UF study: When lobsters and crabs face off over real estate, crabs dominate

GAINESVILLE, Fla. — As dawn approaches, spiny lobsters in the Florida Keys are in search of shelter — a hole, a crevice, any place where they can safely spend the daylight hours. If shelter is scarce, lobsters will often congregate in the same hiding place, and they don’t mind the occasional spider crab as a roommate.

But if a shelter is already occupied by a stone crab and its fierce pincers, the lobster will beat a hasty retreat, according to a recent study by researchers with the University of Florida Institute of Food and Agricultural Sciences.

The study’s findings show that spiny lobsters — technically called Caribbean spiny lobsters — consistently avoid shelters where stone crabs are present, a behavior that’s been noted anecdotally but never scientifically documented, said lead researcher Don Behringer, associate professor of fisheries and aquatic sciences.

These findings have significance for Florida’s multi-million dollar spiny lobster industry. Lobsters seek hiding places to avoid predators, so competition with stone crabs can impact lobster survival rates, according to the study.

“Our findings definitely have implications for the lobster fishery. Good years for stone crab reproduction that lead to more juvenile stone crabs could suppress the abundance or survival of juvenile spiny lobsters where their habitat needs overlap,” Behringer explained. “Our data suggest that this could happen, but would require further research to confirm.”

While spiny lobsters often congregate with each other, lack claws and tend to be non-aggressive, stone crabs are the opposite. “Stone crabs are solitary and have massive claws that they can use for antagonistic or aggressive behaviors,” Behringer said, which explains why lobsters shy away from stone crab encounters.

Field experiments in the Florida Keys showed that the more stone crabs in an area, the fewer juvenile spiny lobsters, and vice versa. Lab experiments likewise demonstrated that lobsters prefer shelters without stone crabs and even keep clear of shelters that smelled like stone crabs.

“Chemosensory cues impact many lobster behaviors, such as avoiding threats, finding shelters, mating, finding new habitat and foraging, among others,” Behringer explained.

In fact, lobsters avoided stone crab-occupied shelters like death — literally. Lobsters bypassed shelters that smelled like diseased lobsters and those that smelled like stone crabs at similar rates.

Florida’s spiny lobsters attract thousands of fishing enthusiasts each year. This year, the recreational season opens with a two-day sport season July 26 and 27, with commercial fishing starting Aug. 6 and continuing through March.

In 2015, Florida’s commercial lobster harvest was valued at $47 million, according to the Florida Department of Agriculture and Consumer Services website.

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By: Samantha Grenrock, 352-294-3307, grenrosa@ufl.edu

The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.

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