Monday, August 13, 2012

The Flint On August 11

We went to the Flint River at Oscar Patterson Road this past Saturday, Aug. 11, in search of silver shiners and scarlet shiners. We haven't caught a fully adult silver shiner since June, but we're getting good at finding sub-adults in the 45-70 mm SL range. This is interesting for us because we're trying to understand the population structure of the species, which no one else has really looked at. Saturday's trip followed over an inch of rain on Friday, so the river was up some and was more turbid than recently. Four of us were there, including Stefanie, Josh and Becca. This time we didn't find fish easily upstream from the bridge, with higher, faster water there, but we found fish under and downstream from the bridge which we haven't since June. Not surprisingly fish move around as the river changes. The first picture is the "parking lot" at this area, which on Saturday was a lot wetter and muddier than it has been for a while. I usually try to park close to the bridge because that's where we enter the river, but I declined the mudding.
Here's the fish we collected, euthanized in formaldehyde. The most obvious fish in this shot are sub-adult silver shiners, but we also collected some large scarlet shiners. We'll have to go out again before the end of the month, assuming Josh doesn't collect enough fish on his own.

Monday, August 06, 2012

Multiple Size Classes Of Silver Shiners In The Flint

I think we're making progress solving one question from the last year. We've caught mostly large, adult silver shiners in our work. This begs the question of the population structure of the species, i.e. what size are given year classes and how many of them are there relative to adults. In the last several weeks we've made several collection of smaller silver shiners. Last Sunday Stefanie and I caught a bunch of fish I thought were all scarlet shiners. Upon closer examination in the lab, we realize that almost half of them are silver shiners, in the size range 50-68 mm SL. And Josh netted a bunch of silver shiners downstream in the Flint that are in the size range 70-85 mm SL, almost the size of ones we've typically caught. As we've learned more about silver shiners in terms of their preferred microhabitats in the river we're finally catching a more diverse population. It doesn't sound like much, but I'm happy!