Published online by Cambridge University Press: 27 August 2014
We examined the distribution, hatch-date, growth, and mortality of larval Benthosema pterotum, a dominant pseudoceanic myctophidin the shelf region of the East China Sea, during early autumn when the mainspawning has been predicted. This species is a key species in the food webof this area. Larvae were abundant in the area south of Cheju Island(60–80 m depth), corresponding with the adult habitat. Occurrence of thelarvae was restricted to the onshore side of the shelf-break salinity front,indicating that this front acted as a barrier restricting the offshoredispersion of the larvae. In the area where the larvae occurred, a cycloniceddy is formed, which is considered to limit the dispersal of the larvae,enabling them to recruit into the area of adult habitat. Modes of hatch-dateappeared from late August to early September and from mid to late September,suggesting that large-scale spawning events occurred at least twice duringthe spawning season. Since the modes coincided with the new moon period, B. pterotum is suggested to spawn periodically once amonth around the new moon, resulting in efficient mating and fertilization.Mean absolute growth rate (0.26 mm d−1) and weight-specificgrowth rate (18.8% of dry body weight d−1) were higher thanpreviously reported values of other subtropical–tropical myctophids, whichwould be related to the high food availability in the study area. Dailyinstantaneous mortality coefficient during the first two weeks afterhatching was estimated to be 0.28 d−1 (equivalent to 24.7% mortality d−1).
Present address: Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Sapporo Laboratory, 2-2 Nakanoshima, Toyohira-ku, Sapporo, Hokkaido 062-0922, Japan