Delayed response of fish abundance to environmental changes: a novel multivariate time-lag approach

摘要

We used long-term juvenile abundance data (2000 to 2010) of dominant fish species in 2 coastal habitats of Southern Brazil to test a novel adaptation of traditional multivariate analyses, as an alternative for evaluating the lag in species response relative to the changes in environmental variables. We investigated the hypothesis that the recruitment response to changes in environmental variables is not immediate. This new approach consisted of traditional multivariate analysis (e.g. canonical redundancy analysis) using an explanatory matrix composed of original and lagged environmental variables, and the performance of this analysis was assessed by comparison with traditional univariate time-lag analysis. Both the univariate and multivariate time-lag analyses showed similar results, but the multivariate approach had advantages and is presented as a useful and uncomplicated alternative to conduct time-lag analysis using a multivariate ecological dataset. Marine and estuarine recruitment processes were better explained by lagged temperature (predominant lags of 1 and 2 mo, respectively) than by in-phase (i.e. time lag = 0) temperature. In contrast, other environmental variables (transparency, salinity and freshwater outflow) did not show significant delays. Hence, our findings show that the species response to environmental variables is not immediate, especially for temperature. Rather, the time lag elapsed between the changes in abiotic factors and juvenile abundance is mediated by ecological and hydrological processes. Our study reaffirms the importance of time-lag analyses as a tool for better understanding of the temporal dynamics of estuarine and marine recruitment.