نشریه پژوهش های ماهی شناسی کاربردی
سال یکم شماره 4 (زمستان 1392)

Early development and Allometric growth pattern is a common feature during early development of fish larvae. This research was conducted to investigate the allometric growth patterns and morphological development of the Green Terror (Aequiden srivulatus)¡ a valuable aquarium species¡ during early development up to 1266 hours post hatching (Hph). Hence¡ its morphological changes during its ontogeny were described. Morphometric data parameters were obtained from 2D pictures of specimens using the software ImageJ and allometric growth pattern was calculated as a power function of total length using non-transformed data: Y=axb. Results revealed that during early development after hatching¡ the allometric growth pattern of head¡ snout¡ eye diameter and tail regions were positive and they changed into isomertic pattern about 156-570 Hph¡ reflecting the dominance of life functions including swimming¡ respiration and sensory systems during this period. Results also showed that at these turning points the growth of most morphological features of body have been occurred along with exogenous feeding. Based on the finding of this study¡ early development of this species can be divided into four stages of Eleuthero-embryo (up to 120 Hph along with yolk sac absorption)¡ Propterygio-larval (156 Hph)¡ Pterygio-larval (570 Hph) and Juvenile.

In order to identify and estimate the population of fish and its relationship with environmental factors, sampling was done seasonally from summer 2009 to spring 2010 by electrofishing (DC, 200-300V) in Shirabad stream. Results show four identified species of fish including: Spirlin (Alburnoides eichwaldii), Sand Goby (Neogobius fluviatilis), Loaches (Paracobitis malapterura) and Chub (Squalius cephalus). The estimated population was calculated as for density in different seasons. Sand goby and Spirlin were caught in different seasons in a way that Sand Goby were estimated as the dominant species with the highest frequency (52%) in all four seasons. However, in some seasons Loaches and Chub were observed. In Shirabad stream, the presence of Sand goby was significantly and positively correlated with turbidity and water temperature and the presence of Chub had the highest positive correlation with pH levels. In addition, the presence of Spirlin were positively correlated with stream width, channel incision and water depth The presence or absence of Loaches were correlated to environmental factors such as phosphate and water discharge rate.

In order to investigate the effect of protexin probiotic on resistance of Sobaity seabream Sparidentex hasta to temperature and salinity stresses, an experiment was carried out with 240 pieces of fish fingerling with average initial weight of 2.99±0.87 g for 10 weeks. Experimental treatments were consisted of four levels of 0, 0.5, 1 and 2 g protexin per kg of diet, each with three replicates in a completely randomized design. During the experimental period, feeding was performed by hand on a daily basis based on full sanitation at three intervals. At the end of the experimental period, the fish were exposed to two temperatures of 15 and 37°C for 30 minutes in thermal stress test and to two salinity levels of 12 and 70 ppt for one hour in salinity stress test. The results showed that in 1 and 2 g protexin treatments, the survival rate in high temperature, low temperature and high salinity stresses increased significantly compared to the control group (P0.05). Among the different levels of protexin used, the most effective dose on survival rate in temperature and salinity stresses in Sobaity seabream fingerling was the level of 2 g protexin per kg of diet. The results of the present research revealed that the dietary supplementation of protexin probiotic could favorably affect the survival rate in high temperature and salinity stresses in Sobaity fingerling.

In this study, morphological characteristics of two populations of Pike (Esox lucius) were compared in Anzali and Amirkelayeh wetlands at Southern Caspian Sea basin using morphometric and meristic characters. A total number of 57 speciemens of Esox lucius including 28 and 29 specimens from Anzali and Amirkelayeh wetlands, respectively, were caught by fyke nets. In this study 32 morphometric and 11 meristic characteristics were investigated and standardized first with Beacham formula, and then the data were subjected to a Principal Components Analysis (PCA), Discriminant Function Analysis (DFA) and UPGMA dendrogram. Based on PCA results, the two populations of Esox lucius were differentiated by 9 principal factors in morphometric characters. DFA revealed that the two populations were distinct in morphometric characters (87%). Also, the UPGMA dendrogram separated E. lucius populations of the Anzali and Amirkelayeh wetlands. It is possible that the different habitat conditions were the cause of distinct fish population of the two wetlands.

Sperm motility is one of the fundamental indices in sperm quality assessment. This study was carried to determine the sensitivity rate of Schizothorax zarudnyi spermatozoa at different concentrations of copper and lead. To do so, sperm from four male mature fish were exposed to 0, 0.01, 0.1, 1, 10 and 100 mg/L of PbCl2 and CuCl2 separately (6 treatments of CuCl2 and 6 treatments of PbCl2) and sperm motility percentage and total motility duration times were compared. Results show that sperm motility parameters decreased significantly with increase of pollutant concentration. Over time, with decrease of percentage of motile spermatozoa, their sensitivity is evident even to less concentration. Due to the fact that changes of sperm motility can influence the reproduction efficiency rate of breeder, increasing exposure to copper and lead will decrease quality of sperm of Schizothorax zarudnyi in the reproduction time.

Parasites influence population structure and population control of fishes by effecting their survival, reproduction and migration behavior. This study has been carried out to focus on relationships of the host and pathogen, emphasizing on the Posthodiplostomum cuticola in native fishes of Zaringol stream over a period of a year (December, 2009 to October, 2010). 1346 specimens were caught by electrofishing (1.7 KW, 10 A and 200-300 V) from 14 research stations along the stream seasonally. Fish health condition was checked through observing the surface of their body and fish populations were estimated by Lecren method. Sampling from Macro-invertebrates also was done by surber sampler (30cm×30cm) and were fixed in formalin (4%). Results showed that the maximum frequency of fishes (individual per square meter) belongs to Capoeta capoeta gracilis (1.15) at station 12 (1.309) in summer (2.36). The results obtained for infested fish (relative frequency) in Neogobius fluviatilis Pallasi at station 12 in winter were 90.9,46 and 53, respectively. Maximum frequency of 8 snails families (individual per square meter) was observed at station 12 (2.18) in winter (1.4). Results show that distribution of fish species based on their biological demand, vegetation cover around the stream, low current velocity at station 12 side by side desirable water temperature, and occurrence of flood in winter have important effect on first intermediate host (snail) assemblage and help the parasite complete its life cycle.

The total number of 460 specimens of Cyprinus carpio was collected from the product of fishery corporation companies located in Gorgan Rud estuary between December 1987 and June 1988. After doing the biometry processes, age of specimens was determined using scales and the fecundity of the fish is calculated by weighting and numerical methods. The mean length and weight of the fish were 466.7±79.92 mm, 1494.4±813.38 g and 430.04±85.26 mm, 1105.62±694.95 g for female and male ones, respectively. Also, the mean values of condition factor were 1.07±0.09 in females and 1.55±0.17 for males. In addition, the dominate age group was observed as 5 (33.48% of total numbers) and 6 (45.2% of total numbers) for females and males, respectively. Weight- length relationship showed a positive allometric growth (b=3.025) for females and a negative allometric growth (b=2.92) for males. The Von Bertalanffy growth equations were calculated as: Lt= 1054 (1-e-0.11(t.041)) and Lt = 901(1-e-0.12(t.402)) for females and males, respectively. Results also showed that growth performance index was equal to 5, mean gonadosomatic index in females was 16.98±2.46 and the maximum value was observed during the end of April to May and finally, average absolute fecundity for Cyprinus carpio was 185254±75778 eggs.

This study was conducted to investigate length-weight relationship and determine condition factor of Squalis cephalus in Shohadaye Songhor Dam reservoir in Kermanshah province. To this end, 113 specimens were caught by gill net with the mesh of 2 to 5 centimeter between July 2011 and December 2011, on a monthly basis. The age range of 2 to 6 were observed in this population and the sex ratio (M: F) was determined 1:0.24. The total length of male and female specimens ranged between 167-281 and 211-254 mm, and the total weight of males and females were ranged from 62-317 to 115-240 gr, respectively. The mean condition factor of males (1.65±0.18) was higher than that of females (1.63±0.13), but the differences between sexes were not statistically significant. The calculated length-weight relationship for this species could be explained by the following equation for male, female and population: W=7e-06L3.112, W=4e-05L2.83 and W=9e-06L3.08, respectively. According to b index amounts in females (b=2.82) and males (b=3.12), the growth pattern for this fish is reported negative isometric and allometric growth for males and females, respectively. As a result, it was observed that fish in Shohadaye Songhor Dam Lack attained higher length compared to the fish of the same age range in other water resources. This may be an indication of better ecological condition and higher food supply in Shohadaye Songhor Dam reservoir.