My field work officially started in June, collecting my first water samples of the season. I'll just get this out of the way now and say that I collected water samples from June-October and unless something interesting happened with regards to those trips (which nothing did that hasn't been mentioned in previous posts) I won't bring them up. My first trip went surprisingly smooth...I think, it was along time ago and I was incredibly vague when I wrote it in my log. The caging experiment portion of my field season was also supposed to start in June. We had ordered a number of cages from Seagear and were set to deploy them in June. However, on April 20, 2010 oil started leaking into the Gulf of Mexico, and the ensuing effort directed toward the Gulf of Mexico pretty much consumed the time Seagear had allotted toward building cages for me. Now, I absolutely do not want to sound like I am complaining Seagear handled the situation extremely professionally, and losing a portion of my research is in no way on the same level as what was lost by residents of the gulf coast as a result of this spill.
July rolled around and I regrouped. I threw together a couple of cages with parts from an experiment done a few years prior to mine and deployed them in July. With cages in the water, I was feeling pretty good, all I needed was some fish. Unfortunately, this is easier said than done. Our goal was to catch juvenile river herring with a seine and plant them in cages however, it's no secret that juvenile river herring aren't particularly abundant, or easy to keep alive, as they have a tendency to die if you look at them the wrong way or make loud noises. Our first seining expedition took place in the Roanoke River.
Despite having a more favorable seining location in the Scuppernong River (shallow, sandy bottom with no stumps) we were never particularly successful in adding fish to this cage. We caught flounder, lady fish, three trillion menhadden, and two 15 inch striped bass. In total we caught one juvenile river herring, this one in fact:
The Alligator River presented the greatest challenge when it came to seining, not only because it is very deep and the bottom is covered by stumps and mud but mostly because I am slightly terrified of bull sharks and alligators.
|boat launch at the Alligator River|
Now, I never saw either of these animals in the river, and there is basically zero chance of being attacked but it's something that hung in the back of my mind every time we were there. The only site we could effectively seine was a downriver section of the river. Seining here was pretty interesting because of the diversity of fish we caught, we pulled in everything from juvenile bluefish and some kind of mackerel (or jack) to an adult hickory shad who had apparently forgotten that she was supposed to be in the Atlantic Ocean. We only caught one juvenile river herring, that never got added to a cage, however given the circumstances I consider this to be a small success.
By far the river where we had the most success was the Chowan River. We never failed to catch river herring here and when we caught them we usually caught pretty decent numbers. I was pretty confident about this river from the very start, part of the river has sandy shores which are perfect for seining, and we caught close to 80 river herring in our very first seine.
To address the issue of vanishing fish we hypothesized a few possible causes. The first was they were escaping through holes in the cage. This was possible but unlikely because there really weren't large holes in the cages, and if we found new holes throughout the season we closed them. Another potential cause was predation. Again this was unlikely as a predator would have to get into the cage, and if it was a very small predator I don't think the whole fish would be devoured so quickly. I think the most likely scenario involved the fish dieing from stress or low oxygen and decaying quickly in the high water temperatures. Towards the end of the season when the water temperatures were slightly cooler we found portions of the fish in the cage, which somewhat supports this hypothesis. In the future, I really think the only way to do an experiment like this would be to do it in the lab which unfortunately doesn't allow you to directly validate the elemental signature from a watershed, but can be used to gauge how elements are incorporated into the otolith.
Looking back if I had to choose one word to describe the field season it would have to be "mediocre". For everything that went right something else would go wrong. We did get a lot of data and were incredibly successful overall in capturing juvenile river herring. We were even pretty successful in keeping the fish alive during transport, which is no easy task. This was the first time I had really been in charge of planning field work and I learned a lot from the experience. I have certain strengths when it comes to field work but I also have weaknesses. At times I was poorly organized and under prepared, but I do think I learned and improved as the season went on.
I definitely have to thank the people who helped me out with field work throughout the season: Coley, Chuck, Jeff, and especially Joey Smith. Joey was the undergrad who worked in the field with me and was there for every trip, I thank him for the knowledge he brought about the Albemarle watershed and his commitment to the project.