Iranian Scientific Fisheries Journal
Year:2004 | Volume:13 | Issue:1|Papers Count:18

This study was carried out from April 1999 to March 2000 in Dez dam reservoir located at North Khouzestan province. From the total number of 607 specimen of collected fish, 267 and 64 were males and females respectively, and276 specimen were immature. Samples were caught by hooks and gill nets. Length range of females was 156-1350 mm and their weight range was 31.7-26500 g. Males ranged 183-1065mm in length and 48-12208g in weight. The males showed more ranges in length and weight comparing to females. The spawning period is very short and occuring in spring after flooding of the river and increase in the reservoir water level. This species is a total spawner and eggs are release in upstream regions and reservoir shallow waters on bottoms gravels. Spawning occurs in 24°C. Fecundity was intermediate. Sex ratio was 4.2:1.0 (male/female). Males show a faster maturation. According to the ratio of gut length to the body length, it seems to be an omnivorous species, but all samples were found to have fish in their stomachs (100%). Feeding intensity was higher in males. Annual growth is slow and asymptomatic length is more than 2m. Relative growth in weight is not in accordance with growth in length for various length groups, and relative growth in weight is increased with increasing of fish length. Growth of this species is positive allometric type. Various length groups were observed in examined specimens. It I seems that it has a longer reproductive life comparing to its pre-maturation life. Relative fatness is higher in females.

During one months study on 33 digestive tracts of Emys orbicularis, caught from pond culture of sturgeon fingerling. All together, three different parasitic worms were identified. These worms belong to genera Anisakis, Camallanus and Hysterothylacium. Anisakis obtaind only from stomach tissue, Camallanus from intenstine and Hysterothylacium infected both mentioned organs. The prevalence and intensity of Anisakis, Camallanus and Hysterothylacium were 21.2%, 3.7%, 36.3%, 4.4, 15.1 and 26.0 respectively.

This study was conducted the optimum salinity for culture of White Indian shrimp juvenile (Penaeus indicus) in Bandar Emam Khomeini fisheries research station in summer 2002. Five levels of salinity (10, 20, 30, 40 and 50 ppt) with four replicates were used in this trial. 35 specimen of White Indian shrimp juvenile (PL35) with mean weight of 0.26:t0.024g have been cultured for 60 dayes in 300 liter fiberglass tanks that each tank was filled with 200 liters water and stocked with 20 shrimp juveniles for estimating the growth and survival rates in different salinities. Results showed that salinity was significantly (P<0.05) affected on growth and survival of P. indicus juveniles. Highest increase in mean weight and the maximum final mean weight of juvenile, highest increase in carapace length and maximum C.L. and also the lowest FCR observed in 30 ppt salinity. According to the obtained results, it can be suggested that the optimal salinity for culture of White Indian shrimp is between 20 and 30ppm.

This study designed with objective on shrimp population structure biomass, management aspects and meterological factors that affect on them. This investigation was carried out monthy by swept area method from Bandar Abbas to Sirik area waters. The optimum time for opening fishing season in Hormuzgan province waters in years 1999,2000, 2001 and 2002 respectively were about 9/10/1999, 4/10/2000, 2/10/2001, 28/9/2002 and total biomass for years 1999 up to 2002 were 731, 1350, 636 and 1708 tonnes, respectively.The Pearson corrlation test between catch per unit of effort (CPUE) and meteorological parameters showed the significant corrlation for mean temperature and moisture (P < 0.05) and for rainfall and evaporation did not show any significant corrlation.

During years 1999-2001. a series of sampling was carried out in Sefidrud river to study morphometric and meristic characteristics of Caspian Vimba. 149 specimen were collected and then necessary measurments were considered and following results were obtained:T.L= 171.2±31.6mm, W= 62.9±19.7g, age= 3.49±0.9 year, average number of scales on lateral line = 50.83±1.8, branched ray of dorsal and anal fins = 7.96±0.2 and 17.58±1.0 respectively. The mean morphometric measurments with respect to body standard length (%) were: head length 24.47±1.9, eye diameter 6.10±1.07, body maximum depth 26.17±1.4, dorsal fin heigth and length 20.22±1.5 and 10.96±0.8, anal fin heigth and length 12.66±0.8 and 18.17±1.5, pectoral fin length 18.17±1.2, ventral fin length 14.97±1.1, pecto-ventral fins distance 24.18±l.7 and ventral-anal distance 20.00±1.5 and pre-dorsal distance 52.21±1.7. Adults and juvenils showed difference in 2 meristic and 15 morphometric parameters. On the other hand, the adult males and females showed difference in 16 morphometric parameters (esp. body depth, lengths of dorsal, pectoral, pelvic and anal fins). Also, adult males have a series of fine epithelial turbecles on head and body and their color is darker with more reddish anal and ventral fins.

A total of 150261 kg of different species were caught in Mahabad reservoir of which 101123.5 kg (tantamount to 67.3 % )was silver carp in the fishing season of 1998-1999. From the beginning of the fishing season, fishing effort of only active fishing cooperative were 69 times beach seine haul and for gill net with stretched mesh size of 7 to 15 cm, 2530.7 fishing effort unit (each unit is equal to 100m gillnet for 24 hours).The mean fork length and weight of Silver carp were 51.15±12.07cm and 2429±2272.1g respectively.Exponential Length-Weight relationship for this species was calculated W=0.013 L 3.04 (R2 = 97.64, n=714) which in this equation W is the total weight of fish in g and L is lenght in cm.The Von-Bertalanfy(s) growth parameters (L¥ , K, to) based on length and age data were estimated as: L¥ = 150cm, K = 0.128 per year, to = - 1.141 years). The instantaneous rate of total (Z), Natural (M) and fishing (F) mortality coefficients were 1.68 year-1, 0.22 year-1 and 1.46 year-1 respectively. The exploitation ratio (E) was calculated as 0.82. The biomass of this species was calculated as 158.5 tonnes and according to Gulland(s) formula, the MSY was estimated as 68 tonnes which is less than the catch of this species and decreasing of the fishing effort is recommended.

Mullet and other bony fishes are caught by beach seine in Iranian coastal zone in Golestan, Mazandaran and Guilan provinces. The catch and CPUE trend of mullets were compared during 1993 to 2001 and some biological characteristics such as: species composition, length, weight, K and age of Liza aurata and L. saliens were analyzed. In 1990s, the results showed that amount of catch has been increased and the maximum catch occured in 2001. CPUE decreased from 114 kg (in each seine) in 1993 to 43 kg in 1996 whereas 2001 increased to 66.4 and 78.4 kg in 2000 and 2001, respectively. The mean fork length, weight and K for L. aurata species were measured 32.7 and 32.3 cm, 418.3 and 419.8 g and 0.61 and 0.93 and for L. saliens species were 27.5 and 25.1 cm, 224.7 and 179.1 g and 0.91 and 0.71 for years 2000 and 2001, respectively. According to this data in spite of increasing in catch, CPUE of L. aurata has increased and there is no changes in respect of biological aspect. Therefore, it was concluded that this species is harvested of a sustainable level.

Effect of the timing of first feeding (9, 10, 11, 12 and 13 days post hatch) with a live food (Anemia naupli) on Persian sturgeon was examined at 17.7±0.8 and 18.1±0.4°C. The results showed that the timing of first feeding affected on weight, length, length-weight ratio and specific growth rate, but one day delay in the timming of initial feeding doesn't affect on the survival and two days delay in the timming of initial feeding doesn't affect on the condition factor. Results of this research showed that some factors such as weight, length, length-weight ratio and specific growth rate, are more suitable than survival and condition factor for exhibiting of effects of delay in the starting time of initial feeding in Persian sturgeon fish larvae. Thus it is better that the initial feeding of Persian sturgeon at 17.7±0.8 and 18.1 ±0.4°C started on 12 and 9 days after hatching, respectively, as well as more delay in intiating exogenous feeding has negative effects on growth of larvae.

Among crayfish species only Astacus leptoductylus eichwaldi Bott, 1950, is found in Bandar Anzali coastal area. The research survey carried out during 2001-2002, by designing twelve transects (transects coverd the depth of 35, 45, 55 and 65m). Foldable traps being used to catch crayfish. The maximum abundance of crayfish was caught at the depth of 40-60m. The average length and weight measured 125.6±0.2mm and 60.6±0.3g. The length and weight range were 72-169mm and 12.5-148g, respectively. Sex ratio during studying period favoured females with 1:0.86. The ovarian and pleopodal eggs calculated 308.98±10.62 and 255.54±10.87, respectively. The fecundity result obtained from A. leptoductylus eichwaldi population showed resemblance to its Turkmenistan counterpart. With the increae of weight in females the number of eggs in each gram of body weight (relative fecundity) is reduced. The breeding season in the studied area occured in 21th January to 22th July. First moulting in males happened in July and the second moulting which are simultaneous with females occured 11th-30th September. Length group 120-129mm were dominant in population and length frequency analysis showed six age groups among the crayfishes in studied area September. Length group 120-129 mm were dominant in population and length frequency analysis showed six age groups among the crayfishes in studied area. Average CPUE in the mentioned year was 2.54 individuals per trap per 24 hours. At present no harvest of crayfish taken-place, CPUE data showed that the density of crayfish between transects of 1-7 have been relatively considerable, and it is recommended that after carrying out stock assessment survey, the exploitation of caryfish resources can be programmed.

The goal of this study was to find a sex-specific DNA sequences in the male and female genomes of beluga (Huso huso), by random amplified polymorphic DNA (RAPD) assays performed on pooled DNA samples. Of the 310 different primers was tested, 7 primers produced no band. The most likely possibility is that PCR conditions have not been suitable for these 7 primers. It is also possible that these RAPD primers did not find suitable binding position to generate fragments. A single band was produced by primer 295 (OPT -17) which was specific to the male DNA. Further analysis of individual male and female beluga demonstrated that this primer yeilded a product that were in fact variable and reproducible, but were the result of variation in some individual males and females and not male-specific. Therefore, of the 4146 RAPDs scored, none were tightly linked to a sex-determining gene. The results support the idea that sex chromosomes are either not present or they weakly differentiated in the genome of beluga.

The increase in production of warm water fishes in Iran, such as carp, produces a need for development of new methods of food production for human consumption. In this research four formula for production of fish cake from carp were investigated. Using the chosen formula which consisted of 52% debonded carp meat, 28% potato, 10% whole egg, 8% flour and 2% of a mixture of garlic, ginger, nutmeg, pepper powder and salt, the fish cake was made. Then during 120 days at 18°C, according to a time schedule, the samples were tested for changes in their total volatile base, peroxide value and total count of bacteria. The results indicate that changes in TVB was from 14.0 to 18.9 mg/100g, peroxide value changed from 4.0 to 4.9 meq/kg. The total count of bacteria for all of the samples was negative. The shelf life of carp cake as the result of peroxide value increase was estimated to be 90 days at 18°C in cold store. This carp cake contains 20% protein, 8% oil, 10% carbohydrate, 6% ash and 56% moisture.

The changes of Ship stocks in the southern Caspian Sea was studied by measuring and considering different population parameters such as fish length, weight, age, sex ratio and caviar weight.Total catch of A. nudiventris in the Iranian waters in only 2 percent of total catch composition of sturgeon and its stock has been decrease during last 3 decades. In 1972 catch and CPUE of Ship had been 67 tonnes and 0.5 kg/boat/day and was decreased up to 15 tonnes and 0.09 kg/boat/day in 2002 and consequently it can be concluded that it's stock is critically endangered. Regarding to resources protection and rehabilitation of Ship stock, it is proposed to ban the fishing of this species (except for artificial propagation as broodstock).

Chlorophyll-a is a main pigment for photosynthetic proccess in marine phytoplankton and by it either amount of biomass can be estimated or can be considered as an index for trophic level of aquatic ecosystem.In year 1996,81 secchi disc depth were measured and 1601 samples of chlorophyll-a were collected seasonaly from the southern Caspian Sea. The results showed that average chlorophyll-a in seasonals of spring, summer, autumn and winter were 1.072,0.550, 1.848,0.966 mg/m3 and depth of transparency were 6.42,8.86, 5.62 and 5.22m, respectively.The statistical analysis showed a significant correlation (P<0.01) between these two parameters in the southern Caspian Sea. More studies are needed to find out higher precise correlation.

The diet survey of Perca fluviatilis of Arnirkelayeh lagoon was carried out during four seasons of 2001. After collecting the fish samples by different fishing gear such as gillnet, seine, castnet and dipnet, fishes were measured and diet was studied. Also according to this research from 143 specimen, fishes were in the age range of 1+- 6+, total length of 9.5-33.5 cm (T.L= 19.83±4.46 cm) and weight of 10.5 - 350 g (Mean weight of 114.45±77.55g).According to obtained results, the relative lenght gut was 0.58±0.09, index of fullness was 129.5±257.4, fullton's condition factor was 1320.7±534.1 and vacuity index was 7.69%.Perca jluviatilis was fed from 18 kinds of food with respect of frequency were: water bug, Odonata, Gammarus, plant materials, Chironomids, Tinca tinca, Hemiptera, Perca fluviatilis, Snail, Syngnathus abaster, Gambusia holbrooki, Pungitius platygaster, diptera, branchiopoda, trichoptera, tubifex, frog and shrimp.By consideration of composition eaten foods and their frequency percentage in Amirkelayeh lagoon Perca fluviatilis, it can be concluded that this fish is an omnivorous and cannibalism species. Also, feeding habit of Perca fluviatilis changes according to age, season and sex.

Gregarines are protozoa that occur within the digestive tract and tissues of various invertebrate animals such as shrimp.In this survey 15 marine broodstocks of Penaeus indicus from Jask area and 119 cultured shrimps from cultured farms were supplied and carried to laboratory.According to life cycle of gregarine, (Johnson, 1989) it is assumed that presence of protozoan gregarine among broodstock shrimps can be due to consumption of natural food and existance of intermediate hosts and as a result to be completion of life cycle of these protozoan in natural conditions. On the other hand absence of these parasites among cultured shrimp can be due to consumption of prepared (inert) food and lack of completion of alternate hosts and intermediate hosts and consequently lack of completion of life cycle of these parasites in the cultured condition.