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Nitrogen and phosphorus loading values in rainbow trout (Oncorhynchus mykiss) farming system in marine floating cage in the Southern Caspian Sea


Journal of Aquaculture & Marine Biology
SM Vahid Farabi, M Golaghaei Darzi, M Sharifian, H Nasrollahzadeh Saravi

Abstract

The aim of this study was to determine the loaded amounts of nitrogen (N) and phosphorus (P) in the Rainbow trout farming system in the floating cage in the south of the Caspian Sea in 2018-2019. Two weight groups of fish (Group 1: 120g; Group 2: 300g) with 30,000 pieces were introduced to each floating cage. The offshore farm had three cages for group 1 (G1) and two cages for group 2 (G2). The fish culture period was 165 days and started in December and ended in May. At the end of the fish farming period, in groups 1 (G1) and 2 (G2), the weights were 780grams and 1450grams, respectively. The fish feed was semi-submerged extruded. The feed conversion ratio for G1 and G2 was determined 1.1 and 1, respectively. Fish survival rate was 95%. The consumption of fish feed in G1 and G2 was 21 tons and 33 tons, respectively in each cage. The N content of the feed was 6.4% and the amount of feed P was 1.25%. The amount of N and P in dry fish was 10% and 3.2%, respectively. The amount of N and P loaded per 21ton and 33ton of fish feed in G1 and G2 was 873.75 and 1292.6 kg N and 112.02 and 150.3kg P respectively. Also, the percentage of N and P in fish feed loaded in G1 and G2 was 65 and 61.2% N and 42.4 and 36.4% P, respectively. Therefore, in this marine farm, with the production of 149.34 tons of Rainbow trout, 5206.45kg N and 636.66kg P were loaded in the environment around the cage. These data are representing average conditions.

Keywords

marine cage culture, caspian sea, nutrient load, rainbow trout (Oncorhynchus mykiss) nitrogen, eutrophication, phosphorus loading,

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