Investigation of foraging habits and prey selection by humpback whales (Megaptera novaeangliae) using acoustic tags and concurrent fish surveys

Abstract

Tags containing acoustic time‐depth transmitters (ATDT) were attached to four humpback whales near Kodiak, Alaska. Tags allowed for whale dive depths to be recorded in real time. Acoustic and mid‐water trawl surveys were conducted concurrent with tagging efforts within the study area to quantify available fish resources and describe potential prey selection by humpback whales. Recorded dives were grouped through visual assessment and t‐tests. Dives that indicated likely foraging occurred at a mean maximum depth of 106.2 m with 62% of dives occurring between 92 m and 120 m. Acoustic backscatter from fish surveys was attributed to potential humpback prey based on known target strength values and 10 net tows. Capelin comprised 84% of the total potential prey abundance in the region followed by age 0 (12%) and juvenile pollock (2%), and eulachon (<1%). Although horizontally segregated in the region, both capelin and age 0 pollock were distributed at depths exceeding 92 m with maximum abundance between 107 m and 120 m. The four‐tagged humpbacks were found to forage in areas with greatest capelin densities but bypassed areas of high age 0 pollock abundance. The location and diving behavior of tagged whales suggested that whales were favoring capelin over pollock as a prey source.

Factors affecting whale detection from large ships in Alaska with implications for whale avoidance

“…Even when shifts in shipping lanes are used, they may result in a reduction, but not elimination, of the risk of ship−whale encounters as whale aggregations may shift within and among years with shifts in prey or oceanographic conditions (e.g. Witteveen et al 2008, Chenoweth et al 2011, Becker et al 2012, Doniol-Valcroze et al 2012, Heide-Jørgensen et al 2012, Keller et al 2012, Pendleton et al 2012, Gregr et al 2013.…”

Geographic variation of persistent organic pollutant levels in humpback whale (Megaptera novaeangliae) feeding areas of the North Pacific and North Atlantic

“…In contrast, humpback whales tagged near Kodiak, Alaska, were shown to target schools of capelin (Mallotus villosus), even when concentrations of other prey such as pollock (Theragra chalcogramma) and euphausiids (Thysanoessa spp.) were available [55].…”

Predicting the acoustic exposure of humpback whales from cruise and tour vessel noise in Glacier Bay, Alaska, under different management strategies

“…The model moves whale animats through the 4 dimensions of space and time, according to species-specific rules defining parameters such as swim speed, dive depth, and change in heading. The values of these parameters were taken from literature on humpback whales (Dolphin 1987a,b, Baker & Herman 1989, Gabriele et al 1996, Dalla Rosa et al 2008, Witteveen et al 2008. Received sound levels (terminology is defined later in this section) are periodically estimated at a user-specified time interval.…”

“…The sound level to which a whale is exposed is primarily a function of the whale's depth and range from the vessel (among other parameters), so an accurate representation of a whale's movements is necessary to simulate the 4-dimensional relationship between whales and vessels. AIM whale animat movement parameters were based on measured dive times, dive depths, and movement patterns from published literature (Dolphin 1987b, 1988, Baker & Herman 1989, Gabriele et al 1996, Dalla Rosa et al 2008, Goldbogen et al 2008, Witteveen et al 2008, Kennedy et al 2014 and are summarized in Table 1. Three types of animats representing feeding, foraging, and traveling whales (Fig.…”