Long‐term stock assessment and growth changes of the Japanese sardine (Sardinops melanostictus) in the Sea of Japan and East China Sea from 1953 to 2006

Abstract

We estimated the stock size of Japanese sardine (Sardinops melanostictus) in the Sea of Japan and East China Sea since 1953 using cohort analysis based on the changes of growth patterns. Growth of Japanese sardine, estimated by using annual rings on archived scales since 1961, showed that body lengths were extremely stunted in the 1980-1987 year-classes. The body length at age 3 from February to April in the 1980-1987 year-classes, a period when the stock size exceeded 4 million tons, was 180.0 ± 2.6 mm (mean ± SD), and in the other year-classes was 195.1 ± 7.6 mm. The body length at age 3 and wet weight of zooplankton in August in the offshore area of the Sea of Japan had a significantly positive correlation. We assumed three scenarios for maturation ratios, and estimated Ricker's spawner-recruitment relationships. We analyzed the correlations between logarithmic recruitment residuals (LNRR) and environmental factors in winter, represented by the North Pacific index (NPI), Aleutian low pressure index (ALPI), Pacific decadal oscillation (PDO), monsoon index (MOI), Arctic oscillation (AO) and Southern oscillation index (SOI). Significant correlations were observed between MOI and LNRR and between AO and LNRR. A combination of strong MOI and weak AO would increase the biomass of phytoplankton and zooplankton and subsequently increase the recruitment of Japanese sardine.

The Response of Fish Communities to Climate and Human-Induced Changes Inferred from Fishery Landings in an Enclosed Bay

“…Sardine harvest in Omura Bay began in 1975, but the shift from anchovies to sardines occurred in 1979, and the sardine regime lasted until the return of anchovies in the late 1980s. Furthermore, in 1979, sardine recruitment and recruitment per spawning stock biomass began to increase in TWC (Ohshimo et al 2009;Tanaka et al 2010), which matched with the shift to the sardine regime in Omura Bay. The shift to the anchovy regime (the second replacement) occurred in 1988.…”

“…The shift to the anchovy regime (the second replacement) occurred in 1988. Low sardine recruitment was reported between 1988 and 1991 (Hiyama et al 1995;Ohshimo et al 2009;Tanaka et al 2010), whereas anchovy recruitment increased between 1987 and 1990 (Kuroda et al 2011). These opposite trends may have been caused by climate and climaterelated environmental changes (Ohshimo et al 2009;Sakuramoto et al 2010;Yatsu et al 2005).…”

“…Low sardine recruitment was reported between 1988 and 1991 (Hiyama et al 1995;Ohshimo et al 2009;Tanaka et al 2010), whereas anchovy recruitment increased between 1987 and 1990 (Kuroda et al 2011). These opposite trends may have been caused by climate and climaterelated environmental changes (Ohshimo et al 2009;Sakuramoto et al 2010;Yatsu et al 2005). Anchovies migrate in Omura Bay from the East China Sea to spawn in spring and spend their life in the bay until winter (Azeta 1981;Akamatsu et al 2010).…”

Biomass fluctuation of two dominant lanternfish Diaphus garmani and D. chrysorhynchus with environmental changes in the East China Sea

“…It is assumed that there is species competition between mesopelagic fish and small pelagic fish in the ECS. The biomass fluctuations of small pelagic fish, such as mackerels Scomber japonicus and S. australasicus and sardine Sardinops melanostictus, in the ECS and adjacent waters were studied, and these fluctuations were affected by environmental factors [8,9]. Decadal change in abundance of myctophid fish, including Diaphus spp., in the Kuroshio region was reported, and the abundance was affected by the Kuroshio flow volume [10].…”

Management Strategy Evaluation of Fisheries Resources in Data-poor Situations Using an Operating Model Based on a Production Model

“…The value for δ was determined during the management period according to the stock level. The maximum harvest rate was fixed at 70% to match the approximate observed maximum harvest rates around Japan 8,13 , and the catch during the management period was assumed to be 0 when the ABC was 0 or less than 0.…”