Climate Change Vulnerability of Native and Alien Freshwater Fishes of California: A Systematic Assessment Approach

Peter B Moyle,Rebecca M Quiñones,Patrick K Crain,Joseph D Kiernan,Maura Geraldine Chapman

doi:10.1371/journal.pone.0063883

Abstract

Freshwater fishes are highly vulnerable to human-caused climate change. Because quantitative data on status and trends are unavailable for most fish species, a systematic assessment approach that incorporates expert knowledge was developed to determine status and future vulnerability to climate change of freshwater fishes in California, USA. The method uses expert knowledge, supported by literature reviews of status and biology of the fishes, to score ten metrics for both (1) current status of each species (baseline vulnerability to extinction) and (2) likely future impacts of climate change (vulnerability to extinction). Baseline and climate change vulnerability scores were derived for 121 native and 43 alien fish species. The two scores were highly correlated and were concordant among different scorers. Native species had both greater baseline and greater climate change vulnerability than did alien species. Fifty percent of California’s native fish fauna was assessed as having critical or high baseline vulnerability to extinction whereas all alien species were classified as being less or least vulnerable. For vulnerability to climate change, 82% of native species were classified as highly vulnerable, compared with only 19% for aliens. Predicted climate change effects on freshwater environments will dramatically change the fish fauna of California. Most native fishes will suffer population declines and become more restricted in their distributions; some will likely be driven to extinction. Fishes requiring cold water (<22°C) are particularly likely to go extinct. In contrast, most alien fishes will thrive, with some species increasing in abundance and range. However, a few alien species will likewise be negatively affected through loss of aquatic habitats during severe droughts and physiologically stressful conditions present in most waterways during summer. Our method has high utility for predicting vulnerability to climate change of diverse fish species. It should be useful for setting conservation priorities in many different regions.

Highlights

Freshwater fishes are in decline worldwide because of humancaused degradation of aquatic habitats [1,2,3,4]
Total scores for Module 1 potentially ranged from a 10 to 42, while scores for Module 2 potentially ranged from 10 to 35
Only 19% of alien fishes showed a high vulnerability to climate change, 86% (37 species) showed at least some vulnerability to climate change, reflecting that aquatic habitat quality and quantity are likely to decline under most scenarios

Summary

Introduction

Freshwater fishes are in decline worldwide because of humancaused degradation of aquatic habitats [1,2,3,4]. Anthropogenic climate change is further accelerating declines of many freshwater fish species, in regions with arid or Mediterranean climates [5,6,7]. These rapid declines are a major conservation challenge, requiring setting priorities for conservation and for devising strategies to prevent widespread extinctions [8]. There is a need for a rapid and repeatable assessment method that can incorporate expert knowledge to determine relative vulnerability of different species to climate change [2,9]. We present a methodology that allows systematic evaluation of climate change impacts on freshwater fishes, using the complete California fish fauna as an example

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Discussion

Conclusion