Surveying Most Efficient Method for Culture of Gammarus as a Live Food in Aquaculture
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AbstractIn order to produce a procedure for production of a natural food source for fish, amphipod Gammarus (Crustacea) were noticed, which inhabits spring-brooks in wide areas of Fars province, especially in its cold regions. Five typical habitats of these animals were firstly identified, and some of their important physical and chemical factors, including depth, current velocity, width of habitat, dissolved oxygen concentration, pH and electrical conductivity were measured monthly for one year, May 2000-April 2001. Some other factors of water quality like calcium, magnesium, and total hardness, sulfate, chloride, and potassium ions concentration were measured just once. Artificial culture were designed and conducted in three steps. At step 1, using 10 individuals in four 1000 cc beakers, firstly the effect of three different sources of water, the city pipe water, ground water (a well), and water from one of the typical springs were investigated measuring survival time in no-food condition. Then, selecting spring water, the effect of three different diet including fresh lettuce leaves, decaying willow leaves, and fish pellets on the specimen s survival were recorded. At step 2, using 400 individuals in four 40 liter glass tanks containing and supplied with fresh lettuce leaves as food source, firstly the probable effect of artificial illumination, and then, introduction of microbial flora from the habitat spring were compared to a control group. In both steps, water was aerated continuously. Finally at step 3, an experimental pond (600cm×200cm, with 50cm depth) was made and 2000 adult amphipods were introduced. Animals were fed by fish pellet. During the experiment, water temperature, dissolved oxygen concentration, and pH, along with the new population density and total body length were measured in consequent repeated times. All the data were processed by calculation of means, standard deviations, and statistical tests including Analysis of Variance and Duncan test. Results showed that in natural habitats current velocity ranged 2.5-100cm/s (Mean=29.3), water depth ranged 5-60cm (mean=25.3), water temperature ranged 11.2-18.4°C (Mean=14.4) dissolved Oxygen ranged 3.45-13.33 ppm (Mean=7.5), pH ranged 6.5-8.8 (Mean7.6), and electrical conductivity ranged 200- 760µs/cm (Mean=357), in the period of our investigation. Range of variation between five habitats was 26.55- 56.64ppm (Mean=43.48) for Chloride ion concentration, 7.20-16.80ppm (Mean=12.77) for sulfate ion, 50.50- 85.77ppm (Mean=63.00) for Calcium hardness, 99.50-246.22ppm (Mean=138.59) for Magnesium hardness, 150-332ppm (Mean=201.6) for total hardness, and 0.15-0.30ppm (Mean=0.25) for Potassium ion concentration. Culture experiments showed that spring water is significantly the only reliable source compared to the well water and city pipe water, and lettuce fresh leaves and decaying willow leaves had showed significant differences compared to fish pellet in feeding amphipods in closed and limited spaces of laboratory containers. Also, artificial photoperiod had a significant negative effect in laboratory situations which their water temperature was not controlled on low ranges, due to a rapid and huge algal growth. Adding microbial flora, which may has benefits for amphipod s better growth, showed no significant effect on their survival in tanks. Culture in pond proposed that the process of growth and reproduction acts continuously through the whole year, but it seemed that new generations did not reach the adulthood and sexual maturation until the coming spring.
Publisher or UniversityIranian Fisheries Science Research Institute
Series : Nr84.222;