Data for: Fisheries shocks provide an opportunity to reveal multiple recruitment sources of sardine in the Sea of Japan

Understanding recruitment sources is essential for stock assessments of marine fish populations. In 2014 and 2019, schools of sardine in the Sea of Japan and East China Sea (SJ-ECS), which come to spawn in Japanese coastal areas every spring, were shockingly sparse. Abundances of eggs and juveniles also declined abruptly, indicating a sharp decline in reproduction in the SJ-ECS. However, in spring of 2015 and 2020, age-1 fish appeared as usual in the coastal areas, challenging the current assumption that sardine in the system is a self-recruiting subpopulation. To test the self-recruiting hypothesis, we analysed the stable oxygen and carbon isotopes (δ18O, δ13C) for otolith areas formed during the first spring and summer in otoliths of age-0 and age-1 sardines in 2010 and 2013–2015 year-classes captured in the SJ-ECS, as indices of temperature and metabolic trajectories. Age-0 sardines generally showed a significant decrease in otolith δ18O from spring to summer, reflecting seasonal war..., Collected fish were frozen after landing or on board at -20 °C, and thawed at a laboratory. After measurements of length and weight, the sagittal otoliths were extracted. The otoliths were cleaned using a thin brush and rinsed with fresh water. These otolith samples were processed in two different protocols, namely low-resolution analysis similar to Sakamoto et al. (2020) and high-resolution analysis similar to Aono et al. (2023). The majority of the otoliths were analysed using a low-resolution protocol. In addition to these, high-resolution data from age-0 fish captured in 2015 around Kyushu and the Noto Peninsula (Aono et al., 2023) were also included in analyses to allow a more comprehensive comparison.
For low-resolution analysis, otoliths were embedded in Petropoxy 154 (Burnham Petrographics LLC) resin and kept at 80 °C for 12 h to cure. Otoliths were ground and polished until the core was revealed using sandpaper and alumina suspension (BAIKOWSKI International Corporation). Using..., , # Data for: Fisheries shocks provide an opportunity to reveal multiple recruitment sources of sardine in the Sea of Japan

[https://doi.org/10.5061/dryad.m37pvmd9g](https://doi.org/10.5061/dryad.m37pvmd9g)

The original data of otolith growth and isotope analysis for sardine in the Sea of Japan are presented here.

## Description of the data and file structure

This csv file contains metadata of the collection and the results of otolith growth and isotope analyses. The empty cells are the missing values. For each row, the following data is shown:

ID: individual identifier

Year: Year of collection

Month: Month of collection

Loc_num: Collection area identifier (0: West Kyushu, 1: Oki Islands, 2: Noto Peninsula, 3: Subarctic western North Pacific).

SL (mm): The size of fish in standard length (mm).

age: Fish age estimated from SL and collected months.

OR60: Otolith radius in micrometers at 60 days post-hatch, estimated from microstructure analysis.

OR120: Otolith radius in micromet...,