Andrew and I seined from seven in the morning until around ten o'clock. Initially my plan was to count the number of seines and divide by the total number of individuals of each species. This would give me the number of individuals per seine and would help to determine the overall abundance of each fish species. However, there was at least one major flaw in this methodology. When we seined and saw a large fish (or fishes) swim into the net, we immediately pulled it up. This would count as one seine but we didn't cover the same length of stream as the standard seines. Thus, the results would be skewed because each trial would not be the same.
With this in mind I have decided to focus my research on the composition of species in Cape LaCroix Creek, with abundance tentatively determined. Although I counted the number of individuals for each species this time, I did not do so on last month's trip, so the exact abundance of each species will be largely speculative. There is also an obvious bias in using mesh seines, as very small fish can slip through the netting and faster fish can out-swim (or outsmart) the net as well. Considering these two things I will avoid any statistical attempt to determine the abundance of fish in the creek. However, I see nothing wrong with unofficially estimating abundance based on observation (and in today's case, total number of individuals).
I may or may not seine one more time, but the most difficult aspect of this research remains to be done. Identification of the cyprinids is incredibly meticulous and keying them out is going to take some time. This would present another difficulty in determining abundance. Since my permit only allows me to capture fifty specimens, I had to release most of the fishes that I captured. Minnow identification in the field is very difficult (especially for someone with very little experience), so I may well have released some specimens that would have been different species.
Since I am in ichthyology and identification of Missouri fishes is a class requirement, I am waiting to key my research specimens until I gain some experience in class. Therefore I will probably begin identification come November. The specimens will have to wait in formalin until then. There are a few species I can already identify with confidence, though. Longear sunfish (Lepomis megalotis) is very common in the stream, much more so than the bluegill (L. macrochirus). Among the Macrochirus basses, the spotted bass (M. punctulatus) looked to be much more common than the largemouth (M. salmoides). Identification was based on jaw size and tail color (in juveniles), although positive ID will be made in the lab. Topminnows (Fundulus; pictured) were abundant, for certain blackspotted (F. olivaceus) and likely blackstripe (F. notatus). Mosquitofish (Gambusia affinis) were especially common under beds of Ludwigia and other emergent vegetation. Brook silversides (Labidesthes sicculus) were present but not abundant. There was also a species of shiner, two Etheostoma darters, a likely bluntnose minnow (Pimephales notatus), stonerollers (Campostoma spp.), and several unknown cyprinids. Positive identification will take place in the lab.
