Age, growth, and mortality of threatened Warsaw grouper, Hyporthodus nigritus, in the Gulf of Mexico
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Age, growth, and mortality of threatened Warsaw grouper, Hyporthodus nigritus, in the Gulf of Mexico

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  • Journal Title:
    Fisheries Research
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    Warsaw grouper (Hyporthodus nigritus) in the Gulf of Mexico (GoM) are currently managed as a single-stock; however, patchy distribution of suitable habitat may promote the development of discrete populations with different life history characteristics thereby complicating conservation policy. We estimated ages and age-length relationships of Warsaw grouper from different geographic regions in the GoM and applied von Bertalanffy growth functions (VBGF) to estimate growth parameters (L∞ and K) for each region. Otolith-based ages ranged from 1 to 91 years and estimated L∞ and growth coefficient (K) derived from the VBGF for all Warsaw grouper combined were 188.8 cm total length (TL) and 0.034 respectively. Region-specific growth parameters were similar for most of the GoM when VBGFs were limited to Warsaw grouper < 25 years old, though growth was considerably faster from the southeast GoM. When our age-length key was applied to fisheries-dependent length data from the GoM in 2001–2006 and 2011–2016, this fishery was comprised primarily of Warsaw grouper < age-1, but the mean age increased between catches from 2001 to 2006 (4.7 ± 8.3) and 2011–2016 (7.6 ± 6.4). Instantaneous mortality rates (Z) based on the decline of log abundance on age indicated relatively low Z rates across the four regions (range: 0.09−0.18), with a significantly higher mortality rate in the western GoM (0.17) than the eastern GoM (0.08). In this study we also observed a greater longevity (91 years) for the species than previously documented, greater than double the longevity used to develop current management policy.
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    Fisheries Research, 243, 106097
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    Accepted Manuscript
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