Whales In Waters Research Articles

Estimating the abundance of Baird’s beaked whales in waters off the Pacific coast of Japan using line transect data (2008–2017)

Estimating the abundance of Baird’s beaked whales in waters off the Pacific coast of Japan using line transect data (2008–2017)

Abundance and spatial distribution of baleen and sperm whales in the Peruvian sea: a historical review

Historical accounts of large whales in Peruvian waters existed before modern commercial whaling. Research on baleen and sperm (Physeter macrocephalus) whales was intense during whaling, thus producing essential knowledge on these species. The populations of large whales have declined considerably with whaling pressure since 1925 in Peruvian waters. After the whaling moratorium in 1985, research on these species decreased, and a considerable gap in knowledge exists until nowadays. This review aims to conduct a historical analysis of the spatial distribution and abundance of baleen and sperm whales in the waters of Peru. During whaling, sperm whale distribution and abundance received most of the research effort as this species was the most important target of the whaling fleet. Also, blue (Balaenoptera musculus) and Bryde’s whale (B. edeni brydei) were considered abundant in Peru. Changes in their distribution and abundance were evaluated mainly based on captures or climatic events. Following the cessation of whaling, sightings of these species were restricted to occasional surveys, limiting the assessment of possible current changes in their distribution and abundance, as well as the updating of existing information. Humpback whales (Megaptera novaeangliae) were considered overexploited at the beginning of commercial whaling. After the moratorium, this species population started to grow, expanding its distribution along the northern coast. Currently, the humpback whale is the most studied species due to the onset of whale-watching activities in 2009. This allowed us to update and increase the knowledge about its distribution and abundance in northern Peru. The findings of this study point at a need to considerably increase the research effort on large whales, particularly surveys to estimate population sizes of the species inhabiting the waters of Peru.

A review of the ecology and status of white whales (Delphinapterus leucas) in Svalbard, Norway

The Norwegian Polar Institute initiated a research programme on white whales in 1995 to gather biological information relevant for the species’ management; the results of which are reviewed herein. Satellite tracking from two periods (1995–2001 and 2013–16), between which sea ice diminished markedly, showed that the whales in waters off the archipelago of Svalbard spent most of their time foraging close to tidewater glaciers. Transits between glaciers typically followed the coastline, with the whales moving rapidly from one glacier to another. During the later period, the whales spent some time out in the fjords, suggesting that they might be targeting prey in the Atlantic Water masses that now prevail in Svalbard’s west-coast fjords. Most of their dives were extremely shallow (13 ± 26 m; maximum 350 m) and of short duration (97 ± 123 s; maximum 31.4 min). Fatty-acid analyses indicated that polar cod (Boreogadus saida) was the main prey during the first sampling period. An aerial survey in 2018 estimated the population numbered 549 (CI: 436–723) animals. Svalbard white whales are genetically separate from populations off west Greenland and in the White Sea. Predation by killer whales appears to have influenced white whale behaviour in Svalbard; they are often silent, despite having a normal vocal repertoire for the species and their coastal movements take place in very shallow water. This population has extremely high contaminant levels. Climate change poses a threat to this small population of white whales.

Blue whale (Balaenoptera musculus) sightings off the coast of Virginia

We report on two sightings of individual blue whales (Balaenoptera musculus) off the coast of Virginia during marine mammal surveys. On 11 April 2018, during a vessel survey off the coast of Virginia, a single blue whale was observed approximately 100 km east-northeast of Virginia Beach. On 10 February 2019, another single blue whale was recorded during an aerial survey approximately 135 km east-southeast of Virginia Beach. These observations mark the first time this endangered species has been documented with photographs off the coast of Virginia, and represent the southernmost confirmed sightings in waters of the United States Atlantic Exclusive Economic Zone (EEZ). At the time of the vessel observation, numerous fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae), and North Atlantic right whales (Eubalaena glacialis), were observed within the same approximately 8 km2 area as the blue whale. For the aerial sighting, the blue whale was seen feeding among at least 15 fin whales in an area approximately 4 km2. These sightings contribute to the small body of information existing for the late winter/early spring distribution of blue whales in waters of the western North Atlantic.

Distribution and Local Movement of Humpback Whales in Okinawan Waters Depend on Sex and Reproductive Status.

The distribution and local movement patterns of humpback whales in waters off the west coast of Okinawa Island, southwest Japan, were investigated using line transect and photo-identification methodologies. Line transect surveys were conducted from 2011 to 2014 and photo-identification survey from 2006 to 2012. During the surveys, humpback whales aggregated in the areas around Ie and Kerama Islands, and tended to travel along the inshore coast of Okinawa Island when they move locally between those two sites. A total of 496 humpback whales of the known sex were photo-identified (322 males, 75 females and 99 females with a calf). Of these, 24.8% were confirmed moving locally between the sites of Ie and Kerama Islands within the same season. Frequency rates of the local movement for males, females and females with a calf were 41.9, 25.0, and 15.1%, respectively; the frequency of local movement for males was significantly higher than that for females and females with a calf. These results indicate that male humpback whales tend to move more actively between the local breeding sites as compared to females and females with a calf. We speculate that the males search for more opportunities to mate, whereas females with a calf tend to remain in the same areas to nurse their calves. These findings extend our knowledge of the habitat use and reproductive ecology of humpback whales in Okinawan waters, which remain poorly understood.

Habitat Use by Different Size Classes of Bowhead Whales in the Central Beaufort Sea during Late Summer and Autumn

The frequency distributions of bowhead whale (Balaena mysticetus) size classes were studied as functions of year, location, water depth, and date. Whales were classified by size and status as calves, small subadults (non-calves < 10 m); large subadults (10–13 m); and adults (> 13 m). Adults include mothers with calves, which were also counted separately. During mid-August to early October of 1982, 1984–86, and 1998–2000, calibrated vertical photography was used to obtain known-scale images of 901 different whales in waters up to 200 m deep between Flaxman and Herschel islands (146? to 139? W) in the central Beaufort Sea. Age composition of the whales photographed over all years of our study was calves 6.2%, small subadults 31.4%, large subadults 33.3%, and adults 29.1%. We found proportionally more subadults and fewer adults than are estimated to be in the overall population, and this result was found both before and after making allowance for reduced effort to obtain photographs early and late in the migration period. Thus parts of the central Beaufort Sea up to 200 m deep appear to be more heavily used by subadult bowheads than by adults in most years. Significant interannual variation existed in length-frequency distributions of whales among years, geographic subdivisions of the study area, water depth categories, and time periods. This variation was due to variable use of the study area by each size class in different years, differences in the water depths used by different size classes, and different migration timing by each size class. In all years, small subadult whales were the dominant group in shallow (< 20 m) nearshore habitats, and the size of the whales increased with increasing water depth. Timing of movements into and through the study area were also related to size class: small subadults arrived first in late August and departed in late September, and adults arrived last in late September. Mothers and calves arrived in early September and were common until at least early October.

New observations and a review of killer whale (<I>Orcinus orca</I>) sightings in Papua New Guinea waters

Although typically considered a temperate to cold water species, killer whales (or orca) ( Orcinus orca ) have been reported intermittently in tropical waters. While the IUCN (IUCN, 2000) does not list the species as present in Papua New Guinea waters, the records presented here indicate it is found in the area for at least 10 months of the year. A total of 94 sightings of killer whales in Papua New Guinea waters were complied. Thirty-seven sightings from April 1987 to July 2002 were recorded with an exact date and location, with a further 57 sightings of unknown date or exact location. Twenty-seven of all records had either photographs or videotape to cone rm species identie cation. The earliest reference to killer whales in this region was from 1956, when they were recorded taking e sh o V long-lines. Killer whales from Papua New Guinea waters have been observed feeding on four species of elasmobranchs (scalloped-hammerhead shark, Sphyrna lewini ; grey reef shark, Carcharhinus amblyrhynchos ; manta ray, Manta birostris; and blue-spotted ray Dasyatis kuhlii ) and four species of e n-e sh (yellow-e n tuna, Thunnus albacares ; bigeye tuna, Thunnus obesus ; Indo-Pacie c saile sh, Istiophorus platypterus; and sunesh, Mola mola). These are the e rst records, worldwide, of killer whales feeding on scalloped-hammerhead sharks, grey reef sharks and blue-spotted rays. Killer whales in these waters have been reported in association with two species of cetaceans (sperm whales, Physeter macrocephalus and spinner dolphins, Stenella longirostris ). Photo-identie cation images were collected for 14 individuals and a catalogue established. Matches were made for two animals— a female sighted approximately 30 n mi and two days apart and a sub-adult male sighted in the same region 16 months apart. Some individual killer whales from these waters have been observed with grey under-e ukes, in contrast to white, which is typically described for this species.

Recent observations of humpback whales (Megaptera novaeangliae) in Japanese waters off Ogasawara and Okinawa

The current status of humpback whales in waters off Ogasawara and Okinawa islands, Japan, and the relationship of these populations to each other and to humpback whales in the central-eastern North Pacific were investigated. Fluke-identification photographs collected from 1987 to 1990 were analyzed to estimate abundance and determine individual behavior patterns, and were compared with humpback photoidentifications from other regions. In total, 177 humpbacks were identified. At the end of the study period the rate of discovery of "new" whales was still high, suggesting a substantially larger overall population. Whales were commonly sighted throughout the Ogasawara archipelago from December to May, and were present during the same period near the Kerama Islands, Okinawa. Humpback whales were not regularly seen near Saipan in the Northern Mariana Islands, or near Kenting, Taiwan. Repeat sightings of individuals indicate that some whales were present for extended periods off Ogasawara. The predominant behavior patterns were those related to calving and mating. Two whales were identified in both the Okinawa and Ogasawara regions in different years, suggesting that both regions are used by the same population. Identification of one whale in both Japan and Hawaii (reported elsewhere) indicates the potential for mixing of western and eastern North Pacific humpback populations; the overall matching effort to date suggests that this interchange is relatively small.

The Diet of Sperm Whales (Physeter Macrocephalus) Captured Between Iceland and Greenland

The stomach contents of 221 sperm whales were examined at the Icelandic whaling station between 1977 and 1981. Evidence of at least eight species of fish and 22 species of cephalopod was found, together with an assortment of foreign bodies including rock fragments and fishing nets. Fish remains were found in 87% and cephalopods in 68% of the sperm whale stomachs in this area, but quantification of dietary input is complicated by differential rates of digestion and variation in the retention of indigestible remains in the stomach. Prey species are benthic or pelagic in habit and are caught by the whale in waters from 400 m to at least 1200 m in depth. One fish, the lumpsucker Cyclopterus lumpus, forms a major part of the diet. Ninety-four per cent of cephalopods are oceanic and neutrally buoyant and 84 % of these are ammoniacal. Cranchiids contribute 57% by number and an estimated 25% of the weight, and histioteuthids 26% by number and 38 % of the weight of cephalopods eaten. Three species offish and two of cephalopod have not been previously recorded in sperm whale diets. Comparison with an earlier study shows that the diet is essentially stable over a 14-year period.