Iranian Scientific Fisheries Journal
Year:2007 | Volume:16 | Issue:3|Papers Count:19

Investigation on pearl oyster, Pinctada radiata growth and mortality parameters was carried out from September 2001 to October 2002 in west of Lavan Island using scuba diving method. Hinge length (H-LL) and Dorso-ventral measurement (D.Y.M) relationship was significantly (r2= 0.98) linear. Weight and dorso-ventral measurement relationship was shown to be W=0.0004 L 2.812(r2= 0.98). Asymptotic length (Loo) and growth rate (K) were estimated at 98 (mm) and 0.96 it respectively. More than 70 percent of the individuals were matured in April 2001. Mortality parameters including natural mortality (M), total mortality (Z) and fishery mortality (F) were estimated to be 1.21y-1, 1.68y-1 and 0.66y-1 respectively. Exploitation rate was estimated to be 0.27 in this survey.

The number of chromosome and karyotype of Garra rufa (Heckel, 1843) was determined by the conventional preparation and Gimsa staining technique, using gill epithelia and kidney cells. In this investigation, 5 specimens of Garra rufa were used which collected from Rodbal River, Firouzabad, Fars Province. Based on 30 chromosome spreads counts, the chromosome number was found to be 2n=50 with arm number NF=84. By using the ratio of long arm to short arm, the karyotype formula of 10 metacentric, 24 sub-metacentric and 16 sub-telocentric (10M +24SM +16St) was obtained.

Molecular comparison of two parasites Lernaea cyprinacea and Lernaea ctenopharyngodoni was carried out using RAPD (Random Amplified Polymorphic DNA) technique. A total of 43 Lernaea specimens belonging to the two species were collected from the Guilan and Khouzestan Provinces. DNA was extracted using the Phenol-chloroform method. The quality and quantity of DNA was assessed using 1% Agarose gel electrophoresis and spectrophotometer. Polymerase Chain Reaction (PCR) was conducted on the target DNA under specific conditions and PCR products were subjected to electrophoresis on polyacrylamide gels (6%). Polyacrylamide gels were stained using silver nitrate and DNA bands were analyzed with BioCapt software. The genetic analysis was conducted using POP GEN 32 software.Forty two primers, 10 nucleotides each were used for PCR reaction. Totally, 397 RAPD loci were counted on polyacrylamide gel where 349 identical loci were polymorphic of which some bands may be used as genetic markers for the identification of both Lernaea species. Data analysis on PCR products showed higher genetic variation (1.15%) of Lernaea ctenopharyngodoni in the Guilan Province as compared to that of the Khouzestan (0.0%).However, genetic variation (27.46%) of Lernaea cyprinacea in the Khouzestan province was 7.26 times higher than that of the Guilan province (3.78%). The two species showed a genetic differentiation of approximately 88%. Based on the observed molecular differences, we state that Lernaea ctenopharyngodoni is a genetically independent species from Lernaea cyprinacea.

The efficacy of different disinfectants (formalin, acetic acid, citric acid, chlorhexidine, sodium iodide, potassium permanganate, sodium hypochlorite and cetrimide-c) was examined on Streptococcus iniae, isolated from diseased fish of Fars province over the years 2002- 2004. In laboratory condition, minimum bactericidal concentration of disinfectants after 15, 30, 45 and 60 minutes were evaluated. Disinfectants were also tested under natural conditions with addition of a known concentration of bacterial suspension into water. An effective concentration of each disinfectant that had been determined in the first part of this study was added to the culture tanks and water samples were collected after 15, 30, 45 and 60 minutes to evaluate streptococcus isolation. A 3-5ppm concentration of chlorhexidine and sodium hypochlorite were powerful disinfectants against Streptococcus iniae. Acetic acid and citric acid were efficient in a concentration ranging between 350-500ppm showing very weak disinfectant activity against Streptococcus iniae. Results of tank tests showed that a bio-film is formed in the tanks may have significant effect on lowering the efficiency of disinfectants, thus most disinfectants were only effective at a higher concentration. Generally, sodium iodide and sodium hypochlorite were more efficient against Streptococcus iniae in tank condition than other disinfectants.

Sea cucumber is commercially important in the world. Reproductive biology of Stichopus hermanni in the coral reefs of the Kish Island was investigated using 252 specimens. Morphology of the gonad of the sea cucumber species of the Kish Island was found to be similar to other species. We showed that the gonad colour is an unreliable character for sex determination except in maturity stage. We reported the gametogenesis sequence of events and found a sex ratio of 1:1 for the species. The sequence begins late in winter and continues until summer. The active stage of gametogenesis coincides with increasing photoperiod and temperature. Very little spawning activity out of season was noticeable and the maximum spawning was seen in summer. Average body length at first maturity was found to be 310 mm and the diameter of mature oocytes was 200 mm. Oocytes moved upward at a rate of 20-30mm per minute that confirms divers' reports of the abundance of developing Stichopus hermanni embryos near the water surface.

We collected 100 specimens of Persian sturgeon broodstocks propagated in Shahid Marjani Fish Culture Center to study internal parasites during March, April, and May 2005. The center is located in the southeast of the Caspian Sea. Three different parasite species were recovered from digestive tract (stomach and intestine) of the fish. Cucullanus sphaerocephalus, Skrjabinopsolus semiarmatus showed the highest incidence and highest mean intensity (with prevalence of 80% and 55% respectively) but Leptorhynchoides plagicephalus had the lower prevalene 2 %. The prevalence of S. semiarmatus and C. sphaerocephalus were higher in males than in females whereas the intensity of these parasites was higher in females than in males. Statistical analysis of data showed a significant relationship between the occurrence of S. semiarmatus and the sex of the fish. There was a significant relationship between the occurrence of C. sphaerocephalus and the length of the fish (P £0.05). Forty nine percent of the fish had less than 10 worms. It was also found that the internal parasites of A. persicus in the southeast of the Caspian Sea are the same as those found in the southwest but the diversity of parasites were fewer in the former.

Sturgeon fish take long time to mature sexually and determination of sex and sexual maturity stages is important in artificial rearing of the fish. Sex determination by macroscopic method has thus far been impossible for the fish at juvenile stages. Gonad biopsy and its histological examination is one way for detecting male and female sturgeon fishes. To do so, we collected gonad samples from 13 five year old and 17 six year old specimens of the cultured Acipenser nudiventris. Samples were studied by light microscope after fixing and histological practices.Of the 13 five years old specimens, only 3 (23.1%) were male and 10 (76.9 %) were females. From 17 six years old fish, 10 (58.8%) were males and 7 (41.2%) were females. Histological studies showed that all male fish were at stage IV, but 5.8 % of all females were at stage I, 41.2 % were at stage II and 53 % were at stage II-III of sexual maturation. We also showed that in the studies sample, males reached maturity sooner than females.

To determine the digestive capacity of larvae in Caspian brown trout and Rainbow trout, activity of digestive enzymes including pepsin, trypsin, chymotrypsin, a-amylase, lipase and alkaline phosphatase in 2/3  and complete yolk-sac absorption stages were assessed. Results showed enzyme activity was significantly higher in Rainbow trout than in Caspian brown trout at 2/3 yolk-sac absorbtion stage (P<0.05). Enzyme activity was increased in Caspian brown trout at complete yolk-sac absorption. The enzymes pepsin, trypsin, a-amylase, lipase and alkaline phosphatase were higher in Caspian brown trout than in Rainbow trout but of these only a-amylase was significantly different between the two (P<005). Chymotrypsin was lower in Caspian brown trout than in Rainbow trout but not significantly (P>0.05). At the start of feeding, activity of pepsin, trypsin, chymotrypsin and alkaline phosphatase were higher in Rainbow trout than in Caspian brown trout but the difference was not significant for pepsin (P>0.05) whereas trypsin, chymotrypsin and alkaline phosphatase were significant different between the two (P<0.05). A-amylase was lower in Rainbow trout than in Caspian brown trout but not significantly (P>0.05). Lipase was similar in both fish. Higher enzyme activity in Rainbow trout than in Caspian brown trout at 2/3  yolk-sac absorption shows the high ability for digesting food in rainbow at this stage. Also, low enzyme activity in Caspian brown trout at this stage is believed to be one of the reasons for low food intake and digestion at this stage.

To decrease cost of the commercial formulated food in culture of freshwater crayfish (Astacus leptodactylus), inexpensive additives like Zeolite can be incorporated into food. An eight week experiment was conducted on juvenile freshwater crayfish to determine the suitable level of Zeolite in food of the fish. Four levels of Zeolite 0.5, 1, 1.5 and 2 percent with three replications each and a digestible energy (DE) of 3500Kcal/kg diet were formulated. Five hundred and forty juvenile crayfish weighing 2±0.8 grams each were randomly distributed between twelve aquariums of 250 liter capacity. Juveniles were fed on pellet foods at 8 percent of body weight four times a day. Different nutritional responses in terms of weight gain (WG), Relative growth rate (RGR), food conversion ratio (FCR), protein efficiency ratio (PER) and survival rate (SR) were calculated and compared. WG, RGR and SR in treatments (1, 2, 3, 4) were not significant statistically (P>0.05) as compared to the control group. FCR and PER improved with Zeolite addition and in treatment four with 2 percent Zeolite level showed significant difference (P<0.05). No significant difference was found between treatments 1, 2, 3 and the control diet. Body carcass composition assessment of the crayfish fed on different levels of Zeolite was not significantly different to that of the treatment.

Diversity, distribution, catch per unit effort (CPUE) and population structure of sturgeon stocks in the Iran coastal areas of the Caspian Sea waters less than 10 meters deep was studied during 2003-2005. We also recorded total length and weight of all sturgeon specimens in five regions which was done by gillnet with mesh sizes 26, 33, 40, 60, 100, 150 mm during seasonal sampling from autumn 2003 to summer 2005 in the south of the Caspian Sea. Totally, 301 fish were sampled in 2003-2004 including Acipenser persicus (244) A. stellatus (35), A. nudiventris (13), and A. guldenstaedti (9). A total of 412 fish were sampled over the years 2004-2005 of which 369 were A. persicus, 14 were A. stellatus, 7 were A. nudiventris, 21 were A. guldenstaedti, and one was Huso huso. In 2003-2004, the CPUE for A. persicus, A. stellatus, A. nudiventris, A. guldenstaedti were 4.07, 0.58,0.22  and 0.15 respectively, whereas for A. persicus, A. stellatus, A. nudiventris, A. guldenstaedti, and for Huso huso the CPUE was 6.15, 0.23, 0.12, 0.35 and 0.02 respectively. In 2003-2004, the mean total length was 26±10.86 cm A. persicus, 49.7±14.5 cm for A. stellatus, 38±13.79 cm for A. nudiventris and 43.1±10.25 em for A. guldenstaedti. In 2004-2005, the mean total length was 21.0±18.56, 5205±25.53, 30±13.09, 23.37±12.2 and 50 cm for A. persicus, A. stellatus, A. nudiventris, A. guldenstaedti, and Huso huso respectively.

Tashk Lake is located in the protected zone of the Bakhtegan Lake in the Fars Province and is a shelter for wildlife. This place is very important environmentally and ecologically. Among entering pollutants to this lake via rivers and side villages, polycyclic aromatic hydrocarbons (PAHs) compounds are noteworthy which are very harmful to humans and others creatures alike. We used naphthalene and anthracene as the only source of carbon to isolate PAHs degrading bacteria from three predefined stations. We found Pseudomonas sp. as the only PAHs degrading bacterium in the water and sediments of the lake. At the station 1 (Dehzir), the mean isolated bacteria acting on naphthalene and anthrecene were 27 and 23 in each ml of water and 57 and 47 in each gram of sediments, respectively. At the station 2 (Tashk), the mean isolated bacteria were 67 and 57 in each ml of water and 120 and 113 in each gram of the sediments which acted on the two carbon sources respectively. At the station  3(Gomban), the figures were 127 and 113 for water and 163 and 147 for the sediments respectively. We found meaningful differences in the mean number of degrading bacteria in the water and sediments of the three stations (P<0.05). The salt concentration for Pseudomonas sp. optimum growth and PAHs degradation was found to be around 6% with and increasing rate of degradation over time.

Length, age frequency, von Bertalanfi growth parameter, reproduction and absolute fecundity of two populations of killifish (Aphanius sophiae) from Cheshmeh-Ali of Damghan and Shour River of Eshtehard were studied monthly from October 2004 to November 2005. There was no significant difference between sex ratios of the two populations (X2=0.679, P=0.410). Age and length frequencies revealed that female fish of Cheshmeh-Ali were taller and longer-lived than those of Shour River. Maximum of Gonadosomatic index of Cheshmeh- Ali fish was in May while in the case of Shour River, it was in April. The absolute fecundity showed no significant difference using ANCOV A whereas egg diameter of Cheshmeh-Ali population was significantly bigger than Shour River population (P<0.001).

The effects of exposure to Zinc and Copper in developing from nauplius to adult stages in two species, A. urmiana and A. franciscana were studied. The growth and lifespan of the specimens under treatments also have been investigated. During the period of the experiments, both species of Artemia were exposed by Zinc-treated groups (23, 68, 114 mg/l) and also copper-treated groups (13, 25, 38 mg/l) and compared with control group without any metal treatment. However, in treatments with Zinc and Copper concentrations, lifespan was reduced in comparison with that of the control treatments. Results showed that Zinc and Copper have toxic effects on A. urmiana and A. franciscana. Although the resistance of both of them was high, but A. urmiana was more endure than A. franciscana. It is, suggested that the two Artemia species might have adopted a strategy to speed up growth and reproduce before metal pollution can cause death for them. Also, this study indicated that Zinc was less toxic than Copper for the two species investigated.

Nursery grounds of Penaeus semisulcatus were surveyed in the main coastal prawn catching areas of the Bushehr waters, Persian Gulf, from July 2003 to March 2005. Sampling stations were selected in waters less than 10m deep and juveniles were collected using a small vessel powered by a 150 hp outboard engine that was equipped with a small beam trawl net with 10 mm mesh size. Prawns less than 15 mm carapace length were classified as juvenile.The catches of P. semisulcatus juveniles were abundant at only a few sites in the shallow waters around southern (Motaf) and middle (Helaileh) regions of the studied area. The maximum number of juveniles was seen in July and November 2003 that amounted to 596 and 24 specimens, respectively. In April and June 2004, only 43 and 85 specimens were recorded respectively. Juvenile abundance was higher in vegetated sites as compared to other sites during this study. The study supports the fact that the extensive shallow reef and open flat coastline areas that are covered with grass and algae communities are critically important for the prawn and should therefore be protected from pollution, fishing gear damage and industrial development.

Physiological changes in cortisol, glucose, testosterone and 17 b-estradiol levels were studied in Rutilus frisii kutum spawners during transportation in April, 2006. The fish were held in plastic tanks in two treatments 1fish/2L and 1fish/1L sea water in several replications. Their blood was collected at 0, 10, 20, 30 and 60 min after capture. A significant increase in concentration of cortisol and glucose was found with the transport time. Initial levels of cortisol were similar in the two treatments ranging between 480.7±22.34 and 476.6±18.61 ng/ml respectively. These values increased gradually and reached a peak at the end of the transport (683±1 and 801.3±11.2ng/ml in treatments 1 and 2) with significant difference between the two (P<0.01). Glucose also changed similar to cortisol. Testosterone and 17b-estradiol concentrations decreased significantly with time. Initial levels of testosterone were 18.6±1.3 and 17.8±1.2ng/ml in the two treatments but decreased significantly at the first 10 min (P<0.01). Initial levels of 17 b-estradiol were 59.23±0.52 and 58.1±0.75 ng/ml but its levels decreased up to the end of transport. Our results clearly indicate the effect of stress during transportation.

An investigation was carried out on the sustainablity and growth rate of Rutilus frissi kutum larvae in polyethylene tanks in Ghazian Aquaculture Research Station, Guilan Province. The results were compared to those recorded for the currently used tanks including fiberglass and glass aquariums. Three treatments each with three replications were designed and the tanks were stocked with 30 fishes, with an average initial weight of 650 to 746 mg. The tanks were filled with 70 liters of water and the experiment was conducted for 60 days. The fish were fed with concentrated food during the rearing period. The fish showed an increase rate of 625.88, 643.54 and 659.48 mg in fiberglass, aquarium and polyethylene tanks, respectively. No significant difference was observed in the indices special growth ratio (SGR), food conversion ratio (FCR) and weight gain (P>0.05). The research indicated that the high-density polyethylene tanks made are more suitable for Rutilus frissi kutum culture than fiberglass and aquarium tanks.

The white leg shrimp (Litopenaeus vannamei) was introduced to Iran in 2005 by Iranian Fisheries Research Organization. In this study which was carried out at the Iran Shrimp Research Center in Bushehr, shrimp growth in three density treatments 50, 100 and 150 PCs/m3 with three replications were compared. The experiment was conducted for 50 days in fiberglass tanks (three ton capacity). Daily tests of salinity, pH, temperature and dissolved oxygen were also carried out. We found that the mean salinity, pH, temperature and dissolved oxygen were 30.2ppt, 7.9, 25.5 degrees centigrade and 6.2 mg/l respectively. We recorded a mean weight of 2.96, 2.17 and 1.87 grams for shrimps in 50, 100 and 150 PCs/m3 respectively. The statistical analysis indicated that there was a significant relationship between mean weight and density of shrimps (P<0.05). The maximum survival rate 95.93% in150 PCs/m3 treatment indicates the tolerance of the species to high density culture. The minimum FCR 0.8 was seen in 50 PCs/m3. The mean FCR 0.81, 1 and 1.1 and the mean survival rate 87.56, 95.11 and 95.93 were seen in 50, 100 and 150PCs/m3 treatments respectively.