Nursery delineation, movement patterns, and migration of the sandbar shark, Carcharhinus plumbeus, in the eastern shore of Virginia coastal bays and lagoons.

摘要

The identification and delineation of nursery areas and areas of aggregation of north Atlantic sharks has been identified as an important information need for future management efforts. The objectives of this project were to use a fishery-independent method to study the overwintering area of juvenile sandbar sharks, to spatially delineate the Eastern Shore nursery area, and to examine movement patterns and space use within this nursery area. Data from 21 satellite transmitters attached to large juvenile sandbar sharks revealed that these sharks primarily occurred off the outer banks of North Carolina, at deeper depths and colder water temperatures during the overwintering period (after November 1). The data from this project support the size and scope of the closed area currently enacted by the Fishery Management Plan. The Eastern Shore of Virginia was found to be an important primary and secondary nursery area for this population of sandbar sharks. Within this nursery area sharks were most concentrated in Great Machipongo Inlet. Abundance of juvenile sandbar sharks was positively correlated to distance from the inlet and water temperature. Smaller juvenile sharks were more concentrated farther from the inlets and were more prevalent in the southern inlets. Juvenile sandbar shark movements were studied using passive acoustic telemetry. Juveniles tended to spend significantly more time farther from the inlets and their space use was positively correlated to time of day with a greater proportion of time spent in the acoustic array during the night time hours. Tidal currents were positively correlated with small scale movements but were unrelated to overall space use. The sharks tracked returned or remained within the array to a greater extent than would be predicted by random movements alone indicating these animals have some site attachment to these areas. Smaller sharks remained within the array area to a greater extent than larger sharks indicating they likely have smaller activity spaces. This study emphasizes the importance of both the Eastern Shore of Virginia nursery area and the overwintering area that occurs off the central coast of North Carolina as essential habitat for the north Atlantic population of sandbar sharks.