Fish Outing – April 14, 2006

About fifteen Sligo residents got a close up and personal look at the fish in Sligo creek near the Dennis Ave. Recreation Center on April 15, thanks to an ecologist whose brought the fish to shore.

Using a handy device called an “electroshocker,” urban ecologist Susan Flanders Cushman and her two student assistants stunned a good number of fish long enough to catch them in nets, deposit them in deep white buckets, and give our enthusiastic participants a chance to hold and observe four species of Sligo fish.

We got to see about fifteen of the tiny blacknose dace, the Creek’s most abundant fish (all of two-inches long, with a stunning dark stripe down each side). One of them was a “pregnant” female — bulging with eggs (hundreds of thousands, according to Susan) which it would later release for male fish to fertilize.

It was surprising for many of us to see that the Creek supports much larger fish, such the White Sucker (about five inches) and especially the Creek Chub (about six inches, growing to a maximum of 12″). Susan showed us how the White Sucker’s mouth is conveniently positioned at the bottom of its head, making it easy for the fish to graze the stream bed for food. On the other hand, the Creek Chub’s gigantic mouth serves its appetite for larger prey, including plenty of smaller minnows like the dace. Our catch also included two Bluegill Sunfish, with their characteristic vertical blue stripes, including one baby.

Susan pointed out that the dace (and other minnows) and suckers are the only Maryland fish species without teeth.

We also looked at two stream habitats: the riffles (fast-moving water over shallow and protruding rocks and pebbles) and pools (slow moving and deeper). Most of the Sligo species are adapted to pool habitat. The numerous blacknose dace in the Creek are highly tolerant of typical urban streams conditions, such as high water temperatures and lots of sediment. One of our participants noted that the Creek is home to northern water snakes, which depend on an abundant supply of small fish for survival and which help cull and manage fish populations.

Susan discusses Sligo fish habitat while student assistants prepare to use the electroshocker.

Team heads out to do some electroshocking

One of a dozen or so blacknose dace we caught

Susan shows some admirers one of our larger fish (probably white sucker).

Report and photos by Michael Wilpers
Natural History Committee