Three decades of longlining in Bimini, Bahamas, reveals long-term trends in lemon shark Negaprion brevirostris (Carcharhinidae) catch per unit effort

• Published in: Journal of fish biology Vol. 88; no. 6; pp. 2144 - 2156
• Main Authors: Kessel, S. T., Hansell, A. C., Gruber, S. H., Guttridge, T. L., Hussey, N. E., Perkins, R. G.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2016; Wiley Subscription Services, Inc
• Subjects: Animal Migration; Animals; Atlantic Ocean; Bahamas; CPUE; Ecosystem; Endangered Species; general additive model; lemon shark; Population Density; population trends; Sexual Behavior, Animal; Sharks - physiology; lemon shark; CPUE; general additive model; population trends
• ISSN: 0022-1112; 1095-8649
• DOI: 10.1111/jfb.12987

In Bimini, Bahamas, the consistent employment of longlines, beginning in 1982, provided a rare opportunity to explore population trends for large resident sharks. This study assessed three shallow water longline survey periods at this location; 1982–1989, 1992–2002 and 2003–2014, with the aim of determining trends in annual catch per unit effort (CPUE) for an IUCN listed near‐threatened species, the lemon shark Negaprion brevirostris. A general additive model (GAM) was used to analyse the non‐linear annual CPUE values over the entire 32‐year research period. The GAM displayed high variability of annual CPUE, with a peak value of 0·026 N. brevirostris per hook day (hooks day−1) in 2000. The temporal pattern of CPUE indicated an abundance trend with a complete cycle, from trough to trough, occurring over a period of approximately 18 years. The 1982–1989 survey period saw the highest proportion of mature individuals (19·8%) and the smallest average pre‐caudal length (LPC; 124·8 cm). The 1992–2002 survey period had the highest average annual CPUE (0·018 hooks day−1), while the 2003–2014 research period saw largest average LPC size (134·8 cm) and the lowest average CPUE values (0·009 hooks day−1) of the entire research period. The long‐term trend identified in this study provides a baseline for future assessment.