The effect of environmental conditions on seasonal and inter-annual abundance of two species in the Yangtze River estuary

Abstract

It is important in fisheries management to evaluate the effects of environmental factors on changes in the abundance of species, particularly those inhabiting estuaries. The Yangtze River estuary is the largest in the western Pacific Ocean and serves as a spawning, feeding and nursery ground to species of economic and ecological importance, such as Collichthys lucidus and Lophiogobius ocellicauda. By using 3 years of environmental variables and data on the abundance of C. lucidus and L. ocellicauda gathered seasonally through trawl surveys, we compared four generalised additive models (GAMs), each comprising different spline terms, to analyse the influence of the measured variables on the abundance of both species. Deviance explained, Akaike information criterion and generalised cross-validation were used to select the optimal GAM after evaluating the fit and predictive performance of the models. Generalised additive model (GAM) with spline ‘te’ was the optimal model, and predicted that the abundance of both species was influenced by season and by variables temperature, salinity and chlorophyll-a concentration. For C. lucidus, abundance increased during spring and summer, and, for L. ocellicauda, it was higher during winter. Given the socioeconomic importance of both species, we contend that determining the drivers causing abundance fluctuations of estuarine species can support the putting in place of robust monitoring and assessment plans for such fisheries.