Tidal and Diel Patterns in Abundance and Feeding of a Marine-Estuarine-Dependent Fish from Macrotidal Mangrove Creeks in the Tropical Eastern Pacific (Colombia)

Abstract

Mangrove ecosystems are nursery habitats for several snapper species worldwide. Yet the short-term dynamics in nursery habitat use of Lutjanidae remain poorly understood, with knowledge biased toward clear water, nonestuarine mangroves. Here, we document the effects of tidal-diel cycles and salinity on patterns in abundance and feeding of the yellow snapper, Lutjanus argentiventris, using samples collected from intertidal creeks in a macrotidal estuarine mangrove during 2009–2010 from Colombia, in the Tropical Eastern Pacific (TEP) region. Abundance and biomass were significantly higher in medium salinity versus low salinity creeks. Contrasting tidal-diel patterns of abundance-densities versus catch mass-biomass were due to a size-based intraspecific variation in mangrove use: fish 20 cm entered at night during both spring and neap tides. L. argentiventris had a generalist diet (mainly fish and porcellanid crabs). Fish <10 cm displayed a narrower diet breadth than larger size classes, with decreasing importance of fish size during ontogeny. The highest stomach fullness index values (especially of individuals <20 cm) during neap tide-daytime inundations contradicted the common assumption that snappers are nocturnal feeders and highlight the role of tidal-diel cycles in determining fish feeding preferences in macrotidal mangrove systems. Comparisons with other studies showed that habitat use and feeding patterns of this and other Lutjanids vary significantly according to size, tidal-diel dynamics, and mangrove settings, e.g., marine microtidal versus estuarine macrotidal systems. Therefore, generalized conclusions derived from a single mangrove setting should be drawn with caution.