Everyone loves photos of the big fish that didn’t get away. However, warming ocean temperatures often mean that young fish grow more quickly but reach smaller adult sizes. This equates to a loss of yield in our commercial fisheries. Scientists are working together to assess the magnitude of the shrinking fish problem in different regional seas and determine what this means for sustainable management now and in the future.
Warming seas can affect fish body sizes, with major implications for size-structured marine ecosystems, species interactions and fisheries productivity. Synchronous shifts towards smaller adult body sizes in marine fish have already been detected in several rapidly warming areas, including the North Sea. Yet, the mechanisms underpinning the temperature size rule (TSR; higher temperatures result in smaller body sizes) remain debated and most fisheries models do not routinely account for the expected temperature-dependent trends in growth. Diagnosing how temperature impacts fish growth and fisheries yields is therefore a priority for fisheries science.
Fish populations are ideally positioned to empirically test whether there is a synchronous common trend in growth rates that is consistent with the TSR. Fish inhabit thermal conditions ranging from cold upwelling regions (non-warming) to shallow regional seas experiencing strong warming. Furthermore, length and age have been routinely measured by fisheries agencies to estimate and monitor fish vital rates and life history traits. In the future, a coordinated analysis of the existing age/length data can produce robust predictive models for forecasting the effects of temperature on growth rates.
The aim of this session is to:
- synthesise ecological and empirical knowledge about trends in fish and other ectotherms' growth rates and body sizes;
- identify mechanisms behind these trends;
- assess the potential impacts of TSR on fisheries yields in the future ocean
The session provides an opportunity to compare different modelling approaches suitable for isolating temperature effects on fish growth, review empirical evidence of changing individual growth rates of fish for a range of marine ecosystems, consider implications of body size changes for fisheries management, and coordinate international-scale research efforts in this field.
Submissions relevant to one of the four topic areas are welcomed:
- assessing the temperature-dependency of growth and body size, as well as possible underlying mechanisms, from experimental and empirical data in the field
- presenting new analytical methods to assess temperature-dependency of growth and body size within multiple drivers
- analysing long-term growth patterns in large marine ecosystems that are experiencing different trends in temperature
- assessing the impacts of warming on commercial fisheries (i.e., yield per recruit, size structure, etc.) and forecast trends in future productivity given plausible warming scenarios.
