A comparison of growth patterns between a stunted and two large predatory Arctic charr populations under identical hatchery conditions |
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Authors: | Matti Janhunen Nina Peuhkuri Jorma Piironen |
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Institution: | (1) Joensuu Game and Fisheries Research, Yliopistokatu 6, FI-80100 Joensuu, Finland;(2) Finnish Game and Fisheries Research Institute, Viikinkaari 4, P.O. Box 2, FI-00791 Helsinki, Finland |
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Abstract: | Arctic charr are characterized by an extensive variability in growth and body size in natural waters. Although growth traits
may involve a significant heritable component, most of this intraspecific variation presumably is environmentally induced
and thus attributable to phenotypic plasticity. In the present study, size-at-age and length–weight relationship (body condition)
were assessed for three Finnish Arctic charr populations of different geographical origins and extreme size forms (a stunted
vs. two large-growing, predatory charr) held under standardized rearing conditions for 3 years (up to 37 months after hatching).
In particular, our interest was to investigate whether the differences in growth between the large and the stunted charr as
observed in the wild populations would diminish when the fish are offered suitable food in abundance. Population-specific
mean body size and condition differed significantly in 0+, 1+, 2+ and 3+ fish. However, the identical rearing conditions resulted
in the originally stunted charr reaching a comparable final mean size (317 mm/427 g) as the large charr populations (343 mm/510 g
and 359 mm/497 g). Some individuals were of the same size as their parents at spawning already at the age of 0+ years. Furthermore,
length–weight regression residuals of the stunted charr developed to a notably high level, indicating the largest final condition
mean. The increase of size variation (CV of weight) in stunted charr lasted for over two growth seasons, whereas in large
charr it remained stable since the end of the first summer. Variations in mortality and sexual maturation at age 2 seemed
to be less relevant factors affecting overall growth performance. The study demonstrates an example of the high plasticity
involved in the growth of fish: the stunted charr possess a tremendous capacity for growth in a benign environment, virtually
corresponding to that observed in the large predatory populations. |
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