Physical Sciences and Mathematics Commons^™

Stability In The Proportion Of Harbor Seals Hauled Out Under Locally Ideal Conditions, Michael Simpkins, David Withrow, Jack Cesarone, Peter Boveng

United States Department of Commerce: Staff Publications

We monitored the haul-out behavior of 68 radio-tagged harbor seals (Phoca vitulina) during the molt season at two Alaskan haul-out sites (Grand Island, August-September 1994; Nanvak Bay, August-September 2000). For each site, we created a statistical model of the proportion of seals hauled out as a function of date, time of day, tide, and weather covariates. Using these models, we identified the conditions that would result in the greatest proportion of seals hauled out. Although those “ideal conditions” differed between sites, the proportion of seals predicted to be hauled out under those conditions was very similar (81.3% for …

A Novel Behavior Observed In Humpback Whales On Wintering Grounds At Abrolhos Bank (Brazil), Maria Morete, Ana Freitas, Marcia Engel, Richard M. Pace Iii, Phillip Clapham

United States Department of Commerce: Staff Publications

We describe a novel behavior, termed “tail-up,” observed in humpback whales (Megaptera novaeangliae) on wintering grounds on Abrolhos Bank, Brazil. The behavior involves the whale positioned vertically in the water column with its tail in the air. Wirh the exception of calves, tail-up was observed in all social classes, and its frequency increased through the end of the season. Tail-ups were recorded in 144 (5.8%) of 2,465 groups of whales observed from a shore station, and in 297 (14.9%) of 1,996 groups observed from vessel surveys; biases in each method suggest that the true frequency lies between these …

Killer Whale Predation On Belugas In Cook Inlet, Alaska: Implications For A Depleted Population, Kim Shelden, David J. Rugh, Barbara Mahoney, Marilyn Dahlheim

United States Department of Commerce: Staff Publications

Killer whale predation on belugas in Cook Inlet, Alaska, has become a concern since the decline of these belugas was documented during the 1990s. Accordingly, killer whale sightings were compiled from systematic surveys, observer databases, and anecdotal accounts. Killer whales have been relatively common in lower Cook Inlet (at least 100 sightings from 1975 to 2002), but in the upper Inlet, north of Kalgin Island, sightings were infrequent (18 in 27 yr), especially prior to the 1990s. Beach cast beluga carcasses with teeth marks and missing flesh also provided evidence of killer whale predation. Most observed killer whale/beluga interactions were …

Whaling As Science, Phillip J. Clapham, Per Berggren, Simon Childerhouse, Nancy A. Friday, Toshio Kasuya, Laurence Kell, Karl-Hermann Kock, Silvia Manzanilla-Naim, Giuseppe Notabartolo Di Sciara, William F. Perrin, Andrew J. Read, Randall R. Reeves, Emer Rogan, Lorenzo Rojas-Bracho, Tim D. Smith, Michael Stachowitsch, Barbara L. Taylor, Deborah Thiele, Paul R. Wade, Robert L. Brownell Jr.

United States Department of Commerce: Staff Publications

In an open letter published last year in the New York Times, 21 distinguished scientists (including three Nobel laureates) criticized Japan's program of scientific research whaling, noting its poor design and unjustified reliance upon lethal sampling. In a recent Forum article in BioScience, Aron, Burke, and Freeman (2002) castigate the letter's signers and accuse them of meddling in political issues without sufficient knowledge of the science involved in those issues.

Gray Whales Off Sakhalin Island, Russia: June – September 2001: A Joint U.S. – Russia Scientific Investigation, David W. Weller, Alexander M. Burdin, Amanda L. Bradford, Grigory A. Tsidulko, Yulia V. Ivashchenko, Robert L. Brownell Jr.

United States Department of Commerce: Staff Publications

Numerous species of marine mammals inhabit the Sea of Okhotsk. Two of the most endangered populations of large whales in the world; the Okhotsk Sea bowhead whale (Balaena mysticetus) and the western North Pacific (Okhotsk-Korean) gray whale are known to occur in this sea (Brownell et al., 1997; Clapham et al., 1999). Concerns regarding the status of these whale populations have been intensified by the onset of offshore oil and gas development programs in Okhotsk waters. Anthropogenic activities related to oil and gas exploration off the northeastern Sakhalin Island shelf include geophysical seismic surveying, drilling and production operations, …

Analysis Of Several Eta Model Severe Weather Indices And Variable In Forecasting Severe Weather Across The High Plains, David Thede, Aaron Johnson

United States Department of Commerce: Staff Publications

Forecasting the onset of severe convective weather across the High Plains can be difficult. Topography differences from one end of a county warning area to the other can differ up to 5,000 feet. These topographical differences are not well handled by numerical weather prediction models (NWP) primarily due to insufficient horizontal resolution. The inability of NWP to accurately represent topography impacts the model depiction of the location and depth of low level moisture, an important contributor to convective instability. Convective Available Potential Energy (CAPE ) is a measure of the amount of energy available for convection. The computation of CAPE …

Terrain Influences On Severe Convective Storms Along The Pine Ridge From East Central Wyoming To Northwest Nebraska, Richard Bann, Michael Weiland, Ray Mcanelly

United States Department of Commerce: Staff Publications

Severe convective weather in the warm season is a common occurrence in the high plains. The storms in the high plains are produced primarily by synoptic and mesoscale features which have been described by Doswell (1980) and Maddox et al (1981). In addition to the weather parameters involved in producing severe convective weather, local terrain can also be a factor. The effects of the large scale Rocky Mountains on development of severe thunderstorms are well known. Since the early to mid 1980s, small scale terrain has been shown to have an effect on the development of severe convective weather, primarily …

Recovering Species Of Conservation Concern-Are Populations Expendable?, May Ruckelshaus, Paul Mcelhany, Michael J. Ford

United States Department of Commerce: Staff Publications

Simply mentioning the notion of species expendability may seem reprehensible, but it is a question raised often when conservation biology meets conservation practice, as in this volume. In particular, when arguing for the value of biodiversity, biologists are faced with the challenge of examining the roles that particular species might play in community function and whether there are redundancies in the functions of certain species. Does every species need to be conserved for our ecosystems to function? The question of expendability also is important in conservation planning that occurs at the species level: does every population need to be saved …

Low Frequency Calls Of Bryde's Whales, Erin M. Oleson, Jay Barlow, Jonathan Gordon, Shannon Rankin, John A. Hildebrand

United States Department of Commerce: Staff Publications

Despite significant effort, only two published reports describe Bryde's whale (Balaenoptera edeni) calls (Cummings et al. 1986, Edds et al. 1993). In both studies fundamental call frequencies were greater than 90 Hz, somewhat higher than the call frequencies attributed to other balaenopterids (Clark 1990, Edds-Walton 1997). Through opportunistic acoustic recordings, we obtained and analyzed numerous examples of Bryde's whale calls from three habitats: the Eastern Tropical Pacific (ETP), the southern Caribbean, and the northwest Pacific near the coast of Japan. In all but a single case, call frequencies of 60 Hz or less were observed.

Letter To The Editor: Comment On ‘‘Hydrocarbon Composition And Toxicity Of Sediments Following The Exxon Valdez Oil Spill In Prince William Sound, Alaska, Usa’’, Stanley D. Rice, Mark G. Carls, Ron A. Heintz, Jeffrey W. Short

United States Department of Commerce: Staff Publications

In their recent paper, Page et al. concluded that spilled oil lost toxicity due to weathering and that it dispersed from beaches so rapidly that the potential for toxicity is now, 13 years after the spill, negligible. Their conclusions, however, are based on insensitive toxicity tests, a statistical design with low power, and invalid assumptions regarding the extent and location of remaining oil.

Although Page et al. make a convincing case that the narcotic toxicity of Exxon Valdez oil declined rapidly after the spill, the claim that all oil toxicity has similarly declined requires a higher standard of evidence. They …

A Model Life Table For Bottlenose Dolphins (Tursiops Truncatus) From The Indian River Lagoon System, Florida, U.S.A., Megan K. Stolen, Jay Barlow

United States Department of Commerce: Staff Publications

Data gathered from 220 stranded bottlenose dolphins (Tzmiop tvuncatlls) in the Indian River Lagoon system, Florida, were used to derive a life table. Survivorship curves were fit to the data using Siler’s competing-risk model and a maximum likelihood approach. Population growth was estimated to be between r = 0.0 and 0.046 based on the observed numbers of stranded dolphins. Variance in survival rates was estimated using an individual-based, age-structured population projection model. We estimate that the overall annual mortality rate for this population was 9.8% per year. Sex-specific differences in survivorship were apparent with females outliving males. The …

Segregation Of Migration By Feeding Ground Origin In North Atlantic Humpback Whales (Megaptera Novaeangliae), Peter T. Stevick, Judith Allen, Martine Berube, Phillip J. Clapham, Steven K. Katona, Finn Larsen, Jon Lien, David K. Mattila, Per J. Palsbøll, Jooke Robbins, Johann Sigurjonsson, Tim D. Smith, Nils Øien, Philip S. Hammond

United States Department of Commerce: Staff Publications

Results from a large-scale, capture–recapture study of humpback whales Megaptera novaeangliae in the North Atlantic show that migration timing is influenced by feeding ground origin. No significant differences were observed in the number of individuals from any feeding area that were re-sighted in the common breeding area in the West Indies. However, there was a relationship between the proportion (logit transformed) of West Indies sightings and longitude (r² = 0.97, F_1,3 = 98.27, P = 0.0022) suggesting that individuals feeding farther to the east are less likely to winter in the West Indies. A relationship was also detected …

Trends In The Benthic Macroinvertebrate Community Of Saginaw Bay, Lake Huron, 1987 To 1996: Responses To Phosphorus Abatement And The Zebra Mussel, Dreissena Polymorpha, Thomas F. Nalepa, David L. Fanslow, Margaret B. Lansing, Gregory A. Lang

United States Department of Commerce: Staff Publications

Trends in benthic macroinvertebrate populations were examined in inner and outer Saginaw Bay, Lake Huron, from 1987 to 1996. These years represent the time period after phosphorus abatement, but immediately before (1987 to 1990) and after (1991 to 1996) colonization of the bay by the zebra mussel, Dreissena polymorpha. In 1987 to 1990, densities of the major macroinvertebrate groups in the inner and outer bay were not significantly different from, or were greater than, densities reported just prior to abatement efforts in the early 1970s. Oligochaete densities in the deepwater/silt region of the inner bay were trending downward between …

Late Twentieth Century Northern Hemisphere Sea-Ice Record From U.S. National Ice Center Ice Charts, Kim Partington, Tom Flynn, Doug Lamb, Cheryl Bertoia, Kyle Dedrick

United States Department of Commerce: Staff Publications

Arctic sea ice plays a key role in the climate system, by acting as the interface between a warm ocean and a cold atmosphere. Establishing the true pattern of recent behavior of the sea ice in this region is critical to simulating the role of sea ice in future climate. Recently released operational ice charts from the U.S. National Ice Center provide insight into the late twentieth century behavior of Northern Hemisphere sea ice, providing more reliable ice concentrations during summer and freeze-up than those available from the passive microwave record. The major winter and summer modes of ice concentration …

The Abundance Of Harbor Seals In The Gulf Of Alaska, Peter Boveng, John Bengtson, David Withrow, Jack Cesarone, Michael Simpkins, Kathryn Frost, John Burns

United States Department of Commerce: Staff Publications

The abundance of harbor seals (Phoca vitulina richardii) has declined in recent decades at several Alaska locations. The causes of these declines are unknown, but there is concern about the status of the populations, especially in the Gulf of Alaska. To assess the status of harbor seals in the Gulf of Alaska, we conducted aerial surveys of seals on their haul-out sites in August-September 1996. Many factors influence the propensity of seals to haul out, including tides, weather, time of day, and time of year. Because these “covariates” cannot simultaneously be controlled through survey design, we used a …

Acoustic Identification Of Nine Delphinid Species In The Eastern Tropical Pacific Ocean, Julie N. Oswald, Jay Barlow, Thomas F. Norris

United States Department of Commerce: Staff Publications

Acoustic methods may improve the ability to identify cetacean species during shipboard surveys. Whistles were recorded from nine odontocete species in the eastern tropical Pacific to determine how reliably these vocalizations can be classified to species based on simple spectrographic measurements. Twelve variables were measured from each whistle (n = 908). Parametric multivariate discriminant function analysis (DFA) correctly classified 41 .l% of whistles to species. Non-parametric classification and regression tree (CART) analysis resulted in 5 1.4% correct classification. Striped dolphin whistles were most difficult to classify. Whistles of bottlenose dolphins, false killer whales, and pilot whales were most distinctive. …

Field Experiments Show That Acoustic Pingers Reduce Marine Mammal Bycatch In The California Drift Gill Net Fishery, Jay Barlow, Grant A. Cameron

United States Department of Commerce: Staff Publications

A controlled experiment was carried out in 19961997 to determine whether acoustic deterrent devices (pingers) reduce marine mammal bycatch in the California drift gill net fishery for swordfish and sharks. Using Fisher’s exact test, bycatch rates with pingers were significantly less for all cetacean species combined (P < 0.001) and for all pinniped species combined (P = 0.003). For species tested separately with this test, bycatch reduction was statistically significant for shortbeaked common dolphins (P = 0.001) and California sea lions (P = 0.02). Bycatch reduction is not statistically significant for the other species tested separately, but sample sizes and statistical power were low, and bycatch rates were lower in pingered nets for six of the eight other cetacean and pinniped species. A log-linear model relating the mean rate of entanglement to the number of pingers deployed was fit to the data for three groups: short-beaked common dolphins, other cetaceans, and pinnipeds. For a net with 40 pingers, the models predict approximately a 12- fold decrease in entanglement for short-beaked common dolphins, a 4-fold decrease for other cetaceans, and a 3-fold decrease for pinnipeds. No other variables were found that could explain this effect. The pinger experiment ended when regulations were enacted to make pingers mandatory in this fishery.