bluuebunny/crossref_metadata_2025 huggingface dataset:
BODY SIZE, SURVIVAL, AND DECLINE OF JUVENILE HAWAIIAN MONK SEALS,MONACHUS SCHAUINSLANDI
Authors: Craig Mitchell P. , Ragen Timothy J.
Published: August 2006

Abstract

In the mid 1980s half of the entire Hawaiian monk seal species was located at French Frigate Shoals, and this colony may have reached environmental carrying capacity. Since 1989 this colony has declined by 55%, primarily from poor juvenile survival. Only 8%–25% of weaned pups have survived to age 2 during this period, compared to at least 80% between 1984 and 1987. We characterize (1) this drop in survival, (2) a strong, but variable, correlation between survival and size at weaning, (3) interisland differences in size from weaning to age 2 in 1991 through 1993, and (4) decadal‐scale changes in mean measures of size at weaning. We compare observations at French Frigate Shoals with the colony at Laysan Island where abundance is well below historical levels and was therefore expected to be below carrying capacity. At Laysan Island juvenile survival has also been poor (30%‐70%), and the size of weaned pups has decreased during the past decade. Our hypothesis is that poor survival may be due to reduced prey availability at both sites, but particularly at French Frigate Shoals. Evidence to support this hypothesis includes a large increase in total abundance at French Frigate Shoals; reduced size of weaned pups; decreased survival, emaciation, and slower growth rates of juvenile seals; and declining primary productivity. Regardless of cause, the immediate consequences at French Frigate Shoals and Laysan Island, and for the species overall, will likely be poor recruitment and productivity. Because the decline is still in progress, the ultimate consequences for the species' viability are of great concern in light of its already low abundance.
A NEW ABUNDANCE ESTIMATE FOR VAQUITAS: FIRST STEP FOR RECOVERY1
Authors: Jaramillo‐Legorreta Armando M. , Rojas‐Bracho Lorenzo , Gerrodette Tim
Published: August 2006

Abstract

A line‐transect survey specifically designed to estimate vaquita (Phocoena sinus) abundance over its entire range was carried out by three boats in the summer of 1997. There was a total of 125 sightings of vaquita groups, mainly due to the use of large 25 ± 150 binoculars, which were seven times more effective in detecting vaquitas than hand‐held 7 ± binoculars. Results confirmed that the range of the vaquita is restricted to the northwestern corner of the Gulf of California, Mexico, but that the boundaries of the Upper Gulf of California and Colorado River Delta Biosphere Reserve do not correspond well with the distribution of vaquitas. The shallow water north of the town of San Felipe was found to have a higher density of animals than had been indicated by previous surveys. The total population size was estimated to be 567 animals, with a 95% confidence interval from 177 to 1,073. This estimate is an improvement over previous estimates, which had low numbers of sightings, relied on parameters taken from other species, and/or did not cover all areas where vaquitas could potentially be found. The 1997 estimate was more than twice the 1993 estimate, but there are several reasons why the numbers cannot be directly compared, and it should not be concluded the population is increasing. This first complete estimate of vaquita abundance can be a beginning for the recovery of this highly endangered species.
BEHAVIORAL ASPECTS OF SLEEP IN PACIFIC WHITE‐SIDED DOLPHINS (LAGENORHYNCHUS OBLIQUIDENS, GILL 1865)1
Authors: Goley Patricia Dawn
Published: August 2006

Abstract

Dolphin sleep is unlike typical mammalian sleep in that slow wave sleep occurs in one hemisphere at a time and rapid eye movement (REM) sleep is apparently reduced or absent (Mukhametov 1987). Lilly (1964) observed that bottlenose dolphins (Tursiops truncatus) sleep with one eye open and one eye closed and suggested that the open eye monitored the immediate area for predators. Mukhametov (1987) and Supin et al. (1978) found no physiological correlation between the active brain hemisphere and the open eye, and suggested that no sentinel function exists. I describe the behavioral and social aspects of sleep in a captive school of four Pacific white‐sided dolphins (Lagenorhynchus obliquidens) at Long Marine Lab at the University of California at Santa Cruz for 32 nights. As the animals swam in formation, I recorded their positions and eye condition. Dolphins did not close their eyes or switch positions in the school randomly. While in formation, dolphins switched positions in bouts while concurrently changing eye condition. This resulted in a sleeping formation in which the dolphins likely had the eye open towards schoolmates, not toward the external environment. I suggest that this allows sleep to proceed while allowing dolphins to maintain visual contact with group members.
HEART RATE AND ELECTROCARDIOGRAM CHARACTERISTICS OF A YOUNG CALIFORNIA GRAY WHALE (ESCHRICHTIUS ROBUSTUS)1
Authors: Ponganis P. J. , Kooyman G. L.
Published: August 2006

Abstract

Electrocardiogram (ECG) analyses of Holter monitor recordings from a young California gray whale were performed to determine ECG waveform characteristics, evaluate the heart rate pattern for sinus arrhythmia, obtain resting heart rates at known body masses as the whale increased in size, and compare those heart rates with predicted heart rates from allometric equations. The PR and QRS intervals (475 ± 35 msec, 208 ± 24 msec, respectively, n= 20) support the concept (Meijler et al. 1992) that atrioventricular transmission and ventricular excitation times do not increase linearly in very large mammals. A sinus arrhythmia pattern at rest (apneic heart rates of 15–25 beats per min [bpm] and eupneic heart rates of 34–40 bpm) is consistent with a relative eupneic tachycardia and apneic bradycardia during diving activity of whales. The heart rate‐body mass measurements (35–24 bpm at body masses of 3,591‐8,200 kg) in this study (1) extend the range of allometric heart rate and body mass data in mammals a full order of magnitude, to almost 10,000 kg, (2) support the use of allometric equations (based primarily on mammals <1,000 kg in body mass) in estimating resting heart rates in whales, and (3) demonstrate that previously reported heart rates in large whales are not representative of resting heart rate, probably secondary to circumstances during measurement.
AN ACOUSTIC LINK BETWEEN BLUE WHALES IN THE EASTERN TROPICAL PACIFIC AND THE NORTHEAST PACIFIC1
Authors: Stafford Kathleen M. , Nieukirk Sharon L. , Fox Christopher G.
Published: August 2006

Abstract

Blue whale calls in the eastern North Pacific Ocean consist of a two‐part call often termed the A‐B call. This call has been described for regions offshore of Oregon, Washington, and California, USA and the Sea of Cortez, Mexico (reviewed in Rivers 1997). Data collected from moored hydrophones in the eastern tropical Pacific (ETP) indicate that the A‐B pattern is common in this region as well. There is consistency in this call type throughout the eastern North Pacific and throughout the year. This acoustic evidence indicates continuity between blue whales in the ETP and those found west of North America. The acoustic data suggest that the population of blue whales generally referred to as the “Californi/Mexico” stock might better be termed the “northeast Pacific” stock of blue whales.
GROWTH LAYER PATTERNS IN TEETH FROM THE FRANCISCANA, PONTOPORIA BLAINVILLEI: DEVELOPING A MODEL FOR PRECISION IN AGE ESTIMATION
Authors: Pinedo Maria Cristina , Hohn Aleta A.
Published: August 2006

Abstract

A model for estimating age from teeth of the franciscana, Pontoporia blainvillei, was developed using teeth from 72 specimens taken incidentally in fishing nets in Brazil and Uruguay. The goal of the model was to allow for accurate and precise age estimates for a larger sample of specimens. Growthlayer characteristics were selected on the basis of similarities in growth layers among various species of cetaceans, including those whose growth layers have been calibrated for time, and on length groups in the franciscana, which calves seasonally. Growth‐layer patterns, including relative size and appearance, in both dentine and cementum did not vary by sex but did vary by the orientation of the tooth when it was sectioned. The model developed proved useful in providing guidelines for consistency in age estimation for biological studies of the larger sample of animals. We recommend the development of this type of model for other species to facilitate standardizing age estimation.
FORAGING STRATEGIES OF SYMPATRIC KILLER WHALE (ORCINUS ORCA) POPULATIONS IN PRINCE WILLIAM SOUND, ALASKA
Authors: Saulitis Eva , Matkin Craig , Barrett‐Lennard Lance , Heise Kathy , Ellis Graeme
Published: August 2006

Abstract

Killer whales (Orcinus orca) feed on a wide variety of fish, cephalopods, and marine mammals throughout their cosmopolitan range; however, the dietary breadth that characterizes the species is not reflected in all populations. Here, we present the findings of a 14‐yr study of the diet and feeding habits of killer whales in Prince William Sound, Alaska. Two non‐associating forms of killer whale, termed resident and transient (Bigg et al. 1987), were identified. All prey seen taken by transients were marine mammals, including harbor seals (Phoca vitulina), Dall's porpoises (Phocoenoides dalli), Steller sea lions (Eumetopias jubatus), and harbor porpoises (Phocoena phocoena). Resident killer whales appeared to prey principally on salmon (Oncorhynchus spp.), preferring coho salmon (O. kisutch) over other, more abundant salmon species. Pacific herring (Clupea pallasi) and Pacific halibut (Hippocampus stenolepis) were also taken. Resident killer whales frequently were seen to interact in non‐predatory ways with Steller sea lions and Dall's porpoises, while transients were not. Differences in the social organization and behavior of the resident and transient killer whales in Prince William Sound are discussed in the light of the dietary differences documented here.
DIVE CHARACTERISTICS OF SATELLITE‐MONITORED BLUE WHALES (BALAENOPTERA MUSCULUS) OFF THE CENTRAL CALIFORNIA COAST
Authors: Lagerquist B. A. , Stafford K. M. , Mate B. R.
Published: August 2006

Abstract

Dive habits of four Northeast Pacific blue whales (Balaenoptera musculus) were studied using satellite‐monitored radio tags. Tags summarized dive‐duration data into eight 3‐h periods daily. One tag additionally summarized dive depth and time‐at‐depth information for these same periods. Tracking periods ranged from 0.6 to 12.7 d and provided data for 17 three‐hour summary periods, representing 2,007 dives (788 of which provided depth information). Total number of dives during a 3‐h summary period ranged from 83 to 128. Seventy‐two percent of dives were ≤ 1 min long. All whales spent >94% of their time submerged. Average duration of true dives (dives >1 min) ranged from 4.2 to 7.2 min. Seventy‐five percent of depth‐monitored dives were to ≤16 m, accounting for 78% of that animal's time. Average depth of dives to >16 m was 105 ± 13 m.
CHARACTERISTICS OF MINKE WHALE (BALAENOPTERA ACUTOROSTRATA) PULSE TRAINS RECORDED NEAR PUERTO RICO
Authors: Mellinger David K. , Carson Carol D. , Clark Christopher W.
Published: August 2006

Abstract

A nine‐day acoustic and visual survey was conducted off the West Indies in March 1994 to study the pulse trains that were detected on SOSUS arrays throughout winter in deep water between the West Indies and Bermuda. During the survey, pulse train sounds were consistently recorded in an area 190–350 km northeast of Puerto Rico. Vocalizing animals were never visually observed, but visual sighting conditions were often poor and observation height was low. Pulse trains occurred in two basic forms. The “speed‐up” pulse train was characterized by an accelerating series of pulses with energy in the 200–400 Hz band, with individual pulses lasting 40‐60 msec. Speedup pulse trains started with average pulse rates of 1.5 pulses/sec, lasted 43.7 ± 6.0 sec, and ended with average pulse rates of 2.8 pulses/sec. The less common “slow‐down” pulse train was characterized by a decelerating series of pulses with energy in the 250‐350 Hz band. Slow‐down pulse trains started at pulse rates averaging 4.5 pulses/sec, lasted 60.9 ± 5.8 sec, and ended with average pulse rates of 2.9 pulses/sec. We believe the recorded pulse trains are from minke whales based on careful reanalysis of, and comparison to, minke whale pulse‐train sounds recorded in the Caribbean by Winn and Perkins (1976).
A REASSESSMENT OF THE IMPACT OF THEEXXON VALDEZOIL SPILL ON HARBOR SEALS (PHOCA VITULINA RICHARDSI) IN PRINCE WILLIAM SOUND, ALASKA
Authors: Hoover‐Miller Anne , Parker Keith R. , Burns John J.
Published: August 2006

Abstract

Analyses of population trends and movements of harbor seals in Prince William Sound (PWS) casts doubt on published findings that 302 seals were killed by theExxon Valdezoil spill in 1989. Assumptions that seals have 100% fidelity to a haul‐out, that they were not displaced by the spill and associated disturbances, and that population trends throughout PWS varied similarly, except for oil spill effects, are not supported. Survey efforts to account for missing seals in 1989 were incomplete, too late in the year, and geographically limited. Basic assumptions required for statistical comparisons of oiled and unoiled haul‐outs were violated. Fourteen dead seals, mostly pups, were recovered in PWS. Cause of death in most instances could not be determined, nor could the proportion that would have died naturally. Evidence does not support high unsubstantiated mortality, but is more consistent with seals avoiding or moving away from some oiled haul‐outs. Interpretation of survey results requires consideration of temporal and regional variation. “Route A” surveys of central and eastern PWS do not represent population trends in western PWS or at glacial haul‐outs. To adequately monitor population trends of PWS as a whole, broader sampling must be conducted on a routine basis.
STATUS AND ECOLOGY OF SOTALIA FLUVIATILIS IN THE CAYOS MISKITO RESERVE, NICARAGUA
Authors: Edwards Holly H. , Schnell Gary D.
Published: August 2006

Abstract

In March through May of 1996–1998, we conducted research in the Cayos Miskito Reserve, Nicaragua, to assess the status, ecology, and distribution of Sotalia fluviatilis, a dolphin known from southern Brazil to Honduras. Aerial and boat surveys of lagoons, inlets, and coastal areas were conducted and observational information collected on Sotalia activity, behavior, and other factors relating to its ecology. During boat surveys 183 groups (536 individuals) were sighted (for areas with Sotalia, mean overall density = 0.604 individuals/km2, coastal areas = 0.647/km2, inlets = 0.578/km2, and lagoons = 0.486/km2). Overall, based on all sightings, mean group size was 3.01 (SD = 1.79, range 1–15) and varied among years (x̄= 4.20 in 1996, 2.58 in 1997, and 3.39 in 1998), but not for different months. We estimate that 49 Sotalia inhabited the portions of the Reserve we studied. Sightings of Sotalia groups were non‐random (nearest‐neighbor analysis); clumping of sightings indicates that some areas were preferred. In both Pahara inlet and Wauhta lagoon, sightings were more frequent after 1200 than in the morning. In coastal areas Sotalia were sighted most often within 100 m of shore (54.0%), less often from 101 to 200 m (39.1%), and infrequently from 201 to 300 m (6.8%). Seldom were animals observed in more than 5 m of water, and usually it was considerably shallower (i. e., <2 m). Feeding was the predominant of five recorded activities (i. e., traveling, feeding, socializing, resting, and other), based on time of group sighting (70.3%) and during instantaneous sampling (56.3%). Resource distribution appears to be an important factor influencing Sotalia distribution in the Reserve.
KILLER WHALE PREDATION ON SPERM WHALES: OBSERVATIONS AND IMPLICATIONS
Authors: Pitman Robert L. , Ballance Lisa T. , Mesnick Sarah I. , Chivers Susan J.
Published: August 2006

Abstract

In October 1997 we observed a herd of approximately 35 killer whales (Orcinus orca) attack a pod of nine sperm whales (Physeter macrocephalus) 130 km off the coast of central California. During the four hours we watched, adult female killer whales, including some with calves, attacked in waves of four to five animals in what was apparently a “wound and withdraw” strategy. Adult male killer whales stood by until the very end when one charged in and quickly killed a seriously wounded sperm whale that had been separated from the group. The sperm whales appeared largely helpless: their main defensive behavior was the formation of a rosette (“marguerite”‐heads together, tails out). When the killer whales were successful in pulling an individual out of the rosette, one or two sperm whales exposed themselves to increased attack by leaving the rosette, flanking the isolated individual, and leading it back into the formation. Despite these efforts, one sperm whale was killed and eaten and the rest were seriously, perhaps mortally, wounded. We also present details of two other encounters between sperm whales and killer whales that we observed. Although sperm whales, because of various behavioral and morphological adaptations, were previously thought to be immune to predation, our observations clearly establish their vulnerability to killer whales. We suggest that killer whale predation has potentially been an important, and underrated, selective factor in the evolution of sperm whale ecology, influencing perhaps the development of their complex social behavior and at‐sea distribution patterns.
PUPPING PHENOLOGY AND DEMOGRAPHY OF HARBOR SEALS (PHOCA VITULINA RICHARDSI)ON TUGIDAK ISLAND, ALASKA
Authors: Jemison Lauri A. , Kelly Brendan P.
Published: August 2006

Abstract

The number of seals on shore at Tugidak Island (Gulf of Alaska) declined 72%–85% between 1976 and 1988 and increased during the 1990s. We compared pupping phenology and the ratio of pupping‐period counts to molting‐period counts between declining (1976–1979) and increasing (1994–1998) years, and examined the sex/age structure of seals ashore during the 1990s. In the 1970s the onset and peak of pupping occurred 6–18 d later than in the 1990s. Rate of pup abandonment was higher in 1978 than in the 1990s. Between 1994 and 1995, the maximum and mean number of seals ashore increased >50%, largely due to an increase in non‐pups. From 1995 to 1998, the sex/age structure of seals ashore was similar among years. We observed three to four times as many seals during the molting period than during the pupping period in the 1970s, whereas similar numbers were ashore during these periods in the 1990s, perhaps reflecting changes in demography and/or haul‐out behavior. Changes in pupping phenology and demography may reflect environmental changes, such as food availability, and when monitored in conjunction with population counts, may help us better interpret changes in the number of seals ashore.
COMPARISON OF METHODS USED TO ESTIMATE NUMBERS OF WALRUSES ON SEA ICE
Authors: Udevitz Mark S. , Gilbert James R. , Fedoseev Gennadii A.
Published: August 2006

Abstract

The US and former USSR conducted joint surveys of Pacific walruses on sea ice and at land haul‐outs in 1975, 1980, 1985, and 1990. One of the difficulties in interpreting results of these surveys has been that, except for the 1990 survey, the Americans and Soviets used different methods for estimating population size from their respective portions of the sea ice data. We used data exchanged between Sovier and American scientists to compare and evaluate the two estimation procedures and to derive a set of alternative estimates from the 1975, 1980, and 1985 surveys based on a single consistent procedure. Estimation method had only a small effect on total population estimates because most walruses were found at land haul‐outs. However, the Sovievr method is subject to bias that depends on the distribution of the population on the sea ice and this has important implications for interpreting the ice portions of previously reported surveys for walruses and other pinniped species. We recommend that the American method be used in future surveys. Future research on survey methods for walruses should focus on other potential sources of bias and variation.
SHORT‐TERM EFFECTS OF BOAT TRAFFIC ON BOTTLENOSE DOLPHINS,TURSIOPS TRUNCATUS, IN SARASOTA BAY, FLORIDA
Authors: Nowacek Stephanie M. , Wells Randall S. , Solow Andrew R.
Published: August 2006

Abstract

Coastal cetaceans are subject to potential injury or disturbance from vessels. In Sarasota, Florida, where about 120 resident bottlenose dolphins,Tursiops truncatus, share the inshore waters with over 34,000 registered boats, disturbance potential is high. We assessed specific behavioral responses of individual dolphins to boat traffic. We conducted focal animal behavioral observations during opportunistic and experimental boat approaches involving 33 well‐known identifiable individual bottlenose dolphins. Dolphins had longer interbreath intervals (IBI) during boat approaches compared to control periods (no boats within 100 m). Treatment IBI length was inversely correlated with distance to the nearest boat in opportunistic observations. During 58 experimental approaches to 18 individuals, a video system suspended from a tethered airship was used to observe subsurface responses of focal dolphins as boats under our control, operating at specified speeds, were directed near dolphins. Dolphins decreased interanimal distance, changed heading, and increased swimming speed significantly more often in response to an approaching vessel than during control periods. Probability of change for both interanimal distance and heading increased when dolphins were approached while in shallow water. Our findings provide additional support for the need to consider disturbance in management plans for cetacean conservation.
DISTRIBUTION OF THE PYGMY RIGHT WHALE, CAPEREA MARGINATA, IN THE AUSTRALASIAN REGION
Authors: Kemper Catherine M.
Published: August 2006

Abstract

The latitudinal range of all records of sightings (n= 9), and live strandings and carcasses (n= 180) of Caperea marginata in the Australasian region was 32°00′–47°00′S. Records were concentrated on the edge of the South Australian gulfs, around Tasmania, at Stewart Island, in Cook Strait, and in the Auckland area. Limited data suggest that these may be related to planktonrich waters nearby. Body lengths ranged from 198 to 650 cm. Overall sex ratio was 0.70 (males: females). In regions north of about 41°S, juveniles (preweaning) made up 41% of the records and subadults (postweaning) were rare (13%). In regions south of about 41°S subadults (36%) were proportionately more abundant than juveniles (17%). Neonates were recorded from 35°37′ to 47°00′S. Adults were found throughout the latitudinal range of the species in Australasia. The diet of the pygmy right whale included copepods and small euphausiids. Behavior consistent with feeding has been observed in coastal waters of Australia.
DETERMINATION OF PREGNANCY STATUS FROM BLUBBER SAMPLES IN MINKE WHALES (BALAENOPTERA ACUTOROSTRATA)
Authors: Mansour Atef A. H. , Mkay Donald W. , Lien Jon , Orr James C. , Banoub Joseph H. , ØIen Nils , Stenson Garry
Published: August 2006

Abstract

Measurement of progesterone concentration in blubber was developed as a method to detect pregnancy in minke whales. Progesterone was extracted and quantified from blubber samples of minke whale carcasses by radioimmunoassay. Results showed a highly significant difference (almost 60‐fold) between blubber progesterone concentrations of anatomically determined pregnant females versus non‐pregnant female or male carcasses. The results of the study suggest that the blubber progesterone concentrations might be used to determine pregnancy status in free‐ranging whales.
HAUL‐OUT ACTIVITY OF RINGED SEALS (PHOCA HISPIDA) DETERMINED FROM SATELLITE TELEMETRY
Authors: Born E. W. , Teilmann J. , Riget F.
Published: August 2006

Abstract

The haul‐out activity of 15 ringed seals (Phoca hispida) equipped with satellite‐linked radio transmitters was studied in NW Greenland (ca.73°‐78°N). Between 19 June 1997 and 30 June 1999, telemetry data on haulout activity were obtained by the “Land‐Sea‐Reporter” (LSR), “Time‐at‐Depth” (TAD), and “Timelines” (TIM) systems housed within the satellite transmitters. The haul‐out activity (% of total time hauled out) reported by the TIM system, which is specifically designed for collecting haul‐out data, was about 1.4 times higher than that inferred from the LSR, but only about 0.7 of that inferred from TAD data. The TIM were used to describe haul‐out activity. A total of 1,011 d with TIM were obtained (64.5% of a total of 1,568 “seal‐days” monitored) representing data from nearly an entire annual cycle. No differences were found in percentage of time hauled out per month among various age categories. At all seasons the haul‐out time showed considerable individual variation. There were no trends in percentage of time hauled out per month during late summer, fall, and winter (August‐February). During the High Arctic winter darkness (November‐January) the percentage of haul‐out per month ranged between 3.9% in an adult (SD = 2.44, range: 1.1%‐5.7%,n= 3 mo) and 15.7% in a subadult (SD = 1.95, range: 13.7%‐17.6%,n= 3 mo). From late March there was a significant increase in haul‐out time. Between 1 and 30 June, when aerial surveys of basking ringed seals usually are conducted, the haul‐out time (% per day) increased from about 25% to about 57%. No tendencies in diel haul‐out activity were revealed.
GROWTH OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) FROM THE INDIAN RIVER LAGOON SYSTEM, FLORIDA, U. S. A.
Authors: Stolen Megan K. , Odell Daniel K. , Barros Nélio B.
Published: August 2006

Abstract

Gompertz growth models were fitted to total lengths and ages from tooth sections of 199 stranded bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon system, eastern Florida. Based on the model, dolphins from this population are estimated to be born at 119 cm and reach asymptotic length at 250 cm. No apparent pubescent growth acceleration was noted for either sex. Males appeared to grow to slightly longer lengths than females. There were small size differences between Indian River dolphins and those in Texas and Sarasota, indicating general size similarities between North Atlantic and Gulf of Mexico bottlenose dolphins stocks.
PRIMARY PRODUCTION REQUIRED TO SUPPORT BOTTLENOSE DOLPHINS IN A SALT MARSH ESTUARINE CREEK SYSTEM
Authors: Young Robert F. , Phillips Heather D.
Published: August 2006

Abstract

We developed a model to estimate the proportion of annual primary production required to support bottlenose dolphins within the 32‐km2 North Inlet salt marsh creek system in South Carolina, U. S. A. The estimated annual prey consumption by dolphins was compared to the total annual production of prey available to dolphins, as determined from estimates of annual primary production, trophic transfer efficiencies, and the mean trophic level of prey. A best estimate range of 3.2%‐6.8% of the total annual primary production of the North Inlet system was required to support an average population of only six dolphins (maximum range of 0.4%–7.0%). Dolphins were estimated to consume 11.1–14.2 metric tons of fish (wet weight) each year in North Inlet. The proportion of North Inlet primary production required to support dolphins increased dramatically during the winter months, when primary production declined but dolphin numbers remained similar. This period was marked by a decline in the abundance of available prey species and by a shift in the creek utilization patterns of dolphins. Despite the numerical scarcity of dolphins in the system, they appear to have a significant ecological impact and may be important predators of overwintering prey species.
UNDERWATER NOISE OF WHALE‐WATCHING BOATS AND POTENTIAL EFFECTS ON KILLER WHALES (ORCINUS ORCA), BASED ON AN ACOUSTIC IMPACT MODEL
Authors: Erbe Christine
Published: August 2006

Abstract

Underwater noise of whale‐watching boats was recorded in the popular killer whale‐watching region of southern British Columbia and northwestern Washington State. A software sound propagation and impact assessment model was applied to estimate zones around whale‐watching boats where boat noise was audible to killer whales, where it interfered with their communication, where it caused behavioral avoidance, and where it possibly caused hearing loss. Boat source levels ranged from 145 to 169 dB re 1 μPa @ 1 m, increasing with speed. The noise of fast boats was modeled to be audible to killer whales over 16 km, to mask killer whale calls over 14 km, to elicit a behavioral response over 200 m, and to cause a temporary threshold shift (TTS) in hearing of 5 dB after 30–50 min within 450 m. For boats cruising at slow speeds, the predicted ranges were 1 km for audibility and masking, 50 m for behavioral responses, and 20 m for TTS. Superposed noise levels of a number of boats circulating around or following the whales were close to the critical level assumed to cause a permanent hearing loss over prolonged exposure. These data should be useful in developing whale‐watching regulations. This study also gave lower estimates of killer whale call source levels of 105–124 dB re 1 μPa.
SUMMER HOME RANGE AND HABITAT SELECTION OF HARBOR SEAL (PHOCA VITULINA) PUPS
Authors: Bjørge Arne , Bekkby Trine , Bryant Edmund B.
Published: August 2006

Abstract

We studied the summer home range and habitat selection of harbor seal pups tracked using VHF radio telemetry along the coast of central Norway in 1997 and 1998. Median fixed kernel home range of six pups tracked in 1998 was 10.4 km2and the median core area was 1.2 km2. One particular deep basin (>100 m deep) was highly selected, and extensively used by four of the pups, probably for feeding. An area adjacent to the deep basin also was selected, probably for haul outs. One pup spent most of the time in inshore, kelp forest areas. Shallow areas without kelp forest and exposed land were used least frequently, possibly because they did not provide suitable areas for feeding and to haul out. The seals hauled out more during calm wind and low tide than during rough wind and high tide. Seals seemed to haul out on intertidal rocks associated with islands, and alternated between several haul‐out sites. We found no pattern in haul‐out activity associated with age, time of day, air/sea temperature, cloud cover, or rainfall. In 1997, seven pups were tracked manually. These data were associated with methodological limitations, and they were used only to illustrate that these seals stayed mainly within the shallow, inshore, kelp forest area, indicating a possible difference in habitat use between years.
EFFECTS OF RESEARCH HANDLING ON THE ENDANGERED HAWAIIAN MONK SEAL
Authors: Baker Jason D. , Johanos Thea C.
Published: August 2006

Abstract

We examined the effects of research handling on free‐ranging endangered Hawaiian monk seals, Monachus schauinslandi, by analyzing differences in subsequent year survival, migration, and condition between handled seals and controls during 1983–1998. Each of 549 handled seals was matched to a control seal of the same age, sex, location, and year. Handling included instrumentation with tel metry devices (n= 93), blood sampling (n= 19), and tagging (n= 437). No significant differences were found between handled seals and their controls in one‐year resighting rates, observed migration rates, or condition. Resighting rates of handled and control seals were high (80%‐100%). Available sample sizes were sufficient to detect reasonably small (9%‐20%) differences in resighting rates had they existed among instrumented or tagged seals and controls (α= 0.05, power = 0.90). Too few seals were captured for blood sampling to detect even large differences in their resighting rates. However, blood samples were drawn from most instrumented seals, and there was no indication that this larger group suffered harmful effects. Duration of restraint during flipper tagging had no effect on subsequent probability of resighting. Our analysis suggests that conservative selection procedures and careful handling techniques have no deleterious effects on Hawaiian monk seals.
DISPERSAL, ROOKERY FIDELITY, AND METAPOPULATION STRUCTURE OF STELLER SEA LIONS (EUMETOPIAS JUBATUS) IN AN INCREASING AND A DECREASING POPULATION IN ALASKA
Authors: Raum‐Suryan Kimberly L. , Pitcher Kenneth W. , Calkins Donald G. , Sease John L. , Loughlin Thomas R.
Published: August 2006

Abstract

Over the past 24 yr, 8,596 Steller sea lion (Eumetopias jubatus) pups were branded on their natal rookeries throughout Alaska with the objectives of determining survival rates, recruitment, movements, and site fidelity. Our objectives here were to examine the extent of dispersal of Steller sea lions away from their natal rookeries, movements between stocks, and degree of natal rookery fidelity. Pups (<1 yr old) usually remained within 500 km of their natal rookery. Branded juveniles dispersed widely and were resighted at distances up to 1,785 km from their natal rookeries. Adults generally remained within 500 km of their natal rookeries. No interchange of breeding animals between the ES (eastern stock) and WS (western stock) was observed. Although natal rookery fidelity was prevalent, 33% of the 12 observations of females branded in the WS during 1987–1988 and 19% of the 29 observations of females branded in the ES during 1994–1995 were observed with newly born pups at sites other than their natal rookeries. Steller sea lions generally conformed to the metapopulation concept as depicted by Hanski and Simberloff (1997), with local breeding populations (rookeries) and movements among these local populations having the potential of affecting local dynamics.
INTERACTIONS BETWEEN THE INDIAN RIVER LAGOON BLUE CRAB FISHERY AND THE BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS
Authors: Noke Wendy D. , Odell Daniel K.
Published: August 2006

Abstract

Anecdotal reports from blue crab fishermen in the Indian River Lagoon (IRL), Florida suggested that bottlenose dolphins (Tursiops truncatus) followed their boats, and stole bait fish from crab pots soon after they were deployed. To investigate these reports, we made biweekly observations from IRL commercial crab boats from January 1998 to January 1999 (670 h). Only 2.8% of the 18,891 crab pots surveyed revealed evidence of dolphin/crab pot interaction. Dolphin interactions included: (1) begging at boats, (2) feeding on discarded bait fish, (3) engaging in crab pot tipping behavior, and (4) dolphin mortality from crab pot float line entanglement. Overall, 16.6% of the 1,296 dolphins sighted interacted with fishing boats. Seasonal trends were evident, with fishery interactions peaking in the summer. Crab pot interactions ranged from 0% to 36% of the traps checked daily. Different methods of securing the bait‐well door and the role of trap locality were tested using a replicated experimental design. Results showed significant differences in successful bait removal by dolphins, among the degrees of door security (P < 0.001) and between trap location (P < 0.01). Thus, increased door security may help to reduce the negative impacts to the fishery and dolphins involved.
EFFECT OF THE SOUND GENERATED BY AN ACOUSTIC HARASSMENT DEVICE ON THE RELATIVE ABUNDANCE AND DISTRIBUTION OF HARBOR PORPOISES (PHOCOENA PHOCOENA) IN RETREAT PASSAGE, BRITISH COLUMBIA
Authors: Olesiuk Peter F. , Nichol Linda M. , Sowden Margaret J. , Ford John K. B.
Published: August 2006

Abstract

We describe an experiment conducted to assess the impact of the sound generated by an acoustic harassment device (AHD) on the relative abundance and distribution of harbor porpoises (Phocoena phocoena) in Retreat Passage, British Columbia. During control periods when the AHD was inactive, the mean number of porpoises observed in the study area was 0.39 for broad area scans conducted with the naked eye and 0.48 for narrow sector scans conducted with binoculars. Abundance declined precipitously when the AHD was activated, to 0.007 porpoises per broad area scan and 0.018 per narrow sector scan. The mean number of porpoise resightings while tracking their movements also declined from 12.2 to 13.6 per sighting during control periods to 1.1–1.9 per sighting when the AHD was activated, which suggested that the few porpoises that ventured into the study area spent less time within it when the AHD was activated. The effect of the AHD diminished with distance. No porpoises were observed within 200 m of the AHD when it was activated. The number of sightings and resightings observed when it was activated was less than 0.2% of the number expected had there been no AHD effect at a range of 200–399 m, 1.4% the number expected at a range of 400–599 m, varied between 2.5% and 3.3% of the number expected at a range of 600–2,499 m, and was 8.1% the number expected at a range of 2,500–3,500 m, which suggested that the impact of the AHD extended beyond our maximum sighting range of 3.5 km.
A BIOPSY SYSTEM FOR SMALL CETACEANS: DARTING SUCCESS AND WOUND HEALING IN TURSIOPS SPP.
Authors: Krützen Michael , Barré Lynne M. , Möller Luciana M. , Heithaus Michael R. , Simms Colleen , Sherwin William B.
Published: August 2006

Abstract

Together with PAXARMS (NZ), we developed a biopsy system for small cetaceans and tested it on four populations of bottlenose dolphins (Tursiops spp.). The system consists of a modified 0.22 caliber rifle, and biopsy darts made out of polycarbonate with stainless steel biopsy tips. Animals were darted at a range of 2–15 m while travelling parallel to the vessel. Overall sampling success for obtaining biopsy samples when an animal was struck ranged from 96.6% to 100% in the four populations. However, hit rate varied for the four different populations. We did not observe a significant difference in strength of the reaction to the darting procedure when an animal was hit or missed, both among and within populations. Data from one population showed no significant difference in the reaction to biopsy sampling by four different age‐sex classes. The only factor that had a significant influence on darting success was the hit location. Furthermore, we observed a significant positive correlation between the size of the sample obtained and the reaction to biopsy sampling. Biopsy samples were sufficient for microsatellite and d‐loop analysis in 95.8% and for genetic sexing in 99% of all cases. In animals that we observed on a daily basis, wounds were healed after approximately 23 d.
DIETS OF BAIRD'S BEAKED WHALES, BERARDIUS BAIRDII, IN THE SOUTHERN SEA OF OKHOTSK AND OFF THE PACIFIC COAST OF HONSHU, JAPAN
Authors: Walker William A. , Mead James G. , Brownell Robert L.
Published: August 2006

Abstract

Stomach contents were analyzed from 127 Baird's beaked whales, Berardius bairdii, taken in coastal waters of Japan. During late July‐August of 1985–1987, 1989, and 1991, 107 samples were collected from off the Pacific coast of Honshu. An additional 20 samples were collected from whales taken in the southern Sea of Okhotsk during late August—September of 1988 and 1989. Prey identification using fish otoliths and cephalopod beaks revealed the whales fed primarily on deep‐water gadiform fishes and cephalopods in both regions. Prey species diversity and the percentage of cephalopods and fish differed between the two regions. Off the Pacific coast of Honshu the whales fed primarily on benthopelagic fishes (81.8%) and only 18.0% on cephalopods. Eight species of fish representing two families, the codlings (Moridae) and the grenadiers (Macrouridae), collectively made up 81.3% of rhe rotal. Thirty species of cephalopods representing 14 families made up 12.7%. In the southern Sea of Okhotsk, cephalopods accounted for 87.1% of stomach contents. The families Gonatidae and Cranchiidae were the predominant cephalopod prey, accounting for 86.7% of the diet. Gadiform fish accounted for only 12.9% of the diet. Longfin codling, Laemonema longipes, was the dominant fish prey in both regions. Depth distribution of the two commonly consumed fish off the Pacific coast of Honshu indicate the whales in this region fed primarily at depths ranging from 800 to 1,200 m.
DISPERSAL and BYCATCH MORTALITY IN GRAY,HALICHOERUS GRYPUS, AND HARBOR,PHOCA VITULINA, SEALS TAGGED AT THE NORWEGIAN COAST
Authors: Bjørge Arne , ØIen Nils , Hartvedt Siri , Bøthun Gjermund , Bekkby Trine
Published: August 2006

Abstract

Between 1975 and 1998, 3,571 gray and 630 harbor seal pups were tagged along the Norwegian coast, and 259 (7%) gray and 80 (13%) harbor seal tags were returned. Incidental mortality, mainly in bottom‐set nets, accounted for the majority of deaths (79% in gray and 48% in harbor seals, respectively). Seals were most vulnerable to incidental mortality in fishing gear during the first three months after birth, but high incidental mortality prevailed during the first 8–10 mo. Gray seals dispersed more widely (mean distance: 120 km) than harbor seals (mean distance: 69 km). Both species dispersed most widely during the two first months after tagging. The maximum distance moved was 739 km for gray and 463 km for harbor seals. Strong fidelity for their place of birth was observed in adult gray seals during breeding season. No significant difference in incidental mortality was detected between the areas of tagging. However, for 37 harbor seals tagged in a 724 km nature reserve no returns were reported.
LENGTH‐MASS AND TOTAL BODY LENGTH OF ADULT FEMALE SEA OTTERS IN PRINCE WILLIAM SOUND BEFORE AND AFTER THE EXXON VALDEZ OIL SPILL
Authors: Rotterman Lisa Mignon , Monnett Charles
Published: August 2006

Abstract

After the 1989 T/V Exxon Valdez oil spill (EVOS), the body condition of non‐pregnant female sea otters (Enhydra lutris) ages 4 yr and older in the EVOS‐affected region of western Prince William Sound, Alaska (WPWS), was significantly poorer than that of individuals captured in the same or adjacent habitat in WPWS approximately a decade earlier, and than that of individuals inhabiting unoiled habitat in eastern PWS (EPWS) between 1984 and 1990. However, the body condition of females of this age category captured in WPWS prior to EVOS was not significantly different from that of pre‐and postspill EPWS females. The mean total body length (TBL) of non‐pregnant females captured prespill in WPWS was significantly less than that of pre‐and postspill EPWS and postspill WPWS females. Evidence from this and other studies suggests that the body condition of at least some classes of sea otters was negatively affected by one or more EVOS‐related factors.
ACOUSTIC IDENTIFICATION OF NINE DELPHINID SPECIES IN THE EASTERN TROPICAL PACIFIC OCEAN
Authors: Oswald Julie N. , Barlow Jay , Norris Thomas F.
Published: August 2006

Abstract

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 41.1% of whistles to species. Non‐parametric classification and regression tree (CART) analysis resulted in 51.4% correct classification. Striped dolphin whistles were most difficult to classify. Whistles of bottlenose dolphins, false killer whales, and pilot whales were most distinctive. Correct classification scores may be improved by adding prior probabilities that reflect species distribution to classification models, by measuring alternative whistle variables, using alternative classification techniques, and by localizing vocalizing dolphins when collecting data for classification models.
DIRECTIONALITY IN THE WHISTLES OF HAWAIIAN SPINNER DOLPHINS (STENELLA LONGIROSTRIS): A SIGNAL FEATURE TO CUE DIRECTION OF MOVEMENT?
Authors: Lammers Marc O. , Au Whitlow W. L.
Published: August 2006

Abstract

Dolphins produce frequency modulated (FM) whistles that are thought to promote the synchrony and coordination of behavior between members of a group. How whistles are used in this regard remains poorly understood. One possibility is that whistles have directionality and thereby convey the orientation and direction of movement of the signaler to nearby listeners. To explore this possibility, whistles from free‐ranging Hawaiian spinner dolphins (Stenella longirostris) were obtained using a towed, three‐hydrophone line array and examined for the presence of directionality. Both the estimated source level and harmonic content of whistles produced by animals traveling with or toward the array were greater than those of animals moving ahead or away from it. In addition, signals produced by animals near the array (within 20 m) were received differently on the three hydrophones spaced 11.5 m apart. These differences were greater than would be expected from transmission loss disparities alone. The results indicate that directivity is present in the transmission pattern of whistles. To infer the form of this directivity, a theoretical whistle beam pattern was established based on the assumption that the dolphin's sound source is approximated by a circular piston transducer (Au 1993). The resulting beam indicates that spinner dolphin whistles become increasingly directional with frequency, especially with respect to harmonics. The orientation‐dependent harmonic structure of whistles thus presents a potential cue that listening animals could interpret to infer the direction of movement of signalers. Harmonics are present in the whistles of many dolphin species and may represent an inherent signal design feature that promotes coordination between animals.
REPRODUCTIVE CYCLE OF THE FEMALE MEDITERRANEAN MONK SEAL IN THE WESTERN SAHARA
Authors: Pastor T. , Aguilar A.
Published: August 2006

Abstract

Mediterranean monk seals at Cap Blanc, western Sahara, pup annually throughout the year, although births are more frequent in autumn (October). Consequently, subsequent events of the cycle are not seasonal. This lack of synchronicity in reproduction can be attributed to the subtropical location of the colony and the presence of a semipermanent upwelling in the area. This contrasts with the consistency in the timing of parturition of individual females, which results in an interbirth period of one year, which varies by a maximum of only 15 d. The duration of lactation, which can last up to five months, correlates with that of the interbirth period. The interbirth and “molt‐to‐parturition” periods are relatively constant, and the only part of the cycle that appears to compensate for variation in lactation length is the “weaning‐to‐molt” period, which correlates negatively with the duration of lactation. As a result of the long lactation period, esrrus probably does not occur at the end of weaning, as it does in most other phocids.