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

Robin Faillettaz,Claire B Paris,Jean-Olivier Irisson

doi:10.3389/fmars.2018.00097

Abstract

Most demersal fishes undergo a dispersal phase as larvae, which strongly influences the connectivity among adult populations and, consequently, their genetic structure and replenishment opportunities. Because this phase is difficult to observe directly, it is frequently simulated through numerical models, most of which consider larvae as passive or only vertically migrating. However, in several locations, including the Mediterranean Sea, many species have been shown to swim fast and orient. Here we use a Lagrangian model to study connectivity patterns among three Mediterranean Marine Protected Areas (MPAs) and compare simulations in which virtual larvae are passive to simulations in which oriented swimming is implemented. The parameterization of behavior is based on observations for two groups of species of the family Sparidae: species with small larvae (i.e. 9-11 mm), displaying a maximum swimming speed of 6 cm s-1 and a pelagic larval duration of 13-19 days (e.g. Diplodus annularis L., Oblada melanura L.) and species with large larvae (i.e. 14-16 mm), displaying a maximum swimming speed of 10 cm s-1 and a PLD of 28-38 days (e.g. Spondyliosoma cantharus L.). Including larval behavior in the model i) increased the overall proportion of successful settlers, ii) enhanced self-recruitment within the MPAs, but also iii) increased the intensity and iv) widened the export of eggs and larvae (recruitment subsidy) from the MPAs; overall, it significantly changed connectivity patterns. These results highlight the need to gather the observational data that are required to correctly parameterize connectivity models.

Highlights

Many coastal fish species undergo a pelagic larval phase while adults generally have a restricted home range, leading most dispersal to occur during the larval phase (Gaines et al, 2007), even if it is not limited to this stage (e.g., Di Franco et al, 2015)
The overall proportion of successful settlers was strongly increased by the inclusion of larval behavior, for both groups of Sparidae (Figure 3): 16.3% vs. 28.4% for small Sparidae and 1.2% vs. 10.2% for large Sparidae
We used a relatively simple example, based on a network of three French marine protected areas (MPAs) located in the Ligurian Sea, a part of the northwestern Mediterranean Sea, to reveal the potential differences in dispersal outcome that may be expected when accounting for oriented swimming by fish larvae

Summary

Introduction

Many coastal fish species undergo a pelagic larval phase while adults generally have a restricted home range, leading most dispersal to occur during the larval phase (Gaines et al, 2007), even if it is not limited to this stage (e.g., Di Franco et al, 2015). Predicting recruitment in adult populations after this larval phase is a major challenge in marine ecology and for the sustainable management of marine resources. It remains difficult because the factors determining larval dispersal and survival are not all identified (Cowen et al, 2007; Botsford et al, 2009). The use of such models have generalized and some even succeeded in predicting the intensity of larval supply to coastal areas (Sponaugle et al, 2012)

Methods

Results

Conclusion