Production, biomass, and yield estimates for walleye populations in the Ceded Territory of Wisconsin from 1990-2017
Recreational fisheries are valued at $190B globally and constitute the predominant use of wild fish stocks in developed countries, with inland systems contributing the dominant fraction of recreational fisheries. Although inland recreational fisheries are thought to be highly resilient and self-regulating, the rapid pace of environmental change is increasing the vulnerability of these fisheries to overharvest and collapse. We evaluate an approach for detecting hidden overharvest of inland recreational fisheries based on empirical comparisons of harvest and biomass production. Using an extensive 28-year dataset of the walleye fisheries in Northern Wisconsin, USA, we compare empirical biomass harvest (Y) and calculated production (P) and biomass (B) for 390 lake-year combinations. Overharvest occurs when harvest exceeds production in that year. Biomass and biomass turnover (P/B) both declined by about 30% and about 20% over time while biomass harvest did not change, causing overharvest to increase. Our analysis revealed 40% of populations were production-overharvested, a rate about 10x higher than current estimates based on numerical harvest used by fisheries managers. Our study highlights the need for novel approaches to evaluate and conserve inland fisheries in the face of global change.
Embke, H., A. Rypel, S. Carpenter, G. Sass, T. Cichosz, J. Hennessy, and J. Vander Zanden. 2019. Production, biomass, and yield estimates for walleye populations in the Ceded Territory of Wisconsin from 1990-2017 ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/611479e438500a56d5085020d3aa16cd. Accessed 2021-04-19.
Production, biomass, and empirical biomass harvest (Y) and calculated production (P) and biomass (B) for 390 lake-year combinations for walleye populations in the Ceded Territory of Wisconsin from 1990-2017
This material is based upon work supported by the National Science Foundation under Cooperative Agreement #DEB-1440297, NTL LTER. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.