Conch Fritters Through Time: Human Predation and Population Demographics of Lobatus Gigas on San Salvador Island, the Bahamas

Abstract

Lobatus gigas, the queen conch, is a central component of Caribbean cuisine but over-fishing of juveniles has threatened the stability of wild populations. Strombid gastropods, upon reaching sexual maturity, cease growing along the shell length axis and continue growing in width via a flared and thickened shell lip. This morphology serves as a useful indicator of an individual's sexual maturity. Here we examine temporal trends in population demographics, size, and morphology of harvested L. gigas individuals over the last ∼1 ky from San Salvador Island, the Bahamas to quantify the dynamics of human-induced stress on the local queen conch fishery. We collected 284 human-harvested individuals from shell middens at seven localities, measured seven morphological variables, and classified the specimens as either adult or juvenile. We randomly selected 64 of these shells for rapid AMS radiocarbon dating in order to establish three geochronological bins: Lucayan (Pre-European invasion, 1492 CE), Modern (∼102 y), and Global (∼101 y). The proportion of juveniles harvested increased significantly from 47% (Lucayan) to 61% (Modern) to 68% (Global) suggesting increasing pressure on the fishery through time. Patterns in body size and morphology diverge between adults and juveniles and are likely the result of an increase in the proportion of harvested juveniles, the selection of smaller juveniles through time, and possibly changes in fishing methods. This size selective predation did not result in the suppression of adult body size as found in other studies. Geohistorical data, such as these, are vital for providing long term ecological context for addressing anthropogenic ecological degradation and are central to the conservation paleobiology approach.

Impact of the the COVID-19 pandemic on a queen conch (Aliger gigas) fishery in The Bahamas

“…Standard morphometric measurements were recorded for all shells that were collected, including total shell length (siphonal length) and shell width as defined by Martin-Mora, James & Stoner (1995). Shells that had a well-defined flared lip (i.e., legal-sized in The Bahamas), aperture length, aperture width and lip thickness were also measured as set out by Ruga, Meyer & Huntley (2019). These measurements were taken using large vernier callipers to the nearest mm, whilst lip thickness was measured using smaller dial callipers to the nearest 0.1 mm as described by Appeldoorn (1988).…”

“…Shells that had a well-defined flared lip ( i.e. , legal-sized in The Bahamas), aperture length, aperture width and lip thickness were also measured as set out by Ruga, Meyer & Huntley (2019) . These measurements were taken using large vernier callipers to the nearest mm, whilst lip thickness was measured using smaller dial callipers to the nearest 0.1 mm as described by Appeldoorn (1988) .…”

Marine conservation palaeobiology: What does the late Quaternary fossil record tell us about modern-day extinctions and biodiversity threats?

“…Life-history changes can be inferred using geohistorical approaches by surveying size frequency distributions of fossil populations and by examining growth rates and longevity, which can be assessed using sclerochronological approaches (e.g., Goodwin et al, 2001;Rowell et al, 2008;Lockwood and Mann, 2019). In addition, the fossil and archaeological records provide numerous examples of studies documenting major shifts in functional traits that could be linked to human activities, especially selective harvesting (e.g., Limburg et al, 2008;O'Dea et al, 2014;Rick et al, 2016;Ruga et al, 2019;Assumpção et al, 2022;reviewed by Sullivan et al, 2017). Whereas in many cases human activities resulted in shorter lifespans and slower growth rates of marine organisms, this was not always the case.…”

Direct Economic Inputs from Internationally Funded Science Projects to the Abaco Islands, The Bahamas

“…At least partially because of the fundamental importance of the environment to the national economy, scientific research flourishes in the country. This is highlighted by recent studies with direct economic relevance, including on recreational fisheries (Adams et al 2019, Ruga et al 2019, coral reefs (Rogers et al 2014), fishery species (Harborne et al 2008, Sherman et al 2018, Arkema et al 2019, marine protected areas (Wielgus et al 2008), and mangroves (Micheletti et al 2016), as well as the study of events affecting natural resources, such as hurricanes (Wallace et al 2019, Winkler et al 2020, Wallace et al 2021.…”