Geographical variation in spawning histories of age-1 Pacific saury Cololabis saira in the North Pacific Ocean during June and July

Abstract

We examine geographical differences in percentages of age-1 Pacific saury Cololabis saira with previous spawning experience collected from 143°E to 165°W during June and July of 2013 and 2014. Previous spawning experience of fish was determined using a new histological method involving Victoria blue (VB)-positive ovarian arterioles. We also compared the radius of the otolith annual ring (ROA), which indicates fish body size at the beginning of the breeding season, with the incidence of previous spawning experience. A generalized linear model was used that treats the occurrence of fish with VBpositive arterioles as a response variable, following the Bernoulli distribution of probability p i , where longitude, latitude, body length, ROA in age-1 fish, year (2013 or 2014), sea surface temperature, and days elapsed from a survey starting date, are used as fixed effect terms. An estimated regression coefficient of longitude was negative while that of ROA was positive, meaning that the probability of previous spawning increases with a latitudinal progression west, and with increased ROA. Our results suggest that differences in the percentage of previously spawned fish in different geographic areas are caused by differences in body length at the beginning of the breeding season.

Spatiotemporal variations and influential factors affecting reproductive dynamics of Pacific saury in the Northwest Pacific during fishing season

“…Previous studies have suggested that month, body length, and SST could affect the spawning activity of Pacific saury (Fuji, Kurita, et al, 2021;Suyama et al, 2019). In addition, maturation states of Pacific saury might be influenced by their migration origin because individual growth rates varied in different locations (Suyama et al, 2019). In this study, GAMMs were applied to examine the effects of month, body length (i.e., KnL), origin (western and eastern groups), and SST on the probability of MOS state occurrence (P MOS )…”

“…Previous studies have suggested that month, body length, and SST could affect the spawning activity of Pacific saury (Fuji, Kurita, et al, 2021;Suyama et al, 2019). In addition, maturation states of Pacific saury might be influenced by their migration origin because individual growth rates varied in different locations (Suyama et al, 2019).…”

“…Kurita (2006) reported that almost all females were actively spawning where SST was >18 C during spring (May-July) of 1995-1997 in the northwestern Pacific, but none were spawning where SST was <13 C during those months. Fuji, Kurita, et al (2021) Furthermore, Suyama et al (2019) indicate that the differences in the percentage of spawned fish in different geographical areas may be related to the longitudinal variation in their growth rate (quantified as the radius of the otolith annual ring [ROA]). Previous literature also suggested that age 0 fish may not migrate widely and most age 1 fish could migrate from east of 160 E to near the coast of Japan from August to December (Suyama et al, 2012b;Miyamoto et al, 2019).…”

Geographic variation in feeding of Pacific saury Cololabis saira in June and July in the North Pacific Ocean

“…Furthermore, differences in the prey environment, such as zooplankton community structure (Shiota et al., 2013) and the composition of subarctic copepod stages (Yamaguchi et al., 2013), differ between eastern and western areas. Pacific saury growth and first spawning age also differ between eastern and western areas (Suyama, Nakagami, Naya, & Ueno, 2012; Suyama et al., 2019).…”

Clarifying the effects of environmental factors and fishing on abundance variability of Pacific saury (Cololabis saira) in the western North Pacific Ocean during 1982–2018

“…According to the image, the spawning period of autumn cohort centered in October, thus became age‐1 in the subsequent October; likewise, the spawning month of winter cohort and spring cohort centered in February and May, respectively, and became age‐1 in the subsequent February and May, respectively. Whereas the spawning period of age‐1 fish extends from autumn to spring, with an intensive spawning period in winter in the subtropical waters including the Kuroshio and Kuroshio Extension Currents (Figure 1), that of age‐0 fish is limited to winter, that is, all age‐1 fish and a part of age‐0 fish spawn (Fuji et al., 2019; Suyama et al., 2019; Watanabe & Lo, 1989).…”