Size at Maturation, Spawning Variability and Fecundity in the Queen Conch, Aliger gigas

Abstract

The queen conch (Aliger gigas) resource is one of the most important in the Caribbean. While aspects of queen conch reproduction have been studied, e.g., size—at—maturity, spawning season, and density—based Allee effects, there is little information on other important aspects. From 210 lipped queen conch collected off southwest Puerto Rico, histological examination of gonads showed that 50% maturation occurred at 9 mm lip thickness. Experimental caged queen conch held on a natural spawning ground were monitored across the spawning season to evaluate fecundity and its variability across individuals and between nominal density treatments (2,000 vs 143 conch/ha). Near daily monitoring identified all egg masses to specific females, and all egg masses were retained to calculate the number of eggs. Conch in the low—density treatment produced more and larger egg masses over a longer spawning season than those in the high—density treatment. Within each density treatment, individual fecundity varied by a factor of 6. The maximum fecundity estimated was 22 million, the maximum number of egg masses spawned was 25, and the largest single egg mass contained 1.48 million eggs. Variability in fecundity was largely driven by length of the individual spawning season, but this may in turn have been dependent on the degree of maturation of females at the start of the spawning season. These results emphasize the importance of allowing queen conch to mature and further grow in lip thickness to ensure sufficient spawning to sustain reproductive capacity. This experimental approach could be used to assess variations in fecundity based on size (length, biomass) and age (lip thickness).

Exploitation Drives Changes in the Population Connectivity of Queen Conch (Aliger gigas)

“…The few studies that have investigated simultaneously the relationship between adult density and reproductive rates found varying results, particularly because the density is dependent on the scale over which observations are recorded (Stoner and Ray-Culp, 2000;Goḿez-Campo et al, 2010;Stoner et al, 2012;Cala et al, 2013;Doerr and Hill, 2018;Appeldoorn, 2020). However, field studies suggest a cross-shelf minimum density of 50-100 adults/ha (Stoner and Ray-Culp, 2000;Stoner et al, 2012) or a spawning aggregation (i.e., intra-aggregation) density of 200-300 adults/ha (Delgado and Glazer, 2020) is necessary for successful encounters and mating.…”

Limiting factors for queen conch (Lobatus gigas) reproduction: A simulation-based evaluation

“…Queen conch are among the most economically, socially, and culturally important fishery resources in the Caribbean [ 21 , 22 ], with high domestic and exported landings [ 23 ]. Queen conch are listed in CITES Appendix II, requiring non-detriment findings to allow for export quotas.…”