Finless Porpoise Abundance in Omura Bay, Japan: Estimation from Aerial Sighting Surveys

Yoshida, Hiderou; Shirakihara, Kunio; Kishino, Hirohisa; Shirakihara, Miki; Takemura, Akira

doi:10.2307/3802290

Cited by 24 publications

(21 citation statements)

References 9 publications

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“…In coastal waters of Kyushu, density was lowest in August, increasing through April, with high densities in summer . Yoshida et al (1998) found that porpoises moved offshore in Omura Bay in spring months. In Chinese waters, lowest density in the Yellow/Bohai seas occurs in winter and the highest in summer and autumn (Wang 1984b).…”

Section: Ontogeny and Reproductionmentioning

confidence: 99%

“…Preliminary work in coastal waters of western Kyushu was only able to estimate densities ), but more recent work has resulted in estimates of 1,983 porpoises in Ariake Sound and 1,110 in Tachibana Bay (Yoshida et al 1997). A total of 187 porpoises were estimated to inhabit nearby Omura Bay (Yoshida et al 1998). The population in the Yangtze River has been surveyed extensively, but a lack of systematic methods has prevented researchers from developing reliable population estimates.…”

Section: Ontogeny and Reproductionmentioning

confidence: 99%

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Neophocaena phocaenoides

Jefferson

Hung²

2004

Mamm sp

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Section: Ontogeny and Reproductionmentioning

confidence: 99%

Section: Ontogeny and Reproductionmentioning

confidence: 99%

Neophocaena phocaenoides

Jefferson

Hung²

2004

Mamm sp

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“…This is because seals are often numerous and clumped, and there is insufficient time to measure the perpendicular distance between the aircraft and each seal group using an inclinometer as in the line‐transect method. However, the line‐transect approach is recommended by Burnham and Anderson (1984) for reasons of efficiency and validity, and it has been used successfully for cetacean surveys (Yoshida et al 1997, 1998; Dahlheim et al 2000) and ship‐based surveys of seals (Leopold et al 1997; Gelatt & Siniff 1999).…”

Section: Methodsmentioning

confidence: 99%

“…We developed a line‐transect survey and calculated the perpendicular distance from the transect line to observed seals following the methods of Yoshida et al (1998). Using their approach, calculations are made from the altitude of the aircraft and the declination angle to the sighting point (θ).…”

Section: Methodsmentioning

confidence: 99%

“…When a seal was detected, observers put a dot on a transparent sheet on the window; each dot was numbered in order of sightings. After finishing a survey, θ was calculated for the horizontal and vertical distance, whereby the horizontal distance was from the observer’s eyes to the fixed mark on the window and the vertical distance was from the mark to each dot (illustrated in Yoshida et al 1998; Fig. 2).…”

Section: Methodsmentioning

confidence: 99%

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Distribution and abundance of spotted seals Phoca largha and ribbon seals Phoca fasciata in the southern Sea of Okhotsk

Mizuno

Wada

Ishinazaka

et al. 2002

Ecological Research

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The distribution and abundance of spotted seals (Phoca largha) and ribbon seals (Phoca fasciata) were assessed in March and April, 2000, by aerial line‐transect surveys along the southern edge of the pack ice off the coast of Hokkaido (southern Sea of Okhotsk), Japan. Five hundred and seventeen spotted seals and 107 ribbon seals were found on the total 2944 km survey line. Total abundance was estimated to be 13 653 spotted (95% CI = 6167–30 252) and 2260 ribbon seals (95% CI = 783–6607) in March, and 6545 spotted (95% CI = 3284–815 644) and 3134 ribbon seals (95% CI = 1247–17 802 512) in April. The pack ice area off Hokkaido had higher densities (0.54 seals km−2 and 0.58 seals km−2 in March and April, respectively) of spotted seals than those reported in eastern Sakhalin, whereas densities (0.09 seals km−2 in March and 0.28 seals km−2 in April) of ribbon seals were lower than those in eastern Sakhalin. The large number of spotted seal pups suggests that the study area is an important breeding center. A greater number of female spotted seals with pups tended to be found in the center of larger and rougher floes than in other categories, and they were more abundant in stable pack ice areas. Observations of ribbon seals were limited because the survey period preceded the peak of pupping season. Ribbon seal surveys were also hampered by the inability to fly over the main breeding area between the Shiretoko Peninsula and Kunashiri Island.

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Abundance decline in the narrow‐ridged finless porpoise population off the Pacific coast of eastern Japan

et al. 2019

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The narrow-ridged finless porpoise Neophocaena asiaeorientalis is a small-toothed whale with a coastal habitat and is sensitive to human activity. Aerial sighting surveys were conducted in 2012 to evaluate the abundance and distribution of the Sendai Bay-Tokyo Bay population off the Pacific coast of eastern Japan. We flew along 35 east-west transects at intervals of 11.6 km over the study area between 34 57 0 and 38 21' N. In total, 25 groups were detected by two observers. The mean group size was 1.44 individuals. Porpoise abundance was estimated to be 1,491 individuals (coefficient of variation = 32.4%

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Finless Porpoise Abundance in Omura Bay, Japan: Estimation from Aerial Sighting Surveys

Cited by 24 publications

References 9 publications

Neophocaena phocaenoides

Neophocaena phocaenoides

Distribution and abundance of spotted seals Phoca largha and ribbon seals Phoca fasciata in the southern Sea of Okhotsk

Abundance decline in the narrow‐ridged finless porpoise population off the Pacific coast of eastern Japan

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