International Journal of Aquatic Biology
Volume:1 Issue: 2, Apr 2013

Effect of dietary free L-Lysine on growth, food intake, and muscle composition of beluga juveniles were investigated over 6 weeks. Control diet lysine content was 2.1% of dry matter (4.4% of dietary protein). Three experimental diets were prepared by adding lysine (0.5, 1 and 1.5%) to control diet to obtain diets containing 2.6, 3.1 and 3.6% of dry matter lysine (corresponding to 5.5, 6.6 and 7.6 of dietary protein). Fish were fed 2.6% of dry matter lysine showed significantly higher final weight, weight gain and SGR and lower FCR compared to other treatments. There was no significant change in food intake and survival between treatments. Lysine supplementation resulted significantly in increase and decrease in muscle protein and lipid, respectively. Dietary lysine has no effect on muscle ash and moisture content. Results showed that lysine supplementation had no significant effect on food intake in beluga juveniles. It seems that dietary lysine level of 2.6% of dry matter (corresponding to 5.5% of dietary protein) is suitable for growth of beluga juveniles.

This study aimed to investigate the spawning season, length at first maturity (LM50) and sex ratio of Metapenaeus affinis in the shrimp fishing grounds of Hormozgan Province, west of the Persian Gulf, Iran. Samples were taken by the swept area method and trawl net with 2 cm mesh size in the cod end from January 2010 to February 2011. Results showed that the sex ratio deviated from 1:1 and female’s number were significantly higher than males. Metapenaeus affinis females had continuous spawning in all seasons but the peak spawning season was found in spring, and stage 3 of maturity was observed in all seasons. Length at maturity (LM50) for females was estimated at 27.12 mm based on carapace length. Our finding showed that LM50 of M. affinis do not change with sex ratio deviates from equal ratio.

Widespread use of nanosilver can be led the contamination of aquatic environment and impact on living organisms such as fishes. We investigated histopathological changes in the gills tissue of Caspian Roach fingerlings after two weeks exposure to sublethal concentrations of nanosilver. Following one and two weeks exposure, necrosis, shortening of secondary lamellae, edema, destruction of epithelial lamella, shortening of secondary lamellae, epithelial lifting and curling of secondary lamellae were observed in fingerlings’ gill tissues. This observation showed that exposure to sub-lethal concentrations of nanosilver is caused damages in the gill tissues of Caspian roach. The results demonstrated direct correlation of gill tissue damage and toxin exposure i.e. increasing nanosilver concentration is caused more tissue damage. Hence, histopathological changes of gill can considered as a proper indicator for nanosilver contamination of aquatic environments.

Heavy metals are the most important pollutants in aquatic ecosystems that may cause adverse effects on its biota. In this study, histopathological effects of zinc (Zn) and their incidence time on swan mussel, Anodonta cygnea, were studied. Exposure to Zn was done during 18 days and histopathological investigations were conducted in mantle, digestive gland and foot in days 0, 4, 9, and 18. Histopathological changes observed were: damages of epithelium cells with increasing mucous cells (in mantle), atrophy of digestive tubules and haemocyte aggregation (in digestive gland), and hypoplasia, increasing mucous cells and myocyte swelling (in foot). Moreover, granuloma and tissue rupture were found in all organs. Primary histopathological changes were observed in fourth day of examination in all of studied organs. Results showed that sensitivity of digestive gland is lesser than mantle and foot in exposure to Zn. Also the results indicated the histopathological alterations in the organs of swan mussel can be considered as reliable biomarkers in biomonitoring of heavy metal pollution in aquatic ecosystems.

This study investigated the relationships between nutrients and chlorophyll-a concentration in the International Alma Gol Wetland. Chlorophyll-a is the major photosynthetic pigment in lots of phytoplanktons and has been used as a trophy index in aquatic ecosystems. Water samples were collected fortnightly from five stations in the wetland during summer and autumn. Chlorophyll-a ranged between 4.38 to 156.55 mg/m3, sulfate ranged between 138 to 190 mg/l, total alkalinity ranged between 80 to 280 mg/l, silica ranged between 3.80 to 35.00 mg/l, phosphate ranged between 0.02 to 3.70 mg/l, ammonia ranged between 0.10 to 11.90 mg/l, nitrate ranged between 0.01 to 2.75 mg/l and nitrite ranged between 0.01 to 0.39 mg/l. There was a significant correlation between chlorophyll a and nitrate, nitrite and ammonia but there was no significant correlation between chlorophyll-a and silica, total alkalinity, sulfate and phosphorus.

The present study investigated effects of dietary tryptophan (TRP) and betaine (BET) on copper (Cu) toxicity tolerance in the Caspian roach (Rutilus rutilus caspicus). The Caspian roach fingerlings were fed diets containing 0, 0.25 and 0.5% TRP or 0, 0.5 and 1 % BET and combination of TRP and BET. Specimens were exposed to Cu (0.8 ppm) after either 30 or 60 days feeding. Mortality was recorded in each treatment 48 h after the Cu exposure. TRP decreased significantly fish mortality. However, BET had no significant effect on fish mortality. Specimens fed on the diet supplemented with 0.25% TRP had the lowest mortality among the treatments. It is concluded that 0.25% TRP reduces mortality of Caspian roach during Cu exposure.

In this study, Geometric morphometrics approach was used to explore body shape variations and growth trajectory among four population of Shemaya (Alburnus chalcoides). The shape of 114 individuals from three rivers (Lisar, Shiroud and Babolroud) and one lagoon (Anzali) from the south of Caspian Sea was extracted by recording the 2-D coordinates of 16 landmark points. We applied a GPA analysis to eliminate non-shape variations. PCA, CVA, MANOVA and DFA analysis were used to examine shape differences among populations. The significant differences found among the shape of populations. Since Shemaya is an anaderemus fish and all their populations have a common origin, we concluded that differences between habitat features might create selective pressures resulting morphological divergence among conspecific populations. We suggest that high level of plasticity, particularly in the depth of body, head and caudal peduncle shape may reflect low costs of maintaining the plastic response even in relatively isolated populations.