Measuring the net biological impact of fisheries enhancement: pink salmon hatcheries can increase yield, but with apparent costs to wild populations

Abstract

Hatchery production of juvenile fish for release into the wild has been practiced for well over a century in an effort to increase the number of salmon available to harvest. In this study, we evaluate the net impact of the largest such program in North America, the hatchery program for pink salmon (Oncorhynchus gorbuscha) in Prince William Sound (PWS), Alaska. At the same time the hatchery program was increasing in output, there was a major change in productivity in the North Pacific so that throughout Alaska pink salmon increased dramatically in abundance between the 1970s and the 2000s. Using other regions of Alaska as reference sites, we estimate that the PWS hatchery program has increased the total catch by an average of 17 million fish, of which 8 million have been allocated to pay hatchery operating expenses. We estimate that the maximum sustainable yield (MSY) of wild spawning fish in PWS has increased slightly (28%), while in regions of Alaska without pink salmon hatchery programs the MSY has tripled. Our results support the use of a precautionary approach to future large-scale stock enhancement efforts.

How ecological processes shape the outcomes of stock enhancement and harvest regulations in recreational fisheries

“…, Amoroso et al. ), the practice can also contribute to the decline of wild fish populations by elevating competition or predation, fostering disease outbreaks, promoting mixing of wild populations with domesticated, hatchery‐reared fishes (Laikre et al. , van Poorten et al.…”

“…), creating a fundamental trade‐off between wild fish conservation and maintaining or enhancing fisheries through (successful) stocking (Lorenzen , Amoroso et al. , Camp et al. ).…”

Effects of increased specialization on revenue of Alaskan salmon fishers over four decades

“…To quantify relationships between hatchery production and catch variability, we used the landed catch from each region and species as a response (following Amoroso et al., ; Hilborn & Eggers, ; Knapp, Roheim, & Anderson, ). Using a variance function regression model, we extended the approach of Amoroso et al.…”

“…Using a variance function regression model, we extended the approach of Amoroso et al. () to model variability in salmon catches as a continuous function of the hatchery contribution of catches. Within each region (Table ), the hatchery contribution to catches and total catches of each species are from Stopha (), with Kodiak and the Alaska Peninsula grouped because of reporting.…”

“…The modern era of Alaska's large‐scale hatchery programme began in the late 1970s in response to low returns (Stopha, ), with substantial increases in hatchery releases during the 1980s (Leber, Kitada, Blankenship, & Svasand, ; Mahnken, Ruggerone, Waknitz, & Flagg, ; Ward, Adkison, et al., ). Many of these hatchery programs increased production in an effort to stabilize the variability in salmon catches (Brooks, ; Hilborn & Eggers, ), and while recent work has suggested these programmes may increase total yield (Amoroso, Tillotson, & Hilborn, ), quantitative support for reduction in revenue variability remains unclear. Previous work has largely concentrated on the ecological effects of hatcheries (Hilborn, ; Hilborn & Eggers, ; Ruggerone & Connors, ; Wertheimer, Smoker, Joyce, & Heard, ), or economic yield (Boyce, Herrmann, Bischak, & Greenberg, ; Leber et al., ).…”