5315 © 2012 Academic Journals
Full Length Research Paper
Flesh quality differentiation of wild and cultured Nile
tilapia (Oreochromis niloticus) populations
Samy Yehya El-Zaeem1,4*, Mohamed Morsi M. Ahmed2,3, Mohamed El-Sayed Salama4 and
Walid N. Abd El-Kader4
1DNA Research Chair, Zoology Department, College of Sciences, P.O. Box 2455, King Saud University, Riyadh 11451,
Saudi Arabia.
2Nucleic Acids Research Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), City for
Scientific Research and Technology Applications, Alexandria, Egypt.
3Biological Sciences Department, Faculty of Sciences, P.O Box 80203, King Abdulaziz University, Jeddah 21589, Saudi
Arabia.
4Animal and Fish Production Department, Faculty of Agriculture (Saba-Bacha), Alexandria University, Alexandria, Egypt.
Accepted 23 January, 2012
Variation in chemical composition and carcass traits among different wild and cultured Nile tilapia,
Oreochromis niloticus populations were analyzed to study and compare the differences among
different wild (Manzalah lake, Nile river and Edku lake) and cultured Nile tilapia populations. Data of
body composition of different Nile tilapia (O. niloticus) populations showed that, the highest mean value
of moisture content (80.32 ± 0.39%) was shown by cultured population and differ significantly (P≤0.05)
from those of other populations studied. The highest mean value of protein content (58.14 ± 0.51%) was
shown by cultured population but did not differ significantly (P≤0.05) from that of River Nile population.
Lipids content showed lower mean (21.74 ± 0.06%) by River Nile population but did not differ
significantly (P≤0.05) from that of cultured population. The results of carcass traits show insignificant
differences (P≤0.05) in all parameters among different Nile tilapia populations studied. The evaluation of
flesh quality of different wild and cultured populations of Nile tilapia studied can result in a genotype
suitable for aquaculture.
Key words: Flesh quality, wild, cultured, Nile tilapia, population.
INTRODUCTION
Tilapias are very important in world fisheries, and are the
second most important group of food fishes in the world.
Nile tilapia, Oreochromis niloticus accounted for a harvest
of nearly 2.54 million tones in 2009 (FAO, 2011), second
only to carp as a warm water food fish and exceeding the
harvest of Atlantic salmon, Salmo salar, although, the
value of the Atlantic salmon catch is more than twice that
of the tilapia catch (Maclean et al., 2002). Although,
native to Africa, tilapias are cultured in Asia and the Far
East, and occupy two rather separate market niches,
*Corresponding author. E-mail: selzaeem@yahoo.com,
selzaeem@ksu.edu.sa or samy.elzaeem@alexagrsaba.
edu.eg. Tel: +20103552398 or +966592299396.
being a poor man’s food fish in countries such as Israel
and the Southern United States (Maclean et al., 2002).
Flesh quality has gained importance among consumers
and in the aquaculture industry because it is directly
related to human health and nutrition. Flesh quality comprises
several different characteristics. Due to the large
number of traits involved and the ensuing complexity,
genetic improvement for flesh quality has been almost
neglected in breeding programs for aquaculture species.
Quality traits can usually be recorded only on dead fish,
and therefore family selection must be practiced in a
breeding program (Gjedrem, 1997).
In order to meet the increase in human fish demand,
aquaculture is increasing along the necessity of supplying
fish products of high quality and also diversified product
(Queméner et al., 2002). Generally, an important success
4086 Afr. J. Biotechnol.
Table 1. Minimum and maximum weight and total length of Nile tilapia population samples collected from
Manzalah Lake, Nile river, Edku Lake and cultured.
Trait Manzalah Lake Nile river Edku Lake Cultured
Average weight 124.69±46.98 184.54±41.62 179.82± 90.11 139.86±60.20
Minimum 46.60 111.90 65.00 30.00
Maximum 208.00 225.00 295.00 209.40
Average total length 18.92±2.02 21.30±1.79 20.43±3.14 19.26±3.31
Minimum 13.30 18.40 15.10 12.30
Maximum 21.70 25.00 24.50 23.20
factor is that consumers accept farmed fish to be
equivalent or superior to the wild fish (Olsson et al.,
2003). Quality terms and how they are perceived differ for
the fish farmer, processing industry and consumer. While
growth and feed conversion are of great importance to
the aquaculturist, these parameters are unlikely to be of
indirect interest to the latter. However, producing fish that
are positively received by processors and consumers
alike is naturally of major concern to the fish farming
industry (Rasmussen, 2001). The quality of farmed fish
has occasionally been reported as being lower than that
of wild fish (Sylvia et al., 1995). Although, contradictory
result have also been obtained (Jahncke et al., 1988).
Hernandez et al. (2001) reported that wild fish
acceptability is greater than that of farmed fish. The term
fish quality is all encompassing and its study is difficult
owing to the fact that specific parameters that are
recognized as being vital in one part of the world are
judged to be less important elsewhere. Salmonid
aquaculture has focused for many years on enhancing
the quantity of fish produced. However, optimization of
the quality of salmonids may lead to improvement of
consumer acceptance and higher price for the farmed
product (Rasmussen, 2001). In these connections, Sahu
et al. (2000) reported that among the commercial characteristics
of fish, flesh quality is becoming more important
to the aquaculture industry. The consumer dictates the
flesh quality and it is a very complex characteristic. An
attempt has to be made to define and analyze flesh
quality and its relation to carcass characteristics. Carcass
quality traits must be defined precisely and should be
able to be measured with a high repeatability. Some of
the quality traits vary within the carcass. Therefore, a
very precise carcass evaluation is necessary to arrive at
any useful conclusion. To have an efficient program for
improving growth and flesh quality traits of fish, it is
necessary to test 10 to 15 fishes from each family for
carcass evaluation each year and to compile a database.
The genetic gain will increase when more families are
tested in each generation.
The evaluation of flesh quality of different populations
can result in a genotype suitable for aquaculture. Therefore,
the present work aimed to evaluate and compare
the flesh quality (chemical composition and carcass
traits) of wild and cultured Nile tilapia, O. niloticus
populations collected from Manzalah lake, Nile river,
Edku lake and cultured.
MATERIALS AND METHODS
The present study was carried out at Animal and Fish Production
Department, Faculty of Agriculture (Saba-Bacha), Alexandria
University, Alexandria, Egypt.
Specimen collection
Fifty mature individuals (both sex) of each of wild and cultured Nile
tilapia, (O. niloticus) populations were randomly collected from
Manzalah Lake, Nile river, Edku Lake and cultured, by professional
fishermen (Table 1).
Chemical composition
Three samples from each population with equal number of fish
were chosen randomly for body chemical analysis. Fish body
moisture, crude protein and crude fat contents were determined
according to A.O.A.C. (1984) methods.
Flesh quality
Dressings were conducted on the same samples of fish collected
from different geographical areas. The following body traits were
recorded individually on each fish within each population:
Inedible parts traits
The following parameters were estimated as percentage values of
whole body weight (BW):
Head weight (%) = head weight / total body weight × 100.
Viscera (%) = weight of viscera / total body weight × 100.
Fins weight (%) = fins weight / total body weight × 100.
Scales weight (%) = scales weight / total body weight × 100.
Backbone weight (%) = backbone weight / total body weight × 100.
Inedible parts weight (%) = inedible parts weight/total body weight × 100.
El-Zaeem et al. 4087
Table 2. Chemical composition of different Nile tilapia (O. niloticus) populations.
Population Moisture
On dry matter basis (%)
Protein Lipid
Manzalah 74.28±0.07b 54.82±0.9d4b 23.32±0.32a
Nile 72.94±0.76b 55.88±1.56ab 21.74±0.06b
Edku 70.80±0.57c 53.59±0.28 b 23.52±0.40a
Cultured 80.32±0.39a 58.14±0.51a 21.95±0.64b
Means within each comparison in the same column with the different superscripts differ
significantly (P ≤ 0.05).
Edible parts traits
Meat yield (%) = Skin with fillet weight / total body weight ×100
(Huang et al., 1994).
Dress-out (D%) = (body weight – head – scales – viscera – gonads
– fins) / body weight x 100.
Headed–gutted body weight (HGBW%) = (gutted body weight –
head) / total body weight (g) × 100.
Head-on dress-out (HD dress%) = (body weight – scales – viscera
– gonad - fins) / body weight × 100.
Gutted body weight (GBW%) = (body weight – viscera - gonads) /
body weight × 100 (Rye and Refstie, 1995).
Statistical analysis
Data were statistically analyzed using the following model (CoStat,
1986):
Yij= μ + Ti+ eij
Where, Yij is observation of the ijth parameter measured; μ, overall
mean; Ti, effect of ith population; eij, random error.
Significant differences (P≤0.05) among means were tested by the
method of Duncan (1955).
RESULTS AND DISCUSSION
The results of chemical composition of different Nile
tilapia, O. niloticus populations on dry matter basis are
presented in Table 2. The highest mean value of
moisture content (80.32 ± 0.39%) was shown by cultured
population and differ significantly (P≤0.05) from those of
the other populations studied. Moreover, the highest
mean value of protein (58.14±0.51%) was achieved by
cultured population, but did not differ significantly
(P≤0.05) from that of Nile River population. Lipids content
showed higher mean (23.52 ± 0.40%) by Edku Lake
population, but did not differ significantly (P≤0.05) from
that of Manzalah Lake population. In these connections,
Abdel-Aziz (2006) found that Nile tilapia (O. niloticus)
from River Nile contains about 80.08% moisture. The
same results were obtained by Abo-Raya (1975) and El-
Akel (1983). Galhom (2002) reported that, moisture
content of fish from Egyptian waters ranged between
70.00 and 79.00%. On the other hand, Abd-Alla (1994)
found a range between 80.50 and 84.00% for moisture
content of fish muscles from various fish cultures. There
is a general trend towards increasing the percentage of
moisture in cultured as compared to wild fish. The results
of the present work are consistent with the ranges
reported by several other investigators that worked on
tilapia O. niloticus obtained from various water sources
and different fishing seasons (Saleh, 1986; Salama,
1990; El-Ebzary and El-Dashlouty, 1992; Keshk, 2004).
Distribution of fat in the carcass is an important economic
trait. It is very difficult to ascertain the optimum level of fat
in a carcass. Generally, it is felt that fat percentage of 16
to 18% in a fillet is too high. Excessive fat deposits
reduce the quality of the fish. Increase in fat depots
increases waste in processing. Dissection in and around
the intestine is a standard method for checking the fat
deposit of a fish. There are several other methods
available to measure fat content in a fish carcass (Wold
and Isaksson, 1997; Sahu et al., 2000). Moreover, Sahu
et al. (2000) reported that protein content and composition
are stable during development. The wide
variability in the characteristics of muscle and connective
tissues in commercial fish is related to their mode of
development. Chemical composition differences among
Nile tilapia, O. niloticus populations may be due to some
environmental factors. In these connections, Svàsand et
al. (1998), Favalora et al. (2002) and Flos et al. (2002),
reported that the quality of fish is affected by parameters
such as feed type, level of dietary intake and growth.
Feed composition has a major influence on the proximate
composition of salmonids. In particular, whole body lipids
as well as the lipid content in the edible fillet are directly
related to dietary fat content, while the fatty acid
composition of the fish flesh is also strongly influenced by
the dietary fatty acid profile. Fish body composition
appears to be largely influenced by feed composition. An
increase in other parameters such as feeding rate and
fish size also result in enhanced adipose deposition and
decrease water content in the fish body. The protein
content, however, remains more or less stable. An
increase in body fat content is generally accompanied by
reduction in slaughter yield, owning to an increase in the
weight of viscera in relation to body weight. The levels of
4088 Afr. J. Biotechnol.
Table 3. Carcass traits (% of body weight) of different Nile tilapia (O. niloticus) populations.
Trait
Population
Manzalah Nile Edku Cultured
Head 23.05±1.62 22.05±1.87 25.01±2.73 23.49±2.21
Viscera 12.48±1.42 12.78±1.58 9.78±2.95 12.25±1.40
Fins 2.73±0.17 2.68±0.17 2.58±0.50 2.95±0.73
Scales 3.65±0.51 3.78±0.45 3.90±0.54 3.80±0.54
Back bone 8.73±0.51 9.05±4.12 9.15±0.47 8.65±0.37
Inedible parts 50.58±2.00 49.70±2.36 50.43±3.35 51.69±2.20
Meat yield 47.27±2.11 47.25±3.41 46.30±2.97 46.33±1.40
Dress out 58.15±2.12 56.08±2.70 55.93±5.60 55.30±3.98
HGBW 63.38±2.97 64.30±2.94 64.30±3.37 63.35±2.66
HD Dress 80.08±1.20 80.38±1.09 82.83±3.90 80.06±0.99
GBW 86.43±1.73 86.75±1.54 90.28±4.36 86.80±1.75
Dress-out (D %) = (body weight – head – scales – viscera – gonads – fins) / body weight × 100; headed – gutted
body weight: (HGBW %) = (gutted body weight– head)/ body weight × 100; head-on dress-out: (HD dress %) =
(body weight with skin-scales-viscera-gonad-fins)/body weight × 100; gutted body weight: (GBW %) = (body
weight–viscera–gonads) / body weight × 100.
proximate constituents in the whole body as well as the
fillet are readily manipulated by feed composition and
feeding strategies, whereas the sensory parameters are
less affected by these variables. Different rearing
systems generate products having variable quality level
which differ from wild fish in color.
Carcass traits of different Nile tilapia, O. niloticus
populations are presented in Table 3. The results show
that insignificant differences (P≤0.05) were detected in all
carcass traits studied among different Nile tilapia
populations tested. Head weight as percentage of body
weight ranged from 22.05 ± 1.87 to 25.01 ± 2.73. Viscera
percentage ranged from 9.78 ± 2.95 to 12.78 ± 1.58. Fins
percentage varied between 2.58 ± 0.50 and 2.95±0.73.
Scales percentage ranged from 3.65 ± 0.51 to 3.90 ±
0.54. Back bone percentage ranged from 8.65 ± 0.37 to
9.15 ± 0.47. Meat yield percentage ranged from 46.30 ±
2.97 to 47.27 ± 2.11. Dress out percentage varied
between 55.30 ± 3.98 and 58.15±2.12. HGBW
percentage ranged from 63.35 ± 2.66 to 64.30 ± 3.37. HD
dress percentage ranged from 80.06 ± 0.99 to 82.83 ±
3.90. GBW percentage varied between 86.43 ± 1.73 and
90.28 ± 4.36. Non-edible parts percentage varied
between 49.70 ± 2.36 to 51.69±2.20. The results of
carcass traits of the present work are consistent with the
ranges reported by several other investigators who
worked on tilapia O. niloticus obtained from various water
sources and different fishing seasons (El-Sagheer, 2001;
Khalifa, 2003; Keshk, 2004; Johnston et al., 2006; Abdel-
Aziz, 2006). The evaluation of flesh quality of different
wild and cultured populations of Nile tilapia studied can
result in a genotype suitable for aquaculture.
ACKNOWLEDGMENT
This Project was supported by King Saud University,
Deanship of Scientific Research, College of Science
Research Center.
REFERENCES
Abd-Alla SOA (1994). Technological and chemical studies on some fish
cultures. Ph.D. Thesis, Fac. Agric., Zagazig, Egypt.
Abdel-Aziz MEE (2006). Effects some cryoprotectant agents on
physicochemical properties of frozen stored Bolti (Tilapia nilotica) fish
fillets. M.Sc. Thesis, Faculty of Agriculture Cairo University, Cairo,
Egypt.
Abo-Raya SH (1975). Chemical studies on fish preservation in Egypt
with special Reference to its Nutritive value. M.Sc. Thesis, Fac.
Agric., Cairo Univ., Egypt.
AOAC (Association of Official Analytical Chemists) (1984). Official
methods of analysis. 14th ed. Association of Official analytical
Chemists, Arlington, Virginia.
CoStat (1986). CoStat 3.03, Copyright, Co Hort Software. P. O. Box
1149, Berkeley, CA 94701, USA.
Duncan DB (1955). Multiple range and multiple F test. Biometrics, 11: 1-
42.
El-Akel AT (1983). The effect of precessing storage on fish quality.
M.Sc. Thesis, Fac. of Agri., Cairo Univ., A.R.E.
El-Ebzary MM, El-Dashlouty AA (1992). Influence of size on the storage
stability of Bolti Fish. Res. Bull. Home Econ. Menoufia Univ., 2: 97-
109.
El-Sagheer FH (2001). Effect of stocking densities, protein levels and
feeding frequencies on growth and production of tilapia monosex in
earthen ponds. Ph.D. Thesis, Fac. of Agric., Alex. Univ.
FAO (2011). The State of World Fisheries and Aquaculture, Food and
Agriculture Organization, Rome, Italy.
Favalora E, Lopiano L, Mazzola A (2002). Rearing of sharpsnout
seabream (Diplodus puntazzo) in Mediterranean fish farm:
monoculture versus polyculture. Aquat. Res. 33: 137-140.
Flos R, Reig L, Oca J, Ginovart M (2002). Influence of marketing and
different land-based systems on gilthead sea bream (Sparus aurata)
quality. Aquact. Int. 10: 189-206.
Galhom GFAM (2002). Chemical and technological studies on some
dried fish products. M. Sc. Thesis. Fac. Agric., Cairo Univ., Cairo,
Egypt.
Gjedrem T (1997). Fish quality improvement in fish through breeding.
Aquaculture Int. 5: 197-206.
Hernandez MD, Martinez FJ, Garcia-Garcia B (2001). Sensory
evaluation of farmed sharpsnout seabream (Dilpdis putazzo).
Aquaculture Int. 9: 519-529.
Huang YW, Lovell RT, Dunham RA (1994). Carcass characteristics of
channel and hybrid catfish and quality changes during refrigerated
storage. J. Food Sci. 59: 64-66.
Jahncke M, Hale MB, Gooch JA, Hopkins JS (1988). Comparison of
pond-raised and wild red drum Sciaenops ocellatus with respect to
proximate composition, fatty acid profile, and sensory evolutions. J.
Food Sci. 58: 286-287.
Johnston IA, Li X, Viera VLA, Nickell D, Dingwall A, Alderson R,
Campbell P, Bickerdike R (2006). Muscle and flesh quality traits in
wild and farmed Atlantic salmon (Salmo salar). Aquaculture, 256:
323-336.
Keshk SAK (2004). Chemical and technological studies on fish. Ph.D.
Thesis. Fac. Agric. Kafr El-Shiekh, Tanta Univ.
Khalifa HM (2003). Statical studies on body traits. M.Sc. Thesis. Fac.
Agric. Cairo Univ.
Maclean N, Rahman MA, Sohm F, Hwang G, Iyengar A, Ayad H, Smith
A, Farahmand H (2002). Transgenic tilapia and the tilapia genome.
Gene, 295: 265-277.
Olsson GB, Olsen RL, Carlehög M, Ofestad R (2003). Seasonal
variations in chemical and sensory characteristics of farmed and wild
Atlantic halibut (Hippoglossus hippoglossus). Aquaculture, 217: 191-
205.
Queméner L, Suquet M, Mero D, Gaignon JL (2002). Selection method
of new candidates for finfish aquaculture: the case of the French
Atlantic, the channel and the North Sea coasts. Aquat. Living Resour,
15: 293-302.
Rasmussen RS (2001). Quality of farmed salmonids with emphasis on
proximate composition, yield and sensory characteristics. Aquat. Res.
32: 767-786.
El-Zaeem et al. 4089
Rye M, Refstie T (1995). Phenotypic and genetic parameters of body
size traits and flesh color Atlantic salmon, Salmo salar L, Aquaculture
Res. 26: 875-885.
Sahu BB, Meher PK, Mohanty S, Reddy PVGK, Ayyappan S (2000).
Evaluation of the Carcass and Commercial Characteristics of Carps.
Naga, The ICLARM Quarterly, 23(2): 10-14.
Salama A (1990). Technological studies on fish. Ph.D. Thesis. Fac.
Agric. Tanta Univ., Kafer El-Sheikh, Egypt.
Saleh SM (1986). Chemical composition and technology studies on fish.
M.Sc. Thesis, Fac. Agric., Tanta Univ., Tanta, Egypt.
Svāsand T, Skilbrei OT, Van der Meeren GI, Holm M (1998). Review of
morphological and behavioural differences between reared and wild
individuals. Fisheries Manage. Ecol. 5: 473-490.
Sylvia G, Morrissey MT, Graham T, Garica S (1995). Organoleptc
qualities of farmed and wild salmon. J. Aquat. Food Prod. Technol. 4:
51-64.
Wold JP, Isaksson T (1997). Non-destructive determination of fat and
moisture in whole Atlantic salmon by near-infrared diffuse
spectroscopy. J. Food Sci. 62 (4): 734-736.

FISH PROCESSING

V-Animal products-D-Fish Processing-1
FISH PROCESSING
Since 1978, New Zealand has had exclusive fishing rights to all its surrounding waters
up to 320 km away from the land. This has resulted in fish becoming an important
resource, and much research has been done to understand the processes involved in fish
ageing, and ways to prevent these processes.
After a fish dies, the flesh quickly becomes rigid, in a process known as rigor mortis.
This rigidity then dissolves, and the fish flesh decomposes.
Rigor mortis
When muscles contract, they absorb calcium ions. After a fish has died, calcium ions
leak into the muscles, causing them to contract. However, ATP, the biochemical
energy carrier that provides energy to relax the muscle again, is no longer present, so
the muscles remain rigid. This locking of the muscles, called rigor mortis, can be
slowed down by chilling the fish immediately after death.
Dissolution of rigor
Over time this rigidity disappears, but by then the fish has significantly deteriorated.
Autolysis
The decomposition of the fish occurs as its constituent compounds break down (called
autolysis). The proteins, nucleotides and sugars break down, bases are released, the pH
falls and the fats are oxidised. These make the fish smelly, rancid and tough.
Tests for freshness
By measuring the pH of the fish and the levels of various compounds present the
amount of autolysis that has occured, and hence the freshness of the fish, can be
measured.
INTRODUCTION
Since the 320 km Exclusive Economic Zone was established in 1978, giving New Zealand
one of the largest fishing zones in the world, the significance of fish as a resource has risen
greatly. Many areas of research, such as the best processing methods, the quality and
composition of the fish landed, and the effects of handling, storage and packaging on fish
quality, have become of great importance.
The Seafood Research Unit, Crop & Food Research was established in 1979 in response to
the industry's need for research. Laboratories are located in Auckland and Nelson. Major
areas of interest include:
Catching and handling. The understanding and control of the physiological changes
occuring during the handling of fish and their effect on quality.
Chemistry and biochemistry. Detection of spoilage indicators and toxic components and
quality evaluation of seafood to establish management guidelines for quality systems.
V-Animal products-D-Fish Processing-2
Microbiology. Improvement of product safety and quality, and assistance with hygiene and
sanitation.
Seafood toxins. Depuration of algae from shellfish bioassays.
Fish proteins. Changes in the structure and biochemistry of proteins and hence the texture of
fish muscle during frozen storage.
Sensory evaluation. Determination of shelf-life changes and consumer evaluation of seafood.
In this article we shall discuss the major biochemical and microbiological changes occurring
post mortem, their effects on the quality of the fish, plus the handling, storage and processing
procedures by which these can be reduced and the quality of the fish maintained.
CHANGES IN FISH FLESH BIOCHEMISTRY POST MORTEM
The demise of a fish begins a series of irreversible changes which lead to spoilage and loss of
quality.
The natural process:
Rigor mortis → Desolution of rigor → Autolysis
can be slowed down if correct handling and storage procedures are followed.
Step 1 - Rigor mortis
Muscle consists of several proteins actively involved in contraction (Figure 1). The two
major proteins, actin and myosin, combine in the presence of calcium ions to form
actomyosin. ATP then supplies the energy for contraction, and later also the energy for the
removal of the calcium ions via a calcium pump. This breaks the actomyosin complex,
leaving the muscle ready for a further contraction.
Relaxed muscle
Ca2+
ATP Actomyosin
complex
Contraction
ATP
-ATP
Rigor
Figure 1 - Muscle contraction reactions
On death, the circulatory system stops and the ATP levels drop. Calcium ions leak, forming
actomyosin. However, there is insufficient ATP for the calcium pump to operate, and so the
actomyosin complex remains unbroken. The muscle is now in a continual state of rigidness,
known as rigor mortis.
V-Animal products-D-Fish Processing-3
Step 2 - Autolysis
Enzymes in the flesh and gut previously involved in metabolism now catalyse autolytic
reactions, in which various compounds decompose. Enzymes in the flesh break down
desirable compounds into tasteless or bitter ones, whilst gut enzymes attack the internal
organs, turning them into a soupy mess and allowing bacteria to enter the flesh.
Bacterial attack
In a living fish, bacteria are present in the gut and skin, but the flesh, which they are
prevented from entering, remains sterile. Once autolysis begins, however, the bacteria are
able to enter the flesh, whereupon they multiply rapidly and decompose the muscle.
Anaerobic bacteria (those which operate in the absence of oxygen) produce a particularly
foul type of spoilage which results in an inedible fish.
A number of chemical changes take place during autolysis, and these are outlined below.
Protein Denaturation
Denaturation of protein involves the destruction of its secondary, tertiary and quaternary
structure, reducing the protein to a simple polypeptide chain. A number of factors, including
slow freezing and variability of storage conditions, cause this denaturation. A denatured
protein has not only lost its ability to function as an enzyme, but also its "water-holding"
ability. This results in denatured fish flesh dripping excessively when thawed (a situation
known as "drip-thaw"), and appearing white, dull and spongy, and upon chewing becoming
fibrous and tasteless.
Decreasing flesh pH
A living fish has a flesh pH of 7.0. However, after death residual glycogen is broken down
via glycolosis to pyruvic acid and then lactic acid. As this happens, the flesh becomes more
acidic. If the pH remains above 6.6, the texture is reasonably soft, but below this level the
flesh becomes firm and eventually unacceptably tough.
TVB-Total Volatile Base
TVB is a measure of the total amount of a variety of nitrogen-containing substances which
are produced during storage. An example of a volatile base present in the flesh is a
trimethylamine (TMA), which is formed from the reduction of trimethylamine oxide. Marine
fish contain a small amount of trimethylamine oxide, the function of which is unknown. This
odourless and tasteless compound is reduced by invading bacteria to TMA, which is
characterised by its "fishy" smell. TMA, though, only becomes useful as a quality index
during the middle and late stages of spoilage after the bacteria have invaded the fish.
Trimethylamine oxide is converted in the muscle tissue into dimethylamine (DMA) and
formaldehyde by enzyme action during frozen storage. This formaldehyde is able to crosslink
with protein, denaturing the muscle structure. This fish loses water when it is thawed,
and when cooked has a tough and fibrous texture.
Nucleotide Breakdown
This involves the enzymatic breakdown of the energy carrier ATP, as outlined below:
V-Animal products-D-Fish Processing-4
O
N
N
N
N
OH OH
H H
H H
OCH2
NH2
P
O
OH
P O
O
OH
P O
O
OH
HO
+
O
N
N
N
N
OH OH
H H
H H
OCH2
NH2
P
O
OH
O
H
H O
N
N
N
N
OH OH
H H
H H
P OCH2
O
OH
O
O
HN
N
N
O HN
+
OH
O
OH OH
H H
H H
OCH2
HN +
N
N
O HN
H
+
ATP-ase
myokinase
AMP-deaminase
5' nucleotidase
nucleoside hydrolase
nucleoside phophorylase
ATP
ADP
AMP
Inosine IMP
Hypoxanthine Ribose
Hypoxanthine Ribose-1-phosphate
O
N
N
N
N
OH OH
H H
H H
OCH2
NH2
P
O
OH
P O
O
OH
H O
P
O
OH
HO OP
O
OH
HO OP
O
OH
HO OO
N
N
N
N
OH OH
H H
H H
OCH2
O
H
OH
O
OH OH
H H
H H
P OCH2
O
OH
HO
V-Animal products-D-Fish Processing-5
Thus as spoilage proceeds the amount of ATP present decreases, causing rigor mortis.
Liquid Oxidation and Hydrolysis
The two major deteriorative changes which occur in fish are:
(i) the enzymatic hydrolysis of lipids (fats) to produce free fatty acids and glycerol:
CH2 OH
CH OH
CH2 OH
CH2 O
CH O
CH2 O
O
C R
O
C R
O
C R R C
O
OH
+ 3
Fat Glycerol Fatty acid
(ii) the oxidation of fish oils yielding the rancid odours and tastes which are the major
problem encountered in fish storage.
TESTS FOR FRESHNESS
Several of the changes described above can be chemically monitored to determine the
freshness of the fish, and these are used in conjunction with taste testing.
Protein denaturation
During cold storage the proteins undergo molecular cross-linking with formaldehyde (see
above), causing the muscle protein to become less soluble. Deterioration can be assessed by
adding 5% NaCl (common salt) and then separating and measuring the soluble and insoluble
proteins present. Increasing insoluble protein indicates longer storage and greater
deterioration, mainly of texture.
Nucleotide breakdown
The concentrations of ATP, ADP, AMP, IMP, inosine and hypoxanthine (i.e. the different
compounds formed over time as ATP breaks down - see above) can be measured by high
performance liquid chromatography. The ratio of inosine and hypoxanthine to the total
amount of the above substances is represented as a percentage value, K. A K value of less
than 20% represents fresh fish, whilst anything greater is indicative of spoilage.
Decreasing pH
pH is a possible test of textural strength, with anything below 6.6 resulting in noticeably
firmer flesh than that of fresh fish.
TVB - Total Volatile Base
The amount of TVB is measured by distilling a fish extract, and determining the base
concentration by titration against acid. A fresh sample of Jack Mackerel would have a value
of 19-21mg TVB N/100g, whilst an ageing sample would be nearer 30 mg TVB N/100g.
V-Animal products-D-Fish Processing-6
The amount of DMA can be measured by spectrophotometry, giving an indication of the
storage time.
Lipid oxidation and hydrolysis
Oxidation leads to rancidity, the degree of which is commonly evaluated by measuring the
free fatty acid and peroxide concentrations. Hydroperoxides can be measured by mixing the
fish oil with potassium iodide, and measuring the amount of iodine liberated by titration
against thiosulphate. The hydroperoxides oxidise the iodide to iodine, which is liberated
according to the following equation:
2I- → I2 + 2e-
A further measure of oxidation is the TBA test. This involves extracting some fish muscle
into trichloroacetic acid and treating it with with thiobarbituric acid (TBA). The TBA reacts
with malonaldehyde, a substance formed during oxidation, to form a red compound. The
intensity of the red colour, which is proportional to the concentration of the malonaldehyde,
can be measured using a spectrophotometer.
C CH2
C
H
O
H
O
malonaldehyde
Written for volume two by Linda Boyd and John Ryder; revised by Ron Wong (Crop and
Food Research) and edited by Heather Wansbrough.

Moringa Oleifera: The Miracle Tree

Moringa Oleifera: The Miracle Tree

moringa alifera ppt

http://www.authorstream.com/Presentation/Octavio-31043-Moringa-AKA-Location-Growing-Conditions-Currently-Cultivated-13-Species-oleifera-Effective-as-Entertainment-ppt-powerpoint/

Oceans of the World - 5 Oceans, World Oceans - Worldatlas.com

In 1947, possessing a unique geographical location, Pakistan consisted two distant parts; the West Pakistan, in the Indus River basin and the East Pakistan (later on became Bangladesh in December 1971) located more than 1000 miles (1600 kilometers) away in the Ganges River delta. Separated from each other, these two wings had 1000km wide Indian territory between them. On the West, Pakistan borders with Afghanistan, whose one kilometer narrow Wahkhan strip kept the defunct Soviet Union away from Pakistani frontiers. To the North, she has the Peoples Republic of China. The oil rich heart of the Persian Gulf region-Iran, is in the northwest of Pakistan. In the South, the Arabian Sea, the northwestern extension of the strategically important Indian Ocean washes Pakistan's coastal shores. The vitality of Indian Ocean has remained unquestionable throughout the known history as it provides not only a commercial and trade link between Europe and the Far East but has also remained a key to the seven seas. The East Pakistan was separating the Pacific Ocean from the Indian Ocean and bordered Burma on the East (Mohammed Ahsen Chaudhri, 1993). Thus, looking from the strategic point of view, Pakistan was and is still at the crossroad of Central, South and Southwest Asia and is the easiest link between the oil-rich Persian Gulf and the East Asia. In short, Pakistan is situated in the region called 'fulcr..

Geo Strategic Importance of Pakistan


Geo strategic means the importance of a country or a region as by virtue of its geographical location. Geo political is defined as, stressing the influence of geographic factors on the state power, international conduct and advantages it derives from its location. Stephen Cohn describes this importance "While history has been unkind to Pakistan, its geography has been its greatest benefit. It has resource rich area in the north-west, people rich in the north-east." Pakistan is a junction of South Asia, West Asia and Central Asia, a way from resource efficient countries to resource deficient countries. The world is facing energy crisis and terrorism. Pakistan is a route for transportation, and a front line state against terrorism.

Geographical Importance:

Bridge between South Asia and South West Asia; Iran and Afghanistan are energy abundant while India and China are lacking of. China finds way to Indian ocean and Arabian Sea through Korakaram. China with its fastest economic growth rate of 9%; is developing its southern provinces because its own port is 4500 km away from Sinkiang but Gawader is 2500 km away. Pakistan offers to CARs the shortest route of 2600 km as compared to Iran (4500 km) or Turkey (5000 km). land locked Afganistan now at the phase of Reconstruction, finds its ways through Pakistan. Gawader port with its deep waters attracts the trade ships of China, CARs and South East Asian Countries.

ASEAN Economic Blocs: SAARC, ECO. Iran is struggling to export its surplus gas and oil to eastern countries. Qatar Pakistan and Turkmenistan Pipeline projects highlights the position. Pakistan would get 400 million dollar annually if IPI gets success. Mountain Ranges: Himalayas, Hindu Kush in the North are plentiful in providing water and natural resources.

Political importance: US interests in the regions to contain the Growing China, nuclear Iran, terrorist Afghanistan, and to benefit from the market of India. Security and Business are two main US interests in the region while Pakistan is playing a front line role against terrorism. Today the political scenario of the region is tinged with pre emption policy and US invasion of Iraq and Afghanistan, Iran's nuclear program, India's geopolitical muscles(new strategic deal with US) to gain the hegemony and to counter the 'The Rise of China' which has earned all the qualities to change unipolar world into Bipolar world. In all these issues, Pakistan is directly or indirectly involved, especially after Al Qaeda operations. The American think tanks have repeatedly accepted that war against terror could never be won without the help of Pakistan. Pakistan has rigorously fought, and ongoing military operation in Wazirstan is also targeting the suspected Taliban in the bordering area.

Main threats to Pakistan: Balochistan and Wazirstan conflicts are posing threats to any economic project like IPI gas pipeline. Negative role of India, US, Iran in this conflict ridden area. Kashmir is flash point, accelerating nuclear race in the South Asia. Instable governments in Pakistan have contributed in weakening the strong position.




Prof. Dr. Zahid Ali Mangi
Head of Pakistan Studies Deptt.
D J Sindh Government Science College Karachi Sindh Pakistan
Contact No 03337102435

Oceans of the World - 5 Oceans, World Oceans - Worldatlas.com

Oceans of the World - 5 Oceans, World Oceans - Worldatlas.com

WORLD OCEAN DAY – Celebrate June 8

WORLD OCEAN DAY – Celebrate June 8

WORLD OCEAN DAY – Celebrate June 8

WORLD OCEAN DAY – Celebrate June 8

Trout farming — a lucrative business :: Pakistan Agricultural News Chennal-:PAKISSAN.com:-

Trout farming — a lucrative business :: Pakistan Agricultural News Chennal-:PAKISSAN.com:-

Trout farming — a lucrative business :: Pakistan Agricultural News Chennal-:PAKISSAN.com:-

Trout farming — a lucrative business :: Pakistan Agricultural News Chennal-:PAKISSAN.com:-

beautiful fishes of world

Even Fish have to suffer to look Beautiful and Pretty

Is it not sufficient that our women (our men are not far behind) are all botox-ed, puffed and filled up with all sorts of artificial chemicals to satisfy the insane current norms of beauty, that it’s now time for our ornamental fish (yes you heard right our poor little fishies), to read beauty magazines and get depressed because they don’t look attractive enough!?

If you have ever wandered into an aquarium store in Beirut or its suburbs, then surely you must have come across a weird geisha looking fish with red lipstick and floral patterns on the rest of its body. Basically, it only needs an improvised kimono and it’s ready to start work at a nearby massage house! It’s no wonder they call it the Lipstick Parrot Cichlid. This freak of nature is in reality not at all that, but rather a man-made hybrid, which appears to be a cross between a South American cichlid, likely the severum (Heros severus) and a Central American cichlid, likely the midas cichlid (Amphilophus citrinellus) or the red devil (Amphilophus labiatus).

It is then artificially coloured to appeal to consumers. The procedure is horrifyingly inhumane and involves injecting repeatedly the fish with colour via hypodermic syringe to achieve the desired patterns tattooed onto the body. The fish is also dipped in a caustic solution to strip its outer slime coat, then dipped in dye, then dipped in more chemicals to restore the protective coat. Women reading this will make the immediate analogy with hair bleaching steps.

This method is reported to have a very high mortality rate. The ones that do survive are actually the unlucky ones, since they lead a painful life, hammered with all sorts of tumours, infections and with an overall shortened life expectancy. Wait there is more! The worst part is that the colouring of the fish is not even permanent, and usually fades away in six to nine months!!! These fish come in all sorts of colours: Blue, green, red, purple, etc...This is why they are also called jellybean cichlids! Many other species, including the Indian Glass Fish, Black Tetra, Oscar, Corydoras, Suckermouth catfish, and goldfish all receive the same honour.

 So please if you were thinking of getting a blood parrot cichlid (or any other dyed type), but haven't yet, we strongly urge you to consider getting another fish. Maybe then retailers will think twice before selling dyed fish and indirectly encouraging these cruel practises, just to make a few easy bucks (or liras).
by Fanoos encyclopedia