Resurrecting failed environment-recruitment relationships: Revisiting cod recruitment in light of the poor-recruitment paradigm

Abstract

Numerous environmental drivers (e.g., temperature, salinity) have been proposed as controls to recruitment. However, these relationships often become discredited over time as further data become available. It remains unclear if these environment-recruitment relationships are spurious results of examining many variables or if environmental drivers’ influences on recruitment change over time, e.g., with shifting climate. We propose that it is of value to re-examine discredited environment-recruitment relationships using the poor-recruitment paradigm (Gross et al. 2022, Fish. Res. 252, 106329). This approach examines whether extreme environmental conditions are associated with poor recruitment, the idea being that non-extreme conditions are uninformative in terms of predicting recruitment. This allows one to detect patterns of poor recruitment regardless of an environment-recruitment relationship’s perceived (lack of) significance. We apply the poor-recruitment paradigm approach to various stocks of Atlantic cod (Gadus morhua) for both historical environment-recruitment data from a metanalysis (Myers 1998, Rev. Fish Biol. Fisher. 8, 285) and for recent environment-recruitment data from the 2023 stock assessments for stocks in the Gulf of Maine and Georges Bank in the northwest Atlantic Ocean. From re-examining historical data, we find poor recruitment can be predicted from previously discredited or uninformative environmental conditions involving temperature, salinity and zooplankton abundance. When re-examining recent data through the poor-recruitment paradigm, we find that temperature continues to have predictive value for poor recruitment, but zooplankton abundance is less informative and does not always follow the poor-recruitment paradigm. These findings suggest that 1) these predictors continue to be important over time for cod recruitment and 2) that for the recent regime, temperature may be a better predictor of poor recruitment than zooplankton abundance, possibly because there is a mismatch between the spatial and temporal measurements of zooplankton abundance and the conditions that cod recruits experience.