Survival and abundance of the blue whale (Balaenoptera musculus) population in the Gulf of St. Lawrence, Canada

A thesis submitted in partial fulfillment of the requirement for a Master Degree in Marine Mammal Science

Abstract

The Northwest Atlantic blue whale (Balaenoptera musculus) population is endangered and therefore knowledge of survival rates and abundance is critical to assist conservation efforts. This study focused on the Gulf of St. Lawrence (GSL), Canada, one of the most productive waters in the North Atlantic due to strong cold upwelling which provides a rich krill diet. Migrating blue whales have been studied annually in the GSL since 1979 by Mingan Island Cetacean Study (MICS). Observation close to coastal areas has allowed for a long-term mark-recapture photo-identification study, recording the unique pigmentation patterns and collection of skin sample biopsies. The aim of this study was to estimate sex- specific survival rates of the Northwest Atlantic blue whale in the GSL and to estimate abundance of the current population with data from the St. Lawrence Estuary (SLE). Apparent survival was modeled with photo-identification data cataloged from the time individuals were sexually identified, 1990 – 2014. The best-supported MARK model had two-age class survival estimates for males and a single estimate for females with a recapture probability including sex, time, and trap dependency. The apparent survival estimates of males were 0.967 (CV=0.008, 95% CI=0.947-0.980) and females were 0.941 (CV=0.011, 95% CI=0.916-0.959). Abundance estimates were modeled from photo-identification data within the St. Lawrence Estuary from 2000 – 2006, a period of relative consistent survey effort and number of sightings. The open super population model, POPAN, and a closed population model, Pledger Mixture Models, estimated abundance at a range of 151 - 190 individuals. Methods applied for these survival and abundance estimates of the endangered Northwest Atlantic blue whale population have been used successfully in various marine mammal studies and will provide scientific data assistance for the ‘Recovery Strategy Plan for the endangered Blue Whale, Northwest Atlantic Population, Canada’ under the Canadian Species at Risk Act.

Miranda Unger (2016). Survival and abundance of the blue whale (Balaenoptera musculus) population in the Gulf of St. Lawrence, Canada.