Effects of bycatch on the population viability of the narrow-ridged finless porpoises in Ariake Sound and Tachibana Bay, Japan

Hashimoto, Midori; Shirakihara, Kunio; Shirakihara, Miki

doi:10.3354/esr00658

Cited by 13 publications

(10 citation statements)

References 25 publications

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“… 2015 ) and to estimate more accurately the true threat level from fisheries and other sources (Hashimoto et al . 2015 ; Huang et al . 2014 ; Parsons et al .…”

Section: Discussionmentioning

confidence: 99%

Conflict between Dolphins and a Data-Scarce Fishery of the European Union

et al. 2018

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Fisheries depredation by marine mammals is an economic concern worldwide. We combined questionnaires, acoustic monitoring, and participatory experiments to investigate the occurrence of bottlenose dolphins in the fisheries of Northern Cyprus, and the extent of their conflict with set-nets, an economically important metier of Mediterranean fisheries. Dolphins were present in fishing grounds throughout the year and were detected at 28% of sets. Net damage was on average six times greater where dolphins were present, was correlated with dolphin presence, and the associated costs were considerable. An acoustic deterrent pinger was tested, but had no significant effect although more powerful pingers could have greater impact. However, our findings indicate that effective management of fish stocks is urgently required to address the overexploitation that is likely driving depredation behaviour in dolphins, that in turn leads to net damage and the associated costs to the fisheries.Electronic supplementary materialThe online version of this article (10.1007/s10745-018-9989-7) contains supplementary material, which is available to authorized users.

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“… 2015 ) and to estimate more accurately the true threat level from fisheries and other sources (Hashimoto et al . 2015 ; Huang et al . 2014 ; Parsons et al .…”

Section: Discussionmentioning

confidence: 99%

Conflict between Dolphins and a Data-Scarce Fishery of the European Union

et al. 2018

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“…Narrow-ridged finless porpoises are an endangered species with a risk of extinction and are only distributed in shallow coastal waters around the western Pacific Ocean from the Taiwan Strait to China, Korea, and Japan [45,46]. Finless porpoises in Japan are strictly controlled under the Act on the protection of fishery resources [47], while various anthropogenic activities, including bycatch from the fisheries and boat strikes, currently threaten their survival [48]. Our findings show that finless porpoises have some flexibility to the anthropogenic impacts they experience daily.…”

Section: Discussionmentioning

confidence: 99%

Social responses of travelling finless porpoises to boat traffic risk in Misumi West Port, Ariake Sound, Japan

Morimura

Mori

2019

PLoS ONE

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Anthropogenic effects have created various risks for wild animals. Boat traffic is one of the most fatal risks for marine mammals. Individual behavioral responses of cetaceans, including diving behavior such as changing swimming direction and lengthing inter-breath interval, to passing boats is relatively well known; however, the social function of cetacean responses to boat traffic in a natural setting remains poorly understood. We focused on describing the behavioral responses of single and aggregated finless porpoises to boats passing at Misumi West Port, Ariake Sound, Japan, by using a drone characterized with a high-precision bird’s-eye angle. During the study period, we collected 25 episodes of finless porpoise responses to boats passing by. A mean (± SEM) of 5.1 ± 1.0 individuals were observed for each episode. The primary response to passing boats was avoidance by dive, which implies boat traffic is a substantial disturbance to finless porpoises that travel along the seawater surface daily. The diving duration decreased significantly with an increase in the number of aggregated individuals. The diving and floating reaction times were 10.9 ± 2.3 s and 18.7 ± 5.0 s, respectively. There was no significant difference between the reaction times indicating that each individual was motivated to keep the group cohesion consistent when floating even after the risk had dissolved, which is comparable to the behavior of porpoises that dive when riskier conditions are present, such as when a boat approaches an aggregation. Our findings provide new insights on the sociality of finless porpoises even though there were limitations, like an inability to identify a specific individual. The drone enabled us to observe the social behavior of finless porpoises and other cetaceans at an unprecedented resolution, which may lead to a better understanding of the evolutionary diversity of intelligence and sociality and the bridge to human evolution.

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“…Although the porpoise is not a commercial target in Japan, gillnet fishermen in Ariake Sound and Tachibana Bay (Figure ) bycaught the porpoises at the rate of 0.237–0.257 individuals per gillnetter per year in 2007–2008 (Shirakihara & Shirakihara, ), which indicates that almost one individual was bycaught by one gillnetter in 4 years. Hashimoto, Shirakihara, and Shirakihara () reported that such high bycatch rates would pose a serious threat to the viability of the Ariake Sound and Tachibana Bay population. Future studies to evaluate the viability of the “Sendai Bay‐Fukushima” population, which is subject to bycatch pressure, will be conducted by estimating its abundance using aerial sighting surveys and evaluating the number of bycaught individuals by interviewing fishermen (Shirakihara & Shirakihara, ).…”

Section: Discussionmentioning

confidence: 99%

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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Effects of bycatch on the population viability of the narrow-ridged finless porpoises in Ariake Sound and Tachibana Bay, Japan

Cited by 13 publications

References 25 publications

Conflict between Dolphins and a Data-Scarce Fishery of the European Union

Conflict between Dolphins and a Data-Scarce Fishery of the European Union

Social responses of travelling finless porpoises to boat traffic risk in Misumi West Port, Ariake Sound, Japan

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

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