نشریه بوم شناسی منابع آبی
سال پنجم شماره 2 (پاییز و زمستان 1400)

Zooplankton sampling was sampling was performed by a sampling net with a spring size of 100 microns. Since 2001, there have been changes in the population composition of zooplankton species, while in 1994 and earlier Eurytemora spp. Zooplankton predominated at depths of more than 20m. Currently, in the years after 2001, more than 95% of the zooplankton population in the southern Caspian basin is Acartia tonsa. Although in this study the dynamics of the zooplankton population was different, in all seasons Copepoda was the predominant group of zooplankton. A total of 24 species of zooplankton from the groups of Copepoda, Rotifera, Protozoa, Cladocera and two species of Meroplankton from Cypris balanus and Lamellibranchiate larvae from bivalve larvae have been observed. Among the factors of entry of non-native animals, including the comb M. Leidyi, nutrient entry through the Nekarood river, different amounts of solar energy intake and consequently temperature and water currents can cause differences in zooplankton population in Goharbaran region.

The Biofluc system is an efficient and effective nutrient replacement method that continuously recycles and refines these substances. The system is based on microbial growth in the breeding environment, which reduces or eliminates water changes in aquaculture systems. Recent years have seen the growth of biofloc-based aquaculture systems, as these systems are able to have the greatest environmental safety and even sustainable production in aquaculture while maintaining biosecurity. Bioflocks improve water quality by adding carbon, removing harmful nitrogenous substances, improving food use, and enhancing the efficiency of growth in aquaculture systems. Aquatic animals are naturally protected from pathogens by phytobiotics, which are plant derivatives that add natural compounds to their diets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .. . . .

In this study, sampling of commercial vessels of Afsoon 1 was carried out in July 2020, at a distance of more than 10 miles in longitude24 50 to 24 60and latitude 61 03 to 61 05. At the time of the study, trawl fishing 13 times was done at different times (8 times during the day and 5 times at night). The total catch during the study period was 12306 kg and 8720 kg were caught during the day (about 71%) and 3586 kg at night (about 29%). The average catch per fishing effort (catch per hour) of the target species was 201 kg (67%) during the day and 63 kg (33%) at night, and the average catch per fishing effort (catch per hour) discard species were 71 kg (28%) during the day and 100 kg (59%) at night (P <0.05). The study of target fish catch in depth different showed that with increasing depth, the target fish catch increased and the highest percentage of target fish catch was seen at depths of more than 120 meters (P <0.05). The rate of discard fish species was about 40% and its rate was more at night than day time and the discard fish species CPUE rate of trawlers showed in the night more than daylight time (P <0.05). In general, it seems that discard fish species ratio of trawler in the night hours is more than during the day and this rate at depths less than 100 meters is higher.

The possibility of algal blooms at the location of the cages and the surrounding water is one of the major risks associated with the management of fish farming in cages. In the present study, the risk of eutrophication (risk of algal blooms), the rate of nutrient enrichment (eutrophication) and the availability of nutrients (for phytoplankton consumption) due to fish farming in the waters adjacent to the cages with Farther from the location of the cages during a six-month rearing period in Qeshm region was compared. In the study, the range of changes related to scale and non-scale trophic indices and trophy efficiency coefficients were equal to 3.75-5.23, 3-4-78 and 3.78-4, respectively. Based on the studied indicators, the trophy status in the waters adjacent to the cages is high (at the mesotrophic level) and the risk of blooming is high, as well as the availability of nutrients by primary producers (phytoplankton) based on the trophy efficiency coefficient was high. However, in the waters farther from the location of the shelves (control station), the trophy status was moderate (at the mesotrophic level) and the risk of blooming and the availability of nutrients were low. The use of superior technologies and proper, principled and scientific management of water and food quality, in addition to reducing the environmental effects of such activities can play an important role in increasing production, exports and further valuation by this industry.

Examining the important relative index of IRI. Index of food preference Fp and gastric emptiness index of CV in this fish showed that this species is a gluttonous fish and the amount of gastric index of this species is calculated in spring and the lowest in summer.CV emptiness index increased from spring to summer, which reached its maximum in summer and decreased after summer, indicating that fish do not feed in summer and most feed in winter. Stomach index and liver index reached the highest in spring and the lowest in summer.In the stomach contents of this species, in order of priority, different groups of bony fish, then crustaceans such as crabs and shrimp were seen, but the largest volume of stomach contents was found in bony fish such as quince. بزماهی. Sardines and squid and pentagonal fish formed in this species. Of the total number of fish studied, three dietary groups of fish, crustaceans and cephalopods formed this species.Index of gastric emptiness (CV) showed that in large mane mane fish, the highest value of this index is in summer and showed that this species in this season, which is its breeding season, is very low in appetite and in spring and autumn It is relatively gluttonous and reaches its minimum in winter and shows a lot of nutrition and overeating of this species in this season.

Sturgeon are valuable species whose stocks have reached the brink of extinction for a variety of reasons, including overfishing, habitat degradation, pollution and climate change, and almost all sturgeon species are on the endangered species list. Given the biological, economic and historical importance of sturgeon, it is necessary to conduct detailed studies on the optimal use of opportunities in the protection and long-term use of their stocks, as well as control and counter threats. The present study is descriptive in nature and survey, and in applied research it is of developmental type; Investigating the factors affecting sturgeon breeding and economic, social and environmental evaluation based on SWOT model, strengths, weaknesses, opportunities and threats were extracted and then approved by experts by Delphi method and economic, social and environmental feasibility by TOPSIS method. The results showed that the development of sturgeon is a very important activity in the agricultural sector that in the current situation, paying attention to sustainability and proper aquaculture education can play an important role in education, environmental protection and achieving sustainable development.