Conservation of coastal stingrays: seasonal abundance and population structure of the short-tailed stingray Dasyatis brevicaudata at a Marine Protected Area

摘要

Elasmobranch (shark, ray, and skate) populations around the world are in decline, and effective conservation measures are urgently needed. Marine Protected Areas (MPA) placed in locations important for key life-history stages may form part of an effective conservation strategy. In this context, we examined the seasonal abundance and population structure of the short-tailed stingray (Dasyatis brevicaudata) at an offshore MPA in northeastern New Zealand, and the reported use of this location as a mating ground. Diver surveys were conducted from 2004 to 2007 at the Poor Knights Islands Marine Reserve (PKIMR). During this time, we observed: (ⅰ) a substantial increase in adult and subadult numbers, particularly females during the suggested breeding season, and a corresponding increase in females bearing fresh mating scars; and (ⅱ) large numbers of smaller (probably immature) D. brevicaudata individuals of both sexes from spring to autumn. These results suggest that the PKIMR acts as both a mating aggregation location and a nursery for this species. We suggest that for coastal stingrays such as D. brevicaudata, small MPAs may be effective at protecting key life-history stages, but that as movements outside of reserve boundaries also occur, additional management tools may also be necessary.