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1.
New blue whale ovarian corpora data from illegal Soviet catches in the Southern Hemisphere and northern Indian Ocean were recovered from the original logbooks. Catches north of 52°S were assumed to be pygmy blue whales ( Balaenoptera musculus brevicauda , n = 1,272); those south of 56°S were assumed to be Antarctic (true) blue whales ( B. m. intermedia , n = 153). Three probable Antarctic blue whales north of 52°S were excluded. Lengths at which 50% and 95% of females become sexually mature ( L 50 and L 95 ) were estimated from a Bayesian logistic model. These estimates are more precise than previous Japanese estimates because Soviet catches below the legal minimum of 70 ft (21.3 m) were 32 times greater. For pygmy blue whales L 50 was 19.2 m (95% interval 19.1–19.3 m) and L 95 was 20.5 m (95% interval 20.4–20.7 m). Antarctic L 50 (23.4 m, 95% interval 22.9–23.9 m) was much longer than L 50 for pygmy blue whale regions (18.4–19.9 m). The median L 50 for the northern Indian Ocean was 0.5–0.6 m shorter than for pygmy blue whales from other regions; although statistically significant, these small length differences provide little support for northern Indian Ocean blue whales being a separate subspecies, B. m. indica . 相似文献
2.
T. A. BRANCH K. M. STAFFORD D. M. PALACIOS C. ALLISON J. L. BANNISTER C. L. K. BURTON E. CABRERA C. A. CARLSON B. GALLETTI VERNAZZANI P. C. GILL R. HUCKE‐GAETE K. C. S. JENNER M.‐N. M. JENNER K. MATSUOKA Y. A. MIKHALEV T. MIYASHITA M. G. MORRICE S. NISHIWAKI V. J. STURROCK D. TORMOSOV R. C. ANDERSON A. N. BAKER P. B. BEST P. BORSA R. L. BROWNELL JR S. CHILDERHOUSE K. P. FINDLAY T. GERRODETTE A. D. ILANGAKOON M. JOERGENSEN B. KAHN D. K. LJUNGBLAD B. MAUGHAN R. D. MCCAULEY S. MCKAY T. F. NORRIS S. RANKIN F. SAMARAN D. THIELE K. VAN WAEREBEEK R. M. WARNEKE 《Mammal Review》2007,37(2):116-175
- 1 Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of ≥8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings.
- 2 Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar.
- 3 Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering.
- 4 Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic.
- 5 Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.
- 6 South‐east Pacific blue whales have a discrete distribution and high sighting rates compared with the Antarctic. Further work is needed to clarify their subspecific status given their distinctive genetics, acoustics and length frequencies.
- 7 Antarctic blue whales numbered 1700 (95% Bayesian interval 860–2900) in 1996 (less than 1% of original levels), but are increasing at 7.3% per annum (95% Bayesian interval 1.4–11.6%). The status of other populations in the Southern Hemisphere and northern Indian Ocean is unknown because few abundance estimates are available, but higher recent sighting rates suggest that they are less depleted than Antarctic blue whales.
3.
Antarctic blue whales ( Balaenoptera musculus intermedia ) are the largest and formerly most abundant blue whale subspecies, but were hunted to near extinction last century. Estimated whaling mortality was unsustainable from 1928 to 1972 (except during 1942–1944), depleting them from 239,000 (95% interval 202,000–311,000) to a low of 360 (150–840) in 1973. Obtaining statistical evidence for subsequent increases has proved difficult due to their scarcity. We fitted Bayesian models to three sighting series (1968–2001), constraining maximum rates of increase to 12% per annum. These models indicated that Antarctic blue whales are increasing at a mean rate of 7.3% per annum (1.4%–11.6%). Informative priors based on blue whale biology (4.3%, SD = 1.9%) and a Bayesian hierarchical meta-analysis of increase rates in other blue whale populations (−3%, SD = 11.6%), suggest plausible increase rates are lower (although the latter has wide intervals), but a meta-analysis of other mysticetes obtains similar rates of increase (6.7%, SD = 4.0%). Possible biases affecting the input abundance estimates are discussed. Although Antarctic blue whales appear to have been increasing since Sovier illegal whaling ended in 1972, they still need to be protected-their estimated 1996 population size, 1,700 (860–2,900), was just 0.7% (0.3%–1.3%) of the pre-exploitation level. 相似文献
4.
T. A. Branch E. M. N. Abubaker †S. Mkango §D. S. Butterworth ¶ 《Marine Mammal Science》2007,23(4):803-833
When sexually mature, Antarctic (true) blue whales are substantially longer than pygmy blue whales. To estimate the proportions of these two subspecies in various regions, Bayesian mixture models were fitted to catch length frequencies of sexually mature females. The extent of rounding to 5-ft intervals was also estimated. Antarctic blue whales dominated (99.2%) pelagic catches south of 52°S, whereas pygmy blue whales dominated (99.9%) north of 52°S and in 35°–180°E. South of 60°S, only 0.7% (95% credibility interval 0.5%–1.0%) were pygmy blue whales, lower than the 7% upper bound currently assumed. Shore-based catches from SW Africa and those before 1937 from South Georgia and the South Shetlands were estimated to contain 90%–92% Antarctic blue whales. Actual proportions were probably higher, but these data show evidence of rounding (up to 19% of records), poor length-estimation methods, and other problems. The mean length of sexually mature female Chilean blue whales (77.1 ft, 23.5 m) was intermediate between pygmy (68.9 ft, 21.0 m) and Antarctic blue whales (83.4–86.3 ft, 25.4–26.6 m). A good fit to these data was obtained only by assuming that the Chilean whales are a separate subspecies or distinctive population. This finding is also consistent with their discrete distribution, and genetic and call type differences, compared to Antarctic and pygmy blue whales. 相似文献
5.
The distribution of blue whales, Balaenoptera musculus , in the eastern tropical Pacific (ETP) was analyzed from 211 sightings of 355 whales recorded during research vessel sighting surveys or by biologists aboard fishing vessels. Over 90% of the sightings were made in just two areas: along Baja California, and in the vicinity of the Costa Rica Dome (a large, stationary eddy centered near 9°N, 89°W), with the rest made along the equator near the Galapagos islands, the coasts of Ecuador and northern Peru. All sightings occurred in relatively cool, upwelling-modified waters. Because these areas are the most productive parts of the ETP, and have relatively large standing stocks of euphausiids, it seems possible that blue whales select low latitude habitats which permit foraging. The waters off western Baja California were occupied seasonally, with a peak in sightings coinciding with the spring peak in upwelling and biological production. The Costa Rica Dome area was occupied year round, suggesting either a resident population, or that both northern and southern hemisphere whales visit, with temporal overlap. The modal group size was one for all areas and seasons, but the frequency of groups with two or more whales was significantly higher in sightings made near the Galapagos Islands and the coast of Ecuador and northern Peru. 相似文献
6.
Kathleen M. Stafford Sharon L. Nieukirk Christopher G. Fox 《Marine Mammal Science》1999,15(4):1258-1268
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. 相似文献
7.
A female hybrid between a fin ( Balaenoptera physalus ) and a blue whale ( B. mnusculus ) was caught in whaling operations in 1984 off northwestern Spain. Its coloration and body proportions were intermediate between those of a fin and a blue whale, although it was anomalously large (19.4 m) when compared to fin whales of similar age (4 yr). It was sexually immature, concomitant with its age but not its length if it were a fin whale. Molecular analyses revealed that the mother of the hybrid was a blue whale and the father a fin whale. Examination of data for the five fin-blue whale hybrids in the literature, plus other anecdotal reports, indicates that hybridization between these two species occurs in various geographic regions and is relatively frequent, notably in light of the absence of reported hybrids between other mysticetes. Either species may act as father or mother, and there does not appear to be a selection for a given sex among the hybrids. The reproductive capacity of these hybrids remains unknown, although incidence of reproductive impairment appears to be higher in hybrid males than in hybrid females. 相似文献
8.
Kathleen M. Stafford Emily Chapp DelWayne R. Bohnenstiel Maya Tolstoy 《Marine Mammal Science》2011,27(4):828-840
The Indian Ocean is an area in which a rich suite of cetacean fauna, including at least two subspecies of blue whale, is found; yet little information beyond stranding data and short‐term surveys for this species is available. Pygmy blue whale (Balaenoptera musculus spp.) call data are presented that provide novel information on the seasonal and geographic distribution of these animals. Acoustic data were recorded from January 2002 to December 2003 by hydrophones at three stations of the International Monitoring System, including two near the subequatorial Diego Garcia Atoll and a third southwest of Cape Leeuwin, Australia. Automated spectrogram correlation methods were used to scan for call types attributed to pygmy blue whales. Sri Lanka calls were the most common and were detected year‐round off Diego Garcia. Madagascar calls were only recorded on the northern Diego Garcia hydrophone during May and July, whereas Australia calls were only recorded at Cape Leeuwin, between December and June. Differences in geographic and seasonal patterns of these three distinct call types suggest that they may represent separate acoustic populations of pygmy blue whales and that these “acoustic populations” should be considered when assessing conservation needs of blue whales in the Indian Ocean. 相似文献
9.
Ana Širović 《Bioacoustics.》2016,25(2):145-160
Spectrogram correlation has been used successfully for automatic detection of baleen whale calls. However, applying this method consistently to long time series can be challenging. To illustrate the potential challenges of the automatic detection process, recordings collected in the Southern California Bight between 2007 and 2012 were used for detection of North-east Pacific blue whale (Balaenoptera musculus) B calls. The effects of the following factors were investigated: blue whale B call frequency shift and appropriate kernel modification, seasonal variability in call abundance, analyst variability and noise. Due to intra- and inter-annual changes in the call frequency of blue whale B calls, seasonal and annual adjustments to the call detection kernel were needed. To account for seasonal variability in call production, evaluation of the detector against ground truth data was performed at multiple times during the year. Analyst variability did not affect overall long-term trends in detection, but it had an impact on the total number of detections, as well as call rate estimation. Noise, particularly from shipping, was negatively correlated with detections at hourly time scales. A detailed analysis of variability in the performance of spectrogram correlation detectors should be performed when applying this method to long-term acoustic data-sets. 相似文献
10.
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. 相似文献
11.
The satellite-acquired locations of 10 blue whales (Balaenoptera musculus) tagged off southern California with Argos radio tags were used to identify (1) their movements during the late summer feeding season; (2) the routes and rate of travel for individuals on their southern fall migration; and (3) a possible winter calving/breeding area. Whales were tracked from 5.1 to 78.1 d and from 393 to 8,668 km. While in the Southern California Bight, most of the locations for individual whales were either clumped or zigzagged in pattern, suggesting feeding or foraging (searching for prey). Average speeds ranged from 2.4 to 7.2 km/h. One whale moved north to Cape Mendocino, and four migrated south along the Baja California, Mexico coast, two passing south of Cabo San Lucas on the same day. One of the latter whales traveled an additional 2,959 km south in 30.5 d to within 450 km of the Costa Rican Dome (CRD), an upwelling feature. The timing of this migration suggests the CRD may be a calving/breeding area for North Pacific blue whales. Although blue whales have previously been sighted in the Eastern Tropical Pacific (ETP), this is the first evidence that whales from the feeding aggregation off California range that far south. The productivity of the CRD may allow blue whales to feed during their winter calving/breeding season, unlike gray whales (Eschrichtius robustus) and humpbacks (Megaptera novaeangliae) which fast during that period. 相似文献
12.
At one time blue whales were found throughout the Gulf of Alaska, however, none have been sighted there in post-whaling era surveys. To determine if blue whales ( Balaenoptera musculus ) might now occur in the Gulf of Alaska, an array of hydrophones was deployed there in October 1999. Data were retrieved in May 2000 and in June 2001. Spectrograms from a random subsample comprising 15% of the ∼63,000 h of data were visually examined for blue whale calls. Call types attributed to both northeastern and northwestern Pacific blue whales were recorded. Both of these call types were recorded seasonally from the initial deployment date in October 1999 through the third week of December 1999 and then from July 2000 through mid-December 2000. Both call types were regularly recorded on the same hydrophone at the same time indicating clear temporal and spatial overlap of the animals producing these calls. Two blue whale call types were recorded in the Gulf of Alaska suggesting that perhaps two stocks use this area. The northeastern call type has now been documented from the equator up to at least 55°N in the eastern North Pacific. 相似文献
13.
Shannon Atkinson Diane Gendron Trevor A. Branch Kendall L. Mashburn Valentina Melica Luis E. Enriquez-Paredes Robert L. Brownell Jr. 《Marine Mammal Science》2020,36(1):6-28
Hormonal biomarkers are useful indicators of mammalian reproductive and metabolic states. The present study validated and applied the use of progesterone and cortisol blubber assays for studies of blue whales from the Gulf of California, Mexico. In a validation study for pregnancy detection, blubber progesterone concentrations were correlated with pregnancy status for four female blue whales: three resighted with a calf the year following sampling and the fourth stranded with a fetus. The progesterone concentrations were significantly higher than those measured in juvenile whales (n = 3). In the application study, blubber samples from blue whales (51 noncalf females, 2 female calves, 48 noncalf males, and 1 male calf) with known sighting histories were analyzed. Putative pregnant females had elevated progesterone concentrations. Cortisol concentrations did not differ between male and female blue whales, or among females in different reproductive classes. After correcting for uncertain ages, hence maturity status, the pregnancy rate of noncalf females was 33.4% (95% CI 32.2%–34.3%). Although interpretation of hormone biomarkers must consider all physiological states that may influence progesterone concentrations, these results demonstrate the utility of pairing hormone biomarkers with sighting histories to help assess environmental or anthropogenic impacts on reproduction in blue whales. 相似文献
14.
Deviations from equal sex ratios in mammals can reveal insights into sex-specific growth, survival, movements, and behavior. We assessed blue whale (Balaenoptera musculus) sex ratios based on 21,542 fetal and 311,901 whaling records, finding that males were slightly but significantly more common than females (51.3% fetal, 52.1% postnatal). Antarctic catches shifted from 52.4% male before 1951 to 48.0% male thereafter, even though larger females were preferentially targeted by whalers and should have declined. The southernmost land stations caught more males than those in southern Africa, and at land stations, sex ratios shifted subtly over the course of a year. Pelagic catches demonstrated spatial structure in sex ratios, including more males being caught in the Ross Sea. In utero, the smallest females were often misidentified as males, and there was some evidence for higher prenatal male mortality. Once born, medium-sized blue whales within each region were more often male, while the longest were nearly all female; explained entirely by females growing faster and reaching longer sizes. Overall, though, sex ratios are remarkably close to equality across time, space, and length; with any deviations best explained by faster female growth and size-selective whaling. 相似文献
15.
Ana &#;irovi&#; John A. Hildebrand Sean M. Wiggins Deborah Thiele † 《Marine Mammal Science》2009,25(1):125-136
Seasonal and spatial variations of blue ( Balaenoptera musculus ) and fin whale ( B. physalus ) calls were analyzed from recordings collected with Acoustic Recording Packages (ARPs) deployed between January 2003 and July 2004 at four circumpolar locations: the Western Antarctic Peninsula (WAP), the Scotia Sea (SS), Eastern Antarctica (EA), and the Ross Sea (RS). Call characteristics were compared among sites using the average pressure spectrum levels from 1 month of data at each location. Presence of calls was analyzed using automatic call detection and acoustic power analysis methods. Blue whale calls were recorded year-round, with the highest detections in February–May and November. This suggests that the blue whale population may not migrate synchronously, and may indicate long duration calls are more common during migrations. Fin whale calls were detected only during February–July. Two distinct fin whale call types were recorded, suggesting a possible separation into two populations. The calls at the EA site had a secondary frequency peak in the pressure spectrum at 99 Hz and the calls at the WAP and the SS sites had a peak at 89 Hz. No fin whale calls were detected at the RS site. Acoustics are a good tool to monitor large whales in the Southern Ocean. 相似文献
16.
Low-frequency calls produced by blue whales, Balaenoptera musculus , were recorded in the northeastern Pacific Ocean off central California. Two blue whales were sighted during a vessel-based marine mammal survey, and when sonobuoys were subsequently deployed, blue whale calls were recorded. A third recording was obtained during the survey from a blue whale that was not seen. Recordings with 15, 25, and 55 min of calls were obtained from these individuals. The three recordings all contain two-part, low-frequency calls with slight interindividual variation. The calls consist of an amplitude modulated (AM) signal with a mean center frequency of 16.5 Hz, followed by a downsweep whose mean center frequency sweeps from 18.2 Hz to 16.6 Hz. The recordings are compared with blue whale recordings from the Pacific and Atlantic Oceans. The geographic variability suggests that blue whale calls may be used as an acoustic indicator of stock identity. 相似文献
17.
Erin M. Oleson John Calambokidis † Jay Barlow ‡ John A. Hildebrand § 《Marine Mammal Science》2007,23(3):574-597
The relationship between blue whale ( Balaenoptera musculus ) visual and acoustic encounter rates was quantitatively evaluated using hourly counts of detected whales during shipboard surveys off southern California. Encounter rates were estimated using temporal, geographic, and weather variables within a generalized additive model framework. Visual encounters (2.06 animals/h, CV = 0.10) varied with subregion, Julian day, time of day, and year. Acoustic encounters of whales producing pulsed A and tonal B call sequences (song; 0.65 animals/h, CV = 0.06) varied by Julian day, survey mode (transit or stationary), and subregion, and encounters of whales producing downswept (D) calls (0.41 animals/h, CV = 0.09) varied by Julian day and the number of animals seen. Inclusion of Julian day in all models reflects the seasonal occurrence of blue whales off southern California; however, the seasonal peak in visual encounters and acoustic encounters of D calling whales (July–August) was offset from the peak in acoustic encounters of singing whales (August–September). The relationship between visual and acoustic encounter rates varied regionally, with significant differences in several northern regions. The number of whales heard D calling was positively related to the number of animals seen, whereas the number of singing whales was not related to visual encounter rate. 相似文献
18.
John Calambokidis Jay Barlow † John K. B. Ford ‡ Todd E. Chandler § Annie B. Douglas § 《Marine Mammal Science》2009,25(4):816-832
Blue whales were widely distributed in the North Pacific prior to the primary period of modern commercial whaling in the early 1900s. Despite concentrations of blue whale catches off British Columbia and in the Gulf of Alaska, there had been few documented sightings in these areas since whaling for blue whales ended in 1965. In contrast, large concentrations of blue whales have been documented off California and Baja California and in the eastern tropical Pacific since the 1970s, but it was not known if these animals were part of the same population that previously ranged into Alaskan waters. We document 15 blue whale sightings off British Columbia and in the Gulf of Alaska made since 1997, and use identification photographs to show that whales in these areas are currently part of the California feeding population. We speculate that this may represent a return to a migration pattern that has existed for earlier periods for eastern North Pacific blue whale population. One possible explanation for a shift in blue whale use is changes in prey driven by changes in oceanographic conditions, including the Pacific Decadal Oscillation (PDO), which coincides with some of the observed shifts in blue whale occurrence. 相似文献
19.
Randall R. Reeves Tim D. Smith Elizabeth A. Josephson Phillip J. Clapham Gillian Woolmer 《Marine Mammal Science》2004,20(4):774-786
The seasonal distributions of humpback and blue whales ( Megaptera novaeangliae and Balaenoptera musculus , respectively) in the North Atlantic Ocean are not fully understood. Although humpbacks have been studied intensively in nearshore or coastal feeding and breeding areas, their migratory movements between these areas have been largely inferred. Blue whales have only been studied intensively along the north shore of the Gulf of St. Lawrence, and their seasonal occurrence and movements elsewhere in the North Atlantic are poorly known. We investigated the historical seasonal distributions of these two species using sighting and catch data extracted from American 18th and 19th century whaling logbooks. These data suggest that humpback whales migrated seasonally from low-latitude calving/ breeding grounds over a protracted period, and that some of them traveled far offshore rather than following coastal routes. Also, at least some humpbacks apparently fed early in the summer west of the Mid-Atlantic Ridge, well south of their known present-day feeding grounds. In assessing the present status of the North Atlantic humpback population, it will be important to determine whether such offshore feeding does in fact occur. Blue whales were present across the southern half of the North Atlantic during the autumn and winter months, and farther north in spring and summer, but we had too few data points to support inferences about these whales' migratory timing and routes. 相似文献
20.
Carter Allen Yuzhou Chang Brian Neelon Won Chang Hang J. Kim Zihai Li Qin Ma Dongjun Chung 《Biometrics》2023,79(3):1775-1787