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6 September 2021 Occurrence of Two-Year Cyclicity, “Saw-Blade Fluctuation”, in Vendace Populations in Finland
Timo J. Marjomäki, Heikki Auvinen, Harri Helminen, Ari Huusko, Hannu Huuskonen, Pekka Hyvärinen, Juha Jurvelius, Jouko Sarvala, Pentti Valkeajärvi, Markku Viljanen, Juha Karjalainen
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Abstract

The tendency towards two-year cyclicity is considered typical of many Fennoscandian vendace populations, especially in fluctuation of recruitment, based on time series of individual lakes. We used two robust indicators to identify and quantify two-year cycles in vendace population proxy time series at different life-stages — spawning stock biomass (SB), density of newly hatched larvae (LD) and recruitment (REC) — from 22 Finnish lakes. Then we applied Fisher's meta-analytical test to assess the adequacy of the evidence to support the hypothesis that vendace population dynamics include two-year cyclicity. The results supported this hypothesis for REC but not for SB or LD. Yet, the indicators and test are conservative and time-series of SB and LD are shorter than those for REC. The appearance of cycles in REC is associated with high post-recruitment mortality, consequently practically only one spawning per cohort. Cycles may be typical for the recovery period from low abundance period also. Still, some populations with moderate post-REC mortality and non-cyclic SB abundance exhibited cycles in REC. Such dynamics presuppose the existence of more complex regulation based on the interaction of different life stages.

© Finnish Zoological and Botanical Publishing Board
Timo J. Marjomäki, Heikki Auvinen, Harri Helminen, Ari Huusko, Hannu Huuskonen, Pekka Hyvärinen, Juha Jurvelius, Jouko Sarvala, Pentti Valkeajärvi, Markku Viljanen, and Juha Karjalainen "Occurrence of Two-Year Cyclicity, “Saw-Blade Fluctuation”, in Vendace Populations in Finland," Annales Zoologici Fennici 58(4-6), 215-229, (6 September 2021). https://doi.org/10.5735/086.058.0408
Received: 21 September 2020; Published: 6 September 2021
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