Iranian Journal of Fisheries Sciences
Year:2001 | Volume:3 | Issue:2|Papers Count:10

The effect of different sublethal concentrations of diazinon at 1, 2 and 4 mg/L on some hematological and biochemical parameters of grass carp (Ctenopharyngodon idella) weighing 850±155g was studied after 1, 7, 15, 30 and 45 days post exposure to the toxicant as a bath for 12 hours at 18-22 C. In one day exposure fish to the toxicant, the values of neutrophiles exposed to 2 and 4mg/L were significantly higher than control fish, while lymphocyte and monocyte counts in fish exposed to 2 and 1mg/L were significantly lower than control one (P<0.05). Also, no significant differences were found in levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) among experimental fish and between experimental fish and control one (P>0.05). Seven day after exposing fish to the toxicant, values of WBC in all experimental fish were significantly higher than control fish, while level of neutrophiles in fish exposed to 1mg/L and values of lymphocytes in fish exposed to 2 and 4mg/L were significantly higher and lower than control fish, respectively. Also, values of ALT, AST and ALP in all experimental fish were significantly lower, higher and lower than control fish, respectively (P<0.05). Fifteen days post-exposing fish to the toxicant, values of MCH, ALT and AST in all experimental fish were significantly lower than control group, while levels of WBC and RBC were significantly higher and lower than control fish, respectively (P.<0.05). Thirty days post-exposing fish to toxicant, the values of neutrophiles, WBC and RBC in fish exposed to 2 mg/L were lower than control fish (P<0.05). Also, levels of heterocytes and lymphocytes in all experimental fish were significantly higher and lower than control fish, respectively. Also, levels of AST, ALP and LDH in almost all experimental fish were significantly lower than control fish (P<0.05), while no significant differences was found in the level of AST among experimental fish and between experimental and control fish (P>0.05). Forty five days post-exposing fish to the toxicant, the values of WBC and heterocytes in all experimental fish were significantly higher than control one, while levels of lymphocytes, ALT and ALP were lower than control fish (P<0.05). Also, the level of AST in fish exposed to 4mg/L and level of LDH in fish exposed to 1 and 4 mg/L were significantly lower than control fish (P<0.05).

The Caspian frisian roach (Rutilus frisii kutum), economically a very important fish species in Iran, is propagated in fishponds, reared into the rivers in fingerling size and then harvested from the Caspian Sea in adult stage. We found six monogenean parasites on the Caspian frisian roach including five Dactylogyrus spp. on fingerlings cultured in fishponds and rivers and two Dactylogyrus spp. on wild adult specimens living in Caspian Sea. With the exception of D. frisii that proved to be the most common monogenean and found a good milieu for its development both in flowing rivers and in Caspian Sea, the other parasites occurred either in Caspian Sea (D. nybelini) or in freshwater (D. haplogonus, D. rarissimus, D. suecicus, D. turaliensis). The objectives of present research work are to clear the sources of infection of Caspian frisian roach fingerlings to monogenean parasites and to recommend approaches for the improvement of pond technology in order to diminish the intensity of parasites without having to use high amounts of organophosphate insecticide in ponds.

This paper presents the results of study on age, growth, mortality rates and yield-per-recruit of Beluga (Huso huso) living in Caspian Sea. The mean length of successive years, mortality rates and yield-per-recruit studies indicated that at present the resource is under heavy fishing pressure. For the female Beluga growth was regarded as comprising of three stages, and the von Bertalanffy parameters were calculated for juveniles, for middle stanza (<8 to 24 years), and third stanza (>24 years). The value of K was the highest (0.065) for the first stanza, lower for the middle (0.029), and the lowest for the third one (0.023). Total mortality of female and male Beluga estimated from the descending limb of the catch curve using the combined data (1990-1994) were: for females, Z=0.48 per year, r=0.982, P<0.01 and for males, Z=0.38 per year, r=0.992, P<0.01. Natural mortality for female and male Beluga was estimated using Richter and Efanovs formula as 0.03 for females and 0.05 for males. Values of fishing mortality (F) were estimated from Z and M, using values of Z from catch curves and M estimated from Richter and Efanovs formula as 0.045 and 0.33 for female and male, respectively. Yield-per-recruit curve was produced for female and male Beluga. It was found that the maximum Y/R (Maximum sustainable yield-per-recruit) were produced at Fs =0.07, for female and Fs=0.16 for male. Inspection of the yield-per-recruit model for the Beluga in the Caspian Sea showed that the fishing mortality should be stopped for this species in the Caspian Sea. This result confirms the over-fishing of the sturgeon in Caspian Sea. Several other authors such as Smith (1990), Birstein (1993), Bemis and Findeis (1994), Dumount (1995) and current catch data, have confirmed the overfishing of the Beluga in the Caspian Sea.

The gold spot mullet fry, mean length of 1.30 0.048 cm and mean weight of 0.05 0.007 g were collected from coastal creeks of Ratnagiri (Maharashtra, India) and then acclimatized to 20 ppt salinity. They were observed for the response to the two anaesthetics: Clove oil and Sodium bicarbonate. Effective dosage of both the anaesthetics viz. clove oil and sodium bicarbonate for the induction and recovery worked out to be 80 and 4000 ppm, respectively. Both the anaesthetics clove oil and sodium bicarbonate were found to be cost effective as compared to MS-222.

Identification of different species of oceanic and neritic squids in Iranian waters of Oman Sea was carried out from December 1996 to February 1997. The trawl surveys were conducted during a 12-months period. Fishing was also undertaken by Mid-water and bottom trawl for species confirmation purposes in deep (200-350m) and shallow (0-100m) waters to collect enough specimens that could be used for later species identification. The RN Ferdows-I was used for sampling with an approximate hauling speed of 3.0 knots.Three oegopsid species including Ancistrocheirus lesueuri, Liocranchia reinhardti, Sthenoteuthis oualaniensis and neritic squid, Loligo duvauceli were identified. Another loliginid squid different from Loligo duvauceli was also observed. A. lesueuri (Enoploteuthidae Family) and Liocranchia reinhardti (Cranchiidae Family) are here reported from this area for the first time. Neither was any report about these two families of oegopsid squids in Oman Sea nor Persian Gulf.

In order to demonstrate filtration rate of edible cockle Cerastoderma edule under different salinity and temperature conditions, two groups namely healthy and parasited with Labratrema minimus (Bucephallidae; Digenea) were compared. Results showed that the parasited ones had difficulties in adaptation to the extreme conditions of salinity and temperature. Our results also showed that a healthy cockle could filter 78 ml min-1g-1 Flesh Dry Weight (FDW) seawater at 200e temperature and 34% salinity while an infested one processed 15.4 ml min-1g-1 FDW under the same conditions. In low salinity, which could happen during a rainy day and low tide, the healthy cockles processed 14.5 ml min-1g-1 FDW while infested cockles filtered 18.9 ml min-1g-1 FDW. Differences were not significant, however. Filtration rate of healthy cockles at a constant salinity but high temperature was 101.9 ml min-1g-1 FDW while the infested ones rated 27.2 ml min-1g-1 FDW. There was not a significant difference between their filtration rates at 20oC and 30oC. Our results showed that the parasited cockles were unable to adapt to extreme conditions when an increase in temperature or a decrease in salinity occurred. If these results could be extrapolated to natural situations, the ecological cause of mortality due to parasites could be proved and explained.

In this study, the benefits of using the first Iranian made GnRHa [D-Ala6 des Gly10] mGnRH ethylamide, to induce spermiation in male rainbow trout, Oncorhynchus mykiss, were evaluated. In addition, its effect on acceleration and synchronization, quality and quantity of milt and the plasma Testosterone (T) fluctuations were examined.For these purposes, 40 non-spermiating male rainbow trouts were injected with a mammalian gonadotropin releasing hormone analog (GnRHa) preparations of 0 (control), 30, 40 and 80 mg/kg B.W. or vehicle (propylen glycole). Spermiation was very synchronous and accelerated in treated groups. Six days after first injection, the cumulative spermiation rates reached respectively 40, 49 and 79% in injected groups (i.e. 30 to 80 mg/kg B.W.) while none of the control fish was spermiated. GnRHa injections advanced spermiation and reduced the average time to spermiation from 16±3.67 days for control group to14.3±2.2, 9.2±0.75 and 6.6±0.29 days for treated groups, respectively (p<0.05).The average volume of total expressible milt of male fish increased significantly after treatment with GnRHa from 8.29±1.59 ml/kg B.W. for control to 11.42±1.55, 14.39±1.55 and 17.14±1.55 ml/kg B.W. in groups 2 to 4, respectively (P<0.05). The fertilization and survival rates to the eyed stage did not show any significant difference among the groups (p>0.05). Circulating levels of testosterone (T) prior to the GnRHa treatment were relatively low in all groups. Treatment with GnRHa induced significant increase in plasma T after 12 h, increasing it to 43.43±5.82, 38.66±5.63, 39.72±5.07 ng/ml in groups 2 to 4, respectively, which were higher than T levels for control (i.e. 24.58±7.13 ng/ml) P<0.05. These levels remained high up until 48 h in treated groups; but after this time, T levels reduced to the basal levels of time 0, except in group 4 which had received its second GnRHa injection at time 48.

Phytoplankton species composition as well as amount of Chlorophyll-a and their relation to physico-chemical parameters were studied. The samples were collected monthly from October 1996 until September 1997 in two stations, i.e. Lavan and Douberkeh coastal waters. In this study, 65 phytoplankton species related to 3 groups of diatoms, dinoflagellats and Blue-Green Algae (24 genus and 44 species of diatoms, 6 genus and 18 species of dinoflagellats and 3 genus blue-green algae) were identified. Diatoms and dinoflagellats were abundant during periods of low salinity and temperature (November-May), while blue-green algae were abundant from July till September.Although the amount of chlorophyll-a was higher during the periods of low salinity and temperature, there was not statically significant difference between the two stations and different seasons (P>5%). Also, there were not significant differences between such physico-chemical factors as temperature, salinity, pH and oxygen content. Transparency between the two stations showed significant differences (P<5%). Correlation matrix test showed no relationship between physico-chemical parameters and the amount of chlorophyll-a in two stations. The results suggest that increasing the temperature and/or salinity cannot cause significant reduction in chlorophyll-a amount in Lavan and Douberkeh regions.