Winter monsoon promotes the transport of Japanese temperate bass Lateolabrax japonicus eggs and larvae toward the innermost part of Tango Bay, the Sea of Japan

Abstract

Northwesterly cold winds characteristic of the East Asian Winter Monsoon (EAWM) dictate winter climatic conditions over the Japanese Archipelago. Japanese temperate bass Lateolabrax japonicus is a commercially important coastal fish that spawns offshore in winter and uses shallow waters as nursery habitats. To investigate the effects of EAWM on the planktonic period of L. japonicus, eggs, larvae, and juveniles were quantitatively collected in Tango Bay on the Sea of Japan side in winter and spring from 2007 to 2017. Although eggs occurred close to the mouth of the bay, planktonic larvae occurred further inside as they developed. The horizontal distribution of planktonic larvae, combined with water velocity data obtained from mooring observations, indicated that planktonic larvae are transported south‐ to westward through Ekman current and an anticyclonic circulation, which are driven by northwesterly winds. To evaluate survival during the planktonic period in each year class, the abundance of benthic larvae/juveniles was divided by winter total landings of Lateolabrax spp. (proxy of the spawning stock size). This survival index exhibited a positive correlation with the northwesterly component of winter winds, and a negative correlation with winter air temperature (average from December to February, Spearman's correlation, p < .05). There was, however, no significant correlation with winter water temperature or winter freshwater discharge in the bay. We conclude that northwesterly cold winds of EAWM play a critical role in transporting L. japonicus eggs and larvae toward nursery habitats, specifically beaches and estuaries fringing the innermost part of Tango Bay.

Embryonic development and effect of water temperature on hatching of Lophius litulon

“…However, variation in recruitment of fish is known to be determined by survival during the early life stage (Hjørt 1914). Thus, variation in water temperature during the egg and early larval stage is considered to effect their passive transport or growth and then recruitment success in Lophius e.g., "Stage duration hypothesis" (Houde 1987), "Transport hypothesis" (North and Houde 2003;Suzuki et al 2019) and "Growth-predation hypothesis" (Litvak and Legget 1992;Takasuka et al 2003). Information that we gained in this study is important to clarify the spatiotemporal distributions of spawning and nursery ground of L. litulon and the effect of temperature on recruitment success in the field.…”