Effects of the octopus fishery on the American horseshoe crab population in the Ría Lagartos Biosphere Reserve, Mexico

Abstract

The American horseshoe crab, Limulus polyphemus, has been reported to be illegally caught for use as Octopus spp. bait in some localities of the Yucatán Peninsula, Mexico. To learn if the octopus fishery could be negatively influencing the limulus populations in the area, L. polyphemus individuals were sampled twice a year, before and after the annual octopus fishing season, over 4 consecutive years (2015)(2016)(2017)(2018) in Río Lagartos and San Felipe, both in the Ría Lagartos Biosphere Reserve (RLBR), Yucatán. Quadrants were drawn perpendicular to the mangrove edge, physicochemical parameters in the water (depth, temperature, dissolved oxygen, pH, salinity, and electrical conductivity) were determined, and granulometry of marine sediments was measured (Folk technique). The number of live specimens, number of females, and average length were recorded. No significant differences were found for the physicochemical properties of water or the recorded sedimentology (P > 0.05). Samplings revealed a low number of organisms per site: 22 in Río Lagartos and 24 in San Felipe, both from data before the start of the 2017 octopus fishing season. In the samplings after the start of the 2018 octopus fishing season, only 2 organisms were observed in Río Lagartos and none in San Felipe. The results showed a significant decrease in the number of live L. polyphemus specimens after the beginning of the octopus fishing season and a decrease in the average length of organisms, suggesting a negative effect of mollusk fishing activities on the horseshoe crab populations. More studies are required that integrate other physicochemical, biological, and socioeconomic factors to elucidate the potential threat of this fishery on L. polyphemus populations in the RLBR.

Assessment of recovery potential for the American horseshoe crab (Limulus polyphemus): An application of the IUCN green status process

“…México prohibits harvest owing to the endangered species status. However, poaching of adult horseshoe crabs as bait for octopus ( Octopus maya ) in Campeche, Yucatán and Quintana Roo threatens the populations when other commercial bait species – swamp ghost crab ( Ucides cordatus ), blue land crab ( Cardisoma guanhumi ), longnose spider crab ( Libinia dubia ) and Atlantic blue crab ( Callinectes sapidus ) – are scarce or become expensive (Sandoval‐Gío et al, 2020).…”

“…Legal status as an endangered species in México protects horseshoe crabs throughout the Yucatán Peninsula. However, lack of law enforcement results in horseshoe crabs being subject to illegal harvest for octopus bait (Sandoval‐Gío et al, 2020). In addition, Laguna de Términos (the southernmost site of the species’ range) has been subject to diverse pressures over the past 50+ years, including coastal development, sewage discharge, oil industry pollution, poaching for octopus bait and SLR (Herrera‐Silveira et al, 2019).…”

“…• Harvest: A significant percentage of up to 1500 small-scale fishers in Campeche illegally use poached adult horseshoe crabs as bait for octopus, especially when commercial bait species (Ucides cordatus, Cardisoma guanhumi, Libinia dubia, Callinectes sapidus) are scarce or become expensive. Horseshoe crabs are harvested while spawning, because their reproductive season coincides with the octopus fishing season (Sandoval-Gío et al, 2020). Given the relatively low local abundances of horseshoe crabs and the fact that all fishermen concentrate on octopus during the season, this harvest can be expected to affect at least 50% of the horseshoe crab population and causes or is likely to cause population fluctuations.…”

Genetic Identification of Bait to Support Sustainability of the Octopus Fishery from the State of Yucatan, Mexico

“…Some reports have voiced concern about using the American horseshoe crab ( Limulus polyphemus ) as bait in the octopus fishery in Yucatan because the species has conservation concerns nationally and internationally (Smith et al 2017, Sandoval-Gío et al 2020). It has been documented previously that horseshoe crabs are taken in Yucatan coastal localities and used as bait by large vessels (Smith et al 2017).…”

Critical Habitats: Reproduction and Nesting Beaches of the Horseshoe Crab (Limulus polyphemus) in Champotón, Campeche, México

“…The size of the sand granules with the abundance of the horseshoe crab shows a strong relationship, with higher abundance in beaches with coarse sands, while flattened slopes are associated with lower number of individuals (Figure 1). Icahao and Flamenco show more suitable characteristics for reproduction and nesting and therefore are considered critical habitats subject to protection [7,10] (Figure 2). It is currently known that the horseshoe crab can detect, at a distance, the nature of the sediments for their reproduction (6).…”