Abstract

Queen conch (Lobatus gigas) is an important food source and export product for Belize. Overfished in many parts of the Caribbean, international trade of L. gigas is regulated by CITES. Extraction in Belize is regulated by a 17.8 cm (7 inch) national shell length limit or 85 g (3 oz) market-clean meat weight limit, 3-month closed season, and full protection in Replenishment Zones. However, PHMR fisheries-independent surveys between 2009 - 2015 indicate population decline to below the 88 conch/ha minimum density threshold recommended by the Belize Fisheries Department with apparent recruitment failure since 2013. Fisheries-dependent surveys between 2009 - 2012 revealed that while fishers are largely adhering to the shell length limit, the proportion of catch with shell lip thickness < 9 mm (males) and < 12 mm (females) - minimum maturity thresholds in other studies - increased from ~30% in 2009 to ~90% in 2012. Other studies show lip thickness is a more reliable indicator of maturity, but varies on local and regional scales and needs to be determined locally. Relationships were compared between gonad development and shell length, lip thickness, meat weight and operculum dimensions to determine the most reliable, easily measured proxy indicator(s) of maturity in L. gigas of PHMR that can be feasibly implemented to ensure immature individuals are protected from harvest. No relationship was found between shell length and maturity at any time. Lip thickness-maturity relationships were strong and most significant during the closed, reproductive season (Period 2) (p < 0.01), likely due to peak gonad development during this time, and indicated 80% probability of being sexually mature with good fecundity at lip thicknesses 18 mm for males and 20 mm for females. An non-linear management approach that integrates initial catch reductions, temporary closures, Replenishment Zone expan-sion and adaptive lip thickness limits could achieve long-term sustainability of L. gigas in PHMR, and minimize short-term impacts yet maximize long-term benefits on fishers’ livelihoods.

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