Annual variation in otolith increment widths of walleye pollock (Gadus chalcogrammus) larvae in Funka Bay, Hokkaido, Japan

Abstract

To clarify relationships between year-class strength and larval growth of walleye pollock (Gadus chalcogrammus), and oceanographic conditions in the Pacific stock off Hokkaido and Tohoku, Japan, we undertook CTD observations and investigated larval 25 densities, larval otolith increment widths, and larval prey densities (of copepod nauplii) of the

Effect of Temperature on the Daily Increment Deposition in the Otoliths of European Sardine Sardina pilchardus (Walbaum, 1792) Larvae

“…The inclusion of uncertainty parameters in age estimation should be considered and adopted to reflect the discrepancies in age estimation according to water temperature. Many studies have used the different patterns of larval growth to distinguish populations and cohorts, but most could not be assigned to any specific environmental variable [10,19,75]. More accurate back-calculations could be possible in fish populations with relatively stable environmental conditions [12].…”

“…Hydrographic backtracking models can complement the otolith analysis by reconstructing the environmental history and spawning origin of larvae, gaining insights into the relationship between larval growth and environmental variability [16]. Validation of the relation between otolith growth increment deposition and larval age is essential to study growth and to reconstruct early life history events such as hatching, first feeding, notochord flexion, and metamorphosis [17][18][19]. Not only is it necessary to know the increment deposition rate and what variables might influence it, but it is also crucial to know the first increment formation age to obtain reliable age estimations [8].…”

Effect of egg size on the growth rate and survival of wild walleye pollock Gadus chalcogrammus larvae

“…Strong year classes have been thought to occur under high water temperature conditions in January–February (Funamoto, 2007; Funamoto et al, 2013), the early occurrence of spawning and hatching (Nishimura et al, 2007; Shida, 2011), enhanced transportation of eggs into the bay driven by the northwesterly wind to continue to the late spawning period in March (Isoda et al, 1998), and elongation of suitable high water temperature conditions for larval survival in years when the intrusion of Coastal Oyashio Water was delayed until April (Isoda et al, 1998). In addition, high larval abundance in March occurred with high larval growth rates estimated from otolith daily increment analysis (Kano et al, 2015), and the high growth rate individuals occurred from the yolk sac larval stage (0–6 days after hatching) before the start of feeding. Furthermore, the prey density in the environment (copepod nauplii; Kamba, 1977; Nakatani, 1995) for the first feeding stage (7–23 days after hatching) had only a small effect on larval growth rate and survival (Kano et al, 2015).…”

“…Strong year classes have been thought to occur under high water temperature conditions in January-February (Funamoto, 2007;Funamoto et al, 2013), the early occurrence of spawning and hatching (Nishimura et al, 2007;Shida, 2011), enhanced transportation of eggs into the bay driven by the northwesterly wind to continue to the late spawning period in March (Isoda et al, 1998), and elongation of suitable high water temperature conditions for larval survival in years when the intrusion of Coastal Oyashio Water was delayed until April (Isoda et al, 1998). In addition, high larval abundance in March occurred with high larval growth rates estimated from otolith daily increment analysis (Kano et al, 2015), and the high growth rate individuals occurred from the yolk sac larval stage (0-6 days after hatching) before the start of feeding. Furthermore, the prey density in the environment (copepod nauplii; Kamba, 1977;Nakatani, 1995) for the F I G U R E 1 Locations of Funka Bay (upper) and the spatial distribution area of walleye pollock Gadus chalcogrammus Japan Pacific stock (JPS, shaded area in upper panel), sampling stations for eggs and larvae of JPS, prey plankton (copepod nauplii) and CTD measurements from December to April (lower; solid circles), and the stations for sea-bottom temperature along the 100-, 200-, and 400-m depth isobaths outside of Funka Bay (lower; Stations D 100 -H 100 , D 200 -H 200 , and D 400 -H 400 as open circles) from late December to March first feeding stage (7-23 days after hatching) had only a small effect on larval growth rate and survival (Kano et al, 2015).…”

“…Recruitments of the 2007 and 2009 year classes were 3.28 and 2.52 billion individuals, respectively, which were relatively high abundance levels in recent years (Sakai et al, 2019). The factors affecting the recruitment of JPS have been verified as water temperature (Funamoto, 2007;Funamoto et al, 2013;Isoda et al, 1998;Nakatani et al, 2003), larval hatching date and growth history (Nishimura et al, 2007;Shida, 2011), feeding success of first feeding stage larvae (Nakatani, 2008;Nakatani et al, 2003), advection of eggs and larvae (Isoda et al, 1998;Shimizu & Isoda, 1997), and larval growth rate (Kano et al, 2015).…”