Queen ConchLobatus gigaspopulation estimates and age structure suggest a potential natural refuge on the Cay Sal Bank, The Bahamas

Abstract

1. Cultural and economic demands for queen conch, Lobatus gigas (Linnaeus, 1758), have led to the overexploitation of this iconic species throughout its range in the wider Caribbean. Fisheries managers have responded in many ways, from remaining idle to placing moratoriums on conch harvest, yet heavily harvested conch populations have been slow to recover, and descriptions of natural baselines are missing.2. The study describes a population of conch surveyed on the isolated, partially submerged, carbonate platform known as the Cay Sal Bank, The Bahamas, using traditional and interpolation techniques. Counts and shell measurements of conch within six study areas were obtained using 118 timed dive surveys over shallow water habitat (<20 m).3. The density and standing stock of adult conch were calculated using raw estimates, estimates retroactively standardized by distance, and estimates from Geographic Information Systems (GIS) kriging interpolation. All methods result in similar abundance estimates and include one of the highest abundances of conch found for decades in legally fishable waters within the Caribbean. 4. Shell measurements revealed multiple-year cohorts within the nurseries encountered, suggesting consistent recruitment. Lip thickness, a proxy for age, significantly increased with distance to Nassau in unprotected areas within The Bahamas, and Cay Sal Bank contains the second oldest average population observed in legally fishable waters. 5. Media reports show that remote Bahamian banks are increasingly threatened by poaching as fishers deplete accessible stocks. Biophysical models demonstrate potential larval connectivity from Cay Sal Bank to both the Grand and Little Bahamas banks. We suggest protecting Cay Sal Bank as a modern baseline for conservation management and as a larval source located upstream of major Bahamian fishing grounds.

Spatial dependency in abundance of Queen conch, Aliger gigas, in the Caribbean, indicates the importance of surveying deep‐water distributions

“…The depth range of conch is affected by fishing: where adult densities in shallow depths are reduced, the remaining conch are often found at greater depths where they are more difficult to reach by fishermen. Also, the proximity of landing areas negatively impacts size an age of the remaining conch populations (Stoner & Schwarte, 1994;Stoner et al, 2018;Souza & Kough, 2020).…”

Empirical support of predicted larval connectivity patterns demand conservation action for queen conch (Aliger gigas) in The Bahamas

“…Three instances of reproductive activity were recorded in animals with a lip thickness <15 mm out of 55 measured individuals (some animals were not measured or disturbed). The mean lip thickness of animals actively mating or laying eggs was 27 mm and the average shell length was 190 mm; however, the majority of the reproductive activity was within the ECLSP, where lip thickness was high, and these values do not reflect a typical conch population in The Bahamas (Souza Jr. & Kough, 2020) nor elsewhere.…”

Anthropause shows differential influence of tourism and a no‐take reserve on the abundance and size of two fished species

“…The combination of low rates of fishing (Davis, 2008) and a high visitor presence, resulting in some of the most valuable reef habitat in The Bahamas (Spalding et al, 2017), should make the Exumas an optimal area in which to detect tourist impacts, which were hypothesized to be negative for both species and to be shown by increased species abundances in 2020. There is little evidence of recent illegal commercial harvesting in the Exumas, but poaching by sportfishing tourists does occur (Souza & Kough, 2020). Local hotel bookings, Ministry of Tourism arrivals and monthly moorings occupancy data within an MPA demonstrate that tourist visitation effectively stopped during government closures and show that, as hypothesized, the spring through the autumn of 2020 was indeed an anthropause in The Bahamas as hypothesized (Figure 3).…”