Electric rays (family Torpedinidae) are distinguished from other batoids by the possession of kidney-shaped electric organs along the anterior-lateral portion of their disks. There are two genera and fourteen species of electric ray, of which only the Atlantic torpedo, Torpedo nobiliana, is found in the Northwest Atlantic Ocean. The Atlantic torpedo is a benthic species that is generally restricted to the continental shelf. They range from Nova Scotia to Venezuela in the western Atlantic, and from northern Scotland to the west coast of Africa in the eastern Atlantic. Adult Atlantic torpedo are believed to range in size from 30 to 180 centimeters total length, with the largest known individuals reaching weights of up to 90 kg. Based on limited evidence, their gestation period is around one year and their size at birth is approximately 20-25 cm total length (Bigelow and Schroeder 2002).
While Atlantic torpedo are commonly caught as by-catch in many fisheries, little biological data exists for this species. The purpose of this study is to examine the age, growth and reproduction of these rays. Knowledge of these life history characteristics will help us better understand the role of this species in the ecosystem. Additionally, it will help us determine how the population would respond to environmental change, increased fishing pressure or fluctuation in the populations of species living within the same range. Age and growth data will form the basis for calculating growth and mortality rates, age at maturity, and estimates of longevity, all of which are necessary for the proper management of a species (Cailliet et al. 1983). We began sampling in March 2006 and will continue to collect samples from commercial fishermen each month through May 2007. Currently, our sample size is quickly approaching 200 rays.
Bigelow, H. B. and W. C. Schroeder. 2002. Torpedoes or electric rays. Family Torpedinidae. Fishes of the Gulf of Maine, 3rd ed. Smithsonian Institution Press. 59-60.
Cailliet, G.M., L.K. Martin, D. Kusher, P. Wolf and B.A. Welden. 1983. Techniques for enhancing vertebral bands in age estimation of California elasmobranchs. NOAA Tech. Rep. NMFS, 8:157-165.
Contact information:
Lisa Natanson, Ph.D.
Lisa.Natanson@noaa.gov
Sandra Downing
isolusine@mail.uri.edu
Sandra graduated from the University of Long Island in 2004 with a BS in biology. She is currently pursuing a Master's degree from the University of Rhode Island in fisheries science.