Iranian Scientific Fisheries Journal
Year:2006 | Volume:15 | Issue:3|Papers Count:23

The urohyal bone is a single median solid bone with anterior tip generally connected to the ventral hypohyal and to the first basibranchial, and the posterior end attached to the pectoral girdle by means of muscle. This bone has been generally used for age determination, but recently it has been distinguished that its morphology is diverse in different groups of fishes such that it could be used in fish taxonomy. The morphology of urohyal in 12 freshwater fishes from 12 genera, 9 families and 6 orders was been studied. Results showed that the urohyals were varied in ratio of length and width relative to total length and fish head length, ventral shape, presence and number of processes in the anterior part, origin of dorsal keel (distance from anterior tip), groove in ventral portion and some other attributes. In all examined cyprinid fish, the ventral part of the urohyal forms a triangular flat facet and there was no process in anterior part of urohyal. In Salmonidae family the ventral part was rhomboid in shape and its anterior end was not completely forked. There was a spine-like process in dorsal part of urohyal in Cyprinodontidae and Poecilidae families. In Hormuz Cichlid, lranocichla hormuzensis (Perciformes) and Abu Mullet Liza abu, (Mugiliformes) the ventral part forms a triangular grooved facet and its dorsal part bears a process. In Tenualosa ilisha (Clupeidae), there are two lateral processes in the anterior end. Based on the findings, we prepared a key for identification of some freshwater fishes of Iran for the first time.

Anzali Lagoon is one of the most important aquatic ecosystems of Iran which was registered as a Ramsar Convention site in 1999. This valuable ecosystem is located in the south west shores of the Caspian Sea, in Guilan Province. We randomly collected 30 and 20 samples of the bivalve Anodonta cygnea in autumn 2004 and spring 2005 respectively. The Selkeh area was chosen for the sampling because of its availability during autumn. The area receives water from the southern part of the lagoon basin. Nutrient content of the soft tissue of the bivalve was measured. Live sampled bivalves were transferred to laboratory and their length, width, height; total body weight and wet weight of the internal soft part were measured. Moisture, ash, protein, T.V.N, lipid and amino acid contents in soft tissue were also determined. Moisture content in spring and autumn samples were 84.84% and 83.6%, respectively. Ash content in autumn samples was higher than spring samples, being 4% and 2.32%, respectively. Assessment showed protein content in the autumn samples to be 12% while in spring samples this was 10.5%. T.V.N content in autumn and spring samples were 0.031 and 0.003% respectively. Measurements showed that autumn bivalves had 4% lipid content whereas this value in spring samples was 3%. We found Sixteen amino acids, including seven essential ones in the samples.

The shrimp farming industry has rapidly expanded in the south of Iran and in particular in the Hormozgan province during the past decade. We studied physico-chemical parameters of water in outlet and inlet channels of shrimp farms in Tiab during July-December 2000. Water samples were collected monthly at four stations during the harvest period. The parameters assessed included pH, salinity, dissolved oxygen, nitrate, nitrite, ammonia, phosphate, total phosphate, total suspended solids and chlorophyll a. The variation of above parameters were determined to be 7.62 - 8.19, 42.75 - 52.55ppt, 2.8 - 8.3mg/l, 4.46 -0.66m/l, 0.21-1.64µg/l, 0.12-2.07µm/l, 0.13-16.1µm/l, 0.59-10.5µm/l, 22-121mg/l and 0.43-5.13µm/l respectively. Results of the analyses showed that salinity, dissolved nutrient, T.S.S and chlorophyll a in the effluent were significantly higher than the influent water (P<0.05). A significant correlation was also found between chlorophyll a and nitrate, phosphate and suspended solid concentration (P<0.05). Comparison of the results with the standards showed that parameters are currently within acceptable limits.

Catch data from Persian Gulf and Sea of Oman during 1973 to 2001 were used to assess the state of the fishery development in these ecosystems. Also, fishery trends were analyzed to determine catch fluctuations during the period. Catch trend for each species from 1997 to 2003 was analyzed and fishing potential of the species for the following year was predicted.Based on the assessments, we can summarize fishing development in the southern waters of Iran into three periods: undeveloped, rapid development stage and developed stage. The undeveloped stage continued till early 1981, continued by a rapid stage until 1997, reaching to maximum level of at this year and continuing ever since. Catch trend analyses for each species during 1997 to 2003 showed different patterns for each species depending on its economic value. However, the mean catch of all species showed a sustainable trend in the two marine ecosystems. It is concluded that the catch quantity for most of the species have already reached a maximum level. Therefore, in order to keep fisheries sustainable in the region, excess fishing should be avoided.

Possibilities of producing all-female rainbow trout (Oncorhynchus mykiss) using neomale stock were investigated in Kelardasht hatchery. To do this, we compared the fertilization, hatching rate and growth parameters of progeny in the first year of culture. Histological studies of gonads showed that progenies produced by mating sex-reversed males and normal females were totally female. Eyed-stage egg, hatching and early survival rate in all-female population were 90:69 %, 97.36 %, 91.49 % and in mix sex population were 70.24%, 98.22%, 90.73%, respectively, showing no significant differences (P>0.05). Lack of maturation in the first year cultured fish led to the identical growth parameters in mix sex and all-female groups (P>0.05). Results showed that use of sex-reversed males can be one of the best and successful methods of producing all-female populations.

Artemia uramiana hatched in the laboratory condition were reared in small glass aquariums for 20 days in 4 replications and fed with Chaetocerus sp. and marine Chlorella sp. as treatments. Culture conditions such as temperature, salinity and pH were kept the same for all treatments and replicates. A one-way analysis of variance, showed a significant difference in the mean growth rate of the Artemia treated with different food items (P<0.05), but no significant differences was found in the Artemia survival rate (P=0.4321). The average survival rate and the mean length of Artemia fed on Chaetocerus sp. were 95%, 97%, 93%, 94% and 7.77, 7.76, 8.01, 7.87; for the four replications. For the Artemia fed on Chlorella sp. The values were 82%, 80%, 77%, 85% and 7.06, 7.66, 7.53, 6.83 respectively.

Biological and reproduction characteristics of female big-eye kilka (Clupeonella grimmi) including body weight, fork length, age, gonad development stages, gonad weight, ganado somatic ratio (GSR) were studied. We sampled 808 fish specimens from the Southern Caspian Sea, Babolsar Area during December 2002 to May 2003. Gonad development stages were assessed through tissue sectioning.Results revealed spawning peak to occur in early January. We also measured body weight as 8.88:f:0.08grams, fork length as 1.03±0.26mm, age as 3.6±0.03 years, gonad development stage as 3.67±0.03, gonad weight as 0.5±0.01 grams and ganado somatic ratio (GSR) as 5.39±0.1 in the specimens. Totally, five age classes, dominated by the 4+ years were distinguished while no 1+ year's age class was observed. The abundance of gonad developmental stages 2-5 was 18.19%, 14.60%, 48.89% and 18.32% respectively. Macroscopic (visual) and microscopic (tissue section) observations of oocyte revealed the same results for gonad development.

A Comprehensive hydrobiological and hydrological investigation was conducted on Hevigh River, west of Guilan Province from 2001 to 2002. Totally, 4 Phyla of phytoplanktons including 21 genera were observed. The maximum phytoplankton density belonged to the Phylum Chrysophyta with genera, Nitzchia, Diatoma, Cocconeis, Navicula and Cymbella comprising 95.7% of the phytoplankton population throughout the year. Chlorophyta ranked second with genera Scenedesmus, Cruciginia and Ankistrodesmus, comprising 2.20% of the population during the year. Cyanophyta with Oscillatoria and Euglenophyta with Euglena consisted the remaining few percents of the phytoplankton population.Zooplankton population in Hevigh River was found to be very poor, and mostly belonged to Protozoa and Rotatoria. However, 4 Phyla and 12 genera of zooplanktons were distinguished in the River the highest density of which belonged to Protozoa with genera Arcella, Difflugia, Cyphoderia and Euglypha, comprising 64% of the total population. Rotatoria with genera Keratella, Cephalodella, Lecane and Rotaria, consisted 14% of the zooplankton population during the year. Arthropoda, Nematoda, Tardigrada were very low in numbers.

A complete random design involving four diets was conducted to determine the effects of Different levels of dietary acorn meal on [mal weigh, food consumption and food conversion ratio of rainbow trout. Juvenile Rainbow Trouts with an average weight of 74 grams were reared after antiseptic processes in Boldaji station of Chaharmahal and Bakhtiari province for 135days. We formulated diet treatments 1-4 containing 0, 2, 4 and 6 percent of acorn meal respectively. In doing so, we considered nutritive requirements of rainbow trout based on NRC using UFFDA dietary software. We also used local material in providing the diet. The food was given three times a day the amount of which was based on fish biomass in each pound. Once every two weeks, after anaesthetizing 50 percent of fishes in each pound, we measured fish weight and length. The results showed that treatment 4 containing 6% of acorn led to the highest fish weight increase while being significantly different with other treatments. In terms of fish length, the longest length was observed in treatment 4, which had significant difference with treatment 1. Food consumption differences was not significant between treatments, but was higher in treatment 4. However, food conversion ratio was significantly affected by treatments, the highest of which was in treatment 4 significantly different with that of treatment 1. The results showed that acorn meal can be used as a nutrient in rainbow trout diet, improving fish weight and length gain while having no physiological effects on the fish.

Fish culture in rice field is an ancient activity in Asia and probably it has been a routine activity in China since decades ago. Countries are now gradually finding out the advantages of the activity putting more and more land under the integrated culture. The integrated culture was first conducted in 1983 in Iran. Since then, the activity has been extended in the rice fields of 11 provinces of the country. In an experimental project in 2003, 13 rice fields totally covering 8.2 hectares and 13 control fields with the same size, physical and chemical conditions were chosen to investigate the outcomes of the integrated culture. For this, 1400 specimens of juvenile fish each weighting on average 35-45 grams and composed of 57% common carp, 29 % grass carp, 14% silver carp and big head carp were stocked per hectare of each field. The average weight for grass carp individuals was 25-35 grams. Feeding rate was based on the fish biomass. In harvesting time, characteristics of the rice were compared between experimental and control fields in order to determine the quality and quantity changes in the product. At the same time, usage of fertilizer, pesticides and herbicides were measured in both experimental and control fields. The pesticide usage in control fields was 15 kg per hectare, but in experimental fields it was only 5kg per hectare. This showed 66% reduction in pesticide use. In each control field, 2 liters of herbicides was used, as compared to only 0.3 liter per hectare in the experimental fields, showing an 85% percent reduction. The chemical fertilizer (urea, phosphate, potassium) used in the control fields was 169 kg per hectare, translating into a 23% reduction in each experimental field. Overall, rice production increased302 kg per hectare in the control fields. In this experiment, the profit of fish and rice integrated farming was estimated to be 4,300,000 Rials (US$505). The results showed that enhancing fish and rice integrated farming might increase farmers' profits; while reducing the need to apply fertilizers and pesticides.

We investigated the survival ratio and the growth rate of offspring of Salmo trutta caspius produced from three groups of brood fish in Shahid Bahonar Rearing and Breeding Center in Klardashtin 2005. The three groups of brood fish belonged the early, mid, and late-migration period. The sampling was done randomly, and in each group 15 female and 5 male fish were included. After spawning and hatching, 22500 eggs were used in each group (3 treatments, repeated 9 times). The results showed no significant difference in the survival ratio of the egg and larva in the three groups of the brood fish in each stage of evolution up to two months after the start of active feeding (P>0.05). However, after the start of active feeding there was a significant difference (P<0.05) in the growth ratio of offspring produced in the groups aged one and two months. The growth ratio of the same age offspring in the first group was higher than those in the third group (P<0.05); but there was no significant difference between the first and the second group, or between the second and the third group (P> 0.05). Based on the results, we suggest that the brood fish from the early migration period are more suitable for producing offspring and their offspring pass through the smoltification stage more rapidly. However, in terms of genetic diversity, it would be appropriate to use brood fish from all migration periods.

Changes in gill histology and mortality rate of juvenile Caspian Sea Brown Trout Salmo trutta caspius Kessler-1877 in different weights and water salinities were studied. The indicators used in this study were the change in number and size of gill chloride cells as well as mortality rate of the juvenile trout. Juveniles weighing 2, 5, 10, 15 and 20 grams were directly transferred into water with salinities of 0, 4, 8 and 12.5 gr/lit and kept for 120 hours. Histological assessment showed that the number of gill chloride cells increases with the increase in weight and their size increases invisibly. Also, we found that the number of gill chloride cells is increased when salinity increases while the size of the cells undergoes an invisible downward trend. During the 120 hour test, mortality rate of the juveniles weighing 2 to 20 grams was zero in water salinities ranging 0 to 12.5 gr/lit. This supports the fact that the fish have a remarkable adaptability to changes in the environmental condition. Considering changes in the histology and mortality rate, it is concluded that the proper weight for release of juvenile Caspian Sea Brown Trout is 10 grams and the best water salinities is in the range 8-12.5gr/lit, the same value found in the estuary.

Effects of stocking density on growth, food conversion ratio, specific growth rate, percentage of body weight increase in Huso huso were studied in two phases. Juveniles below one year old with an average weight of 92.09±1.72 grams and stocking densities of 1.6, 2.8 and 4 kg/m2 in 3 replicates for 100 days were reared as the phase one group. One year old Huso huso with an average weight of 918.13±21.87 grams and stocking densities of 1.5, 2.5, 3.5 and 4.5 kg/m2 reared for 120 days in 2000 liter fiberglass tanks were the second phase. Results revealed negative impact of density on growth, percentage of body weight, and specific growth rate and food conversion ratio in both phases. In the first phase, lower stocking density (1.6 kg/m2) showed significant increase in growth rate (P<0.05) as compared to 2.8 and 4 kg/m2 stocking densities resulting in 42.3% and 61 % growth rate respectively. Fish kept at 4 kg/m2 density showed malformed caudal fins and injured body due to higher tensions and contacts. In the second phase, the growth rate of fish decreased with increase in stocking density where fish with lower density (1.5 kg/m2) showed 7.2%, 15.6%, and 19.8% higher weight gain as compared to fish reared at 2.5, 3.5 and 4 kg/m2 stocking density. Analyses showed that with increase in stocking density, feeding area per fish decreases and tension between fish increases that leads to lower feeding efficiency. Based on the results, the recommended optimum stocking density for Huso huso individuals up to 90 grams is 1.5-2 kg/m2 and for fish individuals over 900 grams each the density should be kept at 2.5-3 kg/m2.

Possible effects of antioxidant Butyl Hydroxy Anisole (BHA) and sodium polyphosphate on the shelf-life of frozen Astacus leptodactylus of the Caspian Sea was studied. Samples of the crayfish were dipped in 0.02 and 0.2% BHA and 0.04 and 0.4% sodium polyphosphate for 30 and 60 minutes. The control samples were packed without immersion in the mixture of BHA and sodium polyphosphate. The Peroxide Value (PV), Total Volatile Nitrogen (TVN), total bacteria count and organoleptic tests were carried out on the samples using a time schedule. The results showed that the minimum increase in PV for the samples which were soaked in a mixture of 0.2% BHA and 0.4% sodium polyphosphate for 1 hour were from 0.59 to 0.88 meq/1000g, as compared to the control samples with an increase in the range 0.59 to 3.53 meq/1000 g after four months. The PV Value after four month started to be decrease and reached 1.4 meq/1000 grams after sixth months. The results showed that the minimum increase of TVN for the samples which were soaked in a mixture of 0.2% BHA and 0.4% sodium polyphosphate for 1 hour were from 12.88 to 17.8 mg/100 grams and for the control samples, the increase was from 12.88 to 19.8 mg/100 grams after sixth month. The results also demonstrated that the minimum increase in Total Bacteria Count of for the samples soaked in a mixture of 0.2% BHA and 0.4% sodium polyphosphate for 1 hour were from 9×103 to 2×101 per gram and for the control samples, the count was from 9×103 to 7×102 per gram after sixth months. Kruskal-Wallis, chi-square and Duncan tests were conducted on five samples for each specific shelf-life time. Using the results, we conclude that immersing the samples into a mixture of 0.2% BHA and 0.4% sodium polyphosphate for one hour gives the best results in terms of shelf-life and organoleptic tests.

The impact of Sefidroud River sediments on the fingerlings of Persian Sturgeon (Acipenser persicus) was studied in 2005. The tests were done in 20 liter aquariums each containing 10 Persian Sturgeons fingerlings weighing 3-5 grams each. We devised 6 treatments and a control with 3 repetitions in the four day investigation through which the lethal concentration (LC5096h) of Sefidroud sediments were studied. During the test, physicochemical parameters of water such as pH, oxygen and temperature were measured as 8, 8.5mg/l and 25±1°C respectively. The results showed that LCso96hand LC5024h of sediments on Persian sturgeon were 15367.39mg/1 and 124882.04mg/l respectively. We determined the maximum allowable concentration (M.A.C) of sediments to be 1536.74mg/1.

Possible effects of various iron concentrations on the growth of green algae, Ankistrodesmus falcatus, were studied at Inland Waters Aquaculture Research Center, in Bandar Anzali, Guilan Province. The algae was grown under laboratory conditions with a water temperature of 25±2°C and light intensity of 3500±350 lux for 96 hours at 6 concentrations of Fe in triplicates, using standard Zander culture medium (Z-8±N) as control. The amount of Fe absorption was measured using spectrophotometry at 750nm, and the number of algal cells at the beginning and final stages were counted, using Toma slide. Maximum growth of Ankistrodesmus falcatus was observed at Fe concentrations of 0.0005 g/l, when the concentration of the element in the control group (Z-8±N) was 0.00019 g/l. It was shown that Fe concentrations higher or lower than 0.0005g/1 had negative effects on the algal growth.

A research experiment was conducted to provide a protocol for seminatural propagation and rearing of Roach up to release size. The attempt was made to combat the declining trend in the population size and catch of the fish in the Caspian Sea. The optimum temperature for spawning brood-stocks lasts from middle March to late April when the ambient temperature range is 12-17°C. During the four months research period, brood stocks were caught in the estuary of the Gorganrood in Golestan Province, north east Iran. The stocks were released into 2 hectare earthen ponds enriched with manure and fertilizers. Artificial spawning grounds made of pine branches were placed in the ponds. Ponds were stocked with 700 female breeders with an average weight of 150 grams and around 350 male breeders weighing 100 grams on average. Spawning and fertilization of eggs occurred in the ponds of which an estimated 80-90% eyed that were observed from the fifth day onwards. The starting of hatching was observed in the 6th day and yolk sac absorption was observed in day 4 to 6. The larvae were fed on natural zooplankton and artificial food. Assessment of 146 fries for ingested food indicated that the fries fed on Rotifer (Rotatoria sp. and Daphnia sp.) in the ponds. The length-weight relationship was not significantly different among the ponds and also specific growth rates (SGR) did not show any difference in the fries. The relative gut length in the fries were smaller than 1 (RLG<I) and fries with an average weight of 0.5 to 1 gram were released into their natural habitat.