Replication Data for: Catch trend and stock assessment of Hilsa Tenualosa ilisha using digital image measured length-frequency data

The annual global average catch shares of the anadromous Hilsa, Tenualosa ilisha of Bangladesh increased rapidly from 74.5% all through 1984–2013 to 86.7% during the 2010–2015 periods. With a few exceptions, an increasing trend of Hilsa production over the last three decades was found in Bangladesh. Initially three options incorporating digital image measurements were compared to determine the best method for obtaining accurate length data. The length-frequency data measured from digital images showed that Hilsa have a moderate growth rate (K = 0.90 year−1) of up to 58.70 cm (L∞) TL. High fishing mortality (F = 2.83 year−1) and exploitation level (E = 0.67) suggest a slight overexploitation of the Hilsa fishery; the maximum sustainable yield (MSY) was estimated at 526,000 metric tons/year if therecommended TL at first capture (Lc) of 27 cm is adhered to. The present annual Hilsa catch is about 496,417 metric tons, which indicates the potential benefit of achieving MSY through sustainable fisheries management by regulating mesh size of nets and protecting brood fish. Size distribution of Hilsa within sanctuaries revealed a remarkable presence of juvenile fish during February–March in some areas, which suggests a need to readjust the fishing ban period from March–April to February–March. More fisheries management is necessary to reduce the exploitation level of Hilsa by 17% and at the same time increase the allowable Lc to potentially increase the MSY and CPUE.

孟加拉国境内溯河洄游的希尔萨鱼（Tenualosa ilisha, Hilsa）的年度全球平均捕获份额，从1984—2013年的74.5%快速升至2010—2015年的86.7%。除少数例外情况外，过去三十年间孟加拉国的希尔萨鱼产量整体呈上升趋势。研究初期，团队比对了三种集成数字图像测量的方案，以筛选出获取精准体长数据的最优方法。通过数字图像测量得到的体长频率数据显示，希尔萨鱼的生长速率适中（生长参数K=0.90年⁻¹），渐近总长度（Total Length, L∞）可达58.70厘米。较高的捕捞死亡率（F=2.83年⁻¹）与开发水平（E=0.67）表明，希尔萨鱼渔业已出现轻度过度开发；若遵循首捕总长度（Lc）为27厘米的建议标准，希尔萨鱼的最大可持续产量（MSY）估算可达52.6万吨/年。当前希尔萨鱼的年度捕获量约为49.64万吨，这表明通过调整网具网目尺寸、保护亲鱼来实施可持续渔业管理，有望达成最大可持续产量目标。渔业保护区内希尔萨鱼的体长分布数据显示，部分区域在2—3月会出现大量幼鱼，这表明需要将禁渔期从3—4月调整为2—3月。需进一步完善渔业管理措施，将希尔萨鱼的开发水平降低17%，同时提高允许的首捕体长标准，以潜在提升最大可持续产量与单位捕捞努力量渔获量（CPUE）。