Selina Agbayani

 Alumni

MSc
IRES

Tel: 604.822.8181

Fax: 604.822.8180

E-mail: s.agbayani@oceans.ubc.ca

Supervisor: Dr. Andrew Trites

Education: BSc. Forest Sciences, Adv. Dipl. GIS

Research Interests: cetaceans, marine mammals, marine megafauna, foraging ecology, bioenergetics, conservation, cumulative effects, climate change

Research Area: Eastern Pacific

Bioenergetic requirements of grey whales in the face of prey shortages

Problem

Eastern North Pacific grey whales (Eschrichtius robustus) rely heavily on energy reserves obtained on their northern feeding grounds to complete their annual 17,000 km round trip between the Arctic and Mexico. Unusually high mortalities of grey whales observed in 1999 and 2000 during their northward migration were attributed to starvation caused by reduced prey availability (likely due to climate change) or competition from increased numbers of whales on the feeding grounds. However, the role that decreased prey intake had on the observed mortalities cannot be evaluated without knowing the minimum amounts of prey required to sustain the annual migration. We addressed this knowledge gap by constructing an age-structured bioenergetics model to predict the energy requirements of each migrating cohort of grey whales and estimated the minimum threshold of daily prey consumption needed during the summer to avoid nutritional stress during the annual migration. Inputs included a comprehensive growth model describing mass-at-age for females and males, and refined estimates of energetic expenditure for different activity states based on field measurements of respiration rates at each life stage or reproductive state. Our model thereby derived daily food requirements (e.g., kg of amphipods, mysid shrimp, etc.) for all age classes of grey whales and also incorporated a range of annual energetic requirement thresholds that has specific life history consequences. Thus, we related death and reproductive failure to the amounts of prey consumed (i.e., expressed as a proportion of daily energy requirements met) to predict future mortality rates of grey whales as a function of varying prey densities. Our results, when combined with measured densities of benthic prey, can be used to assess and anticipate the likelihood of starvation-related mortality events occurring, due to either population or environmental changes.

Click here to view my poster from WMMC 2019:

Publications