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 Cabrera National Park (CNP), an insular Marine Protected Area (MPA) located off southern Mallorca (Western Mediterranean). 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 (ITWs) 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.

Wind Conditions on the Great Barrier Reef Influenced the Recruitment of Snapper (Lutjanus carponotatus)

“…Consequently, the scenarios with these winds had the greatest recruitment potential. Other studies have similarly found that wind induced oscillatory flow patterns can concentrate plumes of fish larvae, facilitating recruitment (Basterretxea et al, 2013). Further, the winds identified to be favorable for recruitment in this study were highly seasonal.…”

“…When they were programmed to swim the upper limit of the modeled rate of return increased significantly, with the projected rates ranging from 0.4 to 28.8%. Many studies have similarly found that the inclusion of behavior in models vastly improved the predicted larval retention and subsequent recruitment (e.g., Paris et al, 2007;Butler et al, 2011;Basterretxea et al, 2013). In addition to improving the overall projected recruitment, when larvae were made to swim, they counteracted the adverse dispersive forces of strong winds and the CE.…”

Larval Fish Swimming Behavior Alters Dispersal Patterns From Marine Protected Areas in the North-Western Mediterranean Sea

“…When no data is available, the bias associated with their absence could be estimated by comparing dispersal patterns obtained from passive simulations and from simulations of caricatured behaviors (e.g., swimming at high speed and perfectly oriented), as part of a sensitivity study. North et al (2009) provide suggestions for the implementation of such sensitivity approaches and Basterretxea et al (2013) is an example of such a study in the Mediterranean.…”

“…Overall, we interpret the predicted patterns of connectivity at scales of tens to hundreds of kilometers, for which the resolution of 1.2 km is not limiting. In contrast, to answer similar questions (regional connectivity and rates of larval retention), other studies used much lower resolutions (e.g., >12 km; Andrello et al, , 2015) or integration time steps allowing larvae to cross more than one grid cell in a single step (Basterretxea et al, 2013). Such use of unsuitable configurations could skew the dispersal patterns obtained (North et al, 2009).…”

“…Basterretxea et al (2012) first assessed the connectivity in a network of MPA and found that passive retention reaches >30% within 10 km of the seeding MPA. Then, Basterretxea et al (2013) tested the influence of swimming at 5 cm s −1 toward the coast, while advection transported the larvae offshore. It resulted in slightly higher retention rates (41%), yet still of the same order of magnitude.…”