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Project Description

As part of the North Pacific Research Board (NPRB) funded Bering Sea Integrated Ecosystem Research Program (BSIERP) project, cetacean observers will be placed on the RACE walleye pollock (Theragra chalcogramma) stock assessment survey in FY08 and FY10. Standard line-transect survey protocols will be used. Estimates of abundance will be calculated for fin, humpback, and minke whales and Dall's and harbor porpoise using multiple covariance distance sampling methods. Estimates of abundance will be calculated by oceanographic domain on the Eastern Bering Sea (EBS) shelf: coastal, middle, outer, and slope domains. Cetacean distribution will be assessed in relation to information on fish and euphausiid schools and oceanographic conditions. Habitat models will be developed modeling cetacean distribution and relative abundance versus oceanographic variables and the distribution of potential prey.

Issues & Justification

This project is part of the NPRB funded Bering Sea Integrated Ecosystem Research Program (BSIERP) project. By placing cetacean observers on the RACE walleye pollock (Theragra chalcogramma) stock assessment survey, BSIERP will be collecting concurrent data on cetacean, fish, plankton, and seabird distribution as well as oceanographic conditions which can be used to assess the Eastern Bering Sea shelf ecosystem. We will work with AFSC pollock survey scientists to assess cetacean distribution in relation to information on fish and euphausiid schools and oceanography which they are collecting. Concurrent visual sampling of cetaceans, their potential prey and oceanographic conditions will support detailed habitat models of cetacean distribution and relative abundance versus oceanographic variables and the distribution of potential prey (Redfern et al. 2006). Line-transect surveys using the walleye pollock transect lines will allow abundances to be estimated for fin, humpback, and minke whales and Dall's and harbor porpoise over a large portion of the Eastern Bering Sea shelf. These estimates will be stratified to be specific to the coastal, middle, outer, and slope oceanographic domains on the EBS shelf (Coachman 1986).

Goals

  • Estimate the abundance of fin, humpback, and minke whales and Dall's and harbor porpoise in each oceanographic domain on the Eastern Bering Sea Shelf.
  • Habitat models of cetacean distribution and relative abundance versus oceanographic variables and the distribution of potential prey.
  • Conduct cetacean sighting survey on the RACE walleye pollock (Theragra chalcogramma) stock assessment survey.

Methods

Standard line-transect survey protocols will be used with two observers using 25X (Big Eye) binoculars at port and starboard stations on the flying bridge. The port observer will scan for cetaceans from 10Aø right to 90Aø left of the trackline, and the starboard observer from 10Aø left to 90Aø right. A third observer will focus on the trackline scanning the entire 180Aø area forward of the ship using Fujinon 7x50 reticled binocular and act as data recorder. Effort data will be recorded including date, time, position of the vessel, observers, observer positions. Environmental variables which will be recorded include beaufort sea state, weather, position of the sun, wind direction, and visibility. For each cetacean sighting, species, vertical distance (taken from reticles in the binoculars), angle relative to the ship's heading (from an angle ring on the binocular mount), and group size will be recorded.

This is the first of two field seasons; the second being in FY10. After completion of the FY10 field season, abundance estimates and sighting rates will be estimated for each EBS shelf oceanographic domain (Coachman 1986) using multiple covariance distance sampling methods (Buckland et al., 2001, 2004) as implemented in the Mark-Recapture Distance Sampling (mrds) package for R. Cetacean habitat models will also be developed to examine cetacean distribution and relative abundance versus oceanographic variables and the distribution of potential prey (Redfern et al. 2006).
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