ACS Research Committee Report

Occurrence of Minke Whales in the Antarctic Waters
Source: Ainley, D.G., Dugger, K.M., Toniolo, V., and Gaffney, I. 2007. Cetacean occurrence patterns in the Amundsen and Southern Bellingshausen Sea Sector, Southern Ocean. Marine Mammal Science 23(2): 287-305.

In the fall of 1994, a survey for minke whales was conducted aboard an icebreaking vessel in the Amundsen and Southern Bellingshausen Seas in the Southern Ocean. Previously, cetacean surveys were conducted aboard vessels that did not have ice breaking capability and could not venture into the pack ice, leaving the question of whale abundance in these areas unanswered.

During the survey, forty sightings comprised of 104 individual minke whales were recorded. Group size ranged from one (most common) to nine individuals. The probability of minke whale presence was higher further into the pack ice. In addition, minke whale sightings were higher south of the Antarctic circumpolar current, in waters that are more productive than those to the north of the current. When ice cover was less extensive, minkes were found in association with coastal polynyas (areas of open water surrounded by sea ice) until the water began to freeze more consistently and then they headed further from the coast, into areas with more transient ice.

Minkes were seen to punch holes in new ice with the tip of their pointed rostrum; distance between holes was 200-300 m. Penguins also used the breathing holes created by the whales, indicating a symbiotic relationship between the species. In open water, minke whales actively avoided the survey ship, often "porpoising" as they fled. This behavior was rarely observed when minke whales were encountered in the pack ice.

The distribution and behavior of Antarctic minke whales leads to the question of whether this species has always had a preference for pack ice or it has developed in response to whaling pressure.

Open Boat Whaling in the Strait of Gibraltar and Surrounding Waters
Source: Aguilar, A. and Borrell, A. 2007. Open-boat whaling on the straits of Gibraltar ground and adjacent waters. Marine Mammal Science 23(2): 322-342.

Logbooks from 19th century whaling expeditions in the North Atlantic were examined to determine the extent of whaling effort in the Gibraltar Straits grounds. A total of 317 logbooks were examined, including 287 American, 24 British, 5 German, and 2 Portuguese, spanning the period 1769 to 1910. Of these, 33 expeditions spent three or more days in the area and were looked at in more detail. Being that not all logs were examined, all estimates here are minimums.

British and German whaling vessels crossed the Gibraltar Straits area quickly on their way to more southerly destinations. Their mean stay in the area was 5.1 days and they had sporadic sightings and catches of whales.

The American fleet, however, headed to this area specifically and stayed an average of 74.5 days. The main target for all of these ships was sperm whales.

Sightings of sperm whales in the Gibraltar Straits area were comparable, but in the lower range, to other whaling grounds including the Cape Verde Islands, the Azores, and the Canary Islands. During this period, there were 121 sightings and 128 catches of sperm whales, most over the continental slope.

The logs referred a number of times to whales being struck and subsequently lost; therefore, the number of whales killed was actually higher (estimated at 30% higher) than the 128 successful catches listed here.

Whaling effort concentrated on the Atlantic side of the Straits but at least two expeditions made relatively unsuccessful forays into the Mediterranean Sea.

Sperm whales were present year-round, with little to no seasonality.

American whaling vessels seemed to spend the early summer in the Gibraltar Straits before moving on to the Canary and Cape Verde Islands; this seasonal shift is likely due to the trade winds, rather than whale abundance.

The Gibraltar Straits population consisted mostly of breeding herds containing females and juveniles; the logs described catching mostly groups of animals, but also some single bull males. Modern whaling in the 20th century took more whales, estimated at 844, than in the previous century.

However, during the 20th century, focus also shifted from sperm to baleen whales; the number of fin whales caught during this period skyrocketed to 4,535. This difference can be attributed to an increased demand for baleen whale products, rather than whale availability.

From recovery of scientific tags and toggle heads from Azorean harpoons, data suggest that the North Atlantic population of sperm whales is homogeneous; currently there is no accurate estimate for this overall population. It is likely that the few hundred sperm whale catches documented in this study had little overall impact on the population, but there may have been cumulative impacts when combined with other whaling efforts going on at the same time and later in the same area. 

Gray Whales in the Gulf of Alaska
Source: Moore, S.E., Wynne, K.M., Kinney, J.C., and Grebmeier, J.M. 2007. Gray whale occurrence and forage southeast of Kodiak Island, Alaska. Marine Mammal Science 23(2): 419-428.

The Bering and Chukchi seas are commonly referred to as the primary summer feeding grounds for eastern North Pacific gray whales, but records indicate that this population also feeds opportunistically from Baja California, Mexico to Alaskan waters. Foraging behavior varies depending on the year, with prey use varying from pelagic, epi-benthic, and benthic prey items in different years.

In the 1980s, the southern Chukchi Sea and the Chirikov Basin in the northern Bering Sea were considered primary feeding grounds for gray whales. However, by 2002, productivity in the Chirikov Basin declined dramatically and whale aggregations were only found in the Chukchi Sea. This decline may have been caused by whale use, ecosystem change, or other unknown factors.

Since 1999, gray whales have been observed feeding year-round in Ugak Bay, on the eastern side of Kodiak Island, Alaska. Little effort has been focused on studying these whales, because it was long assumed that the waters south of Kodiak Island were simply a migratory pathway between northern and southern areas. This study presents results from opportunistic sightings of gray whales and benthic sampling in the waters southeast of Kodiak Island, from 1999 through 2005. Sightings were recorded during surveys for Stellar sea lions, harbor seals, and, in one case, North Pacific right whales.

Gray whales were seen year-round, most frequently and in largest numbers near the entrance to Ugak Bay. Highest sighting rates were during September through November, declined during December through May and reached lowest levels in June through August. Mud plumes indicative of feeding behavior were seen in every month. Approximately 350-400 gray whales were counted along one aerial survey track on July 25, 2000. Whales were clustered in groups of 10-20 individuals and most were associated with conspicuous mud plumes.

To determine prey availability, 36 benthic samples were collected at nine stations where whales were sighted feeding near the entrance to Ugak Bay in August 2002. In addition, ten gray whale fecal samples were collected. Cumaceans (a type of crustacean) were the most abundant fauna in benthic samples; in fact, the densities were among the highest reported anywhere in the world. In addition, polychaete worm and bivalves were also identified. Fecal sample analysis indicated that gray whales were feeding on cumaceans. Amphipods, which are typically primary gray whale prey in other areas, were only found in one station and at low densities.

Although many gray whales seen near Ugak Bay since 1999 may be migrating through the area, some clearly stop there to feed. Gray whales may be flexible foragers, responding to changes in prey abundance in their entire range. Alternatively, the expanding eastern North Pacific gray whale population may be meeting with foraging challenges due to changes in marine ecosystems associated with global climate change.   

   

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