One of the more interesting parts of being a Sea Grant Agent is when people send me their ‘Do you know what this is?’ mystery finds. A recent one came from my friend Kelly. Kelly’s husband Jimmy, a commercial blue crabber, found it in his trap up in the Peace River. Now it’s no surprise that strange creatures lurk amongst us, but every so often one pops up that is just absolutely ‘made for movies’ odd looking, and the photo Kelly sent me was right up there in that category.
When I looked at the picture I immediately thought some kind of prawn (large shrimp) but not being a freshwater guru I really wasn’t certain so I reached out to a few scientist friends. Between them I learned there are native freshwater shrimp, got a couple of papers to help me key Jimmy’s critter out, and got a contact at the Florida Museum of Natural History who would be able to confirm the identification.
Jimmy’s critter turned out to be a big claw river shrimp Macrobrachium carcinus. Big claw river shrimp is the largest of six native freshwater shrimp in Florida and one of the largest found in the United States. This shrimp occurs from Florida to Brazil. I tried to find out where in Florida they are known to occur but the only distribution papers I found were from the 1940s and 50s. Those papers said they occurred in St. Augustine, Silver Springs, Miami, and Big Pine Key. Papers that I found from the 1960s and 70s mostly focused on the aquaculture potential of freshwater prawns, including this species. In fact a 1960 paper I found from the West Indies looked at two freshwater shrimp including this one for aquaculture purposes and indicated they had good economic potential and that “tails were being sold at $1.45 per pound in Tampa, Florida. One restaurant in the same city now offers six small tails as an entre at a price of $1.50 for the complete meal”. It wasn’t clear which of the two shrimp being evaluated they were referring to though.
Some more interesting tidbits about the big claw river shrimp include:
• Adult males can reach 12 inches (300mm) from rostrum to telson (tail). Adult females typically range from 5-8 inches.
• Most species of Macrobrachium have similar life cycles. Adults live primarily in rivers, lakes and canals; whereas larvae require brackish water (mixture of salt and freshwater).
• An average sized female big claw river shrimp carries 120,000-140,000 eggs.
• Development of fertilized eggs takes 16-28 days during which time the eggs of big claw river shrimp change from bright orange to dull greenish gray.
• Larvae usually hatch at night. Big claw river shrimp larvae are free swimming (not all freshwater shrimp are). After metamorphous to juveniles Macrobrachium settle to the bottom and begin migrating to freshwater. Young shrimp reach sexual maturity by their seventh month.
• Adults are nocturnal, aggressive and omnivorous (eat plants and animals).
Back to Jimmy’s critter…after consulting with the Museum of Natural History they indicated they did not have a specimen in their reference library and would love to give Jimmy’s a home. So our Peace River big claw river shrimp was pickled, packed and sent to Gainesville for permanent display in the museum.
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