Regional-Scale Migrations and Habitat Use of Juvenile Lemon Sharks (Negaprion brevirostris) in the US South Atlantic

Eric A Reyier,Demian D Chapman,Bryan R Franks,Eric D Stolen,Douglas M Scheidt,Samuel H Gruber,Stefano Mariani

doi:10.1371/journal.pone.0088470

Abstract

Resolving the geographic extent and timing of coastal shark migrations, as well as their environmental cues, is essential for refining shark management strategies in anticipation of increasing anthropogenic stressors to coastal ecosystems. We employed a regional-scale passive acoustic telemetry array encompassing 300 km of the east Florida coast to assess what factors influence site fidelity of juvenile lemon sharks (Negaprion brevirostris) to an exposed coastal nursery at Cape Canaveral, and to document the timing and rate of their seasonal migrations. Movements of 54 juvenile lemon sharks were monitored for three years with individuals tracked for up to 751 days. While most sharks demonstrated site fidelity to the Cape Canaveral region December through February under typical winter water temperatures, historically extreme declines in ocean temperature were accompanied by rapid and often temporary, southward displacements of up to 190 km along the Florida east coast. From late February through April each year, most sharks initiated a northward migration at speeds of up to 64 km day−1 with several individuals then detected in compatible estuarine telemetry arrays in Georgia and South Carolina up to 472 km from release locations. Nineteen sharks returned for a second or even third consecutive winter, thus demonstrating strong seasonal philopatry to the Cape Canaveral region. The long distance movements and habitat associations of immature lemon sharks along the US southeast coast contrast sharply with the natal site fidelity observed in this species at other sites in the western Atlantic Ocean. These findings validate the existing multi-state management strategies now in place. Results also affirm the value of collaborative passive arrays for resolving seasonal movements and habitat preferences of migratory coastal shark species not easily studied with other tagging techniques.

Highlights

It is widely recognized that as a group, sharks are unusually susceptible to overfishing, relative to most other marine fishes, due to their slow growth, late age of maturation, and low fecundity [1,2]
Management of shark stocks is further complicated by a growing realization that many species undertake seasonal migrations spanning hundreds or thousands of kilometers in which they transit through jurisdictions with incongruous fishing regulations and enforcement strategies [3,4]
The specific objectives of this study were to: (1) use a collaborative regional-scale passive acoustic array to resolve the degree of site fidelity of juvenile lemon sharks to Cape Canaveral, and (2) document the timing, rate, destinations, and temperatures associated with their seasonal migrations

Summary

Introduction

It is widely recognized that as a group, sharks are unusually susceptible to overfishing, relative to most other marine fishes, due to their slow growth, late age of maturation, and low fecundity [1,2]. The migrations of coastal shark species are often closely coupled with seasonal variations in water temperature [6,7,8]. These migrations appear to be adaptations to stay within a preferred temperature range, exploit seasonally productive foraging grounds, utilize optimal mating and parturition sites, or a combination thereof. Even in this region where shark behavior has been a priority research focus for several decades, migrations have not been resolved in detail for most species due to the difficulties of following individual animals as they travel long distances through open water

Objectives

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Results

Conclusion