Berardius Research Articles

Declining abundance of beaked whales (family Ziphiidae) in the California Current large marine ecosystem.

Beaked whales are among the most diverse yet least understood groups of marine mammals. A diverse set of mostly anthropogenic threats necessitates improvement in our ability to assess population status for this cryptic group. The Southwest Fisheries Science Center (NOAA) conducted six ship line-transect cetacean abundance surveys in the California Current off the contiguous western United States between 1991 and 2008. We used a Bayesian hidden-process modeling approach to estimate abundance and population trends of beaked whales using sightings data from these surveys. We also compiled records of beaked whale stranding events (3 genera, at least 8 species) on adjacent beaches from 1900 to 2012, to help assess population status of beaked whales in the northern part of the California Current. Bayesian posterior summaries for trend parameters provide strong evidence of declining beaked whale abundance in the study area. The probability of negative trend for Cuvier's beaked whale (Ziphius cavirostris) during 1991–2008 was 0.84, with 1991 and 2008 estimates of 10771 (CV = 0.51) and ≈7550 (CV = 0.55), respectively. The probability of decline for Mesoplodon spp. (pooled across species) was 0.96, with 1991 and 2008 estimates of 2206 (CV = 0.46) and 811 (CV = 0.65). The mean posterior estimates for average rate of decline were 2.9% and 7.0% per year. There was no evidence of abundance trend for Baird's beaked whale (Berardius bairdii), for which annual abundance estimates in the survey area ranged from ≈900 to 1300 (CV≈1.3). Stranding data were consistent with the survey results. Causes of apparent declines are unknown. Direct impacts of fisheries (bycatch) can be ruled out, but impacts of anthropogenic sound (e.g., naval active sonar) and ecosystem change are plausible hypotheses that merit investigation.

Abundance Estimation of Long‐Diving Animals Using Line Transect Methods

Line transect sampling is one of the most widely used methods for estimating the size of wild animal populations. An assumption in standard line transect sampling is that all the animals on the trackline are detected without fail. This assumption tends to be violated for marine mammals with surfacing/diving behaviors. The detection probability on the trackline is estimated using duplicate sightings from double-platform line transect methods. The double-platform methods, however, are insufficient to estimate the abundance of long-diving animals because these animals can be completely missed while the observers pass. We developed a more flexible hazard probability model that incorporates information on surfacing/diving patterns obtained from telemetry data. The model is based on a stochastic point process and is statistically tractable. A simulation study showed that the new model provides near-unbiased abundance estimates, whereas the traditional hazard rate and hazard probability models produce considerably biased estimates. As an illustration, we applied the model to data on the Baird's beaked whale (Berardius bairdii) in the western North Pacific.

Beaked whale strandings on the Falkland Islands and South Georgia, South Atlantic Ocean, between 1866 and 2008

Records of beaked whales stranded in the Falkland Islands and at South Georgia were collated for the period 1866 to 2008. Thirty-eight records, involving at least seven species in four genera, were documented. Strap-toothed whales (Mesoplodon layardiiGray, 1865) were the most common species with 11 records, including two neonates. Andrews' beaked whales (M. bowdoiniAndrews, 1908), Arnoux's beaked whales (Berardius arnuxiiDuvernoy, 1851), Cuvier's beaked whales (Ziphius cavirostrisGray, 1823), Gray's beaked whale (M. grayivan Haast, 1876), Hector's beaked whales (M. hectoriGray, 1871) and southern bottlenose whales (Hyperoodon planifronsFlower, 1882) were recorded on three to five occasions. In several cases, records suggested potential temporal changes in range. For example, Arnoux's beaked whale has not been recorded in the Falkland Islands since 1965, whilst Gray's beaked whale was not recorded prior to 1981, and Andrews' beaked whale was not recorded before 1987. Although the number of records for each species is low, this could reflect changes in water temperatures and/or prey availability. Overall, this study confirms that the Falkland Islands–Tierra del Fuego region is one of the world's key areas for beaked whales.

Silver speciation in liver of marine mammals by synchrotron X-ray absorption fine structure and X-ray fluorescence spectroscopies

The chemical form of Ag in the livers of five species of marine mammals was examined using X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies. The XAFS analysis suggested that Ag(2)Se was present in the livers of the Franciscana dolphin (Pontoporia blainvillei), Dall's porpoise (Phocoenoides dalli), and Baird's beaked whale (Berardius bairdii), whereas Ag(2)S was present in the livers of the striped dolphin (Stenella coeruleoalba) and pygmy killer whale (Feresa attenuata). XRF spectroscopy results revealed that the distribution patterns of Ag and Se in a thin section of the liver of the Franciscana dolphin were the same; this also implied that Ag was associated with Se in the liver. Thus, the interaction of Ag with Se or S may offer significant protection against the toxicity of Ag in marine mammals. The formation of either Ag(2)Se or Ag(2)S might depend on the Hg levels in the liver. Ag(2)Se was observed in liver samples with relatively high Ag/Hg ratio, whereas liver samples with low Ag/Hg ratio contained Ag(2)S.

Occurrence of killer whales (Orcinus orca) and other cetaceans in Terra Nova Bay, Ross Sea, Antarctica

AbstractDuring January and February 2004, data on presence and distribution of killer whales (Orcinus orca) and other cetaceans were collected by helicopter surveys along the coastline of Terra Nova Bay and adjacent localities (western Ross Sea, Antarctica). A total of 37 sightings of killer whale, of both B and C types, were recorded as well as 17 sightings of Antarctic minke whales (Balaenoptera bonaerensis), nine ofBalaenopteraspp., two of Arnoux’s beaked whale (Berardius arnuxii) and four of undetermined species. The type C killer whale was the most abundant, with 23 sightings, whereas we recorded type B only twice. Group size ranged between 1 and 30 animals, with an average of eight individuals. Seventeen killer whales were photo-identified and 13 resightings occurred during the study period. Killer whales showed a differential pattern in partitioning the study area. Their encounter rate was significantly higher (t-test = 2.6045,P< 0.05) in the northern area extending from Edmonson Point to the Campbell Glacier Tongue (encounter rate, ER = 0.031), compared to the southern area from Mario Zucchelli Station to the Drygalski Ice Tongue (ER = 0.003).

Cetacean records along São Paulo state coast, Southeastern Brazil

The São Paulo state (SP) coast (23º18'S, 44º42'W; 25º14'S, 48º01'W) is of approximately 600 km in length, bordering the Western Atlantic Ocean, in southeastern Brazil. Cetacean sightings and strandings have long been observed throughout this area. Scattered data from scientific publications, skeletal remains in museums, photographs and articles from newspaper files, universities and aquaria have been organised and updated since 1993. Field investigations on strandings and sightings have also been conducted. A total of 29 cetacean species have been recorded, including 7 baleen whales (Mysticeti) and 22 toothed whales (Odontoceti), as follows: Balaenoptera physalus, B. borealis, B. edeni, B. acutorostrata, B. bonaerensis, Megaptera novaeangliae, Eubalaena australis, Physeter macrocephalus, Kogia breviceps, K. sima, Berardius arnuxii, Mesoplodon europaeus, M. mirus, Ziphius cavirostris, Orcinus orca, Feresa attenuata, Globicephala melas, G. macrorhynchus, Pseudorca crassidens, Delphinus capensis, Lagenodelphis hosei, Steno bredanensis, Tursiops truncatus, Stenella frontalis, S. longirostris, S. coeruleoalba, Lissodelphis peronii, Sotalia guianensis and Pontoporia blainvillei. Several species have been observed only once and include strays from their areas of common distribution, as well as species with known preferences for offshore distribution. Others, such as P. blainvillei and S. guianensis, are common coastal dwellers year-round. Z. cavirostris, P. crassidens and L. hosei are reported for the first time on the SP coast.

Multiple sightings of large groups of Arnoux's beaked whales (Berardius arnouxii) in the Gerlache Strait, Antarctica

On 5 May 2009, during the Multi-Scale and Interdisciplinary Study of Humpbacks And Prey (MISHAP09) cruise, a large group of socially active Arnoux’s beaked whales (Berardius arnouxii) was sighted in the southern-central region of the Gerlache Strait near the entrance of the Schollaert Channel between Brabant and Cuverville Islands, Antarctica (64◦33.9′S, 62◦37.1′W) (Fig. 1). Later, on 7 June 2009 in a similar location (64◦37.5′S, 62◦51.8′W), another sighting was made of a large group of Arnoux’s beaked whales. These represent two of the few confirmed sightings of this species in the nearshore waters around the Antarctic Peninsula, one of the only documentations of surface social activity, and the largest number of animals ever reported in a single group. At 1230 local time on 5 May, a large group of animals (approximately 60) was sighted 3 km from the ARSV LM Gould. The water depth around the whales was between 700 and 800 m. The first sighting cue was a series of short, bushy blows. As the ship approached, the animals became visible at the surface and were identified based on coloration, size, and shape of their head and melon, and rostrum shape. After the initial sighting, a second separate subgroup of animals (approximately 15) was sighted in the same area. Both groups of animals were traveling consistently to the southwest, deeper into the Gerlache Strait. Animals were seen surfacing quickly in close proximity to one another (<2 m), and often in physical contact with each other. During the course of the sighting we observed tail slapping by several individuals and three breaches. Photographs were obtained from an inflatable boat at a distance of approximately 100 m (Fig. 2). Several of the whales were visibly scarred with single or two parallel

The Kenneth S. Norris Lifetime Achievement Award Lecture

AbstractSince the early 20th century, Japanese cetacean biology relied heavily on fisheries for their materials. The work environment was challenging because research activities were controlled by industries and the fishery administration. I became a cetacean scientist in 1961 and worked mainly in the western North Pacific. There I witnessed the collapse of coastal populations of striped dolphins and sperm whales as a result of over‐hunting. Nonetheless, my research revealed fascinating aspects of cetacean biology, which still await explanation, such as the following: neighboring populations of the same species having different breeding seasons, the role of reproductively senescent females in some toothed whales, the role of “social sex” in short‐finned pilot whales, and the selective benefit of male Baird's beaked whales living longer than the females. New methodologies are required to address these questions. I propose to include the following aims for the conservation biology of cetaceans: to identify a community as a conservation unit, and to focus on conserving the cultural diversity and variability of such communities, and henceforth to focus increased research on understanding the contribution of individuals within a community. Today, marine mammal biologists of all fields need to pay more attention to conservation.

Annotated odontocete recordings for developing automated detection and classification methods

A free archive has been developed for research in automatic detection/classification of cetacean sounds. The archive contains many datasets, with each dataset comprising recordings and metadata for a given species and geographic area. This archive differs from other sound archives in three important respects: (1) Recordings are annotated to indicate where in time and frequency the sounds of a given species occur. These annotations are done manually to remove the bias of any automatic detection system. (2) The archive deliberately includes poor‐quality recordings, recordings encountered in any realistic detection/classification application. (3) Since performance of detection/classification methods depends heavily on the SNR of target sounds, the archive includes each vocalization's SNR so performance can be effectively represented. Until recently, most recordings in the archive were of baleen whales [Mellinger and Clark, Applied Acoustics 67(11), 2006]. However, datasets for toothed whales and dolphins are now being incorporated. Initial efforts have been focused on beaked whales because of high interest for management and because of the difficulty of visual detection. To date, recordings of Cuvier's, Blainville's, Baird's, and Arnoux's beaked whales have been entered into the archive, as have those of bottlenose whales, pilot whales, and some delphinid species. Further contributions are welcomed.

Diving behaviour of a Baird’s beaked whale, Berardius bairdii, in the slope water region of the western North Pacific: first dive records using a data logger

AbstractA depth and temperature data logger was deployed by air gun on an individual Baird’s beaked whale (Berardius bairdii) off the Pacific coast of Japan. The retrieved data logger recorded 81 dives over approximately 29 h. The maximum recorded depth and the longest dive duration were 1777 m and 64.4 min, respectively. All dives were classified into three categories by depth: deep dives (&gt;1000 m), intermediate dives (100–1000 m), and shallow dives (&lt;100 m). Several intermediate dives generally followed a deep dive, and sequential shallow dives followed several intermediate dives in the record of the Baird’s beaked whale.

Localization of aquaporin-2, renal morphology and urine composition in the bottlenose dolphin and the Baird’s beaked whale

This study examined the distribution pattern of aquaporin-2 (AQP2), relative medullary thickness (RMT) and urine properties in the bottlenose dolphin Tursiops truncatus and Baird's beaked whale Berardius bairdii. Immunohistochemical studies revealed that AQP2 was localized in the collecting tubules/ducts of both species' renicules, as in terrestrial mammals. The collecting ducts with AQP2 were thinner and arranged more densely in the dolphin than in the whale. RMT values in the renicule were moderate in both species, but were significantly higher in the dolphin (6.0 +/- 0.9) than the whale (4.9 +/- 0.7). Urine of the bottlenose dolphin is comparatively concentrated (osmolality: 1715.7 +/- 279.4 mOsm kg(-1), Na(+): 490.1 +/- 87.9 mmol l(-1), Cl(-): 402.7 +/- 79.6 mmol l(-1), K(+): 80.7 +/- 25.8 mmol l(-1), urea nitrogen: 703.5 +/- 253.9 mmol l(-1)), while urine of the dead Baird's beaked whale is less concentrated (osmolality: 837.5 +/- 293.8 mOsm kg(-1), Na(+): 192.9 +/- 81.5 mmol l(-1), Cl(-): 159.9 +/- 71.4 mmol l(-1), K(+): 44.3 +/- 29.5 mmol l(-1), urea nitrogen: 270.7 +/- 120.3 mmol l(-1)). These data suggest it is possible that the differences in these renal morphological features may be related in some way to the difference in urine composition between the species, although further studies are necessary.

Mass stranding of Baird's beaked whales at San Jose Island, Gulf of California, Mexico

The Baird's or giant beaked whale ( Berardius bairdii ) is endemic to the North Pacific Ocean. In the eastern North Pacific, seasonal movements are poorly understood. Historic California catches suggest two peaks of abundance, in July and October. Mass strandings of Baird's beaked whales are rare. Prior to this report only two records were known, in the Bay of La Paz, Mexico in 1986 and Sagami Bay, Japan, in 1987; both mass strandings included male and females. Here we report a mass stranding of 10 Baird's beaked whales at San Jose lsland in the Gulf of California on 31 July 2006. The group was composed only by males ranging from 9.97m to 11.05m. The estimated age, based on the dental group layers, ranged from 9 to 42 years. The cause of this stranding is unknown, although with the large number of squid also found dead in the area, it is possible that the whales could have been following the squid, one of their main prey. The mass stranding of 10 mature males reported here supports the idea of a seasonal presence, during summer, of this species in the waters of the southwest Gulf of California. The group composition supports a reproductive strategy where the old males have a major role in the guidance and protection of inexperienced weaned and young males, unlike sperm whale bachelor groups, where all males are typically the same age.

Stomach anatomy and use in defining systemic relationships of the cetacean family ziphiidae (beaked whales)

Members of the Cetacean family Ziphiidae (Beaked whales) exhibit surprising diversity in stomach anatomy, particularly in the number of connecting chambers between the main and pyloric stomachs. Sixty-one stomachs of five beaked whale species were examined, including Berardius, Hyperoodon, Mesoplodon, Tasmacetus, and Ziphius. Specimens were obtained post mortem from beach-stranded individuals, with the exception of 30 Berardius specimens that were taken at a whaling station in Japan. Most specimens were collected by the Marine Mammal Program of the National Museum of Natural History, with the exception of one specimen of Mesoplodon steinegeri, which from the Los Angeles County Museum and one specimen of Tasmacetus from the Museum of New Zealand. Additional data are included from published accounts. A single species was examined for all of the genera but Mesoplodon, where there was material for 7 of 13 known species. The sample of Berardius bairdii was sufficient (n = 30) to determine species-specific variation in compartment counts. Chamber anatomy was explored by means of manual palpation. Results indicate that ziphiid stomachs can be separated into at least three principal groups: generalized ziphiid stomach (one main stomach, one pyloric stomach), derived stomach type I (two main stomachs, one pyloric stomach), and derived stomach type II (two main stomachs, two pyloric stomachs). Generalized stomachs are found in Hyperoodon, Tasmacetus, Ziphius, Mesoplodon densirostris, M. perrini, and M. stejnegeri. Derived stomachs of type I are found in Berardius, and of type II are found in Mesoplodon bidens, M. europaeus, and M. mirus. The ziphiids clearly form a distinct group of cetaceans in their utilization of differences in stomach morphology. These anatomical differences may serve to elucidate systematic relationships among the ziphiids. Further study is necessary to establish whether these differences correlate with specialized adaptations related to an aquatic environment.

Bioaccumulation of Naturally Occurring Mixed Halogenated Dimethylbipyrroles in Whale and Dolphin Products on the Japanese Market

Mixed halogenated dimethyl bipyrroles (HDBPs), which are thought to be produced naturally, were quantified in whale and dolphin products marketed for human consumption in Japan. The major component of HDBPs was 3,3',4,4'-tetrabromo-5,5'-dichloro-1,1'-dimethyl -2,2'-bipyrrole (Br(4)Cl(2)-DBP), accounting for 85% of the total of five HDBPs detected, followed by Br(3)Cl(2)-DBP. Mean concentrations of HDBPs ranged from 0.27 microg/g lipid (n = 31) in minke whale (Balaenoptera acutorostrata) from the northwest Pacific Ocean to 11.8 microg/g lipid (n = 33) in bottlenose dolphin (Tursiops trucatus) from the southwest Japanese coastal water. At higher levels, HDBPs made up 37% of the total organohalogen body burden in Dall's porpoise (Phocoenoides dalli), whereas the contribution was less than 8.9% in minke whales. In two data subsets from Baird's beaked whale (Berardius bairdii), the products from the Pacific Ocean contained significantly higher concentrations of HDBPs than those from the Sea of Japan. Furthermore, the geographical distribution of HDBPs did not resemble those of ubiquitous anthropogenic organochlorines, such as polychlorinated biphenyl (PCBs). Higher concentration ratios of SigmaHDBP/SigmaPCB and different patterns of HDBP congeners were observed in whale products from the Asia-Pacific as compared to non-Pacific Ocean mammals reported previously. These results support the hypothesis that HDBPs and anthropogenic organochlorines have different sources and that the consumption of HDBPs by Japanese individuals could be an exposure/health risk.

Identification, Quantification, and Synthesis of a Novel Dimethoxylated Polybrominated Biphenyl in Marine Mammals Caught Off the Coast of Japan

Bioaccumulation of persistent organic compounds can eventually lead to concentrations in wildlife and humans that are deleterious to health. The present paper documents the identification, quantification, and synthesis of a novel compound, 2,2'-dimethoxy-3,3',5,5'-tetrabromobiphenyl (2,2'-diMeO-BB80), present in the marine mammals Striped dolphin (Stenella coeruleoalba), Bottlenose dolphin (Tursiops truncatus), Minke whale (Balaenoptera acutorostrata), and Baird's beaked whale (Berardius bairdii) caught in the Pacific Ocean. Identification was based on comparison of the relative retention times of the compound on two gas chromatographic columns of different polarities to those of an authentic standard. Furthermore, this identification was also supported by comparison of the full scan mass spectrometric data collected employing electron ionization (El), positive ion chemical ionization (PICI), and electron capture negative ionization (ECNI). The concentrations of 2,2'-diMeO-BB80 in the samples ranged from 12 to 800 ng/g lipid, making this consistently one of the most abundant compounds among those analyzed, including polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), and methoxylated PBDEs. The known occurrence of 3,3',5,5'-tetrabromo-2,2'-biphenyldiol (2,2'-diOH-BB80) in the marine environment as a natural product suggests that its methylated derivative, 2,2'-diMeO-BB80, is also of natural origin. To obtain the necessary authentic standards, synthesis was performed of 2,2'-diMeO-BB80 and the known natural product 2',6-dimethoxy-2,3',4,5'-tetrabromodiphenyl ether (2',6-diMeO-BDE68).

Microanatomy of the Terminal Air Spaces of Baird's Beaked Whale (Berardius bairdii) Lungs

The terminal airways and microvasculature of five adult Baird's beaked whales (Berardius bairdii) lungs have been examined by means of light and scanning electron microscopy of corrosion casts. The respiratory system of the Baird's beaked whale has various anatomical features which allow them to attain great depths and remain submerged for long periods. The whale lung has components including hyaline cartilage and smooth muscle throughout, reaching as far as the peripheral bronchi, sphincters surrounding the terminal bronchioles, the thick alveolar septa with a connective tissue core and a bi-layer capillary bed, and a distinctive venous plexus of the pulmonary veins. The well-developed venous plexuses of the pulmonary vein are found in the interlobular connective tissue, and around the airways and pulmonary arteries with close apposition. The hyaline cartilage throughout the airways may increase the effective dead air space that accommodates most of the air forced from the collapsed alveoli during a dive. The sphincter might serve as a cock for regulating buoyancy and for trapping air in the alveoli to prevent their complete collapse and a sucking in of alveolar tissue as the dive becomes deeper. The venous plexuses might be for pooling the large volume of blood in the lung to conserve oxygen for deep and prolonged diving.

Morphologic Characteristics of Pulmonary Macrophages in Cetaceans: Particular Reference to Pulmonary Intravascular Macrophages as a Newly Identified Type

We examined the morphologic characteristics of pulmonary macrophages in 42 specimens of Odontoceti (Globicephala macrorhynchus, Grampus griseus, Tursiops truncatus, Stenella attenuata, Stenella coeruleoalba, Berardius bairdii), using light and electron microscopes as well as immunohistochemistry with SRA-E5. SRA-E5-positive alveolar macrophages and pulmonary interstitial macrophages contained graphitic soots, indicating the clearance of airborne, aspirated foreign bodies. Pulmonary intravascular macrophages (PIMs), positive with SRA-E5, were present within pulmonary capillaries, attaching to applied endothelial cells by cell junctions. They showed cytoplasmic tubular structures of micropinocytosis vermiformis and erythrophagocytosis, indicating their contributory role in the clearance of blood-borne particles. The uptake of pathogens by PIMs may be associated with the inducement of acute lung injury, especially bacterial infectious pneumonia. This study revealed for the first time the presence of PIMs in cetaceans.

Distributive and phagocytic characteristics of hepatic macrophages in five cetaceans belonging to Delphinidae and Ziphiidae.

Details of morphology and distribution of hepatic macrophages in cetaceans were investigated using the immunohistochemistry with an antibody (SRA-E5) generated against human macrophage scavenger receptor antigen. Liver samples were obtained from five species of cetaceans (Baird's beaked whales, short-finned pilot whales, Risso's dolphins, bottlenose dolphins, and pantropical spotted dolphins). Except for two species of whales, the number of SRA-E5-positive Kupffer cells was greatest in the perivenous zone (zone 3), followed by the mid-zonal (zone 2) and periportal (zone 1) zones; this distribution pattern was different from that in cattle examined here and previously reported rodents with the highest number in zone 1. The frequency of Kupffer cell in each of zones was significantly different among species, and interestingly, the total mean of the Kupffer cell number in three zones increased as the body-length of species was small. In cetaceans, Kupffer cells in zone 1 appeared larger and more stellate in shape, whereas those in zone 3 were smaller and rounder. All cetaceans but Baird's beaked whales had the black pigment-containing Kupffer cells, with the greatest number in zone 3, and macrophages with the similar pigments were also seen in the hepatic intermediate septa, indicating an active phagocytosis. Most of the black pigments were considered to be lipofuscin and such pigments were not seen in the bovine livers. These results indicate that cetacean hepatic macrophages show differences in the distribution and phagocytosis among hepatic lobular zones, or between cetacean species and terrestrial animals.

Microvasculature in the Terminal Air Spaces of the Lungs of the Baird's Beaked Whale (Berardius bairdii)

Lungs were obtained from five adult Baird's beaked whales (Berardius bairdii) and examined by means of light microscopy and scanning electron microscopy of corrosion casts. The alveolar septa of these whales are thick with a connective tissue core and a bi-layer capillary bed. A double capillary network is regularly found in the alveolar duct and alveolar septa. Occasionally, septa adjacent to alveoli and alveoli themselves show only a single capillary layer. The distance between the two capillary layers has a tendency to decrease toward the end of airspaces, suggesting an end result of capillary fusion. Vascular replicas of venous vessels have annular furrows at regular intervals of 50 to 100 microm, which are caused by focal aggregations of collagen fibers circularly oriented and located immediately underneath the endothelium. The first valves appear in the collecting venules gathering alveolar capillaries. These valves are quite characteristic of flap-, funnel-and/or chimney like structures.

A line transect method to estimate abundance of long-diving animals

Long-diving marine mammals, such as sperm whales and Baird's beaked whales are frequently missed in line transect sampling even though they are on the trackline. The methods so far developed to estimate the proportion of animals missed on the trackline are complicated or sensitive to model assumptions. A simpler model is developed in the present study. The model requires an estimate of mean surfacing rate that is independent of the line transect survey and does not require any complicated survey design and non-robust parameters, such as scan rate of the binoculars of observers. In addition, it can flexibly take account of systematic heterogeneity using covariates. The abundance is estimated using the Horvitz-Thompson estimator. The simulation test showed that the proposed method is promising.