Toxicity and persistence of sodium fluoroacetate (1080) in the land crab (Gecarcinus lagostoma) on Ascension Island

Abstract

An eradication program for introduced feral cats, using sodium fluoroacetate (1080) bait, was planned on Ascension Island to help breeding seabird populations to recover. We investigated the likelihood of mortality and the occurrence of residual 1080 in the ‘non-target’ Ascension land crab (Gecarcinus lagostoma) through simulating ‘realistic’ and ‘worst case’ exposure to 1080 bait. Crabs feeding on 1080 baits ingested an estimated maximum of 9–56 mg 1080 (kg bodyweight)–1 and although two of 32 treatment crabs died, this mortality was not attributed to 1080 poisoning but to other, unknown, causes. Our results suggest that G. lagostoma has relatively low susceptibility to acute toxic effects of 1080. Most residual 1080 was eliminated rapidly from crab tissue, with concentrations of 0.006–0.070 mg (kg bodyweight)–1 measured in crab claw/leg tissue 9–11 days after exposure. Concentrations of 0.200 and 0.650 mg (kg bodyweight)–1 were measured in the claw tissue of two crabs that died from other causes on the third day of exposure to 1080, indicating potential for secondary exposure of sensitive scavengers or predators of 1080-exposed crabs. We recommend a moratorium on human consumption of all crabmeat for a withholding period following the eradication program. The withdrawal period should be defined by further research on the longevity of 1080 in crab tissues, and be confirmed by monitoring of residues in crabs after baiting.