Dynamic regulation of larval fish self‐recruitment in a marine protected area

Abstract

The factors that regulate the self‐recruitment of fish larvae were explored in C abrera N ational P ark ( CNP ), an insular M arine P rotected A rea ( MPA ) located off southern M allorca ( W estern M editerranean). Our study attributes the regulation of larval arrival to the MPA to a combination of retention by topographically generated circulation patterns around the island and shelf break frontal dynamics. Specifically, within the shelf, interaction of the wind‐induced oscillatory flow with the island was shown to generate ephemeral recirculation patterns that, over time, favor larval retention in the proximity of the MPA . According to our measurements, oscillatory flows produced by wind‐forced island‐trapped waves ( ITW s) dominate the flow around CNP . ITW ‐forced dispersion simulations were in agreement with the observed distributions of several typical fish species that breed in the CNP . A second regulator of environmental variability is the influence of boundary currents and open ocean mesoscale structures at the shelf break. These structures generate frontal zones that are comparatively more long‐lived than inner‐shelf circulation patterns, and they were shown to act as barriers to the offshore dispersion of coastal fish larval assemblages. Finally, inferences from larval size distributions around the MPA together with particle‐tracking model simulations suggested the relevance of behavioral processes for larval recruitment to the MPA . Based on these observations, the waters around the CNP can be viewed as a relatively stable system that allows breeding fish populations to rely on self‐recruitment for their long‐term persistence, independent of other source populations along the coast of Mallorca.

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