by Brittany Hall and Gabriel Ramos-Tafur
Scientists in the gut lab process stomachs from fish of all sizes, collected both inshore and offshore, in order to compile comprehensive diet information that is used in various models. Digestion is the biggest obstacle when processing these guts. Our main goal is to identify everything to the lowest taxonomic level possible (this includes amphipods, shrimps, crabs, mysids, and the list goes on and on), and generally we are looking for identifiable parts that are more resistant to digestion. Crabs and shrimps have external hard parts that are a little more resistant to digestion, but fish have fewer of these external parts. Most of the time, things like color, fin-ray counts, pores, and scales are needed to work your way through an identification key, but when a fish is a prey item, these clues are often missing. One of the last parts of a fish to disappear during digestion is its jaws, and we often use jaws to identify fish in stomach contents. Careful study has revealed that jaws are like fingerprints – very distinct teeth and bones that allow us to identify many prey species to family and even species.
Because there are currently no identification keys for the jaws of fish species found Gulf of Mexico and Tampa Bay, scientists have been diligently developing a reference key to be used to identify digested fish prey. This task involves removing the tissues from the jaw bones of fresh specimens, staining the jaws, taking pictures, and writing descriptions of each intricate bone. Although tedious, much headway has been made, and results of this one of a kind project were presented at the upcoming national meeting of the American Fisheries Society in August 2015!