May 10, 2013: Erv's Field Notes #57

Virginia Rail. 5/6/13 (Wolf. Oesterreich)

Friday afternoon, May 10, 2013. Sunny, moderate westerly breeze, Temperature 58 degrees F.

The Story County Soil and Water District distributes trees every year in honor of Arbor Day to fourth grade students in Story County. This year the District selected Bush Cranberry. We had a couple of dozen left over. Today, with the help of Ames Park staff, we added 25 Bush Cranberry to the total of 700 trees in the wildlife habitat plot on the north side. Many of the seedlings we planted last week are beginning to leaf out. This area will take some management in the coming weeks to reduce competition from thick brome grass and the re-sprouting of Siberian elm.

I have been getting reports of large fish splashing around in shallow water near shore of the main lake. Park visitors were congregated today along the north shore watching the sight. I joined the group and determined the fishes were Common Carp, Cyprinus carpio. Others have seen carp jumping up and over the concrete weirs that separate the constructed wetlands from the lake. Everyone wants to know what is going on. Well, its spring and the fish are spawning. Because of the steep banks and deep water of this old gravel pit, the shallow water in the main lake is restricted to a narrow band along the shore. Moreover, the water level is high, nearly covering the large rocky rip rap that lines the shore. The Common Carp is one of the most destructive invasive fishes we have in the Midwest. The species is indigenous to the Danube River system in Europe and was purposely introduced to the Midwest in 1880 as a game fish. They have been introduced all over the world and in some areas they are raised in aquaculture facilities. Once they get into a river system, they reproduce rapidly and spread throughout. Carp were present in the Hayden Park lake before the City obtained ownership. In 2010, the Skunk River overflowed into the park and probably brought more carp into the lake.

Carp are destructive because they are bottom feeders and when they become abundant in shallow wetlands they stir up the sediment releasing phosphorus into the water column and preventing the growth of beneficial emergent vegetation. Later in the summer the suspended phosphorus can cause extensive algal blooms. They are more of a problem in the shallow wetlands than they are in the main lake because the lake has a gravel bottom and relatively little shallow areas.

On the other hand, this is a good time to catch carp on a hook and line and they can put up quite a fight. Today, I saw a young man using light tackle land a large carp on the fishing dock. The fish probably weighed at least 10 pounds are more. He gave the fish to an elderly man who took it home to eat.

There has been a sudden jump in the number of neo-tropical migrant birds in Ames. Over the last two days I have seen the following species in my back yard: Swainson’s Thrush, Baltimore Oriole, Catbird, Redstart, Ovenbird, Rose-breasted Grosbeak, Eastern Towhee, Chipping Sparrow, White-crowned Sparrow, White-throated Sparrow, and Lincoln’s Sparrow.

Erv Klaas