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Published 2004

Read in Norwegian

Publication details

Journal : Journal of Fish Biology , vol. 65 , p. 1526–1542 , 2004

Publisher : John Wiley & Sons

International Standard Numbers :
Printed : 0022-1112
Electronic : 1095-8649

Publication type : Academic article

Contributors : Frantzen, Marianne; Damsgård, Børge; Tveiten, Helge; Moriyama, Shunsuke; Iwata, M; Johnsen, Helge K.

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Kjetil Aune
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Proportions of maturing fish and reproductive output [egg size, relative fecundity, spermatocrit
and gonado-somatic index (IG)] were studied in repeat-spawning (þ4 year old) male and female
Arctic charr Salvelinus alpinus, subjected to periods of fasting. Groups of individually tagged
Arctic charr were fasted for c. 3, 6, 7 and 9 months, from November 1998. In the period
February to November 1999, size (fork length and mass), specific growth rate (G), condition
factor (K) and plasma concentrations of growth hormone (GH), insulin-like growth factor I
(IGF-I), oestradiol-17b (E2; females) and 11-ketotestosterone (11KT; males), were monitored
monthly. Maturing fish in each group started to gain mass soon after food was made available,
and both sexes reached the highest K and G c. 2 months after the onset of feeding. The fasting
regimes resulted in different growth patterns during spring and summer when energy stores are
normally replenished in Arctic charr, and K prior to the breeding season was significantly
higher in the groups fasted for 3 and 6 months compared to the groups fasted for 7 and 9
months. There were significant positive correlations between K during the period prior to
the breeding season and reproductive output in terms of the IG, spermatocrit and relative
fecundity. There was, however, no clear relationship between the length of starvation and the
proportion of maturing fish. Likewise, no clear relationships were found between reproductive
development and plasma levels of GH and IGF-I, although both showed marked seasonal
changes, being ‘down-regulated’ during winter months and ‘up-regulated’ throughout summer
months. # 2004 The Fisheries Society of the British Isles