Fisheries

Cortisol level changes in response to stocking density in the early stages of rainbow trout were measured. Eggs were exposed to low, normal, and high (2.55, 5.10 and 7.65 eggs cm(-2)) densities during the incubation period. Cortisol of maternal origin was found in pre-fertilized eggs (5.09 ± 0.12 ng g(-1)) of rainbow trout. In newly fertilized eggs, resting Cortisol levels (3.68 ± 0.14 ng g(-1)) decreased to 0.58 ± 0.08, 0.60 ± 0.12, and 0.57 ± 0.16 ng g(-1) at low, normal and high densities by day 10 (organo-genesis), respectively. Resting Cortisol levels remained constant until the eyed stage (day 18). Then, Cortisol showed an increase at hatching to 1.16 ± 0.11, 1.20 ± 0.12, and 1.21 ± 0.14 ng g(-1) at low, normal, and high densities, respectively. The pattern of change in Cortisol level was similar in all three densities. Interrenal cells were observed in 1-day old alevins at all three densities. Hematopoietic tissue, renal tubules and nucleated red blood cells were clarified through the head part of kidney. Higher numbers and larger interrenal cells were observed at high-density groups. Chronic density stress test conducted on embryonic stages of rainbow trout revealed no differences in Cortisol levels, but had an effect on the abundance and size of the interrenal cells. Densities were equaled after hatching (200 alevins per replicate) to investigate the different densities of eggs on stress indices in rainbow trout alevins. An acute stress (air exposure of eggs for five minutes) was applied in three treatments two weeks after hatching, and samples were taken at 0, 1, 3, 6, and 24 hps (hours post stress). Cortisol content increased under low density in 1 hps and reached from 5.21 ± 0.13 ng g(-1) to 6.01 ± 0.18 ng g(-1) (P < 0.05). Cortisol levels increased under normal density in 1 hps from 6.03 ± 0.28 ng g(-1) to 10.84 ± 0.18 ng g(-1) (P < 0.05). In high density also Cortisol increased from 6.83 ± 0.23 ng g(-1) to 8.86 ± 0.26 ng g(-1) (P < 0.05). At 3 hps;, Cortisol level was returned to basal level under low (P > 0.05) and normal (P > 0.05) densities, but significantly decreased (P < 0.05) under high density. Results revealed that the Cortisol biosynthesis was observed in rainbow trout between eyeing to the hatching stage. An increase in the density of eggs until 7.65 egg cm(-2) impaired Cortisol secretion and feedback system in alevins. However, more studies are needed to identify the exact time for Cortisol synthesis ability from eyeing to hatching in this species.

In this study, effect replacement of fish meal with plant protein source soybean meal and baker's yeast in diet of juveniles (Mesopotamichthys sharpeyi) were studied. The tests began in October 2013 and ended in November 2013. Five treatments consisted of a control treatment (No Soybean meal and yeast), treatment 1 with 25%, treatment 2 with 50%, treatment 3 with 75% and treatment 4 with 100% replacing fish meal with soybean meal and baker's yeast with ratio of 1:1 in triplicates were examined. In each 300 liter water tank 40 Fish with initial average weight of 4/40 ± 0/29 gr were storage. Experimental fish were fed to satiation triple daily. At the end of the period, the activity of digestive enzymes (Lipase, Amylase and Alkaline phosphatase) and whole body biochemical composition were examined for assessment of fish. The results showed that activity of digestive enzymes and whole body biochemical composition in different levels of replacing fish meal with soybean meal and ...

The objective of this study was to evaluate the impact of short-term starvation and re-feeding on oxidative stress in Mesopotamichthys sharpeyi (Günther, 1874). After two weeks adaptation to new conditions, a total number of 270 fingerlings were distributed into nine 300-L fiberglass tanks, equipped with aeration system in three treatments including 4, 8 and 16 days starvation (each in 3 replicates). After starvation, all groups were fed for 32 days. At the beginning of trial and at the end of starvation and re-feeding periods, blood samples were collected, plasma was separated and activity of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX) and malondialdehyde (MDA) content were assayed. Based on the results, no significant difference was observed in SOD activity at the end of starvation and also after re-feeding between the different treatments. At the end of starvation the activity of the CAT and GPX increased significantly in 8 and 16 days of starvation g...