نشریه علوم آبزی پروری پیشرفته
سال ششم شماره 2 (پاییز و زمستان 1401)

This study was conducted to investigate the possibility of breeding carp juveniles (Cyprinus carpio) in pen conditions in Gorgan Bay in two treatments with a density of 2 and 4 pieces per square meter in order to produce breeders for restocking centers. The first juveniles were raised in earthen ponds with concentrate feed. Then, with an average weight of 93.87± 32.66g, they were transferred to pens with an area of 50 m2each and 16 mm mesh size, in Gorgan Bay. 6 pens were considered for this research and for each treatment, 100 and 200 pieces of juveniles were considered in each pen. Feeding was done with concentrate feed and physical and chemical factors and biometry of fish were done regularly. The results showed 52% survival in first treatment and 49% for second treatment and the mean weight for two treatments were 410± 64.98 and 390±52.8. Results showed that there was no significant differences between weight and length in two treatments. The histological results showed that the male and female were mature in 4th stage. The eggs of the female fish were between 800 and 1200 microns in diameter.

It is very important and necessary to choose the appropriate cold water fish species and check their growth performance in cage fish farming in the Caspian Sea. The results showed that the rainbow trout in Kiashahr region reached an average of 98.3±19.8 to 1149.8±203.5 grams in a period of 4.5 months. Also, although the breeding of salmon from the initial weight of about 100 grams was suitable, but considering the temperature limits for this fish in the Caspian Sea, the introduction of higher weights can reduce the length of the breeding period. Caspian Sea salmon reached in Jaffroud region from the average weight of 120.14±1.98 to 632.5±82.08 grams in a period of 4.5 months from January to May, and in Anzali free zone from 212.7 ± 15.28 to 508.81 ± 76.54 grams in a period of 2 months from January to March in floating cages, which shows the favorable growth of this fish in this region.

Seaweeds contain several biologically active metabolites including polysaccharides. Alginate is one of the polysaccharides isolated from brown seaweeds, which conventionally extracted using the alkaline method. In addition, other methods such as enzyme, ultrasound, microwave, enzyme-ultrasound, extrusion and fermentation have been used to extract alginate. Alginate possess properties such as antioxidant, antitumor, anti-inflammatory, immunomodulatory, prebiotic and emulsifying properties. Based on these properties the alginate is widely used in various industries like food, cosmetic, biomedical, pharmaceutical, Dyeing and printing, textile, papermaking, aquaculture, agriculture and welding. The present study overviews sources, process and extraction methods, properties and applications of alginate in the different industries.

Biofouling in marine aquaculture is a specific problem where both the target culture species and/or infrastructure are exposed to a diverse array of fouling organisms, with significant production impacts. In shellfish aquaculture the key impact is the direct fouling of stock causing physical damage, mechanical interference, biological competition and environmental modification, while infrastructure is also impacted. In contrast, the key impact in finfish aquaculture is the fouling of infrastructure which restricts water exchange, increases disease risk and causes deformation of cages and structures. Consequently, the economic costs associated with biofouling control are substantial. Conservative estimates are consistently between 5–10% of production costs (equivalent to US$ 1.5 to 3 billion yr-1), illustrating the need for effective mitigation methods and technologies. The control of biofouling in aquaculture is achieved through the avoidance of natural recruitment, physical removal and the use of antifoulants. However, the continued rise and expansion of the aquaculture industry and the increasingly stringent legislation for biocides in food production necessitates the development of innovative antifouling strategies. These must meet environmental, societal, and economic benchmarks while effectively preventing the settlement and growth of resilient multi-species consortia of biofouling organisms.

The present study was conducted to investigate the effect of replacing fish meal with corn gluten in the diet and its effect on the growth performance and biochemical composition of common carp fingerlings. For this purpose, 180 common carp fingerlings with an average weight of 5.04±0.5 grams and the average total length of 8±3 mm in 12 tubs with a density of 15 in each tub and in four different treatments of 20, 40 and 60% corn gluten along with a control treatment with a diet formulated with the percentage of protein, fat and The same energy levels were tested over an eight-week period. At the end of the test period, based on the obtained results, there was no significant difference between the growth indices in the investigated treatments and the control sample (P>0.05). Also, the analysis parameters of baby fish carcasses showed that there is no statistically significant difference between the treatments in terms of carcass moisture percentage (P>0.05), but in terms of ash percentage, protein percentage and carcass fat percentage, there is a statistically significant difference between all treatments. was observed (P<0.05). Therefore, it can be said that the use of corn gluten at the levels used in this research was favorable for fingerling carp.

The management of fish-eating birds in fish farms with the aim of minimizing the damages caused by their presence requires planning and using practical methods. Due to the extraordinarily serious and non-negligible threat of fish-eating birds in ponds, breeders use various controlling or aggressive methods to protect their fish and capital, which in most cases are either temporary or lead to killing a lot of birds. In this article, by reviewing sources and using personal experiences to some extent, we have tried to point out various practical methods to prevent the damage of fish-eating birds to fish farms with emphasis on Phalacrocorax carbo. Depending on the conditions of their farm, producers can reduce the invasion of fish-eating birds and increase productivity in their farms by using the mentioned method or combined methods.