Effects of Geostrophic Kinetic Energy on the Distribution of Mesopelagic Fish Larvae in the Southern Gulf of California in Summer/Fall Stratified Seasons.

Fernando Contreras-Catala,Eric D Barton,Laura Sánchez-Velasco,Emilio Beier,Eduardo Santamaría-Del-Angel,Victor M Godínez,Juan Carlos Molinero

doi:10.1371/journal.pone.0164900

Abstract

Effects of geostrophic kinetic energy flux on the three-dimensional distribution of fish larvae of mesopelagic species (Vinciguerria lucetia, Diogenichthys laternatus, Benthosema panamense and Triphoturus mexicanus) in the southern Gulf of California during summer and fall seasons of stronger stratification were analyzed. The greatest larval abundance was found at sampling stations in geostrophic kinetic energy-poor areas (<7.5 J/m3), where the distribution of the dominant species tended to be stratified. Larvae of V. lucetia (average abundance of 318 larvae/10m2) and B. panamense (174 larvae/10m2) were mostly located in and above the pycnocline (typically ~ 40 m depth). In contrast, larvae of D. laternatus (60 larvae/10m2) were mainly located in and below the pycnocline. On the other hand, in sampling stations from geostrophic kinetic energy-rich areas (> 21 J/m3), where mesoscale eddies were present, the larvae of the dominant species had low abundance and were spread more evenly through the water column, in spite of the water column stratification. For example, in a cyclonic eddy, V. lucetia larvae (34 larvae/10m2) extended their distribution to, at least, the limit of sampling 200 m depth below the pycnocline, while D. laternatus larvae (29 larvae/10m2) were found right up to the surface, both probably as a consequence mixing and secondary circulation in the eddy. Results showed that the level of the geostrophic kinetic energy flux affects the abundance and the three-dimensional distribution of mesopelagic fish larvae during the seasons of stronger stratification, indicating that areas with low geostrophic kinetic energy may be advantageous for feeding and development of mesopelagic fish larvae because of greater water column stability.

Highlights

Mesoscale structures, like eddies and upwelling, typically associated with processes of mixing, convergence and divergence, are areas where the geostrophic kinetic energy is high [1,2,3]
The goal of the present paper is to explore the effects of more energetic areas on the three-dimensional distribution of fish larvae of the four abundant mesopelagic species (V. lucetia, D. laternatus, B. panamense and T. mexicanus) in the southern Gulf of California and its entrance during the summer/fall seasons of strongest stratification
This study examines the relation of geostrophic kinetic energy levels on the distribution of mesopelagic fish larvae (V. lucetia, D. laternatus, B. panamense and T. mexicanus) during the period of year with stronger stratification

Summary

Introduction

Like eddies and upwelling, typically associated with processes of mixing, convergence and divergence, are areas where the geostrophic kinetic energy is high [1,2,3]. Enrichment processes in these areas are enhanced by the triggering of primary and secondary productivity as nutrients are introduced into the photic zone [4,5]. Numerous studies have described qualitative relationships between mesoscale eddies and phytoplankton [6,7,8], and eddies with zooplankton [9,10,11]. Nieto et al [13] noted that high values of eddy kinetic energy were favorable for the development of sardine eggs in waters advected by eddies and filaments in the southern and central California

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