Document: MAS-3-84-6

Causes of declining trend in the survival rate of the North Atlantic right whale.

FUJIWARA, M.* ^1,2 and H.CASWELL ¹

Woods Hole Oceanographic Institution, Woods Hole, MA 02543 ¹
Massachusetts Institute of Technology, ²

Abstract:
The North Atlantic right whale (Eubalaena glacialis) is the most endangered large whale species in the world. The current population size is about 300, and declining. Causes of the decline are still unknown; however, entanglement with fishing gear, collision with ships, and changes in food availability due to climatic change are suspected. To evaluate these hypotheses, we introduced environmental factors as covariates in a mark-recapture analysis of survival from sighting of 370 whale from 1980 through 1997. We used data on lobster pot and sink gillnet landings in the North Eastern US, number of ships entering major ports in five regions along the east coast of the US, North Atlantic Oscillation Index (NAO), and Southern Oscillation Index (SOI), and principal components derived from these variables. The Akaike weight method was used to rank the importance of each covariate in explaining the survival trend. Our results show that ship traffic in the mid-south region, NAO, and lobster landings are ranked higher than other covariates, and that the three covariates are not strongly correlated. A combination of these three covariates explained the trend in the survival best. It will require careful analysis to determine the true cause of the decline, but with our current knowledge, none of the three major types of threat to the population (fishing gear, ship collision, and climatic change) can be excluded as potential causes of the increased mortality of the North Atlantic right whale.

Keywords: right whale, survival rate, mark-recapture statistics, information theory, principal component analysis

This abstract is being presented at: 12:00 PM in session:
Oral Session #57: Ocean-Going Fish and Mammals.