Identifying Priority Conservation Areas of Largehead Hairtail (Trichiurus japonicus) Nursery Grounds in the East China Sea

Zunlei Liu,Liping Yan,Hui Zhang,Yan Jin,Chuyi Shen,Jiahua Cheng,Yi Zhang,Linlin Yang

doi:10.3389/fmars.2021.779144

Abstract

Identifying the spatio-temporal distribution hotspots of fishes and allocating priority conservation areas could facilitate the spatial planning and efficient management. As a flagship commercial fishery species, Largehead hairtail (Trichiurus japonicus) has been over-exploited since the early 2000s. Therefore, the spatio-temporal management of largehead hairtail nursery grounds could effective help its recovery. This study aims to predict juvenile largehead hairtail distribution patterns and identify priority conservation areas for nursery grounds. A two-stage hierarchical Bayesian spatio-temporal model was applied on independent scientific survey data (Catch per unit effort, CPUE) and geographic/physical variables (Depth, Distance to the coast, Sea bottom temperature, Dissolved oxygen concentration and Net primary production) to analyze the probability of occurrence and abundance distribution of juvenile largehead hairtail. We assessed the importance of each variable for explaining the occurrence and abundance. Using persistence index, we measured the robustness of hotspots and identified persistent hotspots for priority conservation areas. Selected models showed good predictive capacity on occurrence probability (AUC = 0.81) and abundance distribution (r= 0.89) of juvenile largehead hairtail. Dissolved oxygen, net primary production, and sea bottom temperature significantly affected the probability of occurrence, while distance to the coast also affected the abundance distribution. Three stable nursery grounds were identified in Zhejiang inshore waters, the largest one was located on the east margin of the East China Sea hairtail national aquatic germplasm resources conservation zones (TCZ), suggesting that the core area of nursery grounds occurs outside the protected areas. Therefore, recognition of these sites and their associated geographic/oceanic attributes provides clear targets for optimizing largehead hairtail conservation efforts in the East China Sea. We suggested that the eastern and southern areas of TCZ should be included in conservation planning for an effective management within a network of marine protected areas.

Highlights

Recruitment is a fundamental process in population dynamics, which is highly variable in time, space and vulnerable to fishing gear (Gaillard et al, 2008)
Marine fish spawning grounds and nursery grounds are important for replenishing the stock and maintaining biodiversity, while non-selective fishing often leads to massive bycatch of juveniles
Identifying the spatio-temporal distribution of nursery grounds is a prerequisite for setting the red line of ecological protection

Summary

Introduction

Recruitment is a fundamental process in population dynamics, which is highly variable in time, space and vulnerable to fishing gear (Gaillard et al, 2008). Understanding the spatial pattern of juvenile distribution is of great interest to fishery science and marine ecology, since juvenile is a critical stage of fish stocks. Considering the vulnerability of recruitment and their role in population dynamics and stock size fluctuation, the protection of important habitats is critical for the conservation of marine fish and even the conservation of biodiversity (Hunt et al, 2020). Ensuring the effectiveness of such protected areas requires a comprehensive understanding of species distribution and habitat relationships. This ecological knowledge is becoming increasingly important for the sustainable exploitation of commercially important marine populations (Colloca et al, 2015; Paradinas et al, 2015)

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