What does a crustacean biologist do? Learn about FWRI's current and
past stone crab research.
The Crustacean Fisheries group at the Florida Fish and Wildlife
Conservation Commission's (FWC) Fish and Wildlife Research
Institute (FWRI) studies two species of stone crabs:
the Florida stone crab (Menippe mercenaria) and the Gulf
stone crab (Menippe adina). The two stone crab species are
closely related, readily interbreed (creating
hybrid crabs), and are not managed as separate species by the
Florida Stone Crab and Gulf Stone Crab
A stone crab trapping study that began in 1988 in the Tampa Bay
area continues today. We also began trapping studies in
southwest Florida in January of 2005 and in the Big
Bend region in January of 2006 which follow the same
protocols. Every two weeks, FWRI scientists pull trap
lines of five traps each. In Tampa Bay we sample near the
mouth of the Bay with four trap lines; in SW Florida we sample
in three areas of the Keys and near the Everglades
with four trap lines in each area; in the Big Bend region
we sample in Homassassa, Cedar Key, Steinhatchee, and St.
Marks with four trap lines in each area.
The standard, plastic stone crab traps are baited with fish
(usually mullet). Crabs captured in the traps are measured and
color-coded to determine the species. The article, A Proposed
Evolutionary History of Stone Crabs, provides more information
about the color-coding that determines the species. The crabs are
also checked for injuries and regeneration,
reproductive state, and molt condition.
Bottom-water temperature, salinity, dissolved
oxygen and pH are recorded, as is bycatch (any animals in the
trap besides stone crabs) and trap condition (i.e., open or closed,
intact wooden slat, broken trap). In all, biologists may record up
to 68 variables for each crab.
Every four weeks researchers clean the traps by scraping off
accumulated organisms, such as barnacles and algae. This fouling community is the
perfect habitat for juvenile stone crabs, so
scientists take this opportunity to count the number of juveniles
per trap and measure each juvenile's carapace width (widest part of
the shell); these data provide information on the recruitment
(growth to legal size) of young stone crabs into the bay. Data
collected during these projects are providing new insights into the
population biology of the stone crab and the stone crab fishery.
Information such as changes in catch rates, shifts in sex ratios, and
correlations between juvenile and adult abundances may help FWC
better manage these species in the future.
Past stone crab research conducted by the Crustacean Fisheries
group included the following studies:
- A trapping study in northwest Florida
- Genetic comparisons of the two species and their hybrids
- An analysis of the temperature and salinity tolerances of larvae and juveniles
- A study of the effect of water-borne diesel fuel on
- A comparison of the biology of hybrid stone crabs to the two