Details

Autor(en) / Beteiligte

• Jager, Henriette I.
• Lepla, Ken B.
• Van Winkle, Webb
• James, Brad W.
• McAdam, Steven O.

Titel

The Elusive Minimum Viable Population Size for White Sturgeon

Ist Teil von

• The American naturalist, 2010-09, Vol.139 (5), p.1551-1565

Ort / Verlag

United States: Taylor & Francis Group

Erscheinungsjahr

2010

Link zum Volltext

Quelle

Wiley Blackwell Single Titles

Beschreibungen/Notizen

• Damming of large rivers in the U.S. Pacific Northwest and Canada has divided the historical population of white sturgeon Acipenser transmontanus into more than 36 fragmented populations, few of which are thriving. We now face the challenge of managing these populations to avoid extirpation. Two goals of this study were to identify extinction thresholds related to small size and inadequate habitat for this species. The minimum viable population size (MVP) is the threshold size above which populations support recruitment and grow and below which populations fail to support recruitment and decline. We estimated a single, cross‐population MVP using data from multiple populations and quantile regression, which removed the effects of factors other than population size. Only two populations (those in the Bonneville and Dalles reservoirs on the Columbia River), both with significant increasing trends, were larger than our MVP estimate. We detected significant decreasing trends in two populations—those below Bonneville Dam and in the Kootenai River. To discover how site‐specific differences in river habitat influence MVP, we used a population viability analysis (PVA) model that incorporated Allee mechanisms. The PVA model identified a river segment length below which extinction was certain regardless of initial population size. Above this threshold, simulated populations in river segments that were longer or that provided more frequent recruitment opportunities were able to persist with smaller initial sizes. Two priorities emerged for white sturgeon: monitoring age structure and understanding the circumstances preventing recruitment to age 1. Our results ultimately guided us toward thresholds in rearing habitat and age structure that promise to develop into more useful conservation tools than MVP for this and similar long‐lived species.