Meteorological factors influence marine and resident fish movements in a brackish lagoon

Abstract

Brackish lagoons are vulnerable aquatic environments that host specifically adapted fish species, as well as marine species on a temporary basis. We used long-term passive fishing gear data, to investigate how meteorological factors (i.e., wind and rain) affected resident and marine fish movement between inner and outer habitats in a Northern Mediterranean coastal lagoon. In particular, we used multivariate and threshold analyses to explore the relationship between fish catches in a transitional habitat and wind and rain variables, accounting for other major temporal and environmental variables. Our results indicated that meteorological factors had effects comparable to seasonal and annual variations, for wind and rain, respectively, and thus are potentially relevant drivers of the movement of fish species between coastal lagoons and marine habitats. Overall, prevalent wind direction and rain on the day before sampling were the most effective meteorological variables in enhancing fish movement. Furthermore, movement of lagoon resident species seemed to be enhanced by wind factors (both direction and wind speed), whereas marine species movement was enhanced by rain factors (but it was not possible to disentangle annual and seasonal effects for the latter). Among other factors, dissolved oxygen seemed to be linked to prevailing wind direction and showed significant thresholds around 7–8 mg/l for the increased movement of a number of marine species. Prevailing and gusty wind directions (around WSW) and speed (2–6 m s-1) also showed significant thresholds for at least a resident species and a marine species that uses the lagoon as nursery.