Iranian Scientific Fisheries Journal
Year:2003 | Volume:11 | Issue:4|Papers Count:19

This study was carried out at monthly basis covering six sampling stations in Aras reservoir in 1995. The samples were collected by Ekman grab with 3 replicates. The results showed that Oligocheats were the dominant taxa in this reservoir which were served all year round and had the highest abundance and biomass.The chironomidae were the second dominant family. Gammaridae and Mysidae had the least abundance and biomass. Maximum biomass of Oligochaets was observed in spring with the average figure of 19.03g/m2 and minimum biomass was observed in winter with average biomass of 5.87 g/m2. Maximum and minimum amass of Chironomidae were recorded in summer and spring, of which their correspond average biomass were 1.52 and 0.06g/m2,respectively.The highest and Nest biomass of Mysidae family were observed in summer and spring with the average biomass of 0.46 and 0.00 g/m2,respectively. Gammaridae family observed only summer. The differences of biomass of these 3 families were significant based on uskal-walis nonparametric test (P<0.05).Maximum (26.06 g/m2) and minimum biomass (3.14 g/m2) of benthic organisms are observed in stations 4 and 5, respectively and no remarkable variation was observed in the percentage of total organic matter (TOM,) content during different seasons. Maximum and minimum average percentage of TOM were 6.66 % to 4.799% in spring and winter, respectively.Based on collected data and obtained results, it can be assumed that feeding of fishes, sediment composition, amount of TOM and water temperature were the most important factors affect on temporal and spatial variation in population and biomass of benthic organisms of Aras reservoir.

Maharloo lake (near Fars province) with a considerable restricted abiotic mditions such as very high salinity (300 g/lit) and a relatively high water temperature is inhabited by the brine-shrimp (Artemia parthenogenerica). This species has a worldwide distribution and in this research, biology and biomass estimation of Artemia were studied. The sampling was carried out monthly and in ldition to biomass estimation; spatial and temporal distribution patterns and production behaviour were investigated.Simultaneously with field studies in lake ecosystem, some cysts were transported in  the laboratory and preserved in aquarium for further hatching experiments under suitable condition of light, aeration and feeding. In this way, hatching percentage,the cycle and different larval stages were determined. Also, other information related morphology and physiology characteristics of them were collected. The mean biomass of Artemia in Maharloo lake was estimated 2.53.g/m3 per year.

Samples for monthly variation of phytoplankton species were collected in two stations from October 1996 till September 1997. In this study 65 species of phytoplankton related to diatoms, dinoflagellates and blue-green algae were identified. Diatoms represent 44 species (67%) related to 25 genera, followed by 18 species (26%) related to 7 genera dinoflagellates and only 3 genus (7%) belong to the blue-green algae. The diversity of diatoms species mainly composed of Rhizosolenia (12 species) and Chaetoceros (6 species) were markedly greater than the diversity of dinoflagellates which were composed Ceratium (11 species). The diversity of both groups were significantly greater than the blue-green algae. Diatoms and dinoflagellates were abundant during periods oflow salinity and temperature, meanwhile this situation was vise-versa for bule-green algae with high abundance in warm months.

This project was designed to study the distribution and density of planktonic decapods (Natantia Groups) in Khur-e-musa creek. Sampling was carrid out during period of october 1998 till July 1999, and identified species were classified to two Suborders.Suborder Penaeidea consised of 2 families and 5 genera and suborder Caridea sited of 6 families and 6 genera. The dominant genera were Acetes of family Sergestidae with 32.43% and Alpheus family Alpheidae with 36.88%. It was observed during this study that spawning of these genera take place in the spring season.

The anaesthetic effects of clove oil in juvenile common carp (8-12 g) was investigated under various water quality conditions, consisting of different pH and temperature. The time to loss the equilibrium, induction of anaesthesia, equilibrium recovery and response recovery were measured.The results showed that clove oil induced the desirable anaesthetic condition less than 3 minutes in all experiments. However the time of equilibrium recover and response recovery were longer than 5 minutes in many cases.When using dove oil at concentration of 100ppm, the most suitable anaesthesia effects and recovery times were observed at water temperature of 25°C and pH=7 and 8,as well as at 30°C with pH=9.No morbidity or mortality occurred during induction of anaesthesia by clove and recovery of fishes.

Population growth, urbanisation and rapidly development may be expected to change the pattern of supply and demand of fishery products in Iran. The supply of future fisheries (for consumption) may probably not increase much further, and increased demand of fishery products would have to be met through aquaculture. Aquaculture development may also play an important rule in rural development, employment and export. However, the physical potential for aquaculture development may be clear in Iran, the profitability for producers and the market demand needs to be analysed. However, research on the aquaculture economics plays important role in its development, there is a dearth of research on economics of aquaculture in Iran. Economic research on aquaculture can be classified into four: 1) production, 2) market studies, 3) project evaluation and 4) development policies. In Iran, the major constraints for an economic research in aquaculture are: insufficient economic data, lack of cooperation among experts, and diversity of aquaculture  systems. The main aspects of aquaculture economics in Iran, particularly the result from economics of carp culture development will be addressed in this paper.

In order to evaluate the Persian sturgeon stocks in the southern part of Caspian Sea (Iranian side), the present study was carried out by measuring different population parameters (length, age, weight), and changes of catch effect and CPUE.Although, the amont of sturgeon stocks have considerably been decreased during previous years, but according to the collected data, the stock and amount of catch A. persicus was increased. During last decade, the catch per unit effort flactuated from 2.249 to 2.971 kg. Also, mean length, weight and age of this species were declined and the age-structure showed significant changes. In total, the result showed that the young population of Persian sturgeon is increasing and catch data this species showed an increase, too.

Meiofauna with a size of 100-1000µ having important rule in food webs. This study was carried out in autumn and winter 1992 along 30 transects at depths of 0, 20, 50 and 100m.The sediment samples were collected by grab (0.1m2 area). In addition to identification of meiofauna, the sediments were examined to determine O.M. and grain size parameters.The results showed that bivalvia, foraminifera, nematoda, ostracoda and copepoda were dominant taxa among 12 identified fauna groups, in which, foraminifera and bivalvia were the most abundant.The nonparametric Kroscall-walis test showed sigificant difference among abundance of meiofauna in different depths. The depth of 20m had the most abundance and with increasing depth (50 and 100m), the abundance had a descending trend. The maximum and minimum mean abundance of meiofauna varied from 29315±37248 and 825±498 ind/10 cm2 for depth of 10 and 100m, respectively.The substrate characteristics indicated that the depth of 50 and 10m included the most and the least organic matter. Also all depths indicated the same grain size and sediment composition was mostly silt. Most of meiofauna were found in substrates with 4 to 8 % organic matter.

This study was carried out on endemic and economical fishes of Mahabad reservoir in 1998 to 1999. In this regard, 144 speciemen belong to 13 species of Capoeta capoeta, Chalcalbumus atropatenae, Leuciscus cephalus, Cyprinus carpio, Hypophthalmichthys molitrix, Acantalbumus uremianus, Ctenopharyngodon idella, Hypophthalmichthys nobilis, Carassius auratus, Abramis brama, Barbus lacerta, Nemachilus sp. and Silurus glanis were studied from point of infections on different tissues and organs such as skin, fins and gills.The prevalence of infestation was found 34.72% and the identified parasites based on abundance were as follow:Ergasilus peregrinus Heller, 1865, Lemaea cyprinacea Linnaeus, 1758 and Tracheliastes polycolpus Nordmann, 1832, in which among them L. cyprinacea was found as more dangerous parasite.Among studied fishes, L. cephalus and C. capoeta were contaminated with all above mentioned parasites where as there were not observed any infections for other fishes.