The following is recently released by the Minerals Management Service and might be of interest to listserve subscribers.
Palka, D. and M. Johnson, eds. 2007. Cooperative research to study dive patterns of sperm whales in the Atlantic Ocean. OCS Study MMS 2007-033. New Orleans, Louisiana: Gulf of Mexico Region, Minerals Management Service. It can be downloaded (3 mb) for free at: http://www.gomr.mms.gov/PI/PDFImages/ESPIS/4/4247.pdf Executive Summary: The National Marine Fisheries Service (NMFS) is required to produce stock assessments for all marine mammal stocks within the U.S. Exclusive Economic Zone. The Minerals Management Service (MMS) is evaluating potential environmental impacts of offshore oil and gas activities on marine mammals. Both agencies have a need for similar information on sperm whales and this is the basis for the cooperative research outlined here. This study, conducted in July 2003, has started a baseline of line transect, photo-identification, oceanographic and genetic data for the Atlantic sperm whale. Compared with the Delta region in the Gulf of Mexico, parts of the Atlantic Ocean may serve as a control population of sperm whales with little exposure to sounds of oil and gas related activities. A total of 12 sperm whales were tagged during the four-week, July 2003 cruise yielding a substantial data set spanning both deep foraging and socializing from 9 of the 12 tagged animals. These tag recordings represent the first acquisition of sound and movement data from sperm whales in the North Atlantic. Visual and acoustic surveys were performed whenever weather permitted throughout the cruise and visual focal follows were made when tags were deployed. Complimentary data products included physical oceanographic measurements and skin and fecal samples from tagged and neighboring whales. The tag data set from the cruise has been examined using techniques developed on the Sperm Whale Seismic Study (SWSS) program to parameterize foraging and social behaviors. The data set has also been integrated into a combined data set covering the Gulf of Mexico, North Atlantic and Mediterranean seas to enable comparative analyses. We found that the North Atlantic whales follow a foraging and socializing cycle similar to the Gulf of Mexico whales but dive significantly deeper to forage. Foraging largely occurs at 500-1,100 m but a small amount of food may be taken in water as shallow as 300 m. A wide range of codas was produced but even fairly closely located groups appeared to prefer distinct codas. An unusually high rate of breaching, possibly associated with tag attachment, limited the longevity of the tag attachment. The maximum attachment duration of six hours in this Atlantic Ocean study compares unfavorably with 16 hours in the Gulf of Mexico and Mediterranean. The unknown reason for why there were few long attachments may reduce the number of future successful tagging events from whales in the Atlantic. Breaching, possibly associated with tag attachment, has been observed in other areas, and those breaching rates varied from year to year. So, perhaps this first year in the Atlantic is just on the high side of the inter-annual variability. Further work is needed to address this. In addition, there are areas in the Atlantic, such as off Virginia, where there are, at times, a substantial amount of low frequency impulsive sounds from underwater explosions in Navy test ranges. Such times and areas should not be considered as a future controlled exposure study area. Acoustic data could potentially be used in two ways to improve the sperm whale abundance estimates. One way is to utilize both visual and passive acoustic detections to estimate the abundance. A new project to advance development of such methods was recently funded. The visual and acoustic data collected during the Search Mode in this cruise will be used as a test case. Another way acoustic data could be used to improve visual line-transect abundance estimates is to use the dive time pattern data collected on the acoustic tag (DTAG) in surfacing-based line-transect analysis methods. If we assume the tagged animals are representative of the dive patterns of the Atlantic population, then there is a 27% (CV=0.46) chance that a single sperm whale is at the surface to be able to be detected by a visual sighting team. A simple implementation of using these dive data is to estimate total abundance of sperm whales as a function of (i) the abundance using standard visual line-transect methods, assuming this is an abundance estimate of surface animals and (ii) the percentage of time whales are at the surface using the tag data. Using this over-simplified method the dive time corrected total abundance of sperm whales would then be 14,922 (CV=0.60), which is about 3.5 times greater than the standard visual abundance estimate. However, this abundance estimate is biased upwards due to the facts that the standard abundance estimate is based on detection of groups of whales, where groups are usually greater than one, while the probability of a whale being at the surface using the tag data is based on singleton whales, and individual sperm whales do not dive totally independent of the other animals in its group. Thus, surface-based, not group-based, line-transect analysis methods are required to properly account for the confounding facts. These methods are explained in this report and are under development, thus results are not currently available. Another objective of this and the SWSS cruises is to address the question "Do sperm whales have preferred habitats that can be defined physiologically and/or with oceanographically?" One way to address this is to model the distribution and abundance of the sperm whales with respect to physical and biological parameters, such as water depth, bottom slope, sea-surface temperature, salinity at the surface, mixed layer depth, surface color (primary productivity), and distribution and abundance of other trophic levels (such as that obtained from bongo samples). Such a model can also include nuisance variables, such as Beaufort sea state, which affects the sightability of the whales, but probably does not affect the actual distribution of the whales. To start this process, five-day composites from the middle of the cruise of sea surface temperature (SST) and chlorophyll-a (chl-a) using satellite pictures were produced and the sightings were overlaid. Interestingly, sperm whales appear to be present in more diverse combinations of SST and chl-a than many of the other cetacean species detected during this cruise. This could imply that sperm whales are not cueing in on these two parameters, like some other species do. Or, sperm whales are generalists and so can utilize a variety of habitats or perhaps sperm whales are not cueing in ocean surface factors but are cueing on ocean bottom factors. More data are needed to address this. Because this cruise concentrated on putting tags on sperm whales and not investigating many type of potential habitats, this cruise surveyed a limited number of types of potential habitats. However, the NEFSC conducted a large scale line transect abundance survey in 1998 and is currently conducting one during the summer of 2004. The plan is to merge the line transect data of the 1998, 2003, and 2004 surveys to investigate habitat preferences of sperm whales in the Atlantic. Stepwise selection of Generalized Additive Models (GAM) will be used to define a model that uses physical and biological parameters to describe the sperm whale habitat. To start this modeling exercise, the 1998 data were used to model the distribution and abundance of sperm whales in five nautical mile sections of the track line. The stepwise GAM determined depth and an interaction between two groups of plankton species (groups 2 and 3) were the best predictors for sperm whale distribution and abundance, where depth was the most influential factor. Sperm whales were inversely related to Plankton group 3, which are species generally associated with warm core rings. Sperm whales were positively related to Plankton group 2, which are species most often associated with cooler waters, such as those on the outside edge of a ring or in between warm core rings. Thus, these GAM results can be interpreted as Atlantic sperm whales are most commonly found in waters approximately 2000 meters deep, when those waters are cool, like those found on the outside or in between warm core rings. ****************** Dagmar Fertl Geo-Marine, Inc. 2201 Avenue K, Suite A2 Plano, Texas 75074 USA 972-423-5480 FAX 972-422-2736 [EMAIL PROTECTED] http://www.geo-marine.com
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