• 한국수산과학회지
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• 제50권5호
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• pp.561-566
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• 2017

Few studies on the finless porpoise Neophocaena asiaeorientalis have been conducted on the south coast of Korea. This region includes Gadeok Island, which is located off the Korean peninsula in an area of heavy maritime traffic. Sighting surveys of finless porpoises were conducted at seven predetermined spots around Gadeok Island in January, May, July, September, and November 2016. Finless porpoises (127 individuals in 24 schools) were sighted at all but one (spot P5) of the survey locations. Fewer porpoises were spotted in summer (Jul and Sep) than in other seasons (P<0.05). Porpoises were most abundant around the south coast of the island, where they were spotted in every season, and in significantly higher numbers than at other locations (P<0.05). Single individuals accounted for 20.8% of sightings, while 25.0% of sighted schools consisted of only two porpoises. The mean school size was 5.29 individuals (SD=6.72).

• 한국수산과학회지
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• 제51권4호
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• pp.456-460
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• 2018

Little is known about the movements of finless porpoises Neophocaena asiaeorientalis and their relationship with sea surface temperature (SST). A female finless porpoise that was stranded alive on the shore at Busan was rehabilitated for 16 months at the Sea Life Busan Aquarium. The porpoise was released off Geoje Island with a satellite tag on her mid-ridge and tracking data were received for 7 days. The porpoise moved directly to the southern shore of Gadeok Island, where an earlier study reported that finless porpoises were most abundant around the island. The tracking route revealed two other potential primary habitats. The porpoise moved to the middle of the east coast of the Korean Peninsula at Uljin, beyond the distribution boundary known from earlier studies. Satellite infrared images detected a cold water mass off the Uljin coast and the tracking route showed that the porpoise avoided this low-temperature area.

• 수산해양교육연구
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• 제26권3호
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• pp.578-586
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• 2014

The seasonal appearance and distribution of finless porpoise (Neophocaena asiaeorientalis) was investigated with sighting survey method around Wido in West sea, Korea. Fishing survey with drag net was also conducted to investigate the species composition of inhabitants and the consignment quantity data of fisheries cooperation was collected to confirm the seasonal change of the composition and quantity of them. Finless porpoise didn't emerged around Wido in winter season, but the number of appearance in summer season amounted to 1~15 indv. for 15 observing points and the appearance frequency became lower in open sea than in inshore. There was also significant relationship between the appearances of finless porpoise (Neophocaena asiaeorientalis) and that of inhabitants. we consequently concluded that finless porpoise typically distributes from April to september, and moves to another area for wintering and food consumption from October to March.

• 한국수산과학회지
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• 제56권6호
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• pp.889-898
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• 2023

This study was conducted to estimate the abundance of narrow-ridged finless porpoises Neophocaena asiaeorientalis in the West Coast of Korea, where they predominantly inhabit. Sighting surveys were conducted in March and November 2021-2022 using vessels and aircraft during the same time periods and along the same survey transects. The aerial surveys yielded significantly more sightings than shipboard surveys, with 8.5-21.6 times the abundance and 6.3-16.9 times the number of observations. The detection rates were 0.000-0.047 and 0.0103 to 0.539 per km² for shipboard and aerial surveys, respectively. The densities were estimated to be 0.003-0.061 and 0.236-1.898 individuals per km² in the shipboard and aerial surveys, respectively. The shipboard survey conducted in March 2022 and the aerial survey conducted in November 2021 had the highest detection rates and abundance. In the coastal waters, shipboard sighting surveys face numerous challenges due to factors such as fishing gear, islands, and shallow water depths. In contrast, aerial surveys have the advantage of a shorter survey period and are less affected by weather, fisheries, coastal lines, and other variables. Thus, they are highly suitable for studying narrow-ridged finless porpoises in the coastal areas of the West Sea.

• 수산해양교육연구
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• 제28권3호
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• pp.861-871
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• 2016

The coastal water of Korean Peninsula is the major habitat for finless porpoises. However, hundreds of finless porpoises are currently caught incidentally by stow-net fishery every year. To prevent the mass mortality of finless porpoises and conserve marine animals, Busan Aquarium has been designated as a "Marine Life Ex-Situ Conservation Institution and Marine Animal Conservation Center," and Cetacean Research Institute, under the National Institute of Fisheries Science have started RRR (rescue, rehabilitation and release) project together since 2011. From 2012 to 2013, four individuals of finless porpoises had been rescued and two of them finally released to their original habitat after fully recovered in July 2013. As a result, according to growth curve of finless porpoise of Korea more than 140 cm of body length, 38 kg of total weight referred to adult, results of observation of the change in the hormone revealed that mating time of finless porpoises is January, Jun and July. To become the initial institution which rescues, treatment, husbandry and releases finless porpoise in Korea.

• Fisheries and Aquatic Sciences
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• 제18권4호
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• pp.411-416
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• 2015

We estimated abundance of the finless porpoise Neophocaena asiaeorientalis in the west coast of Korea in 2011 and compared it to the abundance data estimated by Park et al. (2007). The two researches used same line transect method operated by a vessel, and the study area were divided into the offshore and the inshore regions to assess variations in their abundance. In offshore regions population density of finless porpoises was $0.122ind./km^2$, which was lower than $0.565ind./km^2$ estimated in 2004. In inshore regions the population density was $0.151ind./km^2$, which was much lower than $0.638ind./km^2$ estimated in 2005. Thus, we estimate that the population densities of the finless porpoises in both the offshore and the inshore regions of the west coast of Korea has decreased by approximately 70% between 2004/2005 and 2011.

• 한국수산과학회지
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• 제46권6호
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• pp.966-969
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• 2013

Vessel-based sighting surveys for cetaceans have been conducted in Korean waters since 2000. The supporting data estimate the abundance of finless porpoises along the west coast of Korea; however, they are insufficient because of the coverage and frequency of the surveys. A preliminary aerial survey was conducted in 2011, and the results were assessed with respect to a sighting survey operated by a research vessel in order to compare effectiveness and potentiality. A total of 110.00 nautical miles of effective efforts were made with three sightings under Beaufort scale 4 in the aerial survey, while the vessel-operated survey covered 403.38 nautical miles over 7 days without any sightings under Beaufort scale 4. The standard deviation of the altitude in this survey was 22.7 m, which was significantly higher than that of the referenced study of 4.3 m.

• 한국수산과학회지
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• 제45권6호
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• pp.723-729
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• 2012

On 3 February 2011, a mass mortality of finless porpoises Neophocaena asiaeorientalis occurred at a dike of the Saemangeum Sea dike. A total of 249 carcasses were collected; these had been stranded by a sea dike and had floated into the lake formed by the dike. Eight bodies were measured, and four of these were dissected to analyze stomach contents. The blubber thicknesses of five bodies were compared with those of caught finless porpoises in the Yellow Sea from 2010. Finless porpoises at the Saemangeum Sea dike exhibited better nutritive conditions than finless porpoises in the Yellow Sea. Air temperature in January 2011 was lower than the prior 5-year average (P<0.05). Water temperature when the mass mortality occurred was lower than values observed in 2009 and 2010: values below $0^{\circ}C$ had been recorded, and the majority of the dike lake had frozen over. The mass mortality of finless porpoises may have been caused by these unusually low temperatures.

• 한국수산과학회지
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• 제47권6호
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• pp.978-982
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• 2014

A mass mortality of 249 finless porpoises Neophocaena asiaeorientalis occurred in the Saemangeum Dyke in February 2011. It was an extraordinary event, notable due to the death toll and the location of the occurrence, a semi-isolated lake enclosed by a man-made structure. We conducted sighting surveys that consisted of a land-based sighting survey recorded from three different platforms, and a ship-based sighting survey in the lake. The land-based survey was dedicated to clarifying the distribution of finless porpoises and whether they passed through two water gates (Shinsi and Garyek) of the dyke from 2011 to 2013. No finless porpoises were observed in the 2011 or January 2012 surveys. In April 2012, two months and one year after the mass mortality, one finless porpoise, swimming 400 m from the Shinsi water gate, was observed by a land-based survey. The number of observed individuals increased to nine in 2012 and reached 10 by May 2013 at the time of the surveys. Most of the porpoises were detected near the Garyek water gate. The density of the animals was $0.075/km^2$ in 2012 and $0.083/km^2$ in 2013. The density of porpoises was $2.063/km^2$ at the time of the mass mortality.

• 한국수산과학회지
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• 제54권6호
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• pp.989-999
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• 2021

The sound of finless porpoises Neophocaena asiaeorientalis was recorded with an acoustic recorder to confirm their emergence in the South Sea of South Korea in February, June, and November 2020. Sea water temperature and salinity were also measured. In addition, a sighting survey was conducted to observe the behavior of the finless porpoises and the marine environment, and the clicks of the finless porpoises were recorded every day. The results showed that they always emerged in the survey area. The finless porpoises mainly foraged, whereas some played or rested. The water temperature range of areas where the finless porpoises emerged was 7.5-23.5℃. Assuming that the number of clicks corresponds to the number of finless porpoises, the finless porpoises emerged the most during spring. The emergence decreased during winter and was the lowest during autumn. The finless porpoises emerged more during the daytime than during the nighttime in all seasons, indicating a temporal difference in the usage of the survey area. This might be due to the movement of prey organisms according to regional characteristics. A long-term survey and research on habitat use and environment is needed to manage and conserve the finless porpoises.