Exploring the potential use of escape gaps in the Florida spiny lobster, Panulirus argus, fishery

The spiny lobster fishery in Florida uses live, sublegal-size lobsters as bait in the approximately 450,000 traps currently permitted in the fishery. Live baits increase the catch of traps, yet confinement in traps compromises lobster health and causes mortality. We conducted a field experiment to test the suitability of traps fitted with escape gaps to address a priority need for reducing catch and mortality of sublegal-size lobsters and other species in Florida’s spiny lobster trap fishery. We then modeled the potential effect of escape gaps on the Florida commercial spiny lobster trap fishery (via a Monte Carlo simulation technique) to identify the effect on fishery harvest. We measured catch rates and mortality of lobsters in traps with or without a 54 mm escape gap and baited with either a live sublegal-size lobster, a live legal-size lobster, or left unbaited. The relationship between catch in traps fitted with escape gaps vs. catch in control traps determined from the field experiment was applied to commercial fishery landings data from 2010 to 2018 and used to model changes in harvest as result of implementing escape gaps and baiting with a legal-size lobster. We found that traps with escape gaps nearly eliminated catch of sublegal-size lobsters in traps, which would lower mortality caused by such confinement and potentially allow hundreds of thousands of lobsters to remain in the population. Alternatively, replacing live bait lobsters every two weeks reduced bait mortality by half in our field experiment; thus, mortality of sublegal-size lobsters used as bait in the fishery could be reduced through frequent release of bait lobsters. Escape gaps also reduced fish bycatch, including some in the snapper-grouper management complex. Traps with escape gaps and baited with legal-size lobsters caught ~27% ± 16% fewer legal-size lobsters than control lobster traps baited with a sublegal-size lobster. However, these traps caught as many legal-size lobsters as control lobster traps baited with sublegal-size lobsters when lobster abundance was high, demonstrating that self-baiting of traps is density dependent. Although traps with escape gaps caught fewer legal-size lobsters per trap, fishery modeling indicated that increased survival of sublegal-size lobsters could increase landings by the second to fourth year after implementation of escape gaps, depending on which model assumptions are used to predict landings.