0000000001091389
AUTHOR
Harri Helminen
Unpredictability of fish recruitment: interannual variation in young-of-the-year abundance
In 1989-1998, vendace larvae Coregonus albula were sampled in Finnish lakes following a stratified random sampling design. The abundance of young-of-the-year vendace after the first growing season was estimated using catch-per-unit-effort statistics. The number or total area of nursery places hardly limited the recruitment of vendace in the study lakes. The major proportion of prerecruit mortality of vendace occurred in the larval phase and larval sampling produced significant information on young-of-the-year survival. Although larval abundances and recruitment were clearly associated only in Lake Onkamo, generally high larval abundance was needed to produce high number of recruits.
Occurrence of Two-Year Cyclicity, “Saw-Blade Fluctuation”, in Vendace Populations in Finland
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 dynam-ics include two-year cyclicity. The results supported this hypothesis for RECbut not for SB or LD. Yet, the indicators…