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Abstract

DO THE INDIAN RIVER LAGOON WETLAND IMPOUNDMENTS (EASTERN FLORIDA) POSE A THREAT TO THE FIDDLER CRAB (GENUS UCA) POPULATIONS?

Bjorn G. Tunberg
Smithsonian Marine Station at Fort Pierce
Bio

Quantitative sampling of fiddler crabs was performed in June-July between 1992 and 1994 along transects at three St. Lucie County mosquito impoundments, Florida, running from the Indian River Lagoon (IRL) shore and across the impoundment perimeter dikes, and in one impoundment across the perimeter ditch. A total of 929 specimens and four species were found; Uca pugilator, Uca rapax, Uca speciosa, and Uca thayeri. There was no significant correlation between the number of Uca burrows and the number of crabs found in each sample. Differences were recorded in abundance and distributional patterns between impoundments, but no correlation was recorded between substrate organic content and species distributional patterns. The male/female ratio was close to one for all species, except for U. thayeri, where the males dominated (ratio: 1.8). High water temperatures occurred in the summer, potentially lethal to fiddler crabs. U. pugilator and U. rapax are probably not seriously impacted by the impoundment flooding, as they are highly motile and not very site specific. U. speciosa and U. thayeri are more stationary and dependent on the very soft, wet substrate along the perimeter ditch banks, and may therefore be impacted during periods of flooding.