AES has officially begun! The first day of the World Congress of Herpetology (referred to as “AES” from here on out, because that’s the part I care about, no disrespect to the scalies) kicked off with free breakfast, which was appropriately mobbed by the attendees. I caught up with some of the shark people, checked out a nearby sushi place that had some of the best miso soup I’ve ever had, and then the shark talks began. Below the jump are my personal highlights of the day, and is by no means a comprehensive list. For more AES coverage by me and a small army of other shark nerds, check out the Twitter hashtag #AES2012.
Today’s offerings were two concurrent sessions, one on shark physiology and one on ecology. Despite my ecology leanings, I did actually spend about half my time in the physiology room, and there was some interesting stuff going on in there.
Ryan Ford talked about the timing of the reproductive cycle in blacknose sharks, a species I can expect to run into during my survey (if I ever catch any sharks). Blacknoses are weird for a lot of reasons, one of which is the fact that females reproduce every year in the Gulf of Mexico, but every other year in the Atlantic. Well, it gets stranger. Ryan found that female blacknose sharks in the Atlantic can be either annual (pupping each year) or biennial (every other year) and that individuals of either reproductive style can show up in the same exact areas, which suggests something other than habitat is determining which reproductive mode they use.
Brenda Anderson talked about a non-lethal method for determining the reproductive stage of sharks. Usually this type of research requires killing and dissecting the sharks to take measurements on various internal organs. Your other option is the use radio-isotopes to figure out the levels of reproductive hormones. Or, as Brenda points out, you can use a method called CLIA (Chemiluminescence immunoassay) to take blood from the shark and figure out those hormone levels. Brenda tested this method against the radioisotope method and measurements taken during dissection using bonnethead sharks, and found that CLIA works just as well for figuring out the reproductive timing of those sharks. Next step: test it on other sharks.
Over on the ecology side, a couple speakers discussed some creative ways to get the most out of acoustic telemetry. Steve Kessel listed a few novel methods, including towing a receiver under the boat to pick up nearby sharks. This can help figure out whether sharks are hiding in gaps between receivers in an array, and can also help pick out new spots to put a permanent listening station. He also suggested attaching a couple receivers to fishing gear to figure out if your previously-caught and tagged sharks have learned to avoid your gear. David Jacoby spoke more on the analytical side, with some neat ideas about combining acoustic detections with network analysis. Basically, if you treat your stations as “nodes” in a network model, you can look at things like how often your tagged sharks travel between stations and reconstruct the sharks’ regular patrols.
Shawn Larson gave a great talk (with some great video) on something that was apparently happening beneath our feet while we were at the Seattle Aquarium last year. Apparently sixgill sharks show up regularly under the pier the aquarium sits on. Aquarium researchers have constructed a cage from which they can bait in the sixgills and tag them. From their tracking and ID data they estimated that between 2003-2005 a population of 161 sharks showed up under the pier. Lately these sharks seem to have left, with very few sightings from 2008-2012 (the project was suspended for a few years for pier maintenance). Even cooler, they took punch biopsies on the passing sharks, and found that all the sharks that showed up on the same day were related. This combined with the tracking data suggest that the sixgills in Puget Sound may have been a single reproductive cohort and all left at the same time. Now sightings of small sixgills by divers are on the rise, so a new cohort may be moving in.
Back in the physiology room, Arrianne Leary talked about detections of PAHs (polycyclic aromatic compounds) from the Deepwater Horizon spill in the tissues of sharks and bony fishes from the Gulf of Mexico. These animals were all sampled 1-2 years after the spill, and some of the bony fishes showed PAH levels that matched those in the water only 20 days after the spill started. Of the sharks, only tiger sharks came close to that level, possibly due to scavenging oiled animals. Some of the compounds used to measure PAH concentration acted differently in sharks and bony fish, suggesting that the two groups may metabolize oil-related compounds differently.
Good stuff all around. Check back in tomorrow, and of course follow the hashtag (again, #AES2012 on Twitter) for more week-long shark nerd coverage. And if you’re actually at the conference, feel free to say hello (buying me drinks is also welcome).