Intentional release of native species undermines ecological stability

Abstract

The massive release of captive-bred native species (“intentional release”) is a pervasive method to enhance wild populations of commercial and recreational species. However, such external inputs may disrupt the sensitive species interactions that allow competing species to coexist, potentially compromising long-term community stability. Here, we use theory and long-term data of stream fish communities to show that intentional release destabilizes community dynamics with limited demographic benefit to the enhanced species. Our theory predicted that intentional release intensifies interspecific competition, facilitating the competitive exclusion of unenhanced species that otherwise stably coexist. In parallel, the excessive input of captive-bred individuals suppressed the natural recruitment of the enhanced species via intensified within-species competition. Consequently, the ecological community with the intentional release is predicted to show reduced community density with unstable temporal dynamics. Consistent with this prediction, stream fish communities showed greater temporal fluctuations and fewer taxonomic richness in rivers with the intensive release of hatchery salmon—a major fishery resource worldwide. Our findings alarm that the current overreliance on intentional release may accelerate global biodiversity loss with undesired consequences for the provisioning of ecosystem services.

Evaluation of extinction risk for stream fishes within an urban riverscape using population viability analysis

“…Even after including the highest density scenario as the starting population size in Stratum 1, extinction probability was reached faster in Stratum 1 than in Strata 2 or 3. Therefore, supplementing population sizes in Stratum 1 would likely not improve the persistence of sucker and chub unless mechanisms affecting the demographic performance of sucker and chub in this area of the river are addressed (Terui et al, 2023). Several mechanisms affecting the demographic performance of sucker and chub are currently being addressed or planned to be addressed through non‐native fish removals and cool groundwater supplementation during summer months (U.S.…”

A Resilience History of the Columbia River Basin and Salmonid Species: Regimes and Policies

“…Politically, hatcheries gave a way to prevent conflicts between different economic sectors, as hatcheries essentially traded concrete ponds for habitat. Hatcheries failed to live up to the unrealistic and unscientific dreams they were initially founded upon [72]. While they did provide more fish to be captured they also diluted the genetics of local populations due to careless mixing of fish across the region and escaped hatchery fish breeding with wild fish, they promoted diseases due to their dense housing, they degraded water quality locally due to their effluents [73], but they gave politicians something positive to point to as economic development in the region and the consequences of hatcheries accelerated.…”

Go west: Population genomics reveals unexpected population fluctuations and little gene flow in Western hemisphere populations of the predatory lady beetle, Hippodamia convergens

“…Despite the pervasiveness of these mass releases, non-target effects of translocations of native species are largely ignored in policy and research. While population augmentations can be demographically and economically beneficial, they can also adversely impact intraspecific genetic variation by causing the breakdown of local adaptations, loss of genetic variability, and the reshaping of population structure (Laikre et al, 2010;Simberloff & Stiling, 1996;Terui et al, 2023;Wajnberg et al, 2001).…”

“…Despite the pervasiveness of these mass releases, non‐target effects of translocations of native species are largely ignored in policy and research. While population augmentations can be demographically and economically beneficial, they can also adversely impact intraspecific genetic variation by causing the breakdown of local adaptations, loss of genetic variability, and the reshaping of population structure (Laikre et al., 2010; Simberloff & Stiling, 1996; Terui et al., 2023; Wajnberg et al., 2001). Genetic data are important sources of information for gaining insight into historical and recent evolutionary history of species that have had their populations established or augmented by large‐scale releases of individuals, as occurs during biological control (Jones et al., 2023; Kajita et al., 2012; Li et al., 2019, 2020, 2021, 2023; Sentis et al., 2022; Sethuraman et al., 2020; Wang et al., 2023).…”