Current growth,fat reserves and somatic condition of juvenile Baltic herring (<Emphasis Type="Italic">Clupea harengus membras</Emphasis>) reared in different salinities |
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Authors: | Marjut Rajasilta Päivi Laine Jorma Paranko |
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Institution: | (1) Archipelago Research Institute, University of Turku, 20014 Turku, Finland;(2) Department of Cell Biology and Anatomy, Institute of Biomedicine, University of Turku, 20014 Turku, Finland |
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Abstract: | We studied the effect of salinity on growth, fat reserves and condition of the Baltic herring (Clupea harengus membras) juveniles in order to determine their optimum salinity. About 5 months old fish were reared in four salinities (5.7, 8,
12 and 15 psu) over a period of 1.5 months in constant temperature (+6°C) and photoperiod (light:dark = 12 h:12 h). Uptake
of radioactively labelled glycine (14C-glycine) by the scales was used as an indicator of growth rate. The amount of mesenteric fat varied among individuals, but
fish kept in 12 psu had significantly more fat in their body cavity and also their somatic condition was better (P < 0.05) than in juveniles kept in the other salinities. Incorporation of 14C-glycine by the scales was dependent not only on salinity, but also on the method of scale sampling. Part of the scales sampled
was non-growing and therefore unsuitable for the analysis of growth. Using the growing scales in the analysis, the current
growth rate of herring juveniles was highest in salinities of 8 and 12 psu. Fat reserves, somatic condition and growth rate
suggested that Baltic herring juveniles have their optimum salinity in 8–12 psu, which is somewhat higher than the salinity
in most of the nursery grounds in the Baltic Sea. |
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