Vertical sonar beam width of wild belugas (Delphinapterus leucas) in West Greenland

2020 ◽  
Vol 148 (4) ◽  
pp. 2633-2633
Author(s):  
Marie J. Zahn ◽  
Jens Koblitz ◽  
Kristin L. Laidre
Keyword(s):  
Beam Width ◽  
Delphinapterus Leucas ◽  
West Greenland

scholarly journals Vertical sonar beam width and scanning behavior of wild belugas (Delphinapterus leucas) in West Greenland

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257054
Author(s):  
Marie J. Zahn ◽  
Kristin L. Laidre ◽  
Peter Stilz ◽  
Marianne H. Rasmussen ◽  
Jens C. Koblitz
Keyword(s):  
Beam Width ◽  
The Arctic ◽  
Delphinapterus Leucas ◽  
Recording Equipment ◽  
West Greenland ◽  
Beluga Whales ◽  
Pack Ice ◽  
Scanning Behavior ◽  
Hydrophone Array ◽  
Free Ranging

Echolocation signals of wild beluga whales (Delphinapterus leucas) were recorded in 2013 using a vertical, linear 16-hydrophone array at two locations in the pack ice of Baffin Bay, West Greenland. Individual whales were localized for 4:42 minutes of 1:04 hours of recordings. Clicks centered on the recording equipment (i.e. on-axis clicks) were isolated to calculate sonar parameters. We report the first sonar beam estimate of in situ recordings of wild belugas with an average -3 dB asymmetrical vertical beam width of 5.4°, showing a wider ventral beam. This narrow beam width is consistent with estimates from captive belugas; however, our results indicate that beluga sonar beams may not be symmetrical and may differ in wild and captive contexts. The mean apparent source level for on-axis clicks was 212 dB pp re 1 μPa and whales were shown to vertically scan the array from 120 meters distance. Our findings support the hypothesis that highly directional sonar beams and high source levels are an evolutionary adaptation for Arctic odontocetes to reduce unwanted surface echoes from sea ice (i.e., acoustic clutter) and effectively navigate through leads in the pack ice (e.g., find breathing holes). These results provide the first baseline beluga sonar metrics from free-ranging animals using a hydrophone array and are important for acoustic programs throughout the Arctic, particularly for acoustic classification between belugas and narwhals (Monodon monoceros).

Observations on Distribution and Intraspecific Variation in Pigmentation Patterns of Odontocete Cetacea in the Western North Atlantic

1973 ◽  
Vol 30 (8) ◽  
pp. 1111-1130 ◽  
Author(s):  
M. C. Mercer
Keyword(s):  
Intraspecific Variation ◽  
North Atlantic ◽  
Intraspecific Variability ◽  
Delphinapterus Leucas ◽  
Phocoena Phocoena ◽  
Western Atlantic ◽  
Stenella Coeruleoalba ◽  
West Greenland ◽  
Monodon Monoceros

This paper comprises sight records for nine species and morphometries, color descriptions, and miscellaneous notes on the food and parasites of seven species of small odontocetes observed from West Greenland to Florida 1967–72. Of interest are the first western Atlantic extralimital record of Monodon monoceros, first Newfoundland records of Stenella coeruleoalba, and extralimital records of Delphinapterus leucas from Newfoundland. Intraspecific variability is described in the pigmentation patterns of Phocoena phocoena.

scholarly journals Population size and yield of Baffin Bay beluga (Delphinapterus leucas) stocks

2002 ◽  
Vol 4 ◽  
pp. 225 ◽  
Author(s):  
Stuart Innes ◽  
Robert EA Stewart
Keyword(s):  
Population Biology ◽  
Maximum Sustainable Yield ◽  
Production Model ◽  
Delphinapterus Leucas ◽  
Sufficient Information ◽  
Stock Size ◽  
Baffin Bay ◽  
West Greenland ◽  
The North ◽  
North Water

A surplus production model within a Sampling, Importance Resampling (SIR) Bayesian analysis was used to estimate stock sizes and yields of Baffin Bay belugas. The catch of belugas in West Greenland increased in 1968 and has remained well above sustainable rates. SIR analysis indicated a decline of about 50% between 1981 and 1994, with a credibility interval that included a previous estimate of 62%. The estimated stock sizes of belugas wintering off West Greenland in 1998 and 1999 were approximately 5,100 and 4,100 respectively and were not significantly different than an estimate based on aerial surveys combined for both years. Projected to 1999 this stock can sustain median landings of 109 whales with a total kill of about 155, based on posterior estimates of struck and lost plus under-reporting. The declining stock size index series did not provide sufficient information to estimate the potential maximum rate of population growth, the number of whales struck and lost, or the shape of the production curve with precision. Estimating these parameters requires an index time series with a marked step change in catch or a series with increasing stock sizes. The stock size estimate for the belugas wintering in the North Water in 1999 was approximately 14,800 but there is no information about the population biology of these whales. The estimated maximum sustainable yield (landed) for the North Water stock was 317 belugas.

An Index of the Relative Abundance of Wintering Belugas, Delphinapterus leucas, and Narwhals, Monodon monoceros, off West Greenland

1993 ◽  
Vol 50 (11) ◽  
pp. 2323-2335 ◽  
Author(s):  
M. P. Heide-Jørgensen ◽  
H. Lassen ◽  
J. Teilmann ◽  
R. A. Davis
Keyword(s):  
Relative Abundance ◽  
Delphinapterus Leucas ◽  
Late Winter ◽  
The West ◽  
Baffin Bay ◽  
West Greenland ◽  
Abundance Estimate ◽  
Monodon Monoceros ◽  
Pack Ice ◽  
Ice Conditions

Systematic aerial surveys of the wintering grounds of belugas, Delphinapterus leucas, and narwhals, Monodon monoceros, in southern Baffin Bay and northern Davis Strait were conducted in late winter of 1981, 1982, 1990, and 1991. Most belugas were found between 67°N and 69°N and none were seen more than 80 km off the coast of West Greenland. Compared with the surveys in 1981 and 1982, a decline in relative abundance of belugas along West Greenland was evident in 1991. This decline was significant at a probability level of 0.13 of the bootstrapped distribution of the combined abundance estimate. Pod sizes declined significantly between the 1981–82 and 1990–91 surveys. The variations in ice conditions between years did not seem to affect the distribution, clumping, or pod sizes of the belugas. Narwhals were widely distributed in the close pack ice offshore between 65°N and 72°N. Along the West Greenland coast, narwhals were primarily seen at the mouth of Disko Bay. No change in relative abundance or pod sizes could be detected for narwhals.

An estimate of the fraction of belugas (Delphinapterus leucas) in the Canadian high Arctic that winter in West Greenland

Polar Biology ◽  
2003 ◽  
Vol 26 (5) ◽  
pp. 318-326 ◽  
Author(s):  
M. P. Heide-Jørgensen ◽  
P. Richard ◽  
R. Dietz ◽  
K. L. Laidre ◽  
J. Orr ◽  
...  
Keyword(s):  
High Arctic ◽  
Delphinapterus Leucas ◽  
Canadian High Arctic ◽  
West Greenland

scholarly journals A risk assessment of the sustainability of the harvest of beluga (Delphinapterus leucas (Pallas 1776)) in West Greenland

2004 ◽  
Vol 61 (2) ◽  
pp. 274-286 ◽  
Author(s):  
Carlos M. Alvarez-Flores ◽  
Mads Peter Heide-Jørgensen
Keyword(s):  
Risk Assessment ◽  
Population Size ◽  
Bayesian Methods ◽  
Marine Mammals ◽  
Delphinapterus Leucas ◽  
Gradual Reduction ◽  
Harvest Rate ◽  
West Greenland ◽  
Management Procedures ◽  
Reduction Schedule

Abstract Risk assessments to assess the efficiency of management procedures to regulate removals of marine mammals have rarely been conducted. Using Bayesian methods, we conducted a risk assessment on a harvested beluga population off West Greenland. The population size in recent years was estimated to be 22% of the size in 1954. Results indicate that current catches are unsustainable and that continuation of this situation represents a 90% probability that the population will become extinct in 20 years. The analyses suggest that the harvest should be reduced to no more than 130 animals. Constant catch quotas represent a greater risk of depletion compared with catch limits that are a function of harvest rate and population size. An alternative gradual reduction schedule is proposed as a viable strategy, reducing the harvest in 5 years and adjusting the subsequent quota using a harvest rate of 0.5 of Rmax, with updates in the abundance. This analysis is presented as an alternative for cases where an immediate catch reduction is desirable but not feasible for marine mammal populations that appear vulnerable or in danger and where catch and abundance data are available.

scholarly journals The effect of sea-ice loss on beluga whales (Delphinapterus leucas) in West Greenland

2010 ◽  
Vol 29 (2) ◽  
pp. 198-208 ◽  
Author(s):  
M.P. Heide-Jørgensen ◽  
K.L. Laidre ◽  
D. Borchers ◽  
T.A. Marques ◽  
H. Stern ◽  
...  
Keyword(s):  
Sea Ice ◽  
Delphinapterus Leucas ◽  
West Greenland ◽  
Beluga Whales

scholarly journals Catch statistics for belugas in West Greenland 1862 to 1999

2002 ◽  
Vol 4 ◽  
pp. 127 ◽  
Author(s):  
MP Heide-Jørgensen ◽  
A Rosing-Asvid
Keyword(s):  
Delphinapterus Leucas ◽  
West Greenland ◽  
The Past ◽  
Local Residents ◽  
Catch Statistics ◽  
Loss Rates

Information and statistics including trade statistics on catches of white whales or belugas (Delphinapterus leucas) in West Greenland since 1862 are presented. The period before 1952 was dominated by large catches south of 66o N that peaked with 1,380 reported kills in 1922. Catch levels in the past five decades are evaluated on the basis of official catch statistics, trade in mattak (whale skin), sampling of jaws and reports from local residents and other observers. Options are given for corrections of catch statistics based upon auxiliary statistics on trade of mattak, catches in previous decades for areas without reporting and on likely levels of loss rates in different hunting operations. The fractions of the reported catches that are caused by ice entrapments of whales are estimated. During 1954-1999 total reported catches ranged from 216 to 1,874 and they peaked around 1970. Correcting for underreporting and killed-but-lost whales increases the catch reports by 42% on average for 1954-1998. If the whales killed in ice entrapments are removed then the corrected catch estimate is on average 28% larger than the reported catches.

scholarly journals Three recent ice entrapments of Arctic cetaceans in West Greenland and the eastern Canadian High Arctic

2002 ◽  
Vol 4 ◽  
pp. 143 ◽  
Author(s):  
MP Heide-Jørgensen ◽  
P Richard ◽  
M Ramsay ◽  
S Akeeagok
Keyword(s):  
North Atlantic ◽  
Polar Bear ◽  
Canadian Arctic ◽  
High Arctic ◽  
Bowhead Whale ◽  
Delphinapterus Leucas ◽  
Polar Bears ◽  
Canadian High Arctic ◽  
West Greenland ◽  
The One

Three ice entrapments of Monodontids have been reported in the western North Atlantic since 1993. Hunters in Disko Bay, West Greenland, discovered one in March 1994 that included about 150 narwhals (Monodon monoceros). The entrapment occurred during a sudden cold period which caused ice to form rapidly. The trapped whales were subject to hunting, but about 50 of the killed whales could not be retrieved in the ice. The whales were trapped in a small opening in the ice and because of that they would probably have succumbed even if not discovered by hunters. Two entrapments involving white whales or belugas (Delphinapterus leucas) occurred in the eastern Canadian Arctic in May 1999; one in Lancaster Sound discovered by polar bear (Ursus maritimus) researchers and one in Jones Sound discovered by hunters. The first included one bowhead whale (Balaena mysticetus) and about 40 belugas that were being preyed upon by polar bears. The second involved at least 170 belugas, of which about 100 were killed by polar bears and 17 were taken by hunters. The entrapments in Disko Bay and Jones Sound both occurred in areas where entrapments have previously been reported, whereas the one in Lancaster Sound was in a new area.

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