نشریه علوم آبزی پروری پیشرفته
سال پنجم شماره 1 (بهار و تابستان 1400)

Asian seabass (Lates calcarifer) is one of endemic fish of Iranian southern water bodies which is called Barramundi in some scientific references. This species is cultivated widely in some countries around the world including Australia, Indonesia, Singapore, Brunei, Malaysia, Thailand and China. However, there are limited experiences on rearing of this fish in Iran during recent years. Asian seabass has high commercial value due to desired characteristics such as rapid growth, dense ability, high resistance to diseases and unfavorable conditions, high nutritional value and palatability. Despite mentioned profits, still commercial culture of this species is not developed in Iran sufficiently. Development in aquaculture of this valuable fish is needed to accurate and precise information on its biology and biotechniques of propagation and rearing. Therefore, the present information is prepared to present a manual for captive propagation and also methods of rearing of this fish in different aquaculture systems.

In the plan of developing aquaculture and increasing production in the lake behind Golabar dam in Golabar village of Ijroud city of Zanjan province, plankton studies were considered as basic studies to increase fish production in this lake. In this project, 5 study stations were considered in the area of the dam lake and the river entrance. The studies started quarterly from the fall of 2009 and continued for one year until the summer of 2010. For sampling of zooplankton in the dam lake by a 55 micron Juday net was taken from the floor to the surface of a sample of water column, at the entrance of the river by a P.V.C pipe 30 liters of water was filtered by a zooplankton net. finally samples were stabilized with %4 formalin rate and transferred to laboratory for study. In zooplankton studies, a total of 5 zooplankton Phyla and 25 genera were identified, with the highest percentage of the zooplankton population belonging to the Rotifera phylum, which includes %76.2. The most important genera in this group are Polyarthera, Keratella, Filinia and Pompholyx. Comparison of planktonic observations with physical and chemical data of water shows that due to the young age of Glabar Dam Lake, it is equal to the amount of nutrients and organic matter in the Eutroph waters, and This reservoir has talent suitable zooplankton species for feeding, breeding fish and their larvae , so the natural resources of this water source can be used to increase the production of valuable fishery fish.

The effects of different powdered dried diets on density and population growth rate of cyclopoid copepod Acanthocyclops trajani was studied. To this intention, the copepod were mass cultured in 120 liter tanks by feeding on different diets including: dried compound of microalgae: Scenedesmus obliquus and Spirulina maxima (1:1), dried macroalgae Gracilaria corticata and dried composition of vegetables (spinage, parsley and coriander) and the population density were studied by sampling (every 3 days during 1 month). The results indicated that the highest total mean population density (1445±298 ind/L), the highest growth rate (0/145/d) and the shortest population doubling time (4/76d) were obtained from dried microalgae complex diet which was significantly different from other dried diets (p < 0/05). On the basis of the results, Despite the nutritional needs of freshwater cyclopoid copepod to animal protein, dried algae as an available and nutritious diet has resulted good production and growth rate in this copepod.

In the present study, the dietary replacement effects of earthworm meal (Eisenia foetida) instead of fish meal were evaluated on growth, feeding performance, and survival rate of angelfish (Pterophyllum scalare). Fish (n=120; mean initial length and weight of 4 cm and 4.2 g, respectively) were distributed in four treatments (each with three replicates, totally in 12 aquariums) containing: fish meal diet (control), and three different inclusion levels of earthworm meal (10, 20, and 30%) instead of fish meal in a completely randomized design for 8 weeks. The results showed that the average daily growth rate and specific growth rate increased significantly with increasing the replacement level up to 20% but decreased at the level of 30% (p≤0.05). The best feed conversion ratio (FCR = 1.6) was recorded at the replacement level of 20% with a significant difference with other groups (FCR = 2.17-1.82) (p≤0.05). The average percentage of increase in body length at the replacement level of 20% was approximately 1.8 times that of the control group and the replacement level of 30% and 1.5 times the replacement level of 10%. Food efficiency values were in the range of 35-62%; and the highest value was observed at the replacement level of 20% (p≤0.05). Different levels of replacements had no effect on fish survival compared to the control group (p≥0.05). According to the results, a 20% replacement of E. foetida meal instead of fish meal in the diet improved growth and nutritional indices. Therefore, the use of earthworm meal at a rate of 20% is recommended in the functional diet of angelfish.

The present study investigated the potential production of rainbow trout up to 50 g in 9 concrete ponds (19 × 2.2 × 1.5 m) using different stock density comprising 100, 115 and 130 fish/m2 with initial average weight 5 ± 1 g. This experiment carried out in a completely randomized design with three treatments (triplication for each) for 75 days. Total stock for treatments were 4180, 4807 and 5434, respectively. A well with 30 l/s was used as a source of water that divided for 9 ponds uniformly. Firstly, feeding was started with 4.8 percent of biomass of each pond (with 5 times per day) and then decreased at 2.5 percent (with 3 times per day) at the end of rearing period according to fish size and water temperature. The results showed that treatment with 100 fish/m2 had significantly higher body weight gain (50.83 g) and total length (12 cm), and also lower feed conversion ratio (1.37) than other groups (p < 0.05). In addition, the highest specific growth rate (2.57) and protein efficiency ratio (1.81) were significantly observed for 100 fish/m2 compared to other treatments (p < 0.05). Therefore, the optimum stock density at100 fish/m2 up to 50 g is recommended for present ponds without aeration.

Based on the available information and data from research on ecological, biological and climatical characteristics, the area upstream and downstream of Shahcheraghi Dam is not suitable for warm water aquaculture in earthen ponds. But for cold water aquaculture, there is a good situation especially trout farming. Also, different aquaculture systems including raceway with equipment, semi-recycle and recycle method can be suggested and due to water limitation in the area recycle and semi- recycle is preferred. In each of the mentioned methods, it will be possible to produce 126, 800 and 2000 tons of trout in 7 proposed sites, respectively, along the upstream and downstream rivers of Shahcheraghi Dam. It was also suggested that in order to use the water source for multi-purpose in the areas upstream of the dam, sites constructed on the area of agricultural fields and orchards.