Date of Award

Winter 2010

Project Type

Dissertation

Program or Major

Animal and Nutritional Sciences

Degree Name

Doctor of Philosophy

First Advisor

Paul C Tsang

Abstract

Spiny dogfish (Squalus acanthias) are considered to be the most abundant shark species in the Western North Atlantic, but recently there was a decline in biomass estimates following a nearly ten-fold increase in fishery landings. Because fishing pressure has been shown to affect population dynamics in targeted species, an update of previous life history parameters is warranted to effectively manage the population. Although updated and accurate life history parameters are important, it is crucial that these parameters are applied to the correct populations, especially when there is evidence of population structuring in the Western Atlantic. This comprehensive study addressed the need for updated and accurate life history characteristics of spiny dogfish by obtaining year round samples covering the entire size range of spiny dogfish. This also enabled examination of spatial and temporal population structuring in the Western North Atlantic. While the vertebrae of spiny dogfish provided a more accurate and precise age estimate than the dorsal fin spines used in previous studies, there was no significant difference in growth prior to or following the increase in fishing pressure. Also, there was no change in the reproductive seasonality or magnitude of morphological, histological, or physiological parameters in mature individuals over this time. However, using a suite of characteristics to define maturity, there was a decrease in size and age at maturity as well as a decrease in fecundity for female spiny dogfish in the present study compared data obtained prior to the fishing pressure. Population structuring was also observed using microsatellite regions in genomic DNA as molecular markers. With the apparent recovery of the spiny dogfish stock in the Western North Atlantic, the findings from the present study as well as a further elucidation of population structure in this region can be utilized to sustainably manage population(s) and predict the effects of fishing pressure in the future.

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