Humpback whale Megaptera novaeangliae (Cetartiodactyla: Balaenopteridae) group sizes in line transect ship surveys: An evaluation of observer errors

Bortolotto, Guilherme A.; Danilewicz, Daniel; Andriolo, Artur; Zerbini, Alexandre N.

doi:10.1590/s1984-4689zool-20150133

Cited by 5 publications

(1 citation statement)

References 4 publications

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“…An additional observer, labelled tracker , was located at a 12.6 meters platform (at the crow’s nest of the ship) during the 2012 cruise to assess whether estimation of group size by primary observers was biased. Because effectively no bias was detected [ 40 ], the tracker data are not considered here. All observers searched for whales with 7x50 reticled binoculars (model Fujinon Mariner XL), which were used for most of the time.…”

Section: Methodsmentioning

confidence: 99%

Whale, Whale, Everywhere: Increasing Abundance of Western South Atlantic Humpback Whales (Megaptera novaeangliae) in Their Wintering Grounds

et al. 2016

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The western South Atlantic (WSA) humpback whale population inhabits the coast of Brazil during the breeding and calving season in winter and spring. This population was depleted to near extinction by whaling in the mid-twentieth century. Despite recent signs of recovery, increasing coastal and offshore development pose potential threats to these animals. Therefore, continuous monitoring is needed to assess population status and support conservation strategies. The aim of this work was to present ship-based line-transect estimates of abundance for humpback whales in their WSA breeding ground and to investigate potential changes in population size. Two cruises surveyed the coast of Brazil during August-September in 2008 and 2012. The area surveyed in 2008 corresponded to the currently recognized population breeding area; effort in 2012 was limited due to unfavorable weather conditions. WSA humpback whale population size in 2008 was estimated at 16,410 (CV = 0.228, 95% CI = 10,563–25,495) animals. In order to compare abundance between 2008 and 2012, estimates for the area between Salvador and Cabo Frio, which were consistently covered in the two years, were computed at 15,332 (CV = 0.243, 95% CI = 9,595–24,500) and 19,429 (CV = 0.101, 95% CI = 15,958–23,654) whales, respectively. The difference in the two estimates represents an increase of 26.7% in whale numbers in a 4-year period. The estimated abundance for 2008 is considered the most robust for the WSA humpback whale population because the ship survey conducted in that year minimized bias from various sources. Results presented here indicate that in 2008, the WSA humpback whale population was at least around 60% of its estimated pre-modern whaling abundance and that it may recover to its pre-exploitation size sooner than previously estimated.

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Section: Methodsmentioning

confidence: 99%

Whale, Whale, Everywhere: Increasing Abundance of Western South Atlantic Humpback Whales (Megaptera novaeangliae) in Their Wintering Grounds

et al. 2016

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Passive acoustic detection and estimation of the number of sources using compact arrays

Urazghildiiev

Hannay²

2018

The Journal of the Acoustical Society of America

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The problem of estimating the number of sound-producing sources detected using a compact array of hydrophones is addressed. Closed form expressions representing the techniques of automatic detection and estimation of the number of callers are given. Their performance is evaluated on a year-long dataset (1 October 2015-6 October 2016) containing humpback whale and killer whale calls collected in the Strait of Georgia, near Vancouver, British Columbia. Manual verification of the automatic detections produced by the approach required ∼40 h.

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Estimating spatial distribution and density of vocalizing marine animals using compact arrays

Urazghildiiev

Martin²,

Hannay³

2020

The Journal of the Acoustical Society of America

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The problem of estimating spatial distribution and density of vocalizing marine animals is addressed. The proposed solution is based on using a fixed compact array of synchronized hydrophones and statistically optimal detection and estimation algorithms. The closed-form representations of the practical algorithms are presented. The performance of the proposed technique is evaluated analytically and using statistical simulations. The case study involved identifying an area of high residency and estimating the density of vocalizing beluga whales in the St. Lawrence Estuary. The advantages and disadvantages of the proposed technique are demonstrated and the future steps are discussed.

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Humpback whale Megaptera novaeangliae (Cetartiodactyla: Balaenopteridae) group sizes in line transect ship surveys: An evaluation of observer errors

Cited by 5 publications

References 4 publications

Whale, Whale, Everywhere: Increasing Abundance of Western South Atlantic Humpback Whales (Megaptera novaeangliae) in Their Wintering Grounds

Whale, Whale, Everywhere: Increasing Abundance of Western South Atlantic Humpback Whales (Megaptera novaeangliae) in Their Wintering Grounds

Passive acoustic detection and estimation of the number of sources using compact arrays

Estimating spatial distribution and density of vocalizing marine animals using compact arrays

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