ACS Research Committee Report

SPERM WHALE VOCALIZATIONS IN THE GULF OF ALASKA
Source: Mellinger, D.K., Stafford, K.M., and Fox, C.G. 2004. Seasonal occurrence of sperm whale (Physeter macrocephalus) sounds in the Gulf of Alaska, 1999-2001. Mar. Mamm. Sci. 20 (1): 48-62.

Fixed hydrophones were used between October 1999 and June 2001 to continuously record whale sounds in the Gulf of Alaska. Sperm whale clicks were detected on all hydrophones during all months of the year. Clicks were identified on average 20% of days in each month. There was a seasonality to the sounds, with a peak in the summer months, July through September. They decreased into the fall, October through December, and were least common in the winter, January through March, until they started to increase again in April. These results indicate that sperm whales are present within the Gulf of Alaska throughout the year, although perhaps at varying densities. Previous research has shown that 97% of clicks are produced during foraging dives, indicating that these animals may be foraging during their entire residence in the area. Most reproductively active sperm whales will migrate to lower latitudes during the winter to breed, but perhaps some males, especially juveniles that may not be reproductively successful yet due to their small size, may remain in the Gulf of Alaska to feed during this period.    

TRANS-ATLANTIC MIGRATION OF A NORTH ATLANTIC RIGHT WHALE
Source: Jacobsen, K., Marx, M., and Oien, N. 2004. Two-way trans-Atlantic migration of a North Atlantic right whale (Eubalaena glacialis). Mar. Mamm. Sci. 20 (1): 161-166.

A North Atlantic right whale was sighted in the Kvaenangen fjord in northern Norway in the fall of 1999. It was first seen on September 17, and was observed numerous times until its last sighting on October 22. The photos of this animal were sent to the New England Aquarium, where the North Atlantic right whale catalog is maintained, and the whale was identified as an adult male, named "Porter". Porter was last seen in Cape Cod Bay, Massachusetts, in May of 1999. This animal traveled 5700 kilometers in only 117 days, which was an average swimming speed of two kilometers per hour. Porter was re-sighted in Cape Cod Bay in March of 2000, 131 days after its appearance in Norway. This sighting is the first confirmed account of a North Atlantic right whale in Norway since 1926, when one was killed during whaling efforts. In the interim, there have been only unconfirmed reports from fishermen or local residents of right whale presence in the area. Most North Atlantic right whales winter in the U.S. southeast, and summer in the Bay of Fundy; however, there is a portion of the population that do not complete this migration and it is unknown where they spend the winter months. This trans-Atlantic migration of a right whale may begin to shed light on this question.    

ABUNDANCE OF BLUE AND HUMPBACK WHALES IN THE EASTERN NORTH PACIFIC
Source: Calambokidis, J. and Barlow, J. 2004. Abundance of blue and humpback whales in the eastern North Pacific estimated by capture-recapture and line-transect methods. Mar. Mamm. Sci. 20 (1): 63-85.

Abundance estimates of blue and humpback whales off the U.S. west coast were made using photo-identification mark-recapture and line-transects between 1991 and 1997. Line-transect counts were made off of large, government vessels, which were able to remain at sea and travel offshore for extended periods. Photographs of whales were taken from small shore-based boats, or opportunistically from whale watches. Photo-identification estimates were corrected using several mathematical models. The most accurate population estimate for humpback whales was made using photo-identification mark-recapture, followed by a mathematical paired year comparison. This methodology was most accurate because humpback whales have a clumped distribution and most animals are found within 30 miles of shore, allowing easy access by shore-based boats. The humpback whale population between 1991 and 1997 was estimated at 687 individuals. Blue whales, on the other hand, have a broader, more offshore distribution and are harder to sample from small boats; therefore, the line-transect estimate was the most accurate. The blue whale abundance during the study period was 2,997 animals. The population estimates for both humpback and blue whales in this study were much higher than post-whaling numbers and humpback whales demonstrated a clear increase throughout the study. However, the estimates made in this study are still far below pre-exploitation estimates.    

POD COMPOSITION OF RISSO'S DOLPHINS
Source: Amano, M. and Miyazaki, N. 2004. Composition of a school of Risso's dolphins, Grampus griseus. Mar. Mamm. Sci. 20 (1): 152-160.

Risso's dolphins are widely distributed in temperate waters throughout the world; however, there is little known about their group composition. In Japan, Risso's dolphins are killed in both drive and harpoon fisheries. The annual catch was less than 100 dolphins from 1976 to 1981, but has increased recently to over 400 animals taken annually. This study was conducted on a pod of 79 Risso's dolphins that were driven into shore and killed in Taiji, Wakayama, Japan. The most common body length of this pod was 250-260 cm. There was no significant difference in size between males and females, but there were no older males in this pod, so male size may have been underestimated. There were 49 females and 30 males in the pod. Of the females, 65.9% was mature and over half of those were "resting", meaning they were neither pregnant, nor lactating. Of the males, 3.3% (only one animal) was mature. The average calving interval was 2.37 years, but there were two females that were simultaneously pregnant and lactating, indicating consecutive calving was possible. The oldest immature female was 10.5 years, and the youngest mature female was 8.5 years; the average age of maturity for females was estimated at 8-10 years. The oldest immature male was 8.5 years and the youngest late-maturing male was 11.5 years; the age at maturity for males was estimated at 10-12 years. There are a few general conclusions that can be made from the results found here. Mature females of similar condition form pods with each other and with immature offspring, and mature males may move between pods, all of which is similar to other toothed cetacean species.