Impact of minimum catch size on the population viability of Strombus gigas (Mesogastropoda: Strombidae) in Quintana Roo, Mexico

Abstract

Abstract:The queen conch Strombus gigas represents one of the most important fishery resources of the Caribbean but heavy fishing pressure has led to the depletion of stocks throughout the region, causing the inclusion of this species into CITES Appendix II and IUCN's Red-List. In Mexico, the queen conch is managed through a minimum fishing size of 200mm shell length and a fishing quota which usually represents 50% of the adult biomass. The objectives of this study were to determine the intrinsic population growth rate of the queen conch population of Xel-Ha, Quintana Roo, Mexico, and to assess the effects of a regulated fishing impact, simulating the extraction of 50% adult biomass on the population density. We used three different minimum size criteria to demonstrate the effects of minimum catch size on the population density and discuss biological implications. Demographic data was obtained through capture-mark-recapture sampling, collecting all animals encountered during three hours, by three divers, at four different sampling sites of the Xel-Ha inlet. Assuming that the presence of the lip is an indicator for sexual maturity, it can be concluded that many animals may form their lip at greater shell lengths than 200mm and ought to be considered immature. Estimation of relative adult abundance and densities varied greatly depending on the criteria employed for adult classification. When using a minimum fishing size of 200mm shell length, between 26.2% and up to 54.8% of the population qualified as adults, which represented a simulated fishing impact of almost one third of the population. When conch extraction was simulated using a classification criteria based on lip thickness, it had a much smaller impact on the population density. We concluded that the best management strategy for S. gigas is a minimum fishing size based on a lip thickness, since it has lower impact on the population density, and given that selective fishing pressure based on size may lead to the appearance of small adult individuals with reduced fecundity. Furthermore, based on the reproductive biology and the results of the simulated fishing, we suggest a minimum lip thickness of ≥15mm, which ensures the protection of reproductive stages, reduces the risk of overfishing, leading to non-viable density reduction. Rev. Biol. Trop. 62 (4): 1343-1352. Epub 2014 December 01.

Population Structure and Life Table of Dog Conch (Strombus turturella) in Bangka Belitung Islands, Indonesia <i><br>[Struktur Populasi dan Tabel Hidup Siput Gonggong (Strombus turturella) di Kepulauan Bangka Belitung, Indonesia]<i><br>

“…Therefore, adult individuals had the chance to reproduce, then they became the seed donor around that area. This kind of management had been carried out to protect Strombus gigas in the Carribean Islands by managing the shell size, minimum shell clam could be caught, restricting individual adult catch and making marine protection areas (Béné and Tewfik, 2003;Peel and Mandujano, 2014;Stoner et al, 2012).…”