A new analysis has revealed a global decline in fish growth over the last century, with scientists warning that overfishing and environmental change are eroding the biological foundations of many fisheries.
Helen Yan led the study as part of her PhD program at James Cook University. She said human-driven pressures are causing large-scale changes to the ecologies and life histories of fishes.
"We lacked a global evaluation of these impacts on fish life histories over time, so we measured growth performance - a life-history trait that captures the trade-off between growth rate and body size - across 113 years," said Dr Yan.
The scientists analysed 7683 growth curves encompassing 1479 marine species between 1908 and 2021. They found declining growth performance from about 1908 onwards, with the greatest declines concentrated among commercially valuable species.
"Managed fisheries experienced an average 9% decline in growth performance over the last century. This indicates fishes are growing to relatively smaller sizes and/or at slower rates," said Dr Yan.
She said commercial size-based fishing practices, not temperature, are the primary drivers of the global pattern of declining growth.
"Despite relatively consistent increases in ocean temperatures globally, declines in growth performance were detected mainly in temperate regions. Probably because commercially targeted species are overrepresented at higher latitudes.
"This suggests the biological imprint of intensive fishing can overwhelm any direct warming signal on growth at the global scale.
"However, there may still be a synergistic effect between fishing and climate change that could have a larger impact than any one stressor alone," said Dr Yan.
She said the findings carry practical implications for stock productivity, fisheries management and ecosystem resilience.
"Smaller, slower-growing fish alter food webs, reduce yield potential and complicate recovery efforts. We need to seriously consider measures such as stricter catch limits, size protections, habitat protections and longer-term monitoring to detect life-history changes.
"If we don't do these things, and fairly urgently, the biological foundations of many fisheries will continue to erode, with consequences for food security, coastal economies and marine biodiversity," said Dr Yan.
