Modeled buoyancy of eggs and larvae of the deep-sea shrimp Aristeus antennatus (Crustacea: Decapoda) in the northwestern Mediterranean Sea.

Morane Clavel-Henry,Trond Kristiansen,Guiomar Rotllant,Joan B Company,Nixon Bahamon,Jordi Solé,Atsushi Fujimura

doi:10.1371/journal.pone.0223396

Abstract

Information on the buoyancy of eggs and larvae from deep-sea species is rare but necessary for explaining the position of non-swimming larvae in the water column. Due to embryonic morphology and ecology diversities, egg buoyancy has important variations within one species and among other ones. Nevertheless, it has hardly been explored if this buoyancy variability can be a strategy for deep-sea larvae to optimize their transport beyond their spawning areas. In the northwestern Mediterranean Sea, protozoea and mysis larvae of the commercial deep-sea shrimp Aristeus antennatus were recently found in upper layers, but to present, earlier stages like eggs and nauplii have not been collected. Using a Lagrangian transport model and larval characteristics, we evaluate the buoyancy and hydrodynamic effects on the transport of A. antennatus' larvae in the northwestern Mediterranean Sea. The transport models suggested that 75% of buoyant eggs released between 500 and 800 m depth (i.e., known spawning area), reached the upper water layers (0-75 m depth). Then, according to the modeled larval drifts, three spawning regions were defined in the studied area: 1) the northern part, along a continental margin crossed by large submarine canyons; 2) the central part, with two circular circulation structures (i.e., eddies); and 3) the southern part, with currents flowing through a channel. The number of larvae in the most upper layer (0-5 m depth) was higher if the larval transport model accounted for the ascent of eggs and nauplii (81%) instead of eggs reaching the surface before hatching (50%). The larvae reaching the most water upper layer (0-5 m depth) had higher rates of dispersal than the ones transported below the surface layer (deeper than 5 m depth). The results of larval dispersal simulations have implications for the understanding of A. antennatus larval ecology and for management decisions related to the shrimp fisheries in the northwestern Mediterranean Sea.

Highlights

Numerous species have a pelagic larval cycle which links the spawning places to the recruitment areas
Regional Ocean Modeling System (ROMS) is built forced by a high resolution and accurate bathymetry of the western Mediterranean basin, which is fundamental for the drift study of A. antennatus’ eggs and larvae because adults are benthic and females spawn around 800 m depth [33]
The simulated larval drifts significantly varied with the spawning places, the number of buoyant stages, the spawning period and the depth layer reached by buoyant phase

Summary

Introduction

Numerous species have a pelagic larval cycle which links the spawning places to the recruitment areas. Larval cycle is a relatively short time lapse compared to the life cycle of marine animal, but it is the phase when large dispersions occur [1]. The distribution of the species mostly relies on the transported larvae. Larvae have several mechanisms for positioning themselves in productive and favorable waters that optimize their growth and displacement [2]. According to those mechanisms, the larvae can be retained on the spawning places or connect to other areas that are of high interest for species with high commercial value. Many studies addressed larval drifts in order to determine the efficiency of the fisheries management [3, 4]

Methods

Results

Discussion

Conclusion