Parturition time for the Blacktip shark, Carcharhinus limbatus (Carcharhiniformes: Carcharhinidae), in Southwestern Atlantic

Abstract The determination of the period of parturition and identification of nursery areas are fundamental for the management and conservation of a fishing resource. Through combination of monthly abundance, length measurements, and development time of embryos we inferred about parturition time of the Blacktip sharks, Carcharhinus limbatus, from Southwestern Atlantic. Specimens of C. limbatus were caught from 2002 and 2008 by artisanal fleets from three different locations along the Brazilian coast using gillnets (mesh width ranging between 30 and 120 mm between opposite knots and operating from 9 to 120 m in depth), handlines (19 to 140 m depth) and longlines (6 to 90 m depth). Through a comparative analysis of fisheries landing data collected, we have verified neonatal (< 90 cm) catch peaks at specific times of the year in different locations and, matching with birth prediction of embryos, propose that C. limbatuspresents a well-defined parturition time in late spring-early summer in Southwestern Atlantic. Moreover, we indicate supposed nursery grounds for the species along the Brazilian coast. This information will be crucial for stock assessments of the species and may serve as a basis for determining fisheries management measures.

摘要
确定产仔周期与识别育苗场，是渔业资源管理与保护的核心基础工作。本研究结合月度种群丰度数据、体长测量结果与胚胎发育时长，推断了西南大西洋（Southwestern Atlantic）海域黑边鳍真鲨（Carcharhinus limbatus）的产仔时间。2002年至2008年间，研究团队借助巴西沿岸3个不同海域的小型手工渔业船队，通过刺网（网目宽度为相对结节间30~120 mm，作业水深9~120 m）、手钓（作业水深19~140 m）与延绳钓（作业水深6~90 m）采集了黑边鳍真鲨样本。通过对采集到的渔业上岸数据开展对比分析，本研究证实不同海域的新生个体（体长<90 cm）捕捞量在每年特定时段出现峰值；结合胚胎发育的产仔预测结果，我们提出：西南大西洋海域的黑边鳍真鲨存在明确的产仔周期，集中于春末夏初时段。此外，本研究还指明了巴西沿岸海域该物种的推测育苗场分布。该研究结果对于该物种的种群评估至关重要，同时可为制定渔业管理措施提供科学依据。