LE3 .A278 1998

1998

Dadswell, Michael

Acadia University

Master of Science

Masters

Biology

Biology

A total of 1684 dogfish were sampled to determine population characteristics from three regions in Atlantic Canada: the Minas Basin, the outer Bay of Fundy, and the Gulf of St. Lawrence. The posterior dorsal spine was removed from 211 male and 475 female dogfish for ageing. Ages were determined from the spines and annuli lost to wear were calculated using a spine dimension standardized equation. This study was the first attempt to define a complete reproductive stage assessment of a shark. A total of 475 females had the reproductive tracts removed and categorized as one of six stages. The Minas Basin sample exhibited the highest number of reproductively mature females (56.1%) and female dogfish captured in the outer Bay of Fundy were predominantly immature (97.6%). Maturity for 50% of female dogfish in Atlantic Canada was calculated at 17 years of age and a total length of 83.4 cm. Male dogfish age and total length were similar between the three regions but only 11 male dogfish were taken during the entire season in the Minas Basin (male:female ratio; 1:99). The Minas Basin female dogfish were significantly larger, older, and more mature than females in the other two sampling locations. Few comprehensive studies exist on spiny dogfish in the Northwest Atlantic because it is has only recently been commercially exploited. If commercial exploitation of dogfish were to begin in Atlantic Canada it would be more economically and biologically successful as a bycatch fish with other fisheries.

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