Fish and Fisheries in Ecosystem Context: Lake Säkylän Pyhäjärvi, the Most Profitable Freshwater Fishery in Finland
<p id="p1">Fish production and fisheries yield in lakes are ultimately determined by primary production, although these relationships are confounded by numerous other factors. The most productive fisheries are based on short food chains, that is, on planktivorous or benthivorous species. Pyhäj&...
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| Formato: | Capítulo de libro |
| Lenguaje: | inglés |
| Publicado: |
IntechOpen
2024
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| Materias: | |
| Acceso en línea: | https://www.intechopen.com/chapters/89619 |
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| Sumario: | <p id="p1">Fish production and fisheries yield in lakes are ultimately determined by primary production, although these relationships are confounded by numerous other factors. The most productive fisheries are based on short food chains, that is, on planktivorous or benthivorous species. Pyhäjärvi (southwest Finland) is an example of such fishery, where sustained catches were an order of magnitude higher relative to primary production than usual. This fishery focused on two introduced coregonid species, whitefish (<em><italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Coregonus lavaretus</italic></em>) and vendace (<em><italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Coregonus albula</italic></em>). The high catches were based on unusually efficient fishery, harvesting 70–90% of the annual production of vendace. The fishery was sustainable through the 1970s and 1980s, but in 1991–1998, continued intense exploitation after recruitment failure led to overfishing of vendace. Reduced fishing pressure allowed the recovery of the stock, but climate warming and eutrophication seem to be changing the fish assemblage from coregonid to perch dominance: perch (<em><italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Perca fluviatilis</italic></em>), roach (<em><italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Rutilus rutilus</italic></em>) and ruffe (<em><italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Gymnocephalus cernuus</italic></em>) are increasing and whitefish decreasing, while vendace and smelt (<em><italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Osmerus eperlanus</italic></em>) have maintained their abundance. As a specialised zooplankton feeder, vendace controls zooplankton, increasing phytoplankton. But by excluding competitors from the open lake, vendace reduces the deleterious water quality effects of other fish species.</p> |
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| ISBN: | 978-0-85014-309-6 |
| DOI: | 10.5772/intechopen.115282 |