Fisheries and aquaculture potential of the Caribbean spider crab Maguimithrax spinosisimus around Eleuthera, The Bahamas

Zeinert, Logan R. (2020) Fisheries and aquaculture potential of the Caribbean spider crab Maguimithrax spinosisimus around Eleuthera, The Bahamas. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Caribbean spider crab Maguimithrax spinosissimus is the largest brachyuran crab in the Caribbean. In this thesis I investigated the population characteristics of M. spinosissimus on the island of Eleuthera, The Bahamas, as well as the potential of this crab to remove biofouling on marine aquaculture pens. In chapter 2 I investigated the size ranges of crabs at patch reefs, a blue hole and an anchialine pond in Eleuthera (January to June, 2018). Males reached larger mean carapace widths than females at all sites. Principal component analysis and hierarchical cluster analyses were used to determine size at maturity; males reached morphological and behavioural maturity at larger carapace widths than females. Haemolymph BRIX levels were used as an indicator of general condition, the levels were relatively high and not dissimilar between sites. The meat yield from male crabs was higher than that of females and comparable to other decapods. In chapter 3, I showed spider crabs exhibited a nocturnal pattern of activity in laboratory tanks. The crabs consumed 3.91 ± 0.35 and 6.97 ± 0.73 % of their bodyweight of algae in 22 - 24°C and 26 - 28°C water, respectively, and although the species is primarily herbivorous they also readily consumed whole fish. Spider crabs were placed on a heavily fouled, offshore aquaculture cage (SeaStation 3000) in confined mesh enclosures to determine if they could be used to remove biofouling organisms. They effectively removed 40 and 90 % of fouling organisms after two and four weeks, respectively, while showing no discriminatory feeding preferences. The crabs were more effective at removing fouling than manual diver scrubbing. The survival rates of crabs inside the aquaculture cage varied between 66.6% and 73.9% during 3 to 6 month trials. The data gathered for this species could be used to establish management plans for an artisanal fishery in the Bahamian archipelago, it also demonstrated the potential of the crab as an effective, environmentally friendly biofouling removing alternative for sustainable aquaculture.

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