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SEMINAR: Molecular Ecology and Conservation of Hammerhead Sharks

Beginning at 11:00am
June 30, 2008
Stony Brook University
Sponsored by the Institute for Ocean Conservation Science.

SPEAKER: Demian D. Chapman - Pew Institute for Ocean Science / University of Miami

School of Marine and Atmospheric Sciences
Stony Brook University
Stony Brook, NY 11794-5000

Dr. Demian Chapman is a research scientist at the Pew Institute for Ocean Science and head of the Institute's Shark Research Program. Dr. Chapman's research expertise lies in molecular biology and telemetry tracking, which he integrates to address research questions related to the dispersal and reproduction of sharks and rays. He is particularly interested in how shark reproduction and movements impact population dynamics, population genetic diversity and geographic population structure and their implications for conservation. Dr. Chapman is the author of fifteen scientific articles and currently manages field research projects on sharks in Belize, the Bahamas, New Zealand and Florida.

Molecular Ecology and Conservation of Hammerhead Sharks

Dr. Demian D. Chapman

At the interface between molecular biology and ecology, molecular ecology is a relatively young discipline that is proving very useful for elucidating the biology and conservation needs of species that are not amenable to sustained field observation, such as many marine organisms. Severely threatened because their fins fetch premium prices for use in the Asian delicacy shark fin soup, hammerhead sharks (F. Sphyrnidae) are one such group. In this seminar, I will present new information on the reproductive biology and population structure of two species of hammerhead sharks, the bonnethead (Sphyrna tiburo) and the scalloped hammerhead (Sphyrna lewini), derived from analysis of their DNA. In contrast to other sharks where female promiscuity is typical, DNA-based parentage analyses show that female hammerheads typically produce litters sired by one male. This suggests that hammerheads may be prone to lose genetic diversity during population bottlenecks or periods when the population sex ratios are male-biased. Female bonnetheads switch to promiscuity as they get larger, making larger, older females an important demographic for conservation in the context of maintaining population genetic diversity. I also show that female hammerhead sharks can reproduce by parthenogenesis, the first record of asexual reproduction by any of the cartilaginous fishes. Finally, I present phylogeographic data showing that populations of these two hammerhead sharks are highly structured in the Western Atlantic basin and discuss the implications for stock assessment, monitoring the international dried fin trade and scaling management actions to help rebuild and sustain populations of these ocean predators.

Authors highlighted in blue are staff of the Institute for Ocean Conservation Science.

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