Fish heads, fish heads

Post date: Jul 18, 2013 6:10:04 PM

Now that we're back at Clemson, the next (indoor) chapter of the project has begun. Last week, we started sorting through the diet samples regurgitated by the pelicans we captured. Some contained recognizable fish, while others were too digested to identify. To process these, we'll have to dissolve the fish tissue, collect the bones, and pick out otoliths (inner ear bones) that can help us identify fish species and even determine the size of the individual fish. For the less-digested samples, however, processing was much easier: we thawed the frozen mass of fish, separated out individual specimens, and weighed, measured, and photographed each one.

Thawing, half-digested fish... I won't try to describe the smell

Since heads are digested first, only tails remained for many of our specimens

Some fish are in better shape than others...

Samples contained anywhere from one to 100 or more individual fish, ranging in size from a few centimeters to over 40 cm (more than a foot).

One diet sample from Florida contained over 80 Silversides (Menidia sp.)

Our longest fish: an Atlantic Cutlassfish (Trichiurus lepturus)

In most cases, the fish were well-preserved enough for us to identify them to species based on physical characteristics. We may even be able to use some of the best samples to test nutrient composition and caloric density to see how different species might contribute differently to the energy needs of a pelican. In the meantime, it was interesting to begin comparing the diets of pelicans in our different study areas and seeing some unexpected diversity.

Most samples from Louisiana were Gulf Menhaden (Brevoortia patronus), a species fished primarily for its oil

On the other hand, most samples from Texas contained Pinfish (Lagodon rhamboides), a species of bream

This catfish is a Gafftopsail (Bagre marinus) characterized by its venomous spines.

We even found a squid! Species is still unknown.

We still have a lot of work to do identifying and analyzing our fish, but it's a fun (although smelly) process. More to come!