Findings from the cruise were presented orally at the Biennial Conference on the Biology of Marine Mammals in Maui. Citations and abstracts for these two presentations are listed below:
Rasmussen, K., J. Calambokidis, G.H. Steiger, and T.E. Chandler. 1999. Central America as a significant wintering ground for North Pacific humpback whales. in: Abstracts Thirteenth Biennial Conference on the Biology of Marine Mammals, Maui, HI 28 November - 3 December 1999. Society for Marine Mammalogy, Lawrence, KA.
ABSTRACT. North Pacific humpback whales have been reported to use three main wintering areas, Mexico, the Hawaiian islands, and several areas off Japan. An additional North Pacific wintering area has been recently described off southern Costa Rica. However, little is known about the rest of Central America and southern Mexico and how it is used as a wintering area by North Pacific humpback whales. We conducted surveys off of southern Mexico, Guatemala, El Salvador, Nicaragua, and northern Costa Rica during February and March of 1999 using an 18m schooner to determine the density of humpback whales in these areas, collect behavioral data, record song, and obtain individual identification photographs. We also conducted small boat surveys in one area off southern Costa Rica for two to three weeks in January and February from 1996 through 1999 collecting similar data.
Our survey off southern Mexico and Central America covered over 600 nmi in 14 days. We made 19 sightings of 31 humpback whales distributed widely in all areas surveyed. The highest sighting rate of animals was found in northern Costa Rica. Of 18 individuals identified photographically during this survey, 14 of these were also seen feeding off California (78%). In previous years we have identified a total of 35 individuals off southern Costa Rica and Panama, with 30 of these also identified off California (86%). This high rate of matching suggests that southern Mexico and Central America are used almost exclusively by humpback whales that feed off California. Humpback whales that feed off California appear to utilize a broad region from southern Mexico to Panama as a wintering area. Although densities are low, this region is a more significant wintering area for North Pacific humpback whales than previously thought.
Chandler, T.E., J. Calambokidis, and K. Rasmussen. 1999. Population identity of blue whales on the Costa Rica Dome. in: Abstracts Thirteenth Biennial Conference on the Biology of Marine Mammals, Maui, HI 28 November - 3 December 1999. Society for Marine Mammalogy, Lawrence, KA.
ABSTRACT. Little information exists on blue whale use of breeding grounds. The largest known surviving concentration of blue whales feeds of California in the summer and fall but the wintering ground for these animals is not known. Blue whales have been sighted year round in an area of upwelling called the Costa Rica Dome (500 nmi west of Costa Rica) but it was unclear if this reflected a resident population, alternate use of this area by northern and southern hemisphere populations, or a combination of these. We conducted a cruise to this region in January and February 1999 to obtain individual identification photographs, skin samples, recordings of vocalizations, and behavioral data including information on foraging.
We conducted surveys over 1,300 nmi in two 2-3 week periods between 13 January and 22 March 1999 using an 18 m schooner. We made 24 sightings of 28 blue whales, with most (18) from 12-15 March 1999. Of 13 whales that were individually identified, 7 were animals previously seen off California. We have identified about half (1,000) of the blue whales that feed off California, so the high match rate we found indicates whales seen on the Costa Rica Dome at this time of year are comprised almost solely of whales that feed off California. There does not appear to be a resident population on the dome, as previously hypothesized. Blue whales seen in this area in the summer are likely migrants from Southern Hemisphere waters. The density of animals on the dome in winter indicates a substantial portion of the estimated 2,000 blue whales seen off California could be utilizing this area prior to migrating to the waters off Baja Mexico in spring. We observed blue whales defecating on several occasions suggesting blue whales may feed on this wintering ground.
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