Iranian Scientific Fisheries Journal
Year:2005 | Volume:14 | Issue:3|Papers Count:17

We assessed concentration of heavy metals (Zn, Cu, Pb, Cd) in the muscle tissue of Mugil auratus caught from important parts of Caspian Sea in Mazandaran Province in autumn 2002.After biometrical measurements, the muscle tissue of 32 randomly selected fish were separated using standard method MOOPAM 1999. Metals were extracted from the tissues using Closed Digestion method and acidic mixture (Moopam, 1983). Concentrations of the heavy metals were measured by FAAS (AAS4 Zeiss Gennany).Mean concentrations for Zn, Cu, Pb, Cd (14.327, 0.996, 2.337 and 0.321 ppm/dry weight) were compared with the international standards such as WHO, UK (MAFF), and NHMRC. A T. test showed higher than normal concentration of Pb, Cd in the muscle tissues.We found a positive linear relationship between accumulation of Zinc and Cadmium with weight, sex and standard length factors a negative linear relationship between accumulation of Pb with weight, sex and standard length. There was no significant relationship between accumulations of Cu with the biometrical factors of the sampled fish. Also, no relationship was found between sex and accumulation of Zn, Cu, Pb, Cd, while the accumulation ofPb in male samples were more than female ones.

Otoliths were collected from 98 Caspian Roach in the east, centre and west parts of south Caspian Sea during 1999-2000. Trace elements K, Sr, Cu, Fe, Zn, and Br in the otoliths were detected using PIXE method. Our results suggest K, Sr, Cu, Fe, and Zn can be used as discriminating factors for population separation in Caspian Roach. The value of K, Sr, Cu, Fe, and Zn were 7.1, 178.3, 0.1, 2.6, 0.3ppm in the west and 9.5, Il.l, 0.3, 5.7, 0.2ppm in the east. Therefore, Caspian Roach from west and east can be discriminated based on their significantly different concentration of trace element contents (p<0.05). However, this was not the case for fish from central part and Anzali area (p<0.05). This study affirmed earlier results from investigations on morphometric characteristics of Caspian Roach suggesting the presence of two different populations of Ruti/us ruti/us in the south of the Caspian Sea, namely Anzali-Kura, and Gorgan-Turkmen.

We collected sturgeon specimens from seven fishing stations operating 30 to 35 Km away from each other in Guilan province over the years 1999 - 2000.Trawl nets six meters long were drawn using motorboats at each station, repeated three times for each season. Among the studied premature sturgeons, 121 Acipenser persicus specimens with an average age of less than two years and a length of 10 to 49.9 :f:0.77 cm showed full stomachs (57.17 % fullness). Among the mature specimens with an average age of 11 years and a length range of 90 to 194 cm, only three showed full stomachs (11.54 % fullness). The highest gut index in this study belonged to premature A. persicus.A one-way analysis of variance showed no significant difference in condition factor and gastro-somatic index among the different length groups (P<0.05). We found that the food consumed by premature A. persicus was comprised of eight genera of benthic invertebrates Hypania sp., Hypaniola sp., Pterocuma sp., Stenocuma sp., Abra ovata, Paramysis sp., Gammarus sp. and Nereis sp. Adult sturgeons were found feeding mainly on fish species belonging to Gobidae, Atherinidae and Clupeidae families. The main preys of premature A. persicus were polychaet worms Hypania sp. and Hypaniola sp. Belonging to the class Sedantaria. Crustaceans Stenocuma sp. and Pterocuma sp. of the class Cumacea were also seen in the diet of the premature sturgeons. The main preys of adult A. persicus were fishes belonging to the family Gobiidae and secondary prey were fishes of the family Atherinidae.

We treated 150 specimens of Acipenser nudiventris with diazinoll and used 30 individuals as control to assess the haematological effects of the pesticide and LC50(96h) for the fish. The acute toxicity test lasting 96 hours was conducted on juvenile Acipenser nudiventris kept in aerated stagnant water contaminated with diazinon. The LC50(96h) values of diazinon for Acipenser nudiventris juveniles was 4.6 mg/l. The experimental groups of fish showed statistically significant difference in their erythrocyte, haemoglobine, leukocyte and differentialleukocyte count (P<0.05).Acute toxicity effects of diazinon on the fish was recorded as lowered erythrocyte and lymphocyte count with a significant increase in developed neutrophile count (P<0.05). It is suggested that the change in erythrocyte and leukocyte count may have been caused as a result of disruption of haematopoiesis and a decrease in non-specific immunity level of the fish.

We assessed amount of surfactants and their seasonal trend in eight stations in Anzali Lagoon and compared them with allowable levels in the years 2001 - 2002. We obtained 96 water samples and determined their surfactant content using liquid -liquid method applying methylene blue active substance (MBAS).The concentration of surfactants in Pirbazar varied from 0.176 to 0.422 while that of the Sea station was somewhere between 0.098 to 0.049 mg/l. Seasonal concentration of surfactants varied from0.049 to 0.422 mg/l averaging on 0.137 mg/I. A significant difference was found for surfactant concentration in different parts of the lagoon (p<0.05) with the eastern zone being the most polluted area with 0.422 g/l of the pollutants compared to 0.066 mg/l in the Sea. The highest amount of the surfactants was seen in winter in contrast to the lowest amount in spring. No statistically significant difference was found between concentrations of the surfactants in different seasons.

For assessing management efficiency in shrimp hatcheries of Choebdeh (Abadan), we surveyed the physico-chemical properties of water in two culture periods during the years 2001-2002. Different physical and chemical factors were measured in hatcheries under Thai and Philippine management methods.We measured factors such as salinity (17.9-35.3 ppt), BaD5 (6.12-8.72 ppm), DO (10.02-13.7 ppm), COD (4-98.9 ppm), NH3 (0-81104 ppb), NO2- (10-421 ppb), pH (8.04 - 8.68), Turbidity (1-33 NTU), Ca (40004-620.6ppm), Mg (1104-1968 ppm), total hardness (6000-9400 ppm) and water temperature (25.4-32.4˚C while no amount of SH2 was found in the water, samples.The results of this survey were compared with standard levels and safe ranges for aquaculture activities. Most factors were in standard range with only NH3 and NO2- showing a slight excess in some cases. An ANOVA test showed significant differences in levels of oxygen and COD of the tanks at different sampling times.

WE sampled 139 specimen of Acipenser persicus and 103 Acipenser stellatus over the years 1998-1999 in five fishing zones of the southern Caspian Sea for heavy metal contamination assessment. Flame Atomic Absorption Spectrophotometery was used to determine contamination of the specimens with Zn, Cu, Cd, and Pb and cold vapor method for Hg.The mean age for A. persicus and A. stellatus was 17.6±2.6 years and 11.9±1.8 years, respectively. The mean concentrations of heavy metals assessed for dry weight of the muscle tissues and caviar in A. persicus were 26.9 and 65.9 µg/g for Zn, 1.8 and 4.2 µg/g for Cu, 0.61 and 0.111 µg/g for Pb and 0.61 and 0.005 µg/g for Cd. The wet weight concentration of Hg in the muscle tissue and caviar of the fish were 0.06 and 0.007 µg/g respectively. For A. stellatus we determined the mean concentration of heavy metals in dry weight of the muscle tissue and caviar to be 27.4 and 57.8 µg/g for Zn, 1.64 and 4.85 µgig for Cu, 0.481 and 0.112 µg/g for Pb and 0.59 and 0.005 µg/g for Cd while the wet weight concentration of Hg were 0.05 and 0.008 µg/g. By international standards, the contamination of the muscle tissue and caviar samples with the heavy metals in the two sturgeon species are well below maximum allowable for human consumption.

Hatchability of cysts and nutritional value of Artemia urmiana's nauplii in different incubation times were evaluated. The experiments were conducted at five incubation times 18, 20, 22, 24 and 26 hours, in triplicate random groups. Hatchability of cysts during these periods was determined with standard methods.NaupIii were hatched in five litre bottles to determine their biochemical composition. Dry weight, protein, lipid, carbohydrate, ash, caloric content and fatty acid compositions of naupliies were determined at different developmental stages. Also, the dry weight and the biochemical composition of nauplii were determined individually, at different developmental stages.The results showed that the hatching percentage and efficiency increased with time with the hatching percentage being significant (P<0.05). The nutritional value of nauplii decreased slightly with time in most cases, but no significant changes were found (P>0.05). Based on the results, the incubation times 25 or 26 hours are recommended for harvesting nauplii. At these times, hatchability and the amount of harvested nauplii increased while their nutritional value was highest.

To evaluate spawning status of Vimba vimba, population in Sefid-roud river, 621 breeders, 1136 larvae, tries and fingerlings were caught in the river using beach seine, cast-net and electro-choker over the years 1999-2000. We found that the fish started spawning migration in March and continued it until July with its peak occurring between mid-April to late-May. Fork length was 116 - 208 mm (153.1 ± 17.95) in male specimens and 122 - 222 mm (173.5 ± 16.46) in females. Total body weight ranged 21.1-116.1g (52.92±19.23) in males and 23.1 - 170.0 g (77.90± 22.88) in females. Males aged 2-6 years (3.53±0.86) and females aged 3-7 years (4.l9±0.92) participated in the spawning with their maturity age being calculated as 2 and 3 years respectively. In all, breeders were composed of 51.82% males and 48.18% females with the ratio being significantly different only in May. Gonad weight was 1.13-7.92 g (Avg. 2.89±0.29) in males and 3.21-25.47g (Avg. 10.40±1.52)in females. We found the highest gonad weight for the fish in June and that the gonad weight in female breeders increased upwards of the estuary. Gonado-somatic index was 19-21% in 85.7% of the females and 3-8% in 95.5% of the males. Spawning of the species took place during day and night from late May to late June with its peak in May in water temperature ranging 18-29 degrees centigrade on pebble and gravel grounds from 25 to 75kms away from estuary. The Disaam tributary was distinguished as the major spawning area for the species.

The Persian .Sturgeon, Acipenser persicus is the most important sturgeon species in the southern part of the Caspian Sea and it provides 51% of Iran's caviar production.We were used five different age groups of the larvae (7, 17, 22, 28 and 33 days after yolk absorption) in 3 replicates. The larvae were all transferred at the same time to 27 liter aquarium holding 15 liter of water at different salinities (0.5, 7 and 9 ppt) and were provided with continuous aeration.Analysis of data showed that during early stages of life, age is an important factor for development of osmoregulatory organs. However, in later stages, weight and length play a vital role in this regard. The present study reveals that during post hatch and active feeding, in favorable environmental and rearing condition A. persicus fingerlings could be released into rivers and estuaries in Guilan province at an age of 33-35 days after yolk sac absorption and when they attain weight of 1.8-2.4g and length of 6.2-7.5cm.

The Possible effects of dry years 1998-2000 on benthic organisms of Amirkalayeh Wetland was studied in the year 2001. Six sampling stations were defined where we seasonally collected benthic organisms using a grab sampler. We identified nine benthic organisms belonging to class Hirudina and orders Odonata and Ephemeroptera and also six families Chironomidae, Chaoborina, Ammaridae, Tubificidae, Xanthidae and Culicedae. Families Xanthidae and Culinidae had not been reported before for the wetland while orders Coleoptera and Trichoptera and families Planorabidae, Limnaeidae, Coleoptera which were present before the drought, were not detected in the samples. We observed a significant decrease in frequency of benthic organisms changing from 1372 organisms per square meter in 1997 to 165 in 2001.Also, tests showed considerable change in benthic diversity, species richness and distribution in different sampling seasons and stations over the year 2001. These changes may be attributed to the decrease in water depth, dissolved oxygen, available food and increase in water temperature and predation.

Feeding habits of different genera of 354 sturgeon specimens (Acipenser persicus, Acipenser nudiventris, Acipenser stellatus) were compared over the years 1999-2000 caught in the coastal waters less than 20 meters deep of Mazandaran and Golestan provinces, southern Caspian Sea. The caught specimens ranged 30-18cm in length. Overall, 16 families of food items were identified in the digestive system of the sturgeon specimens, of which 11 belonged to macro-benthos.The sturgeon fishes preyed on food items composed of Annelida 50.8%, Amphipoda 41.5%, small fish 4.8%, Decapoda 2% and Bivalvia 0.9%. Fish specimens shorter than 40 cm were mostly found feeding on shrimps, polychaets and gamarids. The 41-80cm length class mostly fed on shrimps, gamarids, polychaets, bivalves and smaller fish. Sturgeons longer than 80cm fed mostly on shrimps and smaller fish. Average fat coefficient for Acipenser stellatus was 0.43. A. persicus showed a fat coefficient 0.63 while that of the A. nudiventris was 0.97. Average stomach fullness was 8.3, for Acipenser stellatus, 100 for A. nudiventris and 165 for A. persicus. We found a similar diet between group one fish less than 40 cm long and group two with fish in the length class 41 to 80cm (r=0.7).

We analysed the physico-chemical properties of estuarine water in Mazandaran Province rivers (Shirood, Tonekabon, Larim, Tajan, Goharbara ) during release of fish fingerlings in spring and summer 2000-2001. Water temperature, pH, DO, BaD5, TSS, TDS, Cl-, PO43-, NH4+, N02- and hardness were determined for 52 samples. The results showed the present condition of rivers Shirood and Tonekabon to be suitable for release of fish fingerlings and classified them as AA to A. Ranking as class e, rivers Larim, Goharbaran .and Tajan were found unsuitable according to EPA standards, due to agricultural water extraction and improper land use development.

We investigated the generation of gynogenetic common carp (Cyprinus carpio L.) during 1989-1990. After selection of suitable breeders containing special transfferin marker in breeding season, we applied ionizing radiation (60 Co gamma ray) for genetic inactivation of spermatozoa of the fish. We found that in the exposure of the sperm to a range 80-120 Krad irradiation, 100 Krad gave the best results. Application of various cold and heat shocks to the eggs at different time intervals after addition of water to the mixture of milk and eggs generated diploid gynogenetic fish. Cold and hot shock treatments generated significantly different gynogenetic fish (7% and 2.5% respectively). The optimum shock treatment was found to be 5 minutes after fertilization in 0°Clasting 50 minutes. For each treatment, 100 fish fingerlings were subjected to electrophoresis which showed the mitotic diploid progenies were all-maternal inherited with BB genotype.