Marine biologist James Sulikowski receives $20,000 SOSF grant to develop noninvasive technique for study of shark, skate and ray reproductive biology
James Sulikowski, Ph.D., University of 51小黄车 associate professor of marine sciences, is principal investigator for a $20,000 Save our Seas Foundation grant to develop methodologies that will allow biomarkers in skeletal muscle tissue to be used as a reliable, noninvasive technique for the study of shark, skate, and ray reproductive biology.
According to the IUCN (International Union for Conservation of Nature and Natural Resources) Red List, approximately 75 percent of all elasmobranchs (sharks, skates, and rays) are threatened, or lacking sufficient data necessary for proper management.
An important step in reversing this trend is developing non-lethal techniques or protocols for the study of their life history characteristics.
Reproduction is one such life history trait that must be fully understood if successful management of these cartilaginous fish is to occur. Without information regarding when elasmobranchs mature and reproduce, population demography or stock assessments can never be adequately conducted.
Unfortunately, existing information regarding sexual maturity and reproductive cycles in elasmobranchs is largely based on gross examination of morphological changes associated with reproductive organs and structures (i.e. testes in males and ovary weight in females).
While this information has proven valuable in obtaining reproductive information, collecting pertinent data requires that specimens be sacrificed. This can be problematic, especially for species that have been classified as endangered or threatened.
Recently, circulating concentrations of plasma steroid hormones, such as 17-beta-estradiol, progesterone, and testosterone, have been used with gross morphological changes to evaluate events associated with reproductive cycles and sexual maturity in a number of sharks, skates, and rays.
The results from such studies indicate that morphological changes in reproductive tracts and gonadal steroid hormone biosynthesis are intimately linked in elasmobranch reproduction. That is, as the reproductive tracts become active, they begin to produce more hormones.
While research suggests that plasma steroid hormone concentrations alone can provide the necessary information to gauge sexual maturity and reproductive cycle status of elasmobranchs by non-lethal means, drawing blood to obtain a plasma sample from large specimens is problematic.
Thus, unless other non-lethal methods can be identified, management-related information regarding reproductive biology for prohibited or large species will remain difficult if not impossible to obtain.