Distribution and life history of Euphausia pacifica off northeastern Japan

Abstract

The abundance, spawning, growth pattern and life span of Euphausia pacifica were examined using widely collected samples off the Japanese coast of the North Pacific. Adults were widely distributed in the Oyashio area [OW; temperature at 100-m depth (T 100 ) £ 5°C] and the transitional area (5°C < T 100 £ 15°C) throughout the year, but the occurrence of large adults (>15 mm) was limited to OW and the cold waters of the transitional area (CW; 5°C < T 100 £ 10°C). Spawning occurred in OW and the transitional area throughout the year, especially in CW in spring but rarely in winter. Two modal cohorts of adults were consistently recognized in OW and CW. Cohorts of small males and females (10-11 mm length), which newly appeared in spring, grew remarkably to about 17 mm from the following spring to early summer, followed by a long period of little growth during spring-winter. Then, both male and female cohorts grew slowly and steadily after summer to a maximum of 18-19 mm by the following spring. The cohort of males disappeared after spring, but the females (about 20 mm length) were still being observed up until late summer. If the cohort of small adults is assumed to develop mainly from the spring hatching, the life span of male and female E. pacifica can be estimated to be 24 and 28 months, respectively, off northeastern Japan.

Abundance, biomass and life cycle patterns of euphausiids (Euphausia pacifica, Thysanoessa inspinata and T. longipes) in the Oyashio region, western subarctic Pacific

“…Spawning season and life span of E. pacifica off northeastern Japan (Taki 2004) is in good agreement with the present results in the Oyashio region, largely because both populations are living in neighboring waters. In Toyama Bay, E. pacifica spawn during February-April, and offspring overwinter, spawn in February-April of the next year and die at the age of Ͻ21 months.…”

“…The life cycle of E. pacifica has been studied at several locations, including off northeastern Japan (Taki 2004), Toyama Bay, southern Japan Sea (Iguchi et al 1993), off Oregon (Smiles & Pearcy 1971, Feinberg & Peterson 2003, and off southern California (Brinton 1976) (Table 4). Spawning season and life span of E. pacifica off northeastern Japan (Taki 2004) is in good agreement with the present results in the Oyashio region, largely because both populations are living in neighboring waters.…”

Seabed foraging by Antarctic krill: Implications for stock assessment, bentho‐pelagic coupling, and the vertical transfer of iron

“…Reports on bentho-pelagic aggregations and feeding at the seabed are not restricted to E. superba but include other euphausiid species also considered to be pelagic, e.g., Meganyctiphanes norvegica (Youngbluth et al 1989;Schmidt 2010), Euphausia pacifica (Nakamura 1992;Taki 2006), and Euphausia vallentini (Hamame and Antezana 2010). Due to difficult access, epibenthic habitats might have been considerably undersampled in the past, especially at depth.…”

Variability in brood size and female length of Euphausia pacifica among three populations in the North Pacific

“…The magnitude of the nighttime vertical migration is reduced after May because of the temperature barrier (> 20°C) located at approximately 50 m depth, probably reducing feeding activity in the euphotic zone (Iguchi et al 1993). Similarly, in the Oyashio Current, highest abundances of eggs in the water column were observed from April through June, when SST ranged from 5 to 12°C; however, eggs were found only rarely in the Kuroshio, where temperatures were always >15°C (Taki 2004). In PS, intense spawning usually occurs during April and May, which is earlier than on the OC, but continues at a low level throughout most of June (Ross et al 1982).…”

“…In the Japan/East Sea (35 to 37°N), spawning is restricted to the period March to May (Ponomareva 1963, Iguchi et al 1993. Spawning occurs year-round in the Oyashio Current off the Sanriku region of Japan and off central and southern California (35 to 37°N), but the most intense spawning activity is between February and August (Brinton 1976, Iguchi et al 1993, Iguchi & Ikeda 1994, 1999, Taki 2004, Dorman et al 2005. Off the Oregon coast (45°N), Smiles & Pearcy (1971) deduced from larval abundance that intense spawning occurs in the fall; however, recent observations indicate that spawning starts as early as February and extends through October (Feinberg & Peterson 2003, Gómez-Gutiérrez 2003, Gómez-Gutiérrez et al 2005).…”