Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 9226
Title: Resilience of endangered sperm whales (Physeter macrocephalus) to foraging disturbance in the Gulf of Mexico, USA: A bioenergetics approach
Author: Nicholas A. Farmer, D. P. Noren, Erin P. Fougères, Abigail Machernis, Kyle Baker
Publication Year: In press
Journal: Marine Ecology Progress Series

Endangered sperm whales (Physeter macrocephalus) spend the majority of their time foraging, relying upon echolocation to locate and consume several hundred kilograms of prey per day. In the northern Gulf of Mexico, sperm whales are exposed to a variety of anthropogenic stressors, including ship strikes, fisheries interactions, habitat loss and degradation due to oil and gas development, and chemical and noise pollution. In particular, they are exposed to high levels of anthropogenic noises related to geological and geophysical surveys for hydrocarbon deposits. The sounds produced by these surveys could reduce sensory volume, increase search effort required to locate resources, and interfere with auditory signal processing critical to foraging success. We developed a stochastic life-stage structured bioenergetic model to evaluate the consequences of reduced foraging efficiency on carbohydrate, lipid, and protein reserves in the blubber, muscle, and viscera. The model indicates individual resilience to foraging disruptions is primarily a function of size (i.e., reserve capacity) and daily energetic demands. Mothers are the most vulnerable life stage due to the high energy demands associated with pregnancy and lactation. Continuous disruption has a greater impact than intermittent disruption; even minor foraging disruptions may lead to terminal starvation if the whales have no opportunity to replenish reduced reserves. Infrequent, minor disruptions in foraging are unlikely to be fatal, but may result in reduced body reserves that may be associated with reduced reproductive success. Our model provides a bioenergetic framework for evaluating the level, frequency, and consequences of foraging disruptions associated with anthropogenic stressors.

Theme: Ecosystem approach to improve management of marine resources