Larval dispersal and population connectivity in harvested species

A fundamental goal of both ecology and conservation biology is to develop hypotheses explaining the abundance and distribution of species. For marine taxa, particularly those that possess pelagic larvae that can potentially disperse hundreds of kilometers in ocean currents, a crucial step towards achieving this objective is the identification of both physical and biological factors influencing rates of larval exchange, or connectivity, among populations. Although ocean circulation has long been thought to be an important predictor of patterns of population differentiation in the sea, the degree to which oceanographic processes influence larval dispersal is an unresolved and controversial issue in marine ecology. That said, most attempts to relate patterns of population differentiation to ocean currents usually only consider mean ocean trajectories over very large spatial scales, yielding unrealistically high expectations for long-distance larval transport and correspondingly weak tests of the importance of physical processes to pelagic larval dispersal.

We have recently characterized the genetic structure of the bay scallop (Argopecten irradians concentricus) on either side of a barrier island inlet that, according to studies of physical transport, serves as a small-scale circulation barrier on the central coast of North Carolina. This work shows that even though bay scallop larvae can be potentially carried hundreds of kilometers in major alongshore currents, nearshore physical processes (tidal currents) operating on relatively small spatial scales can play a significant role in the fate of marine larvae by promoting local retention and generating fine-scale genetic structure. Our lab is also involved with research focused on patterns of dispersal and connectivity in other harvested species, such lingcod (Ophiodon elongatus) and scalloped hammerhead sharks (Sphyrna lewini).

 This work is supported by a grant from the National Science Foundation.

Relevant publications:

Moran, A. L. & P. B. Marko. 2005. A simple technique for physical marking of marine bivalves. Journal of Shellfish Research 24: 567-572. [PDF]

Marko, P. B. & K. B. Barr. Population Genetics, Tidal Circulation, and Population Connectivity in the Bay Scallop, Argopecten irradians (in press).