A high harvest rate induces a tendency to generation cycling in a freshwater fish population

• Published in: Journal of Animal Ecology
• Main Authors: HUUSKO, ARI, HYVÄRINEN, PEKKA
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Northern Finland
• Online Access: http://dx.doi.org/10.1111/j.1365-2656.2005.00951.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2656.2005.00951.x; https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2656.2005.00951.x

Summary The dynamics of exploited populations are clearly affected by two major processes, recruitment and harvesting. The large variation in recruitment is caused mainly by the variation of the brood stock size, which links at least partly to harvesting and consequently is under anthropogenic control. Therefore, harvesting has the potential to modulate the dynamics of exploited populations in many ways. Demonstrated by a pelagic planktivore fish, vendace Coregonus albula L., using population dynamics in Lake Oulujärvi, northern Finland, this study shows that the changes in harvesting induced a tendency to generation cycling in the dynamics of a freshwater fish population. The relatively long‐term oscillation in recruitment and stock dynamics of the vendace population transformed into clear 2‐year cycling in recruitment and also into the same tendency in the spawning stock, both induced by the increase of the harvest rate to a high and stable level. The high harvest rate evidently simplified the spawning population structure from a multigeneration state to an almost totally single‐generation state, followed by generation cycling in the population dynamics. The results demonstrated clearly that harvesting can work as forcing agent and actually dictate the population fluctuations. It is very important to be aware of how natural variations in population abundance interplay with harvesting and also with other human actions. All these support a precautionary policy in harvesting and stress the importance of understanding the basic mechanisms of population dynamics in order to gain sustained yields from the population in space and time.