Ecosystem-based management outperforms species-focused stocking for enhancing fish populations

Abstract

Ecosystem-based management is costly. Therefore, without rigorously showing that it can outperform traditional species-focused alternatives, its broad-scale adoption in conservation is unlikely. We present a large-scale replicated and controlled set of whole-lake experiments in fish conservation (20 lakes monitored over 6 years with more than 150,000 fish sampled) to examine the outcomes of ecosystem-based habitat enhancement (coarse woody habitat addition and shallow littoral zone creation) versus a widespread, species-focused alternative that has long dominated fisheries management practice (i.e., fish stocking). Adding coarse woody habitats alone did not, on average, enhance fish abundance, but creating shallow water habitat consistently did, especially for juvenile fish. Species-focused fish stocking completely failed. We provide strong evidence questioning the performance of species-focused conservation actions in aquatic ecosystems and instead recommend ecosystem-based management of key habitats.

A global synthesis of peer‐reviewed research on the effects of hatchery salmonids on wild salmonids

“…As an example, research on brown trout found long‐term supplementation significantly reduced genetic diversity among locations and compromised the conservation of local genetic variation (Fernández‐Cebrián et al, 2014), which threatened biodiversity in their southern range (Cagigas et al, 1999; Horreo et al, 2014; Splendiani et al, 2019). A tremendous amount of money and effort has been invested in restoring habitat to improve population productivity and increase carrying capacity (ISAB, 2015), and help offset future effects from climate change (Beechie et al, 2013; Bilby et al, 2022), an action demonstrated to increase wild fish abundance more effectively than species‐specific stocking efforts (Radinger et al, 2023). Because the resilience of salmonids also depends on their functional genetic capacity to survive and reproduce in a changing environment (Kardos et al, 2021), future research could help illuminate the extent to which, if any, alterations to genetic diversity may influence returns on habitat investments where both hatchery and wild fish co‐exist.…”

Destabilizing Effects of Environmental Stressors on Aquatic Communities and Interaction Networks across a Major River Basin

“…6,7 Ecosystem-based management has been proven to be superior to other measures. 77 While our results are the result of observational studies and do not imply direct causality, the identified patterns are plausible from a mechanistic perspective and suggest predominant importance for understanding the relationships between the decline of community stability and environmental stressors, at least for the data observed in the Shaying River. The large spatial extent and high realism of the assessed parameters contribute to the relevancy.…”

“…In general, on the basis of 3 years of eDNA data sets, our study revealed potential mechanisms of destabilizing effects of aquatic multiple communities across a major river basin under persistent stressors and found that the decline of community stability mainly depended upon the diversity-mediated pathway, including the increase of species synchrony and the changes of interaction networks. These findings have certain implications for the development of “alert indicators” based on community stability to identify the potential effect thresholds of environmental stressors from the management perspectives, because stability metrics (including species stability and network stability) have strong linkages with ecosystem services and functions. , Ecosystem-based management has been proven to be superior to other measures …”

The One Health approach for allergic diseases and asthma

“…As a result of increased industrialization and overpopulation, the quantity of toxic metals in the environment is increasing, including the air, soil, water, and food 13 . In the wildlife species‐focused stocking for enhancing fish populations should be replaced by eco‐system‐based management 14 . Thus, the low‐specific population sizes necessitate urgent international conservation efforts, prevention of extinction, and species reintroduction 15…”