نشریه ماهیان دریایی
پیاپی 2 (پاییز و زمستان 1396)

This study aimed to a comparison of morphometric characteristics of otolith in Epinephelus coioides (88 specimens), Epinephelus latifasciatus (71 specimens), Epinephelus bleekeri (69 specimens) and Epinephelus diacanthus (145 specimens) in coral reefs of the Persian Gulf and Oman Sea. Species were collected during 2014 - 2015. All fish were identified and their otoliths were extracted to verify them. Investigation of otolith morphometric characteristics (length, breadth, weight, perimeter and, area) was conducted. Data indicate a high correlation between otolith length and otolith weight, fork length, and otolith length and between fish length and weight (R2>0.854), the highest correlation was observed in E. diacanthus (R2= 0.894). Also, the results indicate that in the studied species, biometric differences are observed along with the difference in the shape of the otolith, according to the results, the highest length, the highest weight, the highest area and the highest perimeter of otolith were related to the E. diacanthus with mean total length of 26± 3.2 cm and the average weight of 1357.27 ± 104.27 g, and the highest otolith width was related to the E. coioides with an average total length of 38 ± 1.8 cm and the mean weight of 1289.54 ± 124.42 g. This study indicated that the relationships between sagitta and morphometric characteristics of various species are different and can be used as an indicator in species identification.

One of the principal problems in marine fish larval rearing which includes financial loss is related to increased mortality in the stage while larvae have to shift feeding on formulated from live food. The reasons for applying weaning are high production costs, increased bacterial load and unreliable nutritional value of live foods. The commercial dry feeds can address this concern and decrease the larval production costs and consequently generate a highly profitable investment. In this paper, it was tried to consider recommendation which helps the aquaculturists to pass this larval stage successfully. Attention to the larval development stage, larval behavior, feeding strategies and considering the factors such as effective health management and monitoring the environmental conditions which affect the success of this change are met to discuss.

Aquaculture of marine fish, especially cage culture, is one of the common methods of mariculture in the world, which has been considered in recent years in Iran. One of the species that has been considered for cage culture in Iran is an Epinephelus coioides, which biotechnology of its reproduction was achieved in Bandar Imam Khomeini marine fish research station. In a study carried out at Bandar Imam Khomeini marine fishes research station, it was observed that this species can be stocked with a stocking density of 30 pieces m3 (with an initial weight of about 50 g) and using pellet food and or trash fish from the July to late of the November in cages made of simple raw materials. Orange spotted grouper juveniles were stocked in the floating cages of 27 m3 (3 × 3 × 3 meters) and propagated for 143 days, then harvested with an average weight of 523.7 ± 28.0 g and 317.5 ± 22.1 kg / 27 m3 (11.8 kg/m3) in treatments that fed trash fish and pelet diet, respectively. The results of this study indicated that cage culture of this species in the khuzestan region is justifiable and cost-effective. Moreover, these results suggesting that higher weight gain can be achieved by extending the culture period from the April to the late of March.

The need for more food for humans and especially marine proteins, has led to a growing trend in the production of marine fish cage culture in the country. The issue of rearing various species of marine fish for aquaculture in cages in the south of the country has risen. But now the farmers have chosen as the first option according to the characteristics of the growth and tolerance of suitable environmental conditions, Asian sea bass species. Due to the lack of native species in the country and the specific strategy of this species, the expansion of this industry requires artificial propagation and the supply of larvae fish for rearing. Now the private sector needs a suitable fish through imports of fish larvae, the nursery of larvae in special breeding centers, and the sale and distribution of juvenile fish among farmers. Hence farmers are spending a lot of money to buy juvenile fish at the suitable size and transport to cages. In this article, we will try to provide a brief overview of the various methods of nursery rearing stages of Asian sea bass in cages, tanks and pools in some countries, so breeders can design and implement programs for rearing larvae to prepare to stock in the cage. The development of this industry in the country needs to reduce production costs to achieve better economic efficiency for sustainable production.

Control and preventing the spread of diseases in the farmed fish requires a regular monitoring, eradication or vaccination program. And in this respect, the serology as a monitoring and diagnostic tool can be very useful. In recent years, monoclonal antibodies have been considered a tool in immunological in immunological research. These anti-inflammatory drugs are highly specialized in epitopes and are prepared in large volumes. Due to their high purity, monoclonal antibodies act as standard chemical agents. They have been quickly being used in clinical diagnostic techniques since a lot of them are needed in the production of commercial kits. Like serology in other animals, serum testing in fish also requires the use of anti-antigens (anti-IgM). For the same reason, during the last decade, efforts have been made to produce anti-IgM antibodies for the production of monoclonal antibodies, suitable for each species of freshwater and marine fishes. Therefore, the production of these antibodies in the interior, in addition to the help and development of the rapid and accurate detection of marine fish diseases can lead to currency savings.

Regarding increasing the world population, the marine aquaculture will play a key role in supplying the protein requirement of the human. Therefore, the need for achieving to more production in this industry is necessary and unavoidable. Larvae and fry production also depend on broodstocks, while one of the major bottlenecks in marine fish breeding is to prepare gene pool of breeders having special genetically characteristics. These brood stocks may carry specific genes such as higher growth rate ability or resistance to disease. Since the conventional breeding is a long time and expensive protocol, applying the modern biotechnologies such as transgene would lead to achieving selective broodstocks. In this paper, it tries to introduce successful examples of transgenic marine fish produced worldwide. Moreover, it involves discussion about the important genes transferred to fish leading to raised production, reduced costs, and consequently more profitable investment.