Effects of size grading on growth and survival of juvenile turbot at two temperatures |
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| Authors: | Leif M Sunde Albert K Imsland Arild Folkvord Sigurd O Stefansson |
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| Institution: | (1) Akvaplan-Niva,Strandtorget 2B, PO Box 735, Tromso, Norway;(2) Department of Fisheries and Marine Biology, University of Bergen, High Technology Centre, Bergen, Norway |
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| Abstract: | Juvenile turbot were size graded into three size groups (mean initial size): Small (3.4 g), medium (7.0 g) and large (10.5 g), and additional fish were held in ungraded (6.6 g) groups. Subgroups (n = 396) of fish were tagged and individual growth rates and social interactions within different size categories were studied in fish reared at 13 and 19 °C. Size grading of juvenile turbot did not improve growth. Specific growth rates (SGR) were mainly size-related, and no differences in SGR or mortality between the experimental groups at both tem-peratures were found. A higher level of social interactions was indicated amongst medium-sized fish than amongst those in the smallest and largest categories. Excess feeding may have been important factors in reducing aggression, so that the growth of the smallest individuals was not suppressed by the larger individuals in the present study. Grading seems to be an unnecessary operation to improve the growth and survival of juvenile turbot (5- 150 g). However, as it was mainly the smallest individuals in each group that died, grading of very small turbot (2-5 g) can be recommended. |
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| Keywords: | Grading Growth Survival Turbot (Scophthalmus maximus) |
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