Abstract

The queen conch (Strombus gigas) is a large economically important gastropod that has been severely depleted throughout much of the Caribbean region. The species has determinate growth and reaches maximum shell length before sexual maturation; thereafter the shell grows only in thickness. In this study, queen conch were collected in the Exuma Cays, Bahamas, to evaluate maturity with respect to shell length (SL) (170–255 mm) and shell lip thickness (LT) (2–42 mm). Soft tissue weight and gonad weight increased with SL, but these same variables, along with the gonadosomatic index (gonad weight/soft tissue weight), all had dome-shaped distributions with LT and decreased slightly with LT > 22 mm. This indicates some loss of fecundity with age; however, no loss of reproductive capability was evident in histological data. Gonad maturity lagged substantially behind first formation of the shell lip. Minimum LT for reproductive maturity was 12 mm for females and 9 mm for males, and 50% maturity for the population was achieved at 26 mm LT for females and 24 mm LT for males, higher than previous estimates. A review of fishing regulations indicates that immature queen conch are being harvested legally in most Caribbean nations, providing at least a partial explanation for widespread depletion. While relationships between shell lip thickness, age, and maturity vary geographically, sustainable management of queen conch will require a minimum shell lip thickness for harvest no less than 15 mm, along with other urgently needed management measures. 

The northwest coast of Curaçao is characterized by a series of Pleistocene-age reef terraces at four discrete elevations with dissolutional caves formed in the terraces at specific elevations (highest to lowest terraces, in meters above sea level: 90-175 m, 50-85 m, 10-45 m, and 5-10 m). Large scale rectilinear coastal reentrants called bokas occur in the lowest terrace, and are hundreds of meters long perpendicular to the coast, tens of meters wide, and have steep, vertical walls of up to more than ten meters height. Prominent coastline erosional features formed by a combination of cave collapse and wave erosion are also present in the lowest terrace. Reconnaissance field mapping in March of 2011 and 2012 documented 17 bokas and identified and surveyed numerous flank margin caves related to the reef terraces and the bokas. Quaternary uplift is evident by the position of the four elevated reef terraces adjacent to the coast. Eustatic sea-level changes, interacting with tectonic uplift, played an important role in the development of flank margin caves associated with the reef terraces. The flank margin caves in the inland cliffs fronting the terraces have been exposed by cliff retreat. As the caves form at sea level, and the coral terrace was at wave base when alive, the difference in elevation between the caves today and the terrace today (commonly 2 to 6 m) is an indication of the degree of dissolutional denudation of the terraces since terrace deposition and exposure. A widespread system of fluvial valleys, formed on interior Cretaceous volcanic rocks, has eroded through the limestone terraces into the underlying basaltic bedrock. Large bokas are developed where these inland streams have incised through the lowest limestone terrace. Waves penetrate into the lower portions of the bokas. Their inland termini open to broad valleys on the volcanics. The bokas contain flank margin caves exposed along their vertical walls, including within the broad inland termini, which have facilitated boka wall collapse. Caves located in the lowest reef terrace that are not associated with ephemeral fluvial drainage are exposed by ceiling collapse and are eventually breached by sea-cliff retreat. As wave-influenced coastal erosion proceeds, these flank margin caves are degraded to natural bridges that parallel the coastline and eventually evolve to short coastal reentrants. The assortment of karst, marine, and fluvial features signify polygenetic processes contributing to boka formation and the erosional degradation of the coastline. 

In a survey of the bathyal echinoderms of the Bahama Islands region using manned submersibles, approximately 200 species of echinoderms were encountered and documented; 33 species were echinoids, most of them widespread in the general Caribbean area. Three species were found to exhibit covering behavior, the piling of debris on the upper surface of the body. Active covering is common in at least 20 species of shallow-water echinoids, but it has been reliably documented previously only once in deep-sea habitats. Images of covered deep-sea species, and other species of related interest, are provided. Some of the reasons adduced in the past for covering in shallow-water species, such as reduction of incident light intensity, physical camouflage, ballast in turbulent water, protection from desiccation, presumably do not apply in bathyal species. The main reasons for covering in deep, dark, environments are as yet unknown. Some covering behavior in the deep sea may be related to protection of the genital pores, ocular plates, or madreporite. Covering in some deep-sea species may also be merely a tactile reflex action, as some authors have suggested for shallow-water species.