Archibald, M.

The Morphology of the Queen Conch (Strombus gigas) from the Antigua and Barbuda Shelf – Implications for Fisheries Management

Morphometric measurements were taken from queen conch (Strombus gigas) from various sections of the Antigua and Barbuda shelf to: 1) ascertain if there were spatial variability regarding morphology; 2) analyse length-weight relationships for various maturation stages; 3) develop statistically valid conversion factors for different levels of processed conch meat; and 4) assess current management regimes (e.g., minimum size / weight). For both juvenile and adult conch, shell length differed significantly among the coastal groupings, p < 0.001. Shell lip thickness, an indicator of the age, was also significantly different among the coasts (p < 0.001), where conch from the north and west coast were significantly older than those from the east or south coast of Antigua (p < 0.001). Significant sexual dimorphism was only detected for adult conch (p < 0.001), with females being 4% larger than their male counterpart. The mean lip thickness for conch collected from commercial fishing trips was 25.0 mm (N = 785, S.D. = 5.5 mm) indicating that divers were targeting an old population however the sex ratio of the allowable catch (minimum weight of 225g) was favouring the harvesting of female conch, X2 (1, N = 711) = 4.26, p < 0.05. Conversion factors differed significantly among maturation stages (juvenile, sub adult, adult and old adult), p < 0.001; hence the use of a single conversion factor to transform processed conch to nominal weight is problematic since conversion factor is dependent on the age structure of the population. These morphological differences require a multifaceted management approach (closed season, protected areas, etc) to ensure the long-term sustainability of the fishery. 

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Research and monitoring