Persistent high hatchery recruitment despite advanced reoligotrophication and significant natural spawning in a whitefish

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Version: Final published version
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Serval ID
serval:BIB_9F8E5B53D433
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Persistent high hatchery recruitment despite advanced reoligotrophication and significant natural spawning in a whitefish
Journal
Global Ecology and Conservation
Author(s)
Wedekind Claus, Vonlanthen Pascal, de Guttry Christian, Stadelmann Richard, Stadelmann Noah, Pirat Aurélien, Perroud Giulia
Publication state
Published
Issued date
07/07/2022
Peer-reviewed
Oui
Volume
38
Pages
e02219
Language
english
Abstract
Many lakes of the pre-Alpine region suffered from severe eutrophication that affected the natural reproduction of whitefish (Coregonus spp.) and necessitated large-scale supportive breeding programs. With the advanced reoligotrophication, it is now important to evaluate the relevance of continued artificial breeding for population dynamics. We focused on a whitefish population of a lake that has reached phase III of the reoligotrophication, i.e., lake biomass production is declining since 2012 in response to low phosphorus concentrations. We show that most eggs are naturally spawned, the observed oxygen concentrations would again support embryo development at all depths, and ready-to-hatch embryos can indeed be found on spawning grounds. We marked all hatchery-produced eggs of the 2014 cohort with Alizarin red, stocked them as usual (at larval or early juvenile stages), and recaptured them over a period of five years. Fish were aged from yearly growth rings on scales, and otoliths were checked for marks. We found 90.3% of the 2014 cohort to be hatchery-born. This ratio did not decline with fish age. We also determined juvenile growth of the cohorts 2012-2020 (based on the first annual ring on scales) and found that stocking intensity predicted juvenile growth (r2 = 0.67). This strong density dependence of individual growth suggests that stocking has largely determined cohort size over the first nine years of reoligo¬trophication phase III. We conclude that large areas of spawning grounds allow again for successful embryogenesis, that large quantities of eggs are naturally spawned, but that natural recruitment is significantly reduced by ecological or evolutionary factors, e.g., competition with hatchery-born fish, desynchronization of trophic interactions, or long-term effects of fishing- or hatchery-induced evolution.
Keywords
Eutrophication, supplementary breeding, salmonid, fish growth, density dependence, sediment memory effect, trophic interactions, artificial selection
Open Access
Yes
Funding(s)
Swiss National Science Foundation / Projects / 31003A_182265
Create date
04/07/2022 12:12
Last modification date
08/07/2022 6:11
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