Comparative Study Between Desert Cultivated and Natural Fisheries of Mullet Fish in Egypt
INTRODUCTION
Fish had long been regarded as a nutritious and highly desirable food due to their contribution of high quality animal protein, richness in calcium and phosphorus and generous supply of vitamins. Heavy metals in soil and water may enter the food chain through the biological cycle, which includes bio-concentration by plants and animals. The presence of such metals at significant concentrations in the environment is considered a potential health hazard to humans and animals.
The pollution of the aquatic environment with heavy metals has become a serious health concern during recent years. Untreated municipal and industrial wastes, are the major sources of metal pollution, especially in areas in close vicinity to industrial and agricultural activities. Industrial and agricultural discharges are considered the primary source of metal poisoning of fish (Abdelhamid et al., 2000). Many of these metals such as lead and cadmium have no nutritional importance, and their presence in relatively high concentration in body tissues can result in health problems in human as well as in animals (Goldfrank et al., 2001).
Microorganisms are present everywhere on earth, soil, water and atmosphere. Fish and shellfish harvested from water polluted with human and animal wastes can contain Salmonella, Shigella and Escherchia coli. It may be assumed that aquatic animals, including fish, are continually bathed in an aqueous suspension of microorganisms and that, consequently, external surfaces will be in frequent contact with these microbes.
Similarly, any water or food entering the digestive tract will contain microorganisms; therefore, the initial microbial flora on the caught fish is dependent upon the contamination of the water and bottom sediment from the area of catch. Representatives of family Enterobacteriaceae are usually found among the most prevalent bacteria on the fresh water fish (Austin and Austin, 1987).
Most of the microorganisms in tissue are thought to result from surface, gills, or intestinal contamination (Austin, 1982). Microorganisms, adsorbed on the surfaces of the fish and that found in their intestinal contents, do not affect the fish during life, but after death saprophytic and commensally residents invade the flesh and bring about its decomposition (Ayres et al., 1980), as well as it can induce disease of humans consuming such flesh.
The objective of the present work was to study fish body measurements, chemical analysis of water and flesh from mullet fish, determination of heavy metals (Cd, Pb and Fe) concentration in mullet flesh, water, sediments and feed stuffs of fish, in addition to bacteriological examination of the examined fish muscles, water, sediments and feed stuffs collected during summer and winter seasons from four locations in Egypt (Marsa Matroh – Alexendria – El-Bardaweel and Port Saied).
MATERIALS AND METHODS
Sampling Locations:
1) Marsa Matroh, at the coastal region of Egypt, El-Hammam canal extension 10 Km distance, from Km 60 to Km 70 west Alexandria.
2)Alexandria farm, located at the Alexandria desert road, about 12 feddan divided into ten ponds, source of water from Almahmodia canal, fish culture system is polyculture (mullets and tilapia), artificial fish diet (25% protein).
3) Port Saied farm, located at the Port Saied desert road, Kilo 21 Port Saied – Domietta road, aquaculture system is polyculture (mullet and tilapia), water sources are the Mediterranean sea and Manzala lake, artificial fish diet (25% protein), water is saline.
4) El-Bardaweel lake, located at the far north of Sinai, water salinity range from 37 to 65 part per thousand, mullet annual production 30%.
One hundred and sixty samples of Mugil cephalus fish were collected from these four locations, forty samples per location, each 20 were collected in summer season (from March 2005 to June 2005) while the others 20 were collected in winter season (from November 2005 to January 2006). The collected samples were packed in a sterile polyethylene bags, sealed and cooled in an insulated box contained crushed ice, then immediately transferred to the laboratory for examination. Each sample was divided into two parts, one for the chemical analyses and the other for the bacteriological examinations. At the laboratory, fish weight, length, depth and sex were recorded individually.
Each fish sample was wrapped separately in polyethylene bag, given an identification number and the collection site and date of collection were recorded on it. The fish were kept in ice box until the samples were prepared for analysis. Eight water samples were collected (four samples for each season) from the same locations where the fish were collected. The water samples were collected in clean 1 liter polyethylene bottles from a depth of 50 cm. Each sample was divided for the chemical and the bacteriological examinations.
For heavy metal detection, each sample was preserved by adding 3 ml of pure concentrated nitric acid (99.9%-Merck) per liter of water. Samples were kept for analysis in a refrigerator at + 4oC. Eight samples of sediments were collected from the same locations (four samples / season). A dredge was used for collecting these superficial sediment samples which were transported in polyethylene bags into the laboratory. They were kept at room temperature for analysis. Fish feed samples were collected from Port Saied and Alexandria locations one sample for each season for the chemical and the bacteriological examinations.
Heavy Metals Analysis:
The head and external skeleton of each sample (one fish) were removed. The internal muscles were transferred to a clean, dry container and then minced to obtain a fine mince representing the whole flesh. The samples of fish were prepared for heavy metals determination according to Greig et al. (1982). The same procedures were used for detection of heavy metals in feed stuffs of fish.
Water samples were prepared for heavy metals determination according to Polprasert (1982). For preparing the sediment samples, the procedure outlined by Medina et al. (1986) was performed. Perkin Elmer atomic absorption spectrophotometer (AAS) model 2380 equipped with MHS-10 hydride generation system (Desert Research Center) was used for the quantitative determination of the studied elements according to Medina et al. (1986) and Abdallah et al. (1993). The bioaccumulation factor (BAF%) was calculated as a percent of fish heavy metal level from the heavy metal level in the rearing water.
Bacteriological Techniques:
Under complete aseptic condition, 10 grams of the back muscles was aseptically transferred into a sterile homogenizer containing 90 ml of sterile 0.1% peptone water. The contents were homogenized for 2.5 minutes at 14000 r.p.m to provide a homogenate of 1/10 dilution and then allowed stand for about five minutes. The homogenate was transferred into a sterile test tube and 1 ml was transferred into a sterile test tube containing 9 ml of 0.1 peptone water from which ten-fold serial dilutions up to 106 were prepared (ICMSF, 1978). Prepared samples were examined for detection and enumeration microorganisms in fish as total bacterial count, colony forming unit (CFU)/g of sample.
The pour plate technique recommended by AOAC (1990) was applied. 12 to 15 ml of melted standard plate count agar after cooling was added to each inoculated plate. Then, thoroughly and uniformly mixed with the sample and left to solidify. After solidification, the plates were incubated in inverted position at 35oC for 48 hours. The number of colonies in selected duplicate plates of the same dilution was enumerated, and then the mesophilic count per gram of sample was calculated. Isolation of Escherichia coli using Mac- Conkey broth. Typical pink colored colonies were picked up and purified (Cruickshank et al., 1975).
Isolation of Salmonella according to Fricker (1987) and Vassiliadis (1983). Salmonella produce colonies with black center (Biolife, 1996). Isolation of Shigella using selenite – cystine broth (Twedt, 1978). Shigella appear as colorless colonies (Biolife, 1996). Microscopical examination (Staining), a film was prepared from the pure culture of isolated organisms (E. coli – Salmonella – Shigella), all were stained with Gram stain then examined microscopically to appear the gram negative rods (red rods).
Under complete aseptic conditions, 10 ml of water samples were transferred into a sterile glass bottle containing 90 ml of 10% peptone water, from which ten-fold serial dilutions up to 106 were prepared. For enumeration of mesophiles (Total bacterial count), one ml of the sample as well as of the dilutions were placed in separate Petri dishes and 15 ml of liquefied agar medium at a temperature of 43 to 45oC were added to each dish. The numbers of colonies in selected dishes and the mesophilic count per ml of sample was calculated according to APHA (1992). Isolation of Escherichia coli, Salmonella and Shigella followed the same procedures as mentioned with fish samples. 10 grams of sediment and fish feed samples were aseptically transferred into a sterile homogenizer containing 90 ml of sterile 0.1% peptone water.
The contents were homogenized for 2.5 minutes at 14000 r.p.m. to provide a homogenate of 1/10 dilution and then allowed stand for about five minutes. The homogenate was transferred into a sterile test tube and 1 ml was transferred into a sterile test tube containing 9 ml of 0.1 peptone water from which ten-fold serial dilution up to 106 were prepared (ICMSF, 1978). Prepared samples were examined for detection and enumeration of microorganisms in samples as mentioned before with fish and water samples.
Physicochemical Parameters:
Values of pH of the collected water samples were recorded using a pH meter, concentrations of total dissolved solids (TDS) were carried out using OAKLON, TDS/conductivity meter. Alkalinity, hardness, calcium ion and magnesium ion levels were determined by titrimetric methods. Dissolved oxygen was measured by the modified Winkelr’s method. All these parameters were measured as described in APHA (1992). Water temperature and salinity were determined by a portable thermometer and salinometer. Nitrate and nitrite were estimated using a spectrophotometer at wavelengths 534 and 540 nm, respectively. Finally, CO2 concentration was determined by titration against NaOH N/44.
Proximate Analysis:
Proximate analysis of feed and fish samples was carried out using the standard methods of analysis (AOAC, 2000).
Statistical Analysis:
Using S.A.S. (2001) and Duncan (1955), numerical data collected were statistically analyzed for analysis of variance and least significant difference. Chi-square, t-test and correlation were calculated too when required.
RESULTS AND DISCUSSION
Water quality criteria:
The pH values were slightly higher in winter (7.1 – 7.8) than in summer (7.1 – 7.2), regardless to the sampling locations; yet, it was higher in both seasons in Port Saied (location No. 3) than the other 3 locations. Water temperature was, naturally, higher in summer (18 – 24.5oC) than in winter (13 – 18oC), but was also higher in Port Saied either in summer or winter seasons, than in the other locations. Consequently, the dissolved oxygen (DO) concentration was higher (6.4 – 10.4 mg/l) in winter than in summer (4.2 – 6.8 mg/l), in general. Anyhow, carbon dioxide (CO2) concentrations varied from location to another and from season to another, without fixed trend. Generally, it ranged from 3.9 – 10 mg/l in winter to 5.8 – 10.1 mg/l in summer.
Toxic ammonia (NH3) levels were lower in summer (0.04 – 0.12 mg/l) than in winter (0.04 – 0.20 mg/l) without clear trend of location effect. But, the nitrite (NO2) concentrations were wider in summer (0.002 – 0.056 mg/l) than in winter (0.012 – 0.025 mg/l) without specific effect of sampling location. The same trend was recorded for the nitrate (NO3) levels, being 0.20 – 0.36 vs. 0.18 – 0.22 mg/l during summer and winter, respectively.
The alkalinity and hardness levels reflected the opposite trend, since they were lower in summer (156 – 308 and 4100 – 3100 mg/l, respectively) than in winter (400 – 800 and 3000 – 3900 mg/l, respectively) with the highest levels of both criteria for the location No. 1 (Marsa Matroh). Consequently, the concentrations of magnesium (Mg) and total dissolved solids (T.D.S.) were wider in winter (480 – 8160 and 2884 – 42218 mg/l, respectively) than in summer (624 – 6120 and 9512 – 42025 mg/l, respectively). Calcium (Ca) levels in summer (600 – 2200 mg/l) were higher than in winter (400 – 2000 mg/l). Marsa Matroh reflected the highest Ca and Mg levels in both seasons, but El-Bardaweel (4th sampling location) has the highest T.D.S. and salinity levels in both seasons.
The high salinity in location No. 4, relatively to the other three locations, is due to the nature of fish rearing water, i.e. its source. Since El-Bardaweel lake has salinity range of 37 – 65 ppt (‰), whereas the other locations water brackish. Saleh et al. (1988) found that the increase in salinity may be attributed to evaporation and/or leaching of salts from soil as water moves deep into the desert. In this respect, Abdelhamid (2003) cited that DO levels affected negatively by elevating water temperatures and salinity. He added that, pH value of the deep and surface areas in the open seas are constant (being 8.1 – 8.3 in the surface water).
He cited also that the suitable alkalinity and hardness for fish growth ranged between 50 – 200 and 50 – 300 mg/l, respectively, since the hard water contains more ions than, the soft one. However, the hardness is correlated with the pH and alkalinity. The same author said that, the toxic level of NH3 for fish is 0.6 – 2.0 mg/l. This means that all tested criteria of water quality from all sampling locations were within the normal ranges, which are suitable for normal fish growth. Also, Abdelhamid (2003) mentioned that the critical level of ammonia in water for fish is 2 – 3 mg/l.
Additionally, Abdelhakeem et al. (2002) mentioned also that NH3 level is influenced by pH and temperature of water. They added that, hardness and alkalinity of water are related to each other. They mentioned some water parameters for aquaculture as > 20 ppm alkalinity, 0.005 ppm Cd, 1.5 ppm CO2, > 5 ppm DO, < 0.1 ppm Fe, < 0.02 ppm Pb, < 1 ppm NO3, 6.7 – 8.6 pH, and > 400 ppm TDS.
Fish body measurements:
Physical characteristics of fish examined are shown in Table (1). Sampling locations and seasons affected significantly (P £ 0.05) each of the fish body measurements, but the fish sex affected significantly (P £ 0.05) only fish weight but not (P ³ 0.05) the fish length and depth. The fish of Marsa Matroh (location No. 1) reflected the heaviest, longest and deepest (P £ 0.05) fish among all sampling locations. Also, summer fish were better (P £ 0.05) than winter fish, concerning the three measured parameters. Yet, the female fish were heavier (P £ 0.05) than the male ones (Table 1). The only significant interaction was location x season for all these parameters.
Summer season is the feeding season, where the suitable temperature for fish growth. Therefore, the growth parameters were significantly higher for the summer fish than for the winter fish. Since elevating water temperature within the normal range specific for a fish species leads to improving the growth of this species (Abdelhamid, 2003). The superiority of the tested body measurements for Marsa Matroh fish (Table 1) may be related to the highest concentrations of Ca, Mg, alkalinity and hardness.
Table (1): Fish body measurements (means* + SE) as affected by location, season and sex of M. cephalus.
|
Variables |
Weight, g |
Length, cm |
Depth, cm |
|
Location (L.) | |||
|
1- Marsa Matroh |
153.9a + 1.321 |
21.2a + 0.189 |
4.4a + 0.070 |
|
2- Alexandria |
129.3c + 3.70 |
18.8c + 0.290 |
3.4c + 0.070 |
|
3- Port Saied |
141.1b + 0.55 |
19.8b + 0.238 |
4.1b + 0.060 |
|
4- El-Bardaweel lake |
151.6a + 2.28 |
20.3b + 0.495 |
4.2b + 0.087 |
|
Season (S) | |||
|
1- Summer |
153.8a + 1.296 |
20.9a + 0.264 |
4.1a + 0.071 |
|
2- Winter |
134.1b + 1.860 |
19.2b + 0.187 |
3.9b + 0.057 |
|
Sex | |||
|
1- Male |
142.8b + 2.08 |
19.9a + 0.258 |
3.9a + 0.067 |
|
2- Female |
145.0a + 1.818 |
20.2a + 0.239 |
4.1a + 0.064 |
*Means (within the same variable and column) superscripted with different letters differ significantly (P £ 0.05).
Heavy metals:
The fish diets offered in Alexandria farm contained high levels of Pb, Fe and Cd, respectively in winter (0.574, 7.551 and 0.056) than in summer (0.253, 4.939 and 0.040 ppm). The opposite was true for the diets offered in Port Saied farm, being 0.217, 5.779 and 0.072 in winter and 0.494, 8.551 and 0.117 ppm in summer for Pb, Fe and Cd, respectively.
Generally, these heavy metal’s concentration in the diets, regardless to the sampling location or season, took the descending order Fe > Pb > Cd. Also, the fish rearing water contained higher Pb levels in all tested locations in summer (0.353 – 3.164) than in winter (0.001 – 0.060 ppm), but the opposite was true for Fe, since it was lower in summer (0.376 – 0.549) than in winter (0.815 – 1.553 ppm) for all locations. Cd has different trends in both seasons and different locations, its ranges in summer and winter were 0.083-0.300 and 0.045-0.226 ppm, respectively.
However, Marsa Matroh water was the highest in Pb contents (in both seasons) among the different sampling locations. The other two elements had variable trends from location to another. In summer season, Pb was > Fe > Cd; but in winter, Fe was > Cd > Pb. However, sediments from the same sampling locations reflected higher concentrations in winter (0.049-0.284 and 5.879-500.0 ppm) than in summer (0.030-0.047 and 24.85-28.60 ppm) for Cd and Fe, respectively (except the 2nd location in Fe) but the opposite was true for Pb (0.841-2.780 and 0.064-0.739 ppm in summer and winter, respectively) in all locations. Generally, the sediment samples from the four locations contained concentrations of Fe > Pb > Cd. There was no specific trend for these elements level in the sediments as affected by the sampling locations.
Heavy metals content in the fish flesh is presented in Table (2). The highest (P £ 0.05) levels of the tested heavy metals were found in fish collected from Marsa Matroh (0.851 ppm Pb), Port Saied (2.40 ppm Fe) and El-Bardaweel (0.081 ppm Cd). This may be related to the high content of Pb in water and sediments collected from location No. 1 during both seasons. Also, Fe level of the summer diet and winter collected sediments from Port Saied was the highest. Cd level in El-Bardaweel sediment collected in summer was also the highest. The Fe concentrations range (1.3 – 2.4 ppm) of fish tested was higher than that of Pb (0.172 – 0.851 ppm) than Cd (0.016 – 0.081 ppm), regardless to the sampling locations.
The same order was previously mentioned in heavy metals of the fish diets and sediments. Pb in fish was the only significantly (P £ 0.05) affected by sampling season, being higher in summer than in winter, but not (P ³ 0.05) either of Fe or Cd. This is correlated too with the very high contents of Pb in water and sediments of all locations during summer than in winter.
However, there were no significant (P ³ 0.05) effects of fish sex on the tested heavy metals content in the fish flesh. The heavy metals content in the fish diet (high Pb content in winter) and rearing water (high Fe content in both seasons) may be responsible for the lowest (P £ 0.05) values of body measurements (Table 1) of Alexandria (location No. 2) fish. Also, the highest values of body measurements of Marsa Matroh (location No. 1) may be attributed to the lowest Fe and Cd level in summer water as well as lowest Cd level in summer sediments.
Heavy metals pollution of the Egyptian aquatic media was reviewed by Abdelhamid (2006). However, Pb content was significantly higher in feedstuffs, water and blood in winter than in summer (Abdelhamid and El-Ayouty, 1989). Lead causes hemorrhages and congestion of the gastrointestinal tract and kidneys of fish (Abdelhamid and El-Ayouty, 1991).
Moreover, iron content of the Egyptian feeds is unusually high (Abdelhamid et al., 1992). There were significant effects on water Fe due to sampling seasons and locations. There were variations in the levels of the studied elements due to sampling locations, seasons, and fish species. The elements’ concentrations in the sediments and fishes were much higher than the corresponding values in the water, particularly for iron. Lead and cadmium levels in fish muscles were concentrated more in fish, while iron was highest in sediments followed by fish tissues. Mugil cephalus samples were more frequently contaminated than Liza ramada and Sparus aurata (Abdelhamid et al., 1997).
Table (2): Heavy metals content (means* + SE) in the tested M. cephalus.
|
Variables |
Pb |
Fe |
Cd |
|
Locations |
|
|
|
|
Marsa Matroh |
0.851a + 0.119 |
1.70b + 0.225 |
0.016c + 0.006 |
|
Alexandria |
0.172c + 0.027 |
1.30b + 0.166 |
0.067ab + 0.015 |
|
Port Saied |
0.780a + 0.117 |
2.40a + 0.182 |
0.041bc + 0.008 |
|
El-Bardaweel Lake |
0.572b + 0.082 |
1.60b + 0.113 |
0.081a + 0.020 |
|
Seasons |
|
|
|
|
Summer season |
1.10a + 0.12 |
1.90a + 0.09 |
0.04a + 0.012 |
|
Winter season |
0.08b + 0.007 |
1.50b + 0.157 |
0.06a + 0.013 |
|
Sex |
|
|
|
|
Male |
0.59a + 0.068 |
1.78a + 0.150 |
0.06a + 0.012 |
|
Female |
0.59a + 0.068 |
1.71a + 0.110 |
0.04a + 0.004 |
*Means (within the same variable and column) superscripted with different letters differ significantly (P £ 0.05).
Anyhow, Cd is known to be human carcinogen (Mandel et al., 1995), Bahr El-Bakar drain water contained 0.910 and 0.0242 mg/l Pb and Cd, respectively, whereas its M. cephalus fish flesh contained 0.9376 and 0.0324 mg/Kg Pb and Cd, respectively (Galhoom et al., 2000). Cd reduced fish growth, feed efficiency and mitotic index and led to abnormal chromosomal behavior (Magouz et al., 1996). Additionally, Salem (2003) found that Cd and Pb caused significant reduction in fish performance, survival, and muscular area. Cd and Pb ions were able to induce metallothionein gene expression in fish tissues, e.g liver and gills (Cheung et al., 2004). Its residues in fish flesh increased by dose increase. The protein banding patterns fluctuated in numbers and intensities by Cd concentrations. Cd residues affected the DNA nucleotide sequences (El-Fadly et al., 2006).
The no effect level of Cd, Pb and Fe in water for growing aquatic life are 0.03, 0.10 and 1.00 ppm, respectively (Yokokawa, 2000). However, the commission regulation setting maximum Pb level for muscle meat of fish, released from the European communities (EC, 2001), as 0.2 mg/Kg wet weight. Yet, the Egyptians’ standards are 0.1 ppm Pb and Cd in food fish (ES, 1983). Comparing these standards with the levels obtained herein, it would be indicated that there is a water pollution with heavy metals in all tested locations, particularly with Pb in summer, Fe in winter (locations No. 2 and 4) and Cd in both seasons and all locations.
Abdelhakeem et al. (2002) cited the tolerance limits of Pb, Fe and Cd in fish water as 0.10, 0.35 and 0.10 ppm, respectively and in fish body as 2, 30 and 0.5 ppm, respectively. Heavy metal concentrations in fish varied significantly depending on the type of the tissue, fish species and sampling location. Generally, Mugil cephalus L. showed higher levels of Fe and Pb concentrations than Sparus aurata L. (Yilmaz, 2005). Yet, there was no significant seasonal variation in marine water metal (Cd and Pb) concentrations (Kucuksezgin et al., 2006).
However, heavy metal contamination of water is one of the environmental stressors affecting significantly and negatively lysozyme activity of fish serum, intestinal scrapping and skin mucus as well as serum hemolytic activity, leukocytes count, packed cell volume, hemoglobin concentration, plasma protein and glucose concentrations (Abdelhamid et al., 2006).
The bioaccumulation factors (BAF, of different heavy metals tested) in the M. cephalus studied from four sampling locations during two seasons are presented in Table (3). The significantly (P £ 0.05) highest BAF was in fish from location No. 2 (Alexandria), No. 3 (Port Saied) and No. 4 (El-Bardaweel) for Pb, Fe and Cd, respectively. This is correlated with the lowest (P £ 0.05) fish body measurement of Alexandria fish samples, and to some extend also low body measurements of Port Saied and El-Bardaweel fish samples in comparison with those of Marsa Matroh fish samples.
Winter Pb–BAF and summer Fe–BAF were significantly (P £ 0.05) higher than those of the other season; yet, Cd – BAC did not influence (P ³ 0.05) by sampling seasons. The high Pb – BAF in winter was correlated with the lower (P £ 0.05) fish body measurements in this season. However, fish sex did not affect BAF of all tested heavy metals in the tested M. cephalus. The high (P £ 0.05) Pb – BAF of Alexandria fish samples during winter is also correlated with high Pb content of the winter diet offered to Alexandria fish. Also, the high (P £ 0.05) Fe – BAF of Port Saied fish samples during the summer season is related to high Fe level in summer diet given to this location fish. These BAFs of heavy metals in fish did not influence by the level of these metals in the fish rearing waters, but were correlated with the level of Pb and Fe in winter sediment samples from Port Saied and Cd level in summer sediment samples from El-Bardaweel.
The highest (P £ 0.05) BAF of Fe in Port Saied fish samples was related also to the highest (P £ 0.05) Fe contents in fish of this location. The same relation was confirmed for Cd in El-Bardaweel fish samples, but not for Pb.
This may be due to the store tissue of each metal in/or on the fish, i.e. Pb was probably an external pollutant (Rashed and Awadallah, 1994), whereas Fe and Cd were internal pollutants. Therefore, Fe and Cd contents of fish affected positively their BAFs, but Pb was not.
The same note is available for the effect of season, since BAF of Pb did not influence by its level in/or on the fish, whereas BAF of Fe was correlated with its level in fish, being the highest in summer season. However, all tested metals level and their BAFs were not affected significantly (P ³ 0.05) by fish sex. Also, there were remarkable effects on microelements of fish muscles as well as their bioaccumulation factors due to sampling seasons and locations and fish species (Abdelhamid and El-Zareef, 1996).
To interpret the collective death of fish in Domietta region, it was proved that the water of the studied area (El-Bostan village – Kafr El-Batiekh) has suffered from increase of iron concentrations. This picture is very harmful to fish life and production. Pollution of water was reflected in the form of heavy metal accumulation in different fish tissues. The lowest bioaccumulation factors were calculated in fish muscles, therefore muscles only are suitable for human consumption. The bioconcentration of iron was higher than that of lead in fish muscles (Abdelhamid et al., 2000).
Table 5 presents significant positive correlations between fish weight on one side and Pb, Fe, Fe-BAF, length and depth of fish on the other side, but negative correlations between fish weight and Pb – BAF, Cd, and Cd – BAF. The fish depth correlated positively with Pb, Fe, Fe – BAF and length of fish, but negatively with Pb – BAF, and Cd level in fish. Fish length correlated too with Pb, Fe and Fe – BAF positively, but with Pb – BAC and Cd level negatively. Also, Cd – BAF correlated positively with Cd level (P £ 0.01). Cd correlated (P £ 0.05) negatively with Pb level in fish. Fe – BAF correlated (P £ 0.01) positively with Pb and Fe levels in fish, but negatively with Pb – BAF. Fe level in fish correlated positively with Pb level and negatively with Pb – BAF. Lastly, Pb – BAF correlated (P £ 0.01) negatively with Pb level in fish.
Cd in water negatively affected fish growth and feed and vitamin C utilization. Fe also is toxic for fish, since it damages fish gills and their function. Pb reduces hemoglobin content and red blood cells count of fish (Abdelhamid, 2003). However, any degree of poisoning will weaken the fish, making it vulnerable towards disease. Heavy metals can create problems and be concentrated in waterway organisms up to 9100 times more than the surrounding environment’s levels, so may lead to acute or chronic effects (WRC, 2005).
Hovanec (1998) mentioned that metals are involved in many aspects of fish keeping and aquarium water metals are acutely toxic while others are necessary for the life of the fish nitrifying bacteria. Still others are responsible for such basic water hardness. For a metal to be toxic, it almost always has ionized or free form. Water hardness can have a drastic effect on metal toxicity. Since the toxicity and biological activity of many metals and metalloids is profoundly influenced by their chemical form. The metabolism of ingested metals could significantly modify their toxicity. The micro-organisms in lakes, rivers and soil could biotransform metallic compounds (Rowland, 1981).
Zyadah (1997) reported significant effects on water mineral contents (containing Cd and Pb) due to different locations and seasons. Also, he found high levels of heavy metals in the sediment and fish, exceeded the allowable limit. Yet, Aboul-Naga (2000) confirmed that sediment samples from Abu-Qir Bay and infront of El-Maadiya channel indicate a non-polluted environment with trace elements including Cd, Fe and Pb. However, he reported high trace metal concentrations in front of El-Tabia Pumping Station. Iron was the dominant metal in all humic acids and sediments examined. Humic acids are trace metals holders in the sediments, therefore humic acids play a major role in the geochemical cycling of the elements in the aquatic environment.
Table (3): Bioaccumulation factors (B.A.F.%, means* + SE) of heavy metals in the fish (M. cephalus) flesh.
|
Variables |
B.A.F. - Pb |
B.A.F. – Fe |
B.A.F. – Cd |
|
Locations |
|
|
|
|
Marsa Matroh |
147.92b + 44.17 |
306.36b + 35.66 |
11.18b + 1.91 |
|
Alexandria |
1664.26a + 383.15 |
219.03c + 33.75 |
51.73ab + 11.36 |
|
Port Saied |
174.78b + 21.45 |
528.43a + 38.89 |
102.28a + 12.41 |
|
El-Bardaweel Lake |
140.53b + 20.27 |
226.54bc + 29.59 |
122.92a + 59.14 |
|
Seasons |
|
|
|
|
Summer season |
60.63b + 3.08 |
442.56a + 21.57 |
77.44a + 30.69 |
|
Winter season |
1003.12a + 205.25 |
197.62b + 27.12 |
66.62a + 6.29 |
|
Sex |
|
|
|
|
Male |
594.25a + 174.88 |
319.17a + 31.03 |
85.70a + 31.57 |
|
Female |
476.84a + 135.73 |
320.90a + 25.50 |
59.96a + 9.53 |
*Means (within the same variable and column) superscripted with different letters differ significantly (P £ 0.05).
Moreover, Radwan (2000) reported average values of dissolved heavy metals (Cd, Fe and Pb) in Lake Burullos water as 1.93, 2.46 and 2.67 mg/l, respectively. He added that, levels of heavy metals are correlated with salinity changes due to the discharge of water. Hussein and Mekkawy (2001) revealed that fish reflect further mechanisms to avoid lead impacts such as the secretion of intestinal mucus that bind lead.
Also, it is a fact that body adaptive balance mechanisms for lead impacts were evident in different organ tissues of fish. Yet, Mzimela et al. (2002) reported that lead negatively affected the blood hematology and acid-base balance of the groovy mullet, Liza dumerili.
Usero et al. (2004) reported that heavy metal concentrations in the water, sediment and fish were variable from site to another. Significant correlations were obtained for the levels of numerous metals in water, sediment and fish. The results of Xie and Klerks (2004) suggest that reduced uptake and accumulation of Cd accounted for approximately two-third of the increased resistance in the Cd-adapted lines of fish. However, Cd has been found to accumulate in reproductive organs of fish and disrupt important endocrine processes.
Moreover, responses along the hypothalamus – pituitary – gonadal axis were more sensitive to Cd exposure (Tilton et al., 2003).
Metal concentrations in the sediment at each site depended more on the general characteristics of the sediment, such as the percentage of fine grained sediments and Fe content, than on whether or not there was replanted (Paulson et al., 2001).
Siam (2001) found high level of accumulation of Cd, Fe and Pb in the different organs (gills, liver, stomach and brain) of Alexandria coast fish, with respect to their corresponding in the muscle tissues. He added that the accumulation factors for these metals were higher in the herbivorous fish (Siganus rivulatus) than in the carnivorous ones (Mugil capito). Fe was the more pronounced one reflecting increase the trophic level of the fish. Cd level was generally lower than that of Pb in various organs while brain gained the highest values. Pb concentration ranged from 1.2 to 3.5 mg/kg in the stomach and brain while it ranged from 0.4 to 0.9 mg/kg in fish muscles.
Most of the fish generally showed levels of Cd in the organs, which are close to that of the recommended standard (2.0 mg/kg) of the National Health and Medical Council in Australia. However, none of them contained Cd concentrations above 0.5 mg/kg in their muscle tissues. Total length, body weight and age are mostly correlated biometric parameters with metallothionein and soluble metal concentrations in striped red mullet and golden grey mullet (Filipovic and Raspor, 2003). Cadmium and lead were higher in muscular tissue from mullet (Mugil spp.) than snook (Centropomus spp.) and higher in summer than in winter (Joyeux et al., 2004).
Kirby et al. (2001) mentioned that mullet are directly exposed to trace metal concentrations as a result of feeding and the ingestion of contaminated sediment and detritus. Lower metal concentrations found in mullet tissues are attributed to the burial of highly contaminated sediment with material containing lower trace metal concentrations. Little of the variations in trace metal concentrations between mullet was explained by mass, gender, or age.
Geochemical controls of metal assimilation from contaminated sediment are relatively apparent for Cd. The influences of metal speciation on metal bioavailability can be confounded by the degree to which sediments are contaminated with metals (Fan et al., 2002). Heavy metals (Cd, Fe, and Pb) strongly inhibit the enzyme activity and the hexobarbital metabolism (Medline Repository, 2001). They alter the immune system and lead to increased susceptibility to autoimmune diseases and allergic manifestations (Bernier et al., 2005).
Suciu et al. (2005) reported that Cd-bioaccumulation factor was increased by age. Cd and Pb were accumulated more in males than female sturgeon. However, liver microsomal 7-ethoxyresorufin O-deethylase (EROD) activity of leaping mullet inhibits the toxicity of divalent metal ions through the inhibitory effect of the glutathione (GSH) on Cd inhibition of EROD activity indicating the protective action of GSH (Bozcaarmutlu and Arinc, 2004).
Staniskiene et al. (2005) found high concentrations of Fe in 15 fish species as a direct result of water contamination with heavy metals. Metal concentrations were found to be influenced by fish type. Cadmium – binding protein level in the cells of the intestine was increased after exposure to Cd, so it appears that this protein is synthesized as a response to Cd exposure. This is a mechanism of the regulation of Cd levels (Demuynck et al., 2004). Summer cadmium and lead concentrations in mullet (Mugil spp.) were higher than in winter (Joyeux et al., 2004).
Bacterial count:
Total bacterial count (TBC) in fish diets ranged between 6.6 – 8 x 104 CFU/g in summer and 8 – 9.5 x 104 CFU/g in winter. E. coli, Shigella and Salmonella were presented in both locations and seasons, but no Shigella was found in diet of Port Saied in summer. In rearing water, TBC reached 1 – 3 x 105 CFU/ml in summer and 2.8 – 9.5 x 104 CFU/ml in winter. The three bacterial genera were found in location No. 2 in summer and locations No. 3 and 4 in winter. Shigella presented in all sampling locations, except in Marsa Matroh water during summer and in Alexandria water during winter. E. coli was presented in all locations in winter water, but only in Alexandria water in summer. The incidence of these bacteria in water was related to their presence in the diets. The sediments contained TBC as 1.2 – 2.5 x 105 CFU/g and 1.5 – 3 x 105 CFU/g in summer and winter, respectively.
All tested bacterial genera were found in all sediment samples collected from different locations. From Table (4), Marsa Matroh fish contained TBC significantly (P £ 0.05) higher than those of the other locations. The summer TBC was significantly (P £ 0.05) higher than that of winter fish samples. Yet, fish sex had no significant (P ³ 0.05) effect on TBC of fish.
However, the high TBC of summer fish is related to the high TBC in summer water. From Chi-square test data for distributing the negative and positive samples of fish for different genera of tested bacteria, it is clear that 115 (71.9%) samples of fish were positive for E. coli, 54 (33.8%) for Shigella and 21 (13.1%) for Salmonella. Marsa Matroh fish were the most contaminated (55%) with Shigella. Summer fish presented more E. coli (73.8%) and Shigella (38.8%) positive samples than those of winter fish samples (70.0 & 28.8%, respectively) , whereas Salmonella positive fish samples were more in winter (13.8%) than in summer (12.5%).
Male fish samples were more positive for E. coli (73.3%) and Salmonella (16.0%) than the other fish sex (70.6 & 10.6%, respectively). However, these data confirmed the previous mentioned results of the significantly (P £ 0.05) higher TBC in summer than in winter fish samples, although the non significant (P ³ 0.05) effect of fish sex on the TBC of fish (Table 4). Yet, female fish contained more (36.5%) Shigella positive samples than the males (30.7%). Generally, Chi-sqare test was not significant (P ³ 0.05), except for fish Shigella in different locations.
To correlate TBC with the other tested parameters, whether of body measurements, heavy metals concentration in fish flesh, or their BAFs, correlation coefficients were calculated and presented in Table (5).
Significant positive correlations were found between TBC on one side and Pb level in fish and fish length, depth and weight, on the other side. T-test data cleared that the E. coli, Shigella and Salmonella positive samples were 115, 54 and 21, respectively from total of 160 samples. T-values between each of these bacterial genera and the other tested parameters (heavy metals and their BAF as well as body measurements) of the tested M. cephalus were not significant (P ³ 0.05), except between Shigella, from one side, and Pb content and TBC, on the other side.
Yet, Tate (1995) cited that the diversity of the soil microbial genome suggests that a variety of organisms must exist in soil with augmented resistance to heavy metal pollutants. For example, a variety of soil bacteria have been isolated with augmented resistance to metal contaminants. He added that microbial populations may be inhibited by release of organic-matter-associated cautions through microbial catabolism of the soil’s organic matter. The availability of the toxic caution may become the controlling factor in bacterial population development with the impact of those environmental properties normally considered to determine community diversity being minimized.
Table (4): Total bacterial count (means* + SE) of the tested M. cephalus (CFU/g).
|
Variables |
T.B.C. |
|
Locations |
|
|
Marsa Matroh |
204975a + 22430.59 |
|
Alexandria |
132125b + 8128.39 |
|
Port Saied |
135900b + 11132.00 |
|
El-Bardaweel Lake |
135400b + 10378.46 |
|
Seasons |
|
|
Summer season |
171075a + 12320.91 |
|
Winter season |
133125b + 7771.79 |
|
Sex |
|
|
Male |
151160a + 12048.15 |
|
Female |
152929.412a + 9113.33 |
*Means within the same variable superscripted with different letters differ significantly (P £ 0.05).
Nile tilapia fish grew in treated-waste effluents reflected very low total aerobic bacterial count (9.3 x 102 CFU/g) in the edible muscles and complied with WHO guidelines (< 105 CFU/g). Salmonella, Shigella and Staphylococcus were absent. In addition, toxic metals (Cd and Pb) were at much lower levels than the international advisory limits for human consumption (Khalil and Hussein, 1997). Although the general microbial quality differed significantly among the production systems (source of rearing water); yet, human bacterial pathogens like E. coli and Schigella spp. were isolated from Egyptian naturally infected fishes of freshwater, mainly Oreochromis spp., Clarias lazera and common carp (Enany et al., 2004).
Table (5): Correlation coefficients between different variables measured for M. cephalus.
|
|
Pb |
BAF-Pb |
Fe |
BAF-Fe |
Cd |
BAF-Cd |
Length |
Depth |
Weight |
TBC |
|
Pb Pearson Correlat. |
1 160 |
|
|
|
|
|
|
|
|
|
|
BAF-Pb Pearson Correlat. |
-.273** |
1 160 |
|
|
|
|
|
|
|
|
|
Fe Pearson Correlat. |
.196* |
-.295** |
1 160 |
|
|
|
|
|
|
|
|
BAF-Fe Pearson Correlat. |
.496** |
-.332** |
.886** |
1 160 |
|
|
|
|
|
|
|
Cd Pearson Correlat. |
-.184* |
.071 |
-.042 |
-.118 |
1 160 |
|
|
|
|
|
|
BAF-Cd Pearson Correlat. |
.026 |
-.017 |
.021 |
.043 |
.851** |
1 160 |
|
|
|
|
|
Length Pearson Correlat. |
.330** |
-.352** |
.266** |
.337** |
-.209** |
-.057 |
1 160 |
|
|
|
|
Depth Pearson Correlat. |
.327** |
-.445** |
.263** |
.282** |
-.168* |
-.064 |
.709** |
1 160 |
|
|
|
Weight Pearson Correlat. |
.470** |
-.642** |
.308** |
.377** |
-.178* |
-.045 |
.803** |
.719** |
1 160 |
|
|
TBC Pearson Correlat. |
.322** |
-.054 |
-.062 |
.035 |
-.028 |
-.011 |
.209** |
.178* |
.171* |
1 |
*Correlation is significant at the 0.05 level (2-tailed). **Correlation is significant at the 0.01 level (2-tailed).
Egyptian General Authority of Standardization and Quality Control (2000); recommended 106 total bacterial count per gram as a maximum permitted limit for fish, and added that fish must be free from Salmonella and Shigellia. Food fish, whether under cooked, fecally contaminated, or inadequate refrigerated, may be contaminated by bacteria, e.g. Salmonella, Shigella and Escherichia coli causing foodborne illness, such as salmonellosis, shigellosis and Hamburger disease, respectively. Their toxicity symptoms including abdominal pains, vomiting, fever, diarrhea, chills, and cramps (Work book, 2005).
Eating fish at least once a week is good for the brain, may help slow age-related mental decline by the equivalent of three to four years (10% slower annual decline in thinking), and helps keep the mind sharp. It lowers the risk of Alzheimer’s disease and stroke.
Fish which are rich in omega-3 fatty acids also have been shown to prevent heart disease (Morris, 2001). Yet, pathogens are parasites which cause diseases (WRC, 2005). Particularly, sea foods may cause acute diarrhea due to Salmonella contamination (Harrison’s, 2005). So, Salmonella, Shigella, and E. coli, all capable of inducing gut-wrenching gastroenteritis. But, the incidence of diagnosed infections for pathogens was increased for E. coli and Shigella but decreased for Salmonella in 2000 than before (Colorado, 2001).
A recent report (Anon., 2005) showed important declines in food borne infections due to common bacterial pathogens in 2004. From 1996 – 2004, the incidence of E. coli infections decreased 42%. Salmonella infections dropped 8%. The incidence of Shigella did not change significantly. However, 76 million food borne illness, or food poisoning, cases occur in the USA every year (30% are caused by bacteria, e.g. E. coli, Salmonella and Shigella).
Morbidity and mortality cases of food borne pathogens (Salmonella spp. and E. coli) in the United States reduced between 1987 and 2000, and even estimated to be reduced sharply till 2010 (Wesley et al., 2005). Yet, five commercial systems of freshwater fish culture contained E. coli. The presence of such organisms creates a potential for microbiological hazards in these systems. That could indicate the presence of human pathogens that may be hazardous to fish handlers and consumers. That indicates also that monitoring fish culture facilities for microbiological safety should be considered.
In addition, workers should be aware of personal hygiene when entering, while working in, and when departing fish culture facilities (Mc Keon et al., 2000). However, all strains of Shigella and Salmonella are considered pathogen, but only the pathogenic strains of Escherichia are associated with food borne illness (Ray, 2001). Goosney et al. (2001) reported that bacterial pathogens can survive and persist to exploit their host’s cellular processes to mediate their effects extracellularly or intracellular.
In either case, the pathogen hijacks the host’s cytoskeleton, so the pathogen is involved in mediating numerous cellular functions, from cell shape and structure to programmed cell death. The incidence of salmonellosis has generally been declining since 1997 (Ethelberg et al., 2005). Yet, Guerin et al. (2004) reported that in February 2001, an increased incidence of infection caused by S. livingstone was observed in Norway and Sweden. By July 2001, 44 cases wee notified in Norway and 16 in Sweden. There were three deaths, and 22 patients were hospitalized.
S. livingstone was subsequently recovered from a processed fish product at the retail level. Salmonella enterica was responsible for the food borne outbreaks in Portugal, 2002 due to inadequate processing, preparing or handling of foods (Correial et al., 2004). There was no correlation between sediment metal content and the total hyporheic microbial biomass present within each site. However, microbial community structure showed a significant linear relationship with the sediment metal loads (Feris et al., 2003).
Proximate analysis:
Table 6 presents data of chemical analysis of mullet flesh. There were significant effects of sampling locations and seasons on all components tested. Port Saied and Marsa Matroh fish reflected higher (P £ 0.05) protein than Alexandria and El-Bardaweel fish. Yet, the fat and ash contents differed also but not in a clear trend.
However, winter fish contained more protein and less fat percentages (P £ 0.05) than those of summer. This means that aquaculture or artificial feeding did not affect chemical composition of the fish. Also, better protein content in fish flesh from Port Saied and Marsa Matroh may be attributed to the lower total bacterial count in sediments from these both locations than the others.
Elevated protein content in winter may be due to the lower (P £ 0.05) heavy metals content (Pb and Fe) in fish flesh during this season than in summer as well as to the significantly (P £ 0.05) lower total bacterial count of the fish (Table 4). The negative correlation between protein and fat percentages was proved too by El-Ebiary and Zaki (2003) and Abdelhamid et al. (2004 and 2005-a & b).
Table (6): Chemical analysis of the experimented fish flesh as affected by sampling location and season (means ± SE) as % dry matter basis.
| Location/season |
Protein |
Fat |
Ash |
|
Alexandria |
58.29b + 0.933 |
28.00c + 0.357 |
11.50a + 0.549 |
|
El-Bardaweel |
58.88b + 0.744 |
32.59a + 0.173 |
6.948c + 0.797 |
|
Port Saied |
61.23a + 0.853 |
25.71d + 0.659 |
11.91a + 0.302 |
|
Marsa Matroh |
60.75a + 0.630 |
29.67b + 0.540 |
7.968b + 1.132 |
|
Summer |
58.23b + 0.463 |
29.11a + 0.561 |
11.06a + 0.504 |
|
Winter |
61.34a + 0.450 |
28.77b + 0.981 |
8.103b + 0.849 |
a – c: Means in the same column within the same category superscripted with different letters differ significantly (P £ 0.05).
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Authors: Abdelhamid 1, A. M.; Maha M. M. Gawish 2 and K.A. Soryal 2
1 Animal Production Department, Faculty of Agriculture, Al-Mansourah University
2 Desert Research Center, Ministry of Agriculture
United States
