基于耳石微化学的东海大黄鱼洄游路线推测

近年来，东海频现对大黄鱼（Larimichthys crocea）大网捕获（吨级规模以上），引起了对衰退中的野生大黄鱼资源保护的担忧。为查明东海野生大黄鱼洄游规律，本文根据2020−2022年在浙江近海产卵场和外海越冬场采集的不同批次野生大黄鱼样本，利用激光剥蚀电感耦合等离子体质谱法（LA-ICP-MS）测定耳石微化学元素，结合聚类分析和主成分分析（PCA），对不同大黄鱼群体进行了划分，结合耳石的年轮特征，研究大黄鱼群体的栖息生境，推测大黄鱼洄游路线。结果表明，Ba/Ca $leqslant$0.004 2时可以判定为海洋栖息生境，Ba/Ca $geqslant$ 0 .008 1时可以判定为河口栖息生境，0.004 2 < Ba/Ca< 0.008 1时可以判定为混合栖息生境。根据该阈值范围，判定本次采样的大黄鱼的5种生境类型：（1）近海产卵，近海混合水域短暂栖息类型（占22.2%）；（2）近海产卵，阶段性往复混合生境栖息类型（占15.6%）；（3）近海产卵，河口水域育幼索饵，外海越冬栖息类型（31.1%）；（4）河口产卵、混合水域育幼，外海越冬栖息类型（6.7%）；（5）近海混合水域短暂产卵，绝大部分时间海洋生境栖息类型（24.4%）。对所有样本的Ba/Ca核心、峰值和边缘值进行PCA，5种栖息类型的样本均匀分布在第一轴的两侧，大部分时间都在海洋生境中的G1、G2和G5，以及受陆源影响较大的G3和G4。同时，PCA结果同时也显示，5种类型样本均会近同步地在近海岛礁处出现，这表明外海、近海和河口的群体由于洄游等因素的影响会出现混合，说明了舟山岛礁水域对大黄鱼产卵育幼的重要性。本研究为东海大黄鱼近海产卵场、索饵场和外海越冬场之间洄游履历，以及大黄鱼洄游路线推测提供一定依据。

Speculation of migration routes of Larimichthys crocea in the East China Sea based on otolith microchemistry

In recent years, large yellow croaker (LYC) has been caught with high abundance in the East China Sea (ECS), which raises concerns about the conservation of LYC resources. We collected LYC samples from spawning grounds and wintering grounds in the offshore Zhejiang from 2020 to 2022. In order to find out the migration route of LYC in the ECS, we made use of otolith microchemical elements by LA-ICP-MS analysis, combined with the clustering analysis and PCA of trace elements such as Ba/Ca, to classify different LYC groups. With the age characteristics of otolith, the habitat patterns of LYC group was studied, and the updated migration route of LYC was speculated. The results showed that groups with Ba/Ca $leqslant$ 0.004 2 was inhabited in the marine region. That with Ba/Ca $geqslant$ 0.008 1 was inhabited in the estuary region, and that with 0.004 2 < Ba/Ca < 0.008 1 was inhabited in the mixed (estuary and oceanic) habitat. The five group types of LYC were: (1) offshore spawning, short-term mixed waters inhabited (accounting for 22.2%); (2) offshore spawning, periodically back and forth with mixed water inhabited (accounting for 15.6%); (3) offshore spawning, feeding and nursering in estuary waters, and wintering inhabited in the open sea (31.1%); (4) estuary spawning, nursering in the mixed waters, overwintering inhabited in the open sea (6.7%); (5) shortly spawning in the mixed waters, most of the time inhabited in the open ocean (24.4%). PCA was performed with Ba/Ca core, peak and edge values of all samples, and the results showed that samples from five groups were evenly distributed on both sides of the first axis: G1, G2 and G5 groups, which spent most of their time in the ocean, and G3 and G4 groups, which were heavily influenced by terrestrial sources. At the same time, the PCA results also showed that all the samples appeared nearly synchronously near the island or reefs, indicating that populations in the open sea, offshore and estuary waters may mix due to factors such as migration, indicating the importance of Zhoushan offshore waters for LYC nursering and spawning. This study provides a certain basis for the migration history of the LYC in the ECS between its coastal spawning, feeding grounds and its overwintering grounds in the open sea, as well as for the speculation of its migration routes.