A BUTTERFLY AMONG OYSTERS
I grow oysters for a living, and came across this little fish while tending my oysters in the beginning of October. The fish was about the size of a dime and looked very tropical, which is odd, especially during fall on the Cape. Any help identifying the fish would be greatly appreciated. Jeff Orcutt Orleans, Cape Cod, Massachusetts
Your fish is a very early juvenile spotfin butterflyfish, Chaetodon ocellatus. Two species of butterflyfishes commonly drift north in the Gulf Stream from more-tropical waters while in a specialized tholichthys pelagic-juvenile stage. After transforming to the stage exhibited by your specimen, many of these migrate into estuaries along the mid-Atlantic states and settle into habitats that mimic reefs. Blocks of peat sloughing off marsh surfaces serve as one of these reef habitats. These young fish use such habitats as nurseries, growing through the summer to lengths of 2½ inches or more. However, these faux nurseries prove to be sinks; with temperatures cooling in fall and winter, the small fish succumb when temperatures reach below 54 degrees Fahrenheit. Some other southern juveniles, however, use mid-Atlantic estuaries as nurseries in which to grow and successfully migrate back to more-tropical waters before winter. Jacks in the genus Caranx are an example.
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