Spawning stock recovery of Pacific bluefin tuna (Thunnus orientalis): Evidence from length, age and catch data of Taiwanese longline fishery in 2010–2023
Journal
Fisheries Research
Journal Volume
292
Start Page
107602
ISSN
0165-7836
Date Issued
2025-12
Author(s)
Abstract
Pacific bluefin tuna (Thunnus orientalis, PBF), a highly migratory and commercially important species, faces intense fishing pressure. Taiwanese PBF catches, which reached a nadir in 2012, gradually increased from 2014 onwards, culminating in a dramatic fivefold surge after 2019. This study analyzed the adult population from PBF landings in Taiwan from 2010 to 2023 to inform fisheries management. We found a strong correlation between declining juvenile catches in Japanese troll or purse seine fishery and increasing adult catches in Taiwanese and Japanese longline fishery, with a 7–9 year lag. Age estimation, using otolith annuli and age-length keys, revealed a temporal shift in age composition. Despite the substantial increase in Taiwanese catch size, the average age of landed PBF decreased. The spawning stock, previously dominated by older individuals (14–18 years), now primarily consisted of younger fish (8–12 years). Prior to 2014, most PBF measured between 220 and 240 cm in fork length; after 2017, this range generally decreased to 200–220 cm. Permutation test using fish size and otolith direct ageing data suggested a lower mean fork length at age for the PBF landed in the recent years compared to earlier years. Furthermore, a linear mixed model showed a relationship between fork length and fishing year, indicating a consistent decrease in fork length across all age groups. These results suggest that reduced fishing pressure on juvenile PBF (0–1 years old) has allowed more individuals to reach adulthood, contributing to the observed recovery of the spawning population. These findings provide valuable insights into the effective fishery management and PBF stock rebuilding in Taiwan and other regions.
Subjects
Life history traits
Overfishing
Population rebuild
SDGs
Publisher
Elsevier BV
Type
journal article