# Global Marine Fishery Stock Productivity Under Climate Change

## TL;DR

This study examines how climate change affects global marine fishery productivity, finding mixed impacts with some regions gaining while others lose.

## Contribution

The study introduces stock productivity as a novel metric to assess climate change impacts on fisheries, using extensive global data.

## Key findings

- Global marine stock productivity showed a moderate decline from 1980–2022 with regional and stock-specific variability.
- Climate projections suggest a 3.0% decline in productivity by 2100 under a 'business-as-usual' scenario.
- Fishery productivity is equally split between 'winners' and 'losers' across regions under climate change.

## Abstract

Marine capture fisheries play crucial roles in global aquatic protein supply and livelihoods of millions of people. Anthropogenic climate change comes as an overlying threat, potentially necessitating substantial adjustments of harvest control rules or rebuilding plans, especially for species (stocks) that are naturally adapted to restricted environmental fluctuations. Stock productivity, defined as surplus production provided by per unit of stock biomass, offers an informative yet underutilized metric for assessing these impacts. With the help of global fishery‐related databases and earth system models, stock productivity estimates were related to key biophysical drivers by state‐of‐the‐art statistical methods. The ultimate goal thereby is to clarify how climate change has affected and will continue to affect this harvest potential. Results show that the hindcasted global stock productivity (710 stocks) exhibited pronounced stock‐specific and regional heterogeneity, with signs of an overall decline (1980–2022). Variations in sea temperature and chlorophyll concentration significantly affected the productivity of about half of the assessed stocks (1993–2020). The subsequent productivity projections indicated relatively moderate reductions in the global mean productivity proxy (2021–2100), though these projections were characterized by uncertainty and with different data availability depending on the regions. However, the important finding of a general balanced prevalence of stock ‘winners’ and ‘losers’ lessened this regional quantification problem. As inferred, by the end of the century, global productivity (also applied to fishery landings) is projected to decline by 3.0% (−6.3% to +0.4%) under a ‘business‐as‐usual’ scenario and 1.0% (−1.6% to −0.3%) under a ‘sustainability’ scenario. Thus, our research indicates relatively moderate effects of climate change on the global fisheries productivity, though with the above‐mentioned existence of clear winners and losers. This finding contrasts with previous investigations that depict remarkable declines in future fishery landings.

In this uniquely extensive global analysis on the productivity of commercial fishery stocks, a common factor was the existence of pronounced heterogeneity, as documented for 710 stocks in the undertaken hindcast over the last decades. Importantly, both winners and losers appear under on‐going climate change, and then seemingly are equally present across waters, that is, at ca. 1:1. Consequently, the noticed shortage of stock inventories in some regions did not methodologically impede scaling up to global trends; the subsequent projections for 657 stocks indicated relatively moderate reductions in the global mean productivity proxy, a result in contrast with commonly conveyed messages.