Abstract
AbstractThe queen conch Lobatus gigas continues to support a commercial fishery in Puerto Rico despite a history of overfishing and low population densities. The goals of this study were to generate density estimates for the queen conch, to assess temporal trends, and to evaluate hypotheses of management interest using generalized linear models. Density data were supplemented by size‐ and age‐class data. Total mean density was 14.1/ha (adults = 7.3/ha; juveniles = 6.6/ha). Year plus habitat and depth (associated effects) were significant factors influencing adult and juvenile density. Lower densities of both juvenile and adult queen conchs were observed in 1997 and 2001 than in 2013, but there have been no differences since 2006. This indicates an improvement in the population, though not recently. A location effect compared sites within the U.S. Exclusive Economic Zone (EEZ), which is closed to fishing, with those in local waters, which are open to fishing. The location term was significant for adults, with lower densities inshore regardless of year. For juveniles, both the location and year × location terms were significant; the EEZ had a higher juvenile density and a proportionally greater density increase (from 2.3/h to 10.0/ha) from 1997 to 2013. Length‐frequency diagrams showed an increase in the proportion of adult conchs of 16–20‐cm shell length in 2013 relative to 1997. This suggests an effect of the 22.86‐cm minimum size limit implemented in 2004. Juveniles comprised 50% of the population in 2013, compared with 70% in 1997, and adults were found in the oldest age‐class during the 2013 survey. This suggests an overall decrease in fishing mortality since 1997. Changes in survey methodology are recommended, including but not limited to shortening transects to increase the number of sites, utilizing a two‐stage design, not utilizing scooters, standardizing the areas surveyed, and stratifying by depth and habitat.Received November 30, 2015; accepted July 12, 2016
Highlights
The queen conch Lobatus gigas continues to support a commercial fishery in Puerto Rico despite a history of overfishing and low population densities
A location effect compared sites within the U.S Exclusive Economic Zone (EEZ), which is closed to fishing, with those in local waters, which are open to fishing
Management of this commercially important species throughout the Caribbean is difficult due to a variety of factors. Key among these is that queen conchs change the manner in which they grow. As juveniles they increase in shell length, but about the onset of maturity they cease growing in length and form a broad shell lip that thickens over time (Appeldoorn 1988; Tewfik et al 1998)
Summary
The queen conch Lobatus gigas continues to support a commercial fishery in Puerto Rico despite a history of overfishing and low population densities. Management of this commercially important species throughout the Caribbean is difficult due to a variety of factors Key among these is that queen conchs change the manner in which they grow. In 1992, following the collapse of queen conch fisheries in a number of countries, queen conchs were listed under Appendix II of the Convention on International Trade in Endangered Species, which requires that exporting countries certify through their local scientific authority that harvest and export are not negatively affecting the stock This has helped by forcing exporting countries to obtain nondetrimental findings to ensure that exports do not negatively affect the wild population (Theile 2001)
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