Production dynamics reveal hidden overharvest of inland recreational fisheries

Holly S. Embke; Andrew L. Rypel; Stephen R. Carpenter; Greg G. Sass; Derek Ogle; Thomas Cichosz; Joseph Hennessy; Timothy E. Essington; M. Jake Vander Zanden

doi:10.1073/pnas.1913196116

New Research In

Contributed by Stephen R. Carpenter, October 17, 2019 (sent for review August 6, 2019; reviewed by Ian Cowx and John M. Gunn)

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Significance

Despite the great economic and cultural importance of inland recreational fisheries, overharvest of inland fish stocks is rarely studied. We compared biomass harvest and biomass production in a unique 28-y, 179-lake dataset of a valuable inland fishery and found ∼40% of stocks to be overharvested, a rate >10× higher than population thresholds used to manage these fisheries. This is an empirical example of recreational fisheries overharvest in a declining fishery revealed through a biomass production approach. The high level of production overharvest we found highlights the value of ecosystem approaches to inform recreational fisheries management in an era of rapid environmental change.

Abstract

Recreational fisheries are valued at $190B globally and constitute the predominant way in which people use wild fish stocks in developed countries, with inland systems contributing the main 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. Here we directly evaluate angler harvest relative to the biomass production of individual stocks for a major inland recreational fishery. Using an extensive 28-y dataset of the walleye (Sander vitreus) fisheries in northern Wisconsin, United States, we compare empirical biomass harvest (Y) and calculated production (P) and biomass (B) for 390 lake year combinations. Production overharvest occurs when harvest exceeds production in that year. Biomass and biomass turnover (P/B) declined by ∼30 and ∼20%, respectively, over time, while biomass harvest did not change, causing overharvest to increase. Our analysis revealed that ∼40% of populations were production-overharvested, a rate >10× higher than estimates based on population thresholds often used by fisheries managers. Our study highlights the need to adapt harvest to changes in production due to environmental change.

Footnotes

↵¹To whom correspondence may be addressed. Email: hembke{at}wisc.edu or srcarpen{at}wisc.edu.

Author contributions: H.S.E., A.L.R., S.R.C., G.G.S., and M.J.V.Z. designed research; H.S.E. performed research; D.O., T.C., J.H., and T.E.E. contributed new reagents/analytic tools; H.S.E., A.L.R., S.R.C., G.G.S., and M.J.V.Z. analyzed data; and H.S.E., A.L.R., S.R.C., G.G.S., D.O., T.C., J.H., T.E.E., and M.J.V.Z. wrote the paper.
Reviewers: I.C., University of Hull; and J.M.G., Laurentian University.
The authors declare no competing interest.
Data Deposition: All code detailing production and biomass calculations have been deposited on GitHub (https://github.com/hembke/Production-and-Biomass-Calculation). All data have been deposited in the Environmental Data Initiative repository (https://doi.org/10.6073/pasta/611479e438500a56d5085020d3aa16cd).
This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1913196116/-/DCSupplemental.

Published under the PNAS license.

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