title: Three decades of longlining in Bimini, Bahamas, reveals long-term trends in lemon shark Negaprion brevirostris (Carcharhinidae) catch per unit effort.
abstract: 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.
authors.affiliation: Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, N9B 3P4, Canada.|School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, U.K.
authors.forename: S T
authors.initials: ST
authors.lastname: Kessel
authors.affiliation: School for Marine Science and Technology, University of Massachusetts-Dartmouth, Fairhaven, MA, U.S.A.
authors.forename: A C
authors.initials: AC
authors.lastname: Hansell
authors.affiliation: Bimini Biological Field Station Foundation, South Bimini, Bahamas.
authors.forename: S H
authors.initials: SH
authors.lastname: Gruber
authors.affiliation: Bimini Biological Field Station Foundation, South Bimini, Bahamas.
authors.forename: T L
authors.initials: TL
authors.lastname: Guttridge
authors.affiliation: Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, N9B 3P4, Canada.
authors.forename: N E
authors.initials: NE
authors.lastname: Hussey
authors.affiliation: School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, U.K.
authors.forename: R G
authors.initials: RG
authors.lastname: Perkins
mesh_terms: D025041:Animal Migration; D000818:Animals; D001267:Atlantic Ocean; D001444:Bahamas; D017753:Ecosystem; D056727:Endangered Species; D011156:Population Density; D012726:Sexual Behavior, Animal; D012754:Sharks / Q000502:physiology*
keywords: CPUE; general additive model; lemon shark; population trends