The effect of polychaete (Hediste divercicolor) on growth performance and body composition of sea bass (Dicentrarchus labrax) larvae

In this thesis, it was aimed to determine the effect of polychaete (Hediste diversicolor) as an alternative raw material source on the growth performance and body composition of juvenile sea bass (Dicentrarchus labrax). Experimental diets were prepared as iso-protein (48%) and iso-lipidic (14%) by using polychaete meal (PU) instead of 0%, 5%, 10%, 15% and 20% of fish meal protein. Experimental fish (with an initial weight of 14.56±0.01 g) were stocked in 15 tanks of 400 liters, 10 fish of each tank. The experimental treatments were tried with 3 replications. The diets were fed by hand 2 times a day until satiation for 53 days. According to the data obtained at the end of the experiment, the growth, feed efficiency and organ index values of the sea bass fry in the experimental groups were found to be comparable regardless of polychaete level (P> 0.05). It was observed that the feed consumption of experimental fish tended to increase depending on the increase in the polychaete meal ratio in the feed (Plinear = 0.068). While a significant linear decrease was observed in the body moisture levels of the experimental group fish with the increase of dietary polychaete (Plinear = 0.003), an opposite increasing linear effect was determined in the body protein and lipid levels (P<0.05). Daily nitrogen, lipid and energy consumptions of the experimental fish were not significantly affected by the increase of dietary polychaete (P> 0.05). However, the daily lipid gains of fish increased with the increase of PU levels (P<0.05). The increase in daily lipid gains of the experimental group fish was positively reflected in the daily energy gain values (Plinear = 0.075). While the increasing dietary polychaete levels linearly increased the percentage of lipid retained by the fish (Plinear = 0.043), the nitrogen and energy retention percentages of the fish were not affected. There were significant impacts of increasing dietary polychaete concentrations on some individual fatty acids or fatty acid groups of the liver and muscle of the experimental fish. For instance, there was a linear increase with dietary polychaete levels in terms of liver total SFA whereas an opposite significant trend was the case in total PUFA (Plinear <0.05). Total SFA levels of fish muscle linearly increased with dietary polychaete but an inverse relation was observed for total muscle MUFA and PUFA (Plinear <0.05). As a result, polychaete meal inclusion into the diets of Eurpean sea bass up to 20% in place of fishmeal did not adversely affect the growth and feed utilization performance. Plus, polychaete meal had a nutritional value equivalent to or superior to fishmeal in terms of nutrient digestion coefficients and environmental impact.