# Over a century of global decline in the growth performance of marine fishes

## TL;DR

Marine fish growth performance has declined globally over the past century, mainly due to overfishing rather than warming oceans.

## Contribution

This study reveals a 9% global decline in marine fish growth performance, primarily driven by commercial fishing practices.

## Key findings

- Growth performance of marine teleosts declined by 9% from 1908 to present, with larger drops in commercially valuable species.
- Temperate regions showed significant declines despite global temperature increases, likely due to overfishing of high-latitude species.
- Overfishing impacts on fish size structure and demographics likely overshadow warming effects on growth performance.

## Abstract

Human-driven pressures are causing large-scale changes in the ecologies and life histories of fishes. Growth performance is a composite life-history trait that captures the trade-off between two fundamental traits: growth and body size. Here, we assess the impacts of fishing and temperature on the growth performance of marine teleost fishes globally over the last century. Using 7683 growth curves encompassing 1479 species, we find a global pattern of decline in growth performance from 1908 onwards, with the greatest declines in commercially valuable fishes. Indeed, managed fisheries experienced a 9% decline in growth performance over the last century, which can equate to an average decline of up to 23% in asymptotic body size or a 45% decline in the von Bertalanffy growth coefficient (K). Despite relatively consistent increases in ocean temperatures globally, we only detect a decline in the growth performance of fishes in temperate regions, which is probably indicative of an overrepresentation of commercially valuable fishes at higher latitudes. The declines in growth performance likely reflect legacy effects, shaped by overfishing, on changes in the underlying size structure and demographic processes of fished stocks. Therefore, the potential impacts of warmer temperatures on growth performance may be overwhelmingly masked by the impacts of overfishing.

Critical life-history traits, like growth and body size, can influence species’ survival. Using more than 7500 observations, this study suggests that the growth performance of marine fish has declined by 9% over the past century as a result of commercial size-based harvesting.