Your first trip: setting up the transect
Your second trip: sampling the fish
When you have finished all the sampling
Data Analysis
Fish Communities in Great Lakes Marshes: HOME
 
Instructions for Monitoring Marsh Fishes
and
Calculation of an Index of Biotic Integrity

Ecosystems are comprised of various plants, animals, and microorganisms living together in communities. Green plants are the primary producers that capture energy from the sun to make foods. These are consumer by plant-eating herbivores, in turn eaten by carnivores. Wastes from animals and dead plants and animals are processed largely by microorganisms that recycle materials to be reused by plants.

Fish are integral parts of most aquatic communities. A few fish are herbivores, some eat the products of decay, and most are carnivores. The Great Lakes marshes that are such a prominent feature of Les Cheneaux are productive and provide shelter making them attractive to fish as feeding grounds, for reproduction, and as nursery areas. Marshes are shallow and easily freeze in winter so that most marsh fishes over-winter in deeper water. They come inshore to the marshes as the ice retreats, not all together, but at different times. Perch are among the earlier arrivals, spawning in the marshes. Minnows tend to arrive next, and different species become abundant and then decline as the summer progresses. Bass and sunfish follow a similar, pattern. Late in the fall, whitefish spawn in gravel areas and when their larvae hatch, they are the earliest spring signs of the importance of marshes for fish reproduction.

As with all communities and their components, the fish community in Les Cheneaux marshes can be described in terms of the number of species of fishes and their abundance. Over time, samples from year to year can be used to monitor changes in the fish community, and hence provide warning of degradation of the marshes in time to prevent further damage or to guide restoring the habitat.

Many of the small fishes living in the marshes can be caught with minnow traps. This monitoring method uses a line of five minnow traps, or a transect, running through a variety of habitats typical of marshes to sample common marsh fishes. 

 Each minnow trap is made up of two wire mesh baskets, secured together with two fixed hooks and eyes and a third double eye with a locking clip. One end has a funnel with an entrance facing the open water of the marsh. 
 The trap is baited with a teaspoon of canned dog food, closed with the locking clip, and submerged in the water. Fish swim into the trap as they move around the marsh, or are attracted by the bait. They swim through the entrance, pass through the narrow funnel and enter the center of the trap. Then they cannot find their way out.

You return after a whole day, recover the trap, unclip the lock and shake the fish into a bucket of water to be counted and identified.

 
Your first trip: setting up the transect
Your second trip: sampling the fish
When you have finished all the sampling
Data Analysis
 The monitoring program was developed for The Nature Conservancy (Michigan Chapter) by:

Paul W. Webb, James S. Diana, James A. Teeri and students,
The University of Michigan Biological Station,
Pellston, MI 49769,

and

School of Natural Resources and Environment,
The University of Michigan,
Ann Arbor, MI 48109-1115. 

Fish Communities in Great Lakes Marshes: HOME