Fish stock assessments in Lake Konnevesi

Toivonen, Jaakko; Auvinen, Heikki; Valkeajärvi, Pentti

doi:10.1007/978-94-009-8003-7_34

Cited by 2 publications

(2 citation statements)

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“…Compared with this the yield of 1.0 kg/ha of whitefish may be characterized as moderate exploitation, whereas 0.12 kg/ha of vendace is low and may be increased. The mortality rates fit data reported elsewhere for whitefish (Toivonen et al, 1982;Salojarvi et af., 1981, cited in Auvinen, 1987 and vendace (Salojarvi et ~l . , 1981, cited in Auvinen, 1987, but M might be too high, caused by biased density estimates in 1987 and 1990 leading to an underestimated survival S .…”

Section: Discussionmentioning

confidence: 99%

Monitoring pelagic whitefish (Coregonus lavaretus) and vendace (Coregonus albula) in a hydroelectric reservoir using hydroacoustics

Linløkken¹

1995

Regul. Rivers: Res. Mgmt.

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Stock assessment consisting of hydroacoustics each year and gill-netting every third year was performed in May 1986May -1993 in the regulated Lake Osensjaren. Osensjeren, situated 438m as1 in south-eastern Norway, has a surface area of 45 km2 and a mean depth of 37 m; the water level varies by 6.6 m and the pelagic fish stock consists of whitefish (Coregonus Iavaretus L.) and vendace (Coregonus albulu L.). The total density of large fish (228cm) varied from 10.4 to 70-2 specimens/ha, with a mean value of 39.8 specimens/ha, corresponding to ca. 9 kg/ha. Owing to catches in pelagic gill-nets the fraction of whitefish was 41 -68% in number of the estimated stock, and the mean weights of whitefish and vendace were 270-371 and 153-172g, respectively, so whitefish constituted 62-76% of the biomass. The variation in total density and the variation between whitefish and vendace was caused by the fluctuating recruitment of both species. The mean lengths of two-year old whitefish and vendace showed reduced growth in years with strong recruitment. Strong year classes seemed to arise only in years when tapping off the lake, which is performed through a tunnel from the bottom, was minor about the time when larvae hatch in April-May.The yield was estimated in 1989 to be 1.0 kg/ha of whitefish and 0.12 kg/ha of vendace. Survival was estimated from stock assessment of large fish to be S = 0.55 for whitefish and S = 0.66 for vendace. The difference in survival rates was due to differences in exploitation, and the natural mortality and fishing mortality, respectively, were estimated to be M = 0.46 and F = 0.14 for whitefish and M = 0.36 and F = 0.05 for vendace. The best time for echosounding is May, before feeding activity results in the fish moving into the littoral zone, or closer to the surface in the pelagic zone. The fact that Osensjaren is regulated probably diminishes the fraction of fish in the littoral zone, especially immediately after filling of the lake.

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Section: Discussionmentioning

confidence: 99%

Monitoring pelagic whitefish (Coregonus lavaretus) and vendace (Coregonus albula) in a hydroelectric reservoir using hydroacoustics

Linløkken¹

1995

Regul. Rivers: Res. Mgmt.

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“…One reason for the selection of this lake was the existence of a considerable biological data base (TOIVONEN 1972). Densities of pelagic fish were mapped in 1978, and 50,000 vendace fin-clipped the same year.…”

Section: Lake Konnevesimentioning

confidence: 99%

Review of the European Inland Fisheries Advisory Commission (EIFAC) experiments on stock assessment in lakes

Dahm

Hartman²,

Jurvelius³

et al. 1992

J Appl Ichthyol

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A series of international collaborative experiments carried out under the auspices of EIFAC sought to compare various sampling methods for stock abundance estimation in European inland waters. Four water bodies were used: the Evo lakes (Finland), Lake Konnevesi (Finland), Lake Constance (Germany) and LakeTegel (Germany). The experiments emphasized the difficulties in obtaining reliable fish stock estimates when using different sampling methods. Comparisons between the various methods were also limited. Poor data reliability was attributed both to problems inherent in the various methods and to deficiencies in the sampling design. These results emphasize the caution with which sampling data from inland water bodies should be interpreted. Suggestions are made by the EIFAC group for further studies. Zusammenfassung Uberblick uber die EIFAC-Experimente zur Bestandsabschatzung bei SeenIn internationaler Zusammenarbeit wurde eine Serie von Ex erimenten auf Anregung der EIFAC durchgefuhrt. Dabei wurden Methoden der Fischbestandsabsciatzung in europaischen Binnengewassern verglichen. Die Experimente wurden an 4 Orten durchgefuhrt: den Evo-Seen und dem Konnevesisee in Finnland sowie dem Bodensee und dem Tegeler See in Deutschland. Es zeigte sich die Schwierigkeit, die Ergebnisse verschiedener Methoden zu vergleichen und zu einer befriedi enden Bestandsschatzung zu kommen. Die Schwierigkeiten gehen auf die Methoden selbst wie auf B e Art ihres Einsatzes zuriick. Die Ergebnisse der Experimente rnahnen zur Vorsicht bei der Interpretation von Bestandsabschatzungen in Binnengewassern. Es werden Vorschlage fur das kiinftige Vorgehen der EIFACArbeitsgruppe und anderer Bearbeiter gemacht.

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Fish stock assessments in Lake Konnevesi

Cited by 2 publications

References 1 publication

Monitoring pelagic whitefish (Coregonus lavaretus) and vendace (Coregonus albula) in a hydroelectric reservoir using hydroacoustics

Monitoring pelagic whitefish (Coregonus lavaretus) and vendace (Coregonus albula) in a hydroelectric reservoir using hydroacoustics

Review of the European Inland Fisheries Advisory Commission (EIFAC) experiments on stock assessment in lakes

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