Kay Sakuma

National Fisheries Resources Research Institute · Fisheries Management Department

Tuna and tuna-like fishes (tribe Thunnini) are pelagic species that are important worldwide for their ecological and economic value. Understanding the ecology of Thunnini at the early life stages is necessary for proper resource management and conservation. However, the morphological similarity among Thunnini species and the often physically damage...

Ricuzenius toyamensis Matsubara and Iwai, 1951 was originally described on the basis of eight specimens collected from Toyama Bay, the Sea of Japan coast of central Honshu Island, Japan. The species has subsequently been considered as a valid species of the genus Icelus Krøyer, 1845, diagnosed by the following characters: supraocular and parietal s...

As a factor controlling the vertical distribution of larvae, changes in phototaxis, geotaxis, and sinking velocity concerning larval development in the snow crab (Chionoecetes opilio), a relatively shallower water species, and red snow crab (Chionoecetes japonicus), a relatively deeper water species, were investigated using laboratory-raised indivi...

Distinguishing between Beryx splendens and Beryx mollis (Actinopterygii: Beryciformes) on the basis of external morphology is difficult, and a reliable method of differentiation must be established. In this study, we developed a multiplex polymerase chain reaction (PCR) method with species-specific primers for distinguishing B. splendens from B. mo...

Individuals of a deep-sea snailfish, Careproctus trachysoma, endemic to the Japan Sea have been classified into the lighter and darker color morphotypes, which are sympatrically distributed. These morphotypes have only been described qualitatively, with individuals that could not be classified as either morphotype. Therefore, in this study, we quan...

The deep-sea environment has historically been regarded as representative of oceanic connectivity and homogeneity, and the Japanese seas provide an ideal model system for testing the assumptions of deep-sea connectivity. The Pacific Ocean and the three marginal seas (Sea of Okhotsk, Sea of Japan, and East China Sea) surrounding the Japanese Archipe...

A new species of the sand-burrowing dogielinotid amphipod genus Haustorioides Oldevig, 1958, Haustorioides furotai Ogawa, sp. nov., is described from Banzu tidal flat, east coast of Tokyo Bay, Japan. The new species is mainly characterized by a slender and triangular outer plate of the maxilliped, poorly setose antennae and pereopods, straightly ac...

Detecting drivers of population divergence across phylogeographic breaks is a major challenge in marine population genetics, partly due to uncertainties in molecular dating. Although the calibration of demographic transition (CDT) method is the most promising rate calibration technique for population-level events, there is a risk of making the fals...

Genetic deviation between two deep-sea snailfishes, Careproctus pellucidus from the Pacific Ocean and Careproctus rastrinus from the Okhotsk Sea, of the Careproctus rastrinus species complex was analyzed, based on the nucleotide sequences of the mitochondrial cytochrome b (Cytb) gene. Our sampling revealed the occurrence of individuals with C. rast...

Larvae of Auxis rochei and Auxis thazard are commonly found in tropical to temperate waters around the world; however, their identification is difficult due to their similar morphological characteristics. In order to determine the morphological differences between larvae of these two species, we identified larvae of 192 A. rochei and 119 A. thazard...

To quantitatively evaluate the distribution of tuna larvae relative to oceanographic conditions, we conducted investigations off the Nansei Islands in the western North Pacific in June from 2015 to 2017. Five species, namely Pacific bluefin tuna Thunnus orientalis (PBF), yellowfin tuna T. albacares (YFT), skipjack tuna Katsuwonus pelamis (SKJ), fri...

Calibration of the molecular rate is one of the major challenges in marine population genetics. Although the use of an appropriate evolutionary rate is crucial in exploring population histories, calibration of the rate is always difficult because fossil records and geological events are rarely applicable for rate calibration. The acceleration of th...

A total of 113 and 73 individuals of the North Pacific lightfish Maurolicus japonicus were collected from the Japan Sea and the Pacific Ocean off the Japanese Islands, respectively. Based on nucleotide sequences of mitochondrial genes for cytochrome oxidase c subunit I (COI) and 16S ribosomal RNA, they were classified into the ‘Southern’ clade by R...

Skipjack tuna Katsuwonus pelamis migrating off Kyushu Island are an important resource for the pole and line fisheries in Japan. Skipjack tuna caught in the area west of Kyushu and off Tokara Islands were compared based on fork length (FL), condition factor (CF) and genetic structure. The results indicate differences in FL and CF of the skipjack tu...

Many coastal barnacles are introduced to non-native regions. However, data are lacking on cryptic invasion, which is defined as an invasion that remains unrecognised because the invader is mistaken for a native or previously introduced species or clade. In this work, cryptic invasions of an intertidal barnacle, Semibalanus cariosus, between Japan a...

Recent findings of genetic breaks within apparently continuous marine populations challenge the traditional vicariance paradigm in population genetics. Such “invisible” boundaries are sometimes associated with potential geographic barriers that have forced divergence of an ancestral population, habitat discontinuities, biogeographic disjunctions du...

Based on nucleotide substitutions in four mitochondrial DNA regions, we developed multiplex PCR assays for identifying species/lineages in yellowfin Thunnus albacares and bigeye T. obesus tunas. The validity of the assays was tested on 3247 individuals of seven Thunnus tuna species (T. orientalis, T. thynnus, T. maccoyii, T. alalunga, T. albacares,...

Recent studies have revealed the impact of the drastic climate change during the last glacial period on coastal marine and anadromous species in the marginal seas of the northwestern Pacific Ocean; however, its influence on deep-sea species remains poorly understood. To compare the effects of the last glacial period on populations from the Sea of J...

We examined morphological and molecular characteristics of individuals of Macroramphosus in Japanese waters (the East China Sea and the northwestern Pacific). Two morphotypes (M. scolopax-type and M. gracilis-type) that were differentiated based on 10 quantitative morphological characters were not supported by molecular analyses using nuclear and m...

We compared the population histories of two deep-sea eelpouts, Lycodes japonicus and Lycodes ocellatus, to elucidate the impacts of the last glacial period on deep-sea species in the western North Pacific area. The results of phylogenetic analyses based on the nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I and cytochrome b...