Information on age and growth is essential to modern stock assessment and the development of management plans for fish resources. To provide quality otolith-based estimates of growth parameters, this study performed five types of analyses on the two important croakers that were under high fishing pressure in southwestern Taiwan: Pennahia macrocephalus (big-head pennah croaker) and Atrobucca nibe (blackmouth croaker): (1) Estimation of length–weight relationships (LWR) with discussion on the differences with previous studies; (2) validation of the periodicity of ring formation using edge analysis; (3) examination of three age determination methods (integral, quartile and back-calculation methods) and selection of the most appropriate one using a k-fold cross-validation simulation; (4) determination of the representative growth models from four candidate models using a multimodel inference approach; and, (5) compilation of growth parameters for all Pennahia and Atrobucca species published globally for reviewing the clusters of estimates using auximetric plots of logged growth parameters. The study observed that features of samples affected the LWR estimates. Edge analysis supported the growth rings were formed annually, and the cross-validation study supported the quartile method (age was determined as the number of opaque bands on otolith plus the quartile of the width of the marginal translucent band) provided more appropriate estimates of age. The multimodel inference approach suggested the von Bertalanffy growth model as the optimal model for P. macrocephalus and logistic growth model for A. nibe, with asymptotic lengths and relative growth rates of 18.0 cm TL and 0.789 year⁻¹ and 55.21 cm, 0.374 year⁻¹, respectively. Auximetric plots of global estimates showed a downward trend with clusters by species. Growth rates of the two species were higher than in previous studies using the same aging structure (otolith) and from similar locations conducted a decade ago, suggesting a possible effect of increased fishing pressure and the need to establish a management framework. This study adds updated information to the global literature and provides an overview of growth parameters for the two important croakers.

The adult population of Tachypleus tridentatus on the main island of Taiwan has long been considered extinct. However, it remains unclear whether this apparent absence reflects true extirpation or simply a lack of sustained large‐scale monitoring. To address this knowledge gap, a multiyear field investigation was conducted from 2018 to 2024 across three key subregions of the Taiwan Strait, namely, Kinmen, Penghu, and mainland Taiwan. Mark–recapture methods were used to estimate the adult population size using two statistical approaches. Population size estimated from the Schnabel method presented 73,629 (95% CI: 59,555–96,415) in Kinmen, 1551 (968–3899) in Penghu, and 1099 (623–4627) in Taiwan main island. Multinomial N‐mixture models showed a population size of 65,428 (63,704–67,156) in Kinmen, 3193 (2818–3588) in Penghu, and 1198 (387–2269) in Taiwan main island. Species distribution modeling (MaxEnt) and connectivity network analyses showed the major habitats in the Taiwan Bank and Changyun Ridge. Recapture records from five tagged individuals supported the predicted dispersal pathways, with the longest recorded straight‐line movement exceeding 110 km, showing ecological connectivity within the Taiwan Strait. Based on these findings, three key conservation strategies are proposed, namely, implementation of standardized long‐term monitoring, habitat restoration and stock enhancement efforts, and preparation for potentially assisted migration under future climate scenarios. The findings have provided a detailed assessment of adult T. tridentatus populations in the Taiwan Strait and offer actionable guidance for regional and international conservation planning in the context of environmental changes.

The adult population of tri-spine horseshoe crabs (Tachypleus tridentatus) in Taiwan has been considered nearly extinct for decades, resulting in its exclusion from data moderation assessments in previous studies. This highlights a significant gap between historical baseline data and recent research efforts in the Taiwan Strait. In this study, the population size was estimated using five years of mark-recapture data and identified potential habitat to simulate suitable habitats through the MaxEnt model. This is the first comprehensive assessment of the adult T. tridentatus population in the Taiwan Strait in decades. The result of the population size of T. tridentatus was estimated to be approximately 64,243 individuals in Taiwan. Habitat predication was identified not only the well-documented inshore where function was breeding and nursery areas critical for juveniles but also highlighted central strait regions, including the Taiwan Bank and Changyun Ridge, as high probability of occurrence for potential adult foraging ground with that may been overlooked in the historical baseline data. These findings indicated that the importance ecological niches of the Taiwan Strait for T. tridentatus, functioning as a breeding ground, conservation zone, foraging area, and migration corridor that connects Taiwan and the eastern coast of China. Based on these results, we propose a regional conservation strategy emphasizing international collaborative monitoring, cross-border conservation measures, the implementation of conservation practices, and benefit assessments. This work provides valuable insights for developing and implementing an action plan for the conservation of Asian horseshoe crabs.