A Day in the Field

This past Friday I began my research of the fish fauna of Cape LaCroix Creek.  My friend Andrew and I gathered the seine, formalin, and other materials and ventured out to the creek in the middle of the morning.

The weather was overcast and quite humid.  The forecast called for rain but we didn't receive any until the early afternoon.  Our first stop was a deep, rocky part of the creek near Shawnee Park, relatively close to where the stream empties into the Mississippi River.  Seining here proved to be nearly impossible as we both found ourselves treading for water at times.  We did observe several silver carp (Hypophthalmichthys molitrix) that leaped from the water when they discovered our presence.  According to Pflieger's Fishes of Missouri this highly invasive species has not been seen at many localities in the state, but the book is now fifteen years old and recent propagation has likely led to greater abundance than it indicates.

We had much greater luck when we moved to shallower waters, in particular those with heavy weed growth.  Water primrose (Ludwigia spp.) was abundant in the creek, as were several other small aquatic plants whose identity currently eludes me.  I intend to try to identify the aquatic flora of Cape LaCroix as well, but that will have to wait for another day.  There was abundance of terrestrial plants along the shoreline as well, including mist flower (Conoclinium coelestinum), monkey flower (Mimulus ringens), cup plant (Silphium perfoliatum; pictured).  In fact, the plant life is diverse enough that I intend to speak with the city of Cape Girardeau to see if I need a permit to collect along the creek.  I think a floral survey of the area would be a great asset as well.

Topminnows (Fundulus spp.) were the most abundant species in the creek, with several specimens captured in every seine attempt.  Although I need to further examine the specimens, I believe we caught both blackstripe (F. notatus) and blackspotted topminnow (F. olivaceus) Other common species included mosquitofish (Gambusia affinis), an unknown cyprinid with a definitive golden hue above the lateral line, several catostomids (suckers), two darters, longear sunfish (Lepomis megalotis), bluegill (L. macrochirus), largemouth bass (Micropterus salmoides), brook silverside (Labidesthes sicculus), and two unmarked, unknown cyprinids just over a decimeter in length.  Exact identification is pending and will involve meticulous keying in the lab.

Even though it was only one day, I believe that our sample is a good overall indication of the fish fauna of Cape LaCroix Creek.  I have at least two more trips planned, one near the source of the creek and one just before the concrete channel in the center of Cape Girardeau.  During most of the summer this channel remains too dry for most fish to cross, isolating individuals away from the Mississippi River.  I am curious as to whether different fish are present east of the concrete.  I would hypothesize that larger species (such as the silver carp we observed) enter the creek via the river but do not swim through the shallow impounded channel, and are therefore limited to the deeper, easternmost portion of the stream.