Last week (January 22nd-26th) a couple of my labmates and I headed down to Charleston, South Carolina for the spring meeting of the American Fisheries Society’s Southern Division (referred to from here on in as SDAFS). This meeting gets researchers from the Southeast and Gulf states to talk fisheries science, and usually provides a good cross-section of topics. Charleston is also an incredibly nice city and a great place to put on a conference. Here’s what piqued my interest at this meeting…
For the sake of simplicity, I’m going to group the talks, posters, and workshops I found interesting enough to share into three categories by subject: Telemetry, Sharks, and General Fisheries. This recap shamelessly reflects my own biases, so if you were at the meeting and gave or saw a presentation on, say, freshwater fisheries, feel free to call it out in the comments. Also, SDAFS records most of the talks in podcast form (for example, here are all the recorded talks from last year’s meeting in Nashville), and I’ll make sure to spread the word when they put them up (there are quite a few talks I wanted to see and missed, especially in the sturgeon and telemetry sections). Until then, I suppose you’ll have to make do with these text descriptions from me.
The meeting kicked off with a full-day workshop addressing issues with running acoustic arrays, in particular problems with data ownership and collaboration. Researchers are running acoustic arrays all up and down the coast, with a handful of groups (such as the Atlantic Cooperative Telemetry network) compiling the data to make sure everyone knows when their tags show up on an array run by someone else. Both horror and triumphant stories were shared, as well as hypothetical scenarios involving who gets to publish on what data. The goal of this workshop was to work up a set of ground rules for these situations to publish as an official AFS policy at the parent society meeting in Quebec City. If you’ve been interested in doing some acoustic tagging, you probably should have been at this meeting, but you should definitely go to that one. While the rules haven’t been finalized, the gist of the discussion was to communicate openly whenever possible, and that the original tagger has priority whenever analysis or publishing of data on their fish are involved.
Telemetry doesn’t necessarily mean “acoustic telemetry,” and encompasses any research involving tagging and tracking of animals. This year’s SDAFS included an entire day and a half symposium dedicated to telemetry methods. Sturgeon were also a hot topic, and many of the talks involving these species also involved tagging. Will Smith (not the Fresh Prince) summarized an enormous tagging study encompassing the entire Atlantic coast and over 21,000 tagged fish, which fed data in to a mutlistate model to estimate sturgeon bycatch by area. Bycatch seems to peak around North Carolina and really fall off farther south, though there’s still a lot of uncertainty. Dewayne Fox, who normally works with Atlantic sturgeon, presented on a project of his looking at a second, cryptic spawning migration within the population of Gulf sturgeon. Using acoustically-tagged fish, Fox found that as much as 25 % of the Gulf sturgeon population show a delayed spawning migration, spawning in the fall instead of in the spring with the rest of the sturgeon.
Sturgeon were not the only fish being tagged, and it’s always cool to see how tagging methods are used on fish other than sharks. The snapper/grouper fishery in the Gulf of Mexico seems to be a big focus of acoustic tagging effort, and because these fish tend to hang out around the same reefs much of the time it’s possible to get really fine-scale data on their movements. Laura Jay Williams and Jenny Herbig acoustically tagged red snapper and grey triggerfish, respectively, to get an idea of their movements to and from artificial reefs off of Alabama, as well as estimates of their natural and fishing mortality. Overall, triggerfish seem to fare better in both post-release survival and fishing mortality than red snapper, and triggerfish seem to eventually come back to the same reefs after leaving detection range. Judd Curtis showed how the use of sensor tag data can show how long a fish survives after tagging and can reveal abnormal behavior immediately after release. For red snapper, it can take up to 10 days for normal behavior to set in after tagging. Looking at the arrays themselves, Joy Young showed how network analysis can identify “communities” of receivers based on the individual fish that are detected on them. On the non-acoustic side of things, Tim Ellis conducted a tagging study on North Carolina spotted seatrout and found that natural mortality in this species can vary wildly based on the severity of the winter. Since North Carolina sits at the northern limit of the range of this species, their populations can be significantly affected by cold snaps. Eric Johnson tagged female blue crabs in the Potomac River, and was able to trace their movements down the river to spawn. This helped inform a fishery management decision on time/area closures along the river to protect the spawning migration.
My own talk was a mixture of telemetry and sharks and I’ll have more detail on that coming up, but in summary I was able to follow juvenile sandbar sharks as they moved from their tagging sites off of Cape Hatteras into the Chesapeake Bay. This is largely thanks to the kind of collaboration among researchers with acoustic arrays that was discussed during the telemetry workshop. It was good to be able to present these results and feedback was great. So far, the Winter of the Shark is off to a good start.
The Gelsleichter lab turned out in force to dominate the remainder of the elasmobranch talks. Jim Gelsleichter himself presented evidence for hermaphrodism in smalltooth sawfish, a species that can be difficult to get data from since it’s listed on the Endangered Species Act. Even among the handful of sawfish he was legally allowed to tag, supplemented by necropsies on stranded or bycaught individuals, Gelsleichter was able to time the sawfish reproductive cycle, and found an unusually high number of functional males that also had ovaries. Melissa Gonzales de Avecedo and Amanda Brown performed similar research on bonnethead and finetooth sharks, respectively. Currently the life histories of these species have only been thoroughly researched in the Gulf of Mexico. Melissa found that bonnetheads in the Atlantic have a longer gestation period and lower number of pups than those found in the Gulf, which means management decisions based on Gulf data may overestimate the population of bonnetheads in the Atlantic. Amanda found that based on size at maturity and reproductive output, finetooth sharks in the Atlantic are probably better classified as a Large Coastal Shark than a Small Coastal Shark for fishery management purposes. Mike McCallister discovered a nursery ground for scalloped hammerheads in the Tolomato River, Florida, where juvenile hammerheads outnumber even the ubiquitous Atlantic sharpnose shark. Use of this nursery area by hammerheads seems to be salinity-dependent, with fewer sharks present in rainy years that flushed freshwater into the system. Over in the poster session, Sarah Ramsden acoustically-tracked Atlantic stingrays in tidal rivers near Savannah, Georgia, and found that these batoids can spend a long time far up in the “skinny water,” in the upper parts of the estuary.
There were a number of interesting presentations that didn’t directly involve telemetry or sharks. First off, I have to give shouts out to my ECU labmates, Dan Zurlo and Evan Knight, who are working on striped bass migration and spawning within estuaries other than the famous Roanoke River. Dan found evidence within otolith microchemistry for possible mixing between striped bass in Tar-Pamlico River with those from the Roanoke population. Evan found age at reproductive maturity to be significantly lower in the Tar and Neuse Rivers than in the Roanoke, which is a sign that these rivers may be a more stressed environment (fishes tend to reproduce at an earlier age in more stressful environments). My labmate Coley Hughes was also present talking about striped bass, but I missed her talk entirely (sorry Coley!).
Among the other fish talks, Paul Ruderhausen (in one of his three talks at this conference!) showed the results from a study on a modified gillnet design intended to reduce bycatch of “round” fish like red drum and encourage catches of flounder. Essentially, the fisherman he was working with cut the mesh in his gillnet to make larger, more rectangular mesh than the square-shaped mesh typically found in gillnets. This reduced both bycatch of non-target species but also decreased bycatch of undersized flounder. Alison Deary was another overachiever with two talks, one on tuna habitat preferences and another on the diets of scianid fishes (spots, croakers, drums) during their early life stages. Tuna appear to follow a boundary of low oxygen in the water column, rarely diving below it into the low-oxygen zone. In the scianids, both pelagic and benthic fishes seem to feed on benthic prey as their jaws develop, and then benthic fishes expand their diet diversity into adulthood while pelagic species become more specialized feeders on pelagic prey. Mark Stratton looked at large-scale species assemblages and found a break point between marine communities at Cape Hatteras in the spring, which was already pretty well-known. What was less-known is that in the fall the coldwater community appears to extend south of Cape Hatteras to Cape Lookout.
Overall, a great meeting and I’m sure I missed plenty of presentations that were worth talking about. I know some of the good folks at The Fisheries Blog were also there, so they may be able to fill in the huge gaps I left.