The Temperature Size Rule (TSR) proposes that fish living at warmer temperatures will have rapid early growth but lower adult size (Forster et al. 2012). Several North Sea fish stocks have exhibited a synchronous, common trend towards smaller maximum body sizes that was correlated with increasing temperature. This “shrinking” decreased per-capita yields of those stocks by ca. 23% (Baudron et al. 2014). Similarly, it has been projected that by 2050 global fish yields will decrease by
14-24% due to shifting biogeography and the TSR (Cheung et al 2012). Forecasting climate impacts on food security require establishing how past warming has impacted fish growth rates and subsequently fisheries yield.
The aim of WGGRAFY is to determine whether temporal trends in individual growth rates of marine fish are consistent with the TSR and, if so, evaluate the impacts of these responses for fisheries yields. Length and age have been routinely measured for many commercial fish stocks around the world on time scales that are associated with warming. These substantial data have never been compiled as a single, analytical resource for climate change research on global scales.
The WG will compile decadal-scale length at age datasets for large marine ecosystems experiencing differential rates of warming or cooling or no overall trend (e.g., upwelling regions). A standardized statistical approach for modelling average somatic growth will be developed to specifically test whether there is a component of the total variation in growth rates that can be attributed to temperature. This knowledge could provide an empirical foundation for forecasting the impacts of future climate warming on yields.
The unique spatial and temporal scale of length-at-age data are a valuable resource for ecological research. The WG will also develop a strategic plan for archiving length-at-age data similar to how ICES archives data for European waters (Datras) or how global data on recruitment and catch are reported and maintained (e.g., RAM Legacy). This strategic plan will require active and considered engagement with a range of agencies (ICES, EMODnet, FAO, universities, tech specialists) and national fisheries laboratories as well as potential funding sources.
In addition, contribution of PICES WG-43
(Joint PICES/ICES Working Group on Small Pelagic Fish) is expected.