AES 2012: Day 2 Highlights

What a busy day.  I’ve only got a little bit of time to get this up before I have to head over to the poster session, and I saw a lot of very good talks today.  Keep following #AES2012 on Twitter to keep up with stuff as it’s happening, and keep checking back here for daily recaps.  Here’s what piqued my interest today.

The AES Plenary session happened this morning, with new president Lara Ferry talking about the stereotype of shark researchers (we’re apparently not all Shark Wranglers) and how our awesome study animals can both help and hurt us being taken seriously as scientists.  Fortunately, there was very little doom and gloom and most of the talk focused on how to rope people in with sharks then hit them with science.

Austin Gallagher had one of the more thought-provoking talks I’ve seen so far (and it’s only day 2) with his discussion of the “evolutionary trap” that seems to have snared hammerheads.  A lot of the ways they’ve adapted and become specialized in their environment may also contribute to their high mortality in fishing gear.  In particular, they have proportionately smaller mouths than most sharks, and as a result can’t breathe as well when snared on a line or net.

Melissa Giresi (who is also tweeting the conference) talked about the perils of identifying various smoothhound (genus Mustelus) species in the Gulf of Mexico.  Current guides aren’t good enough to tell them apart morphologically, so many sharks identified as smooth dogfish are actually one of two other species found in the Gulf.  Fortunately Melissa was able to use genetics to tell them apart, and is now helping develop new guides for those of us without sequencing equipment on hand.

Bianca Prohaska gave a presentation on the use of steroid hormones from muscle tissue as a quick, easy, non-lethal way to observe reproductive timing in spiny dogfish and sharpnose sharks.  I’m digging the emphasis on non-lethal methods at this meeting.

Andrea Kroetz brought up some interesting points about human effects on the environment with her talk on how Hurricane Katrina and the Deepwater Horizon spill affected bonnethead movement around Dauphin Island in Alabama.  The hurricane cut an inlet that the sharks were happy to use, until humans built a wall across it to keep the oil spill out.  As a result, the sharks went elsewhere.  Will they return if/when the wall comes down?

A few talks focused on predator/prey theory and how it relates to nursery habitat, and these were practically required viewing for me.  Kristine Stump simulated predation risk by releasing a large lemon shark into a pen full of juveniles and PVC pipes meant to simulate mangrove roots.  The juveniles hid in the “roots” in the presence of the larger shark, but were a little braver when they were in a group.  Phil Matich used stable isotopes to identify dietary shifts in juvenile bull sharks in response to the mass exodus of fish from the Everglades during the dry season.  The shift from marine to marsh fish came later than expected, and hypotheses for this included a diet of estuarine fish or the sharks targeting the larger marsh fish that followed the initial pulse of smaller fishes.  Mike McCallister attempted to use prey abundance to predict sharpnose shark abundance, and it didn’t really work out.  However, in the case of small sharks predation risk may actually be a bigger factor than prey abundance, and prey availability may actually be more important for larger sharks that don’t have to worry about predators.

Matt Kolman looked at the bite mechanics of our friend the cownose ray, and found that it can crush like no other elasmobranch.  It can chomp hard enough by the time it’s one year old to smash all size classes of Coquina clams, and that’s just the first shellfish he’ll be testing.

Finally, James Sulikowski gave a doozy of a spiny dogfish talk, summarizing most of the findings his lab has come up with so far regarding the New England population.  First, they might not migrate out of New England very much.  Second, they may have a gestation period of 18 months instead of the traditionally-accepted 24.  And third, they seem to be breeding and eating off of Southern New England.  Unfortunately his grad student Amy Carlson gave a talk that wasn’t in the schedule and I missed it to write this very recap.  Fortunately, the twitterers were on it and it looks like the southern population (my friends off the coast of North Carolina) may not be that well-connected to the New England dags.  All this is still preliminary and really we still have very little idea of what these sharks are actually doing.  That’s why they’re awesome.

Now I’m off to the poster session and whatever awaits on the other side.  Stay tuned for more dispatches from the front lines of shark research.