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    Effect of dietary Ulva and Spirulina on weight loss and body composition of rainbow trout, Oncorhynchus mykiss (Walbaum), during a starvation period
    (Wiley-Blackwell, 2011) Guroy, D.; Guroy, B.; Merrifield, D. L.; Ergun, S.; Tekinay, A. A.; Yigit, M.
    P>A study was conducted to determine the effect of dietary algal supplementation on weight loss and proximate composition in rainbow trout, Oncorhynchus mykiss, during starvation. An algae-free control diet (C) and four experimental diets, including varying levels of raw Ulva meal (5% = U5; 10% = U10) and Spirulina meal (5% = S5; 10% = S10) were formulated. Fish were fed to satiation for 12 weeks and then subjected to a 3-week starvation period. Body weight, viscerosomatic index (VSI, %), hepatosomatic index (HSI, %), dress-out (DO, %) and chemical composition of carcass were analysed at the end of each starvation week. The accumulated weight loss of the fish fed dietary algae was almost 50% less than the control group (p < 0.05) after 2 and 3 weeks starvation. No significant differences in weight loss were observed among the fish fed different algal diets during the starvation period. Total body protein and ash contents remained constant in all groups throughout the starvation period. Fish in all treatments lost a significant level of total lipids and changes of liver fatty acid profiles were also observed. Results indicate that low level inclusion of algae in aquafeeds may have economical advantages in terms of reducing weight loss in fish when subjected to a short-term fasting period, that sometimes is necessary after a heavy rainfall or when fish stocks are held back to meet market demand.
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    Effects of dietary protein and lipid levels on growth and feed utilization of wild-caught striped sea bream, Lithognathus mormyrus
    (Wiley, 2011) Kusku, H.; Bulut, M.; Guroy, D.; Ergun, S.; Bilen, S.; Tekinay, A. A.
    P>A feeding trial was carried out to determine the effects of dietary protein and lipid levels on the growth performance and feed utilization of wild-caught striped sea bream (Lithognathus mormyrus). The experimental fish were collected from a local lagoon (Cardak Lagoon, Canakkale, Turkey), transferred to the Marine Net Cage Unit and fed by hand to apparent satiation with a commercial sea bream feed (Biomar; 42% crude protein, 16% crude lipid). Approximately 4 weeks were needed to acclimate the fish to farming conditions. No pathological signs were observed and no fish losses occurred during the adaptation period. For the test trials four test diets with different levels of protein and lipid were formulated [low protein and low lipid (LP:LL), low protein and high lipid (LP:HL), high protein and low lipid (HP:LL), and high protein and high lipid (HP:HL)] and fed to L. mormyrus (mean weight 85.0 +/- 4.6 g SEM) in the net cages (circle divide 2 m, depth 2.5 m) for 60 days. During the experiment water temperature varied between 21.1 and 26.4 degrees C; dissolved oxygen 8.4-9.6 mg L-1; pH 7.2-8.6; and salinity 23.3-25.6 parts per thousand. Growth performances of fish fed high protein diets were higher compared to fish fed low protein diets, irrespective of the dietary lipid level (P < 0.05). Feed conversion ratio (FCR) and protein efficiency ratio (PER) were not influenced by dietary protein or lipid levels (P > 0.05). Preliminary results indicate that striped sea bream can be easily adapted to farming conditions in net cages, and that a diet containing 50% crude protein and 15% crude lipid (HP:LL) levels with 23.0 g protein MJ-1 gross energy of protein/energy ratio would be suitable for striped sea bream growth.