Estimation of movement and mortality of Atlantic menhaden during 1966–1969 using a Bayesian multi-state mark-recovery model Fisheries Research

Atlantic Menhaden Brevoortia tyrannus is an economically and ecologically important forage fish targeted by large-scale commercial reduction and bait fisheries. In the late 1960s, the National Marine Fisheries Service conducted a mark-recovery study in which they tagged over one million adult Atlantic Menhaden. Mark-recapture models at the time did not allow for estimation of movement rates. Our objective was to reanalyze these data to simultaneously estimate natural mortality, fishing mortality, and movement probability during 1966–1969. We developed a Bayesian version of the Brownie model that incorporated fishing mortality, natural mortality, and movement among four regions of the northwest Atlantic continental shelf ecosystem at a monthly time step. The model also accounted for both tag loss and tag detection probability. During May-June, an estimated 91% of Atlantic Menhaden from North and South Carolina moved northwards. Atlantic Menhaden largely remained within the same coastal region from June to October. In the winter, an estimated 55% of the tagged sample north of the Chesapeake Bay moved southward to the Chesapeake Bay and North and South Carolina. However, the fraction of the tagged sample undertaking these movements was substantially smaller than previously described. The estimated instantaneous natural mortality rate, 1.17 yr−1 (1.09–1.23 yr−1, 95% CI), was greater than previously reported. Instantaneous fishing mortality was spatially and temporally variable and as high as 1.74 yr−1 in North and South Carolina during 1967. Understanding the historical seasonal spatial dynamics of this stock will improve contemporary survey design and management, as these dynamics may persist today. Grant no. NA14OAR4170090

大西洋油鲱（Atlantic Menhaden，学名*Brevoortia tyrannus*）是兼具经济与生态价值的关键饵料鱼类，为大规模商业减渔渔业与饵料渔业的主要捕捞对象。20世纪60年代末，美国国家海洋渔业局（National Marine Fisheries Service）开展了一项标记回收研究，共标记超过100万尾成年大西洋油鲱。彼时的标记重捕模型无法估算种群移动速率。本研究旨在重新分析这批数据，以同时估算1966—1969年间的自然死亡率、捕捞死亡率与个体移动概率。我们构建了贝叶斯版布朗尼模型（Brownie model），该模型以月为时间步长，纳入了西北大西洋大陆架生态系统四个区域间的捕捞死亡率、自然死亡率与种群移动情况，同时考虑了标记脱落率与标记检出概率。研究结果显示：5—6月期间，来自北卡罗来纳州与南卡罗来纳州的大西洋油鲱中约91%向北移动；6—10月期间，大西洋油鲱基本停留在同一沿岸区域内；冬季时，切萨皮克湾以北的标记样本中约55%向南移动至切萨皮克湾以及南北卡罗来纳州海域。不过，开展此类移动的标记样本占比远低于此前的报道结果。估算得到的瞬时自然死亡率为1.17年⁻¹（95%置信区间：1.09—1.23年⁻¹），高于此前的报道值。瞬时捕捞死亡率存在时空异质性，1967年在南北卡罗来纳州海域最高可达1.74年⁻¹。明晰该渔业种群的历史季节空间动态，有助于优化当代渔业调查设计与资源管理，因为此类种群动态可能至今仍在延续。资助项目编号：NA14OAR4170090