Identifying drivers of tropical riverine larval fish abundance and diversity

Abstract

Several hypotheses and conceptual models propose to explain mechanisms mediating riverine fish abundance, but few empirical studies to date have explored their utility in tropical systems. This study assesses key components of previous fish recruitment models by exploring spatiotemporal variation in larval fish assemblages in response to predicted key drivers in a tropical Australian river catchment. Data on larval fish composition and abundance, alongside hydrological, hydraulic, habitat and food variables, were collected monthly to bimonthly over one year at eight sites. Variables which best predicted larval fish abundance and diversity were determined with Boosted Regression Trees. The most commonly important predictors were microfauna abundance, structural habitat complexity and temperature, with high values of each predicting high larval fish abundance and diversity. Maximum larval diversity occurred when discharge was highest because several wet-season spawning taxa occurred alongside aseasonally spawning taxa. These findings support previous generic fish recruitment models, demonstrating the utility of their inclusion in the recent Riverine Recruitment Synthesis Model and the applicability of this model for describing processes important for tropical riverine fish recruitment.