Rising Temperatures & Moving Water Cue Fish Movement

Warm, moving water from the West Marsh discharging into the relatively cooler Sandusky Bay prompts a predictable but still strangely mesmerizing congregation of fish in our concrete spillway. Most fish near the surface are common carp, but there are also a few solitary gizzard shad, yellow bullheads, bowfin, and goldfish that pass by.

As the video above (taken yesterday) demonstrates, most of the species readily visible are the less “desirable” varieties often referred to as “rough fish.” This designation lumps a good number of species into the same category because they are (a) not commonly considered ideal as table fare, (b) not associated with the more recognizable “sport fish” that traditionally are pursued with hook and line, (c) not the most “attractive” (my wife often reminds me that’s definitely an ‘eye of the beholder’ situation), (d) they are considered “bottom feeders,” or (e) all of the above.

All of these species have value. As I briefly touched on back on April 4th, even carp can have beneficial uses -- not only in the commercial fishing trade but even ecologically -- in helping to curb the proliferation of certain undesirable plants by adding turbidity to the water. 

But our interests, now and in the long-run are to determine how to best promote fish species diversity. Improving connectivity to the open bay is step one. We are actually pursuing a funding tool right now that would replace our aging (and failing) spillway with a completely open-topped culvert. While fish currently have to swim through a pipe to enter or exit the marsh, this new design mimic natural conditions. And it would also allow us to "bar the door" when carp migrations are at their peak. More on this story as it develops.

P.S. To provide some perspective, most of the carp on the clip above are in the 5-15 lb. range. The biggest of the big may have exceeded the 20-lb mark. 

Some of the species we were able to see or hand net but not capture on camera yesterday include: largemouth bass, bluegill, black crappie, golden shiner, and sheephead. I also got a glimpse of what looked like a shorthead redhorse, which would be pretty cool. This particular species is intolerant of pollution and turbid (murky) water and is an indicator of good water quality. We hope to conduct more comprehensive sampling over the coming weeks to get a better handle on what fish are currently utilizing the marsh -- at least by gathering a snapshot in time. 

Common Carp: These (Not-So) Little Piggies Can Still Go to Market

Common carp and goldfish hand-dipped from our spillway thanks to moving water and a temperature gradient
(largest carp could go 12-lbs and goldfish could tip the scales near 3-lbs)

There is a formula that holds true on marshes connected to Lake Erie:

Moving Water + Water Temperature Variation = Carp (usually big carp)

Roy just witnessed this universal truth as the West Pump got underway. Within an hour of being turned on, the warmer/shallower marsh water being pumped into the cooler/deeper bay water had drawn a crowd. While a broad spectrum of fish species are attracted to moving water and temperature variations, carp are the proverbial bulls in the china shop. Their size (probably averaging 5-lbs at our spillway but often surpassing 15 or even 20-lbs) makes them hard to miss. But so does their behavior. They pride themselves in wallowing in the mud, sucking at the surface of the water, or usually both. Schools look like a displaced barnyard scene, and as such, they always remind me of unruly pigs either vying for the last kernels of corn or playing rugby -- it looks about the same.

While both of the above are again invasive species, they have been here a long time and as such have become integrated -- like it or not -- into the broader ecosystem. Numbers of common carp have boomed and busted over the ~125 years they have been in Lake Erie. They were originally brought from Europe as a prized food source, but their propensity to pull bottom sediment ("mud") through their mouths to filter out food items has made them less palatable for many. This behavior, along with their size, makes them prone to bioaccumulation -- or the cumulative increase of substances of nasties such as pesticides, heavy metals, and the like into an organism's tissue.

Still, there is and has been a fairly consistent market for carp -- particularly live carp -- in the commercial fishing industry. Many of the fish are trucked in "live trucks" or "live cars" (by rail) to large markets on both the East and West Coasts. I will definitely get further into the topic of commercial fishing, as it is integral to the human history of the lake shore and our property.

SIDEBARS:
(1) Common carp can be both a blessing and a curse when it comes to vegetative management in the marsh. Too many means excessive water turbidity (cloudiness) and a dramatic reduction in plant diversity; none at all can mean excessive water clarity which can actually lead to the proliferation of undesirable, often invasive species (e.g., Flowering Rush, Butomus umbellatus). As with so many things, it is a balancing act.
(2) A future post will have to address the topic of "carp exclusions" or metal grates specifically designed to prevent the passage of carp through a given area. Our spillway is equipped with a very rudimentary set, but at one time the concrete sluice was actually designed not only to attract but to trap carp so that commercial fishermen could readily (note I didn't say simply) net them and transfer them to live tanks. The spillway was essentially a carp trap.