Diet of long-beaked common dolphin (Delphinus capensis) in the East Sea, Korea

Abstract

The long-beaked common dolphin is one of the most abundant cetaceans in Korean waters, and their population has been estimated to comprise of more than 35,000 individuals. Delphinus capensis generally appear close to the coast and primarily feed on epipelagic small fishes and cephalopods. Thirty long-beaked common dolphins were collected from the East Sea from February to September in 2012. For stomach content analysis (SCA), the fresh prey items were identified to their lowest taxonomic level, and unidentified preys due to digestion were identified using remnants such as fish otoliths and cephalopod beaks. Fatty acid (FA) patterns of 20 dolphins from the inner layer of blubber were compared with those in samples of prey items. Enoploteuthis chunii was the dominant prey in SCA, representing 55.8% by number and 75.9% by occurrence. Common squid (Todarodes pacificus) and Pacific herring (Clupea pallasii) were the next major preys at more than 80% occurrence. Even though a distinctive difference was not observed between genders, there was a significant diet variation related to maturity. Immature dolphins consumed a higher diversity of prey, and consumed more equally than the sexually mature group, who showed a high dominance of cephalopods. Furthermore, this result fairly corresponded to FAs composition of mature dolphins with the raised percent of 20:6n-3, which is relatively abundant in T. pacificus.

A First Study on Home Range Characteristics of Common Dolphin in Korean Waters: A Study Using Data Collected During the Past 20 Years

“…It seems that shallow waters, such as the coastal region of YS, are not suitable habitats for common dolphins. In addition, Ahn et al (2014) [47] reported that prey items found from stomach contents of common dolphins were mostly Enoploteuthis chunii (a squid species), common squid, and Pacific herring. In Korea, both common squid and Pacific herring were mostly caught in ES [48,49].…”

Environmental Factors Influencing Annual Changes in Bycatch per Unit Effort of Delphinus delphis around Their Main Hotspot in Korean Waters

“…Prey abundance and primary production were considered as nutritional variables of the common dolphin in the study area. Two species (Pacific herring and common squid) of the three species known to be the main prey species of common dolphin [5] have been regarded as major fishery resources in Korean waters, and their catch data have been recorded as National Statistics. Pacific herring and common squid catches from set nets in the coastal region of Gyeongsangbuk-do were considered as prey abundance variables of common dolphins in the study area.…”

“…It has been known that common dolphins calving in the offshore waters of the North Pacific Ocean and Black Sea peaks in May-June and June-August, respectively, and their prey consists largely of small epipelagic schooling fishes and squid [1,3]. In Korean waters, most studies on the ecology of common dolphins have focused on the distribution characteristics and composition of prey species [4,5]. For example, Ahn et al [5] reported that the prey species found in the stomach contents of common dolphins were mostly Enoploteuthis chunii (a squid species), common squid, and Pacific herring.…”

“…In Korean waters, most studies on the ecology of common dolphins have focused on the distribution characteristics and composition of prey species [4,5]. For example, Ahn et al [5] reported that the prey species found in the stomach contents of common dolphins were mostly Enoploteuthis chunii (a squid species), common squid, and Pacific herring. According to several prior studies [6][7][8], common dolphins are mostly found in the East Sea of Korea.…”

Can the annual bycatch per unit effort of common dolphins (Delphinus delphis) be used to index the species' relative abundance in the East Sea of Korea?

“…The common dolphin, Delphinus delphis , is a globally abundant species that is mainly distributed in tropical and temperate waters of the Atlantic and Pacific Oceans (Jefferson et al, 2015; Perrin, 2009). In Korean waters, the common dolphin is mostly observed in the coastal regions of the East Sea (Kim et al, 2013; Sohn et al, 2012) and is one of the most abundant cetaceans, including in terms of bycatch (Ahn et al, 2014; Kim et al, 2013; Sohn et al, 2012). The present study attempts to determine whether temporal changes in BPUE are associated with changes in common dolphin relative abundance.…”