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Upper Midwest Environmental Sciences Center

folder.gifLa Crosse field station

Fish

Fish communities are monitored on Pool 8 through indices such as relative abundance and species richness, along with the size structure of important species. The fisheries component of the Wisconsin field station employs a standardized array of active and passive gears (see photos) to monitor fish and follows standard LTRM procedures (manual # 95-P002-1).

More specific information needed to interpret LTRM fisheries data can be found at the following link: (fish data format file.)
Fish data can downloaded in text format at this site as well (fish data browser).

Night shocking (photo)

Night shocking was an optional gear used by the WDNR La Crosse Field Station and some others. This method picked up some additional fish species because fish move in and out of areas based on the time of day or night.
(Photo by Terry Dukerschein)


seining (jpg)

seining (photo 2)

seining (photo 3)

seining (photo 4)

seining (photo 5)

Like electroshocking, seining is an active gear in that fish are pursued and caught within a brief period of time. A net is swung in a 90-degree arc against a shoreline to trap small fish. Seining is limited to side-channel and channel-border areas relatively clear of structure and weeds that would interfere with the action of the net. It takes time to pick and sort through seined samples. Many of the fish caught in seines are preserved for later laboratory identication because microscopes and time are needed to examine structures critical for correct identification of species.
Following program wide evaluation seining was discontinued in 2003.
(Photos by Terry Dukerschein)


Minihoop net Flatdhead catfish
Hoop nets are trap nets without leaders. A standard amount of soybean cake bait attracts fish such as catfish, and hoop nets can be set in deep water as well as shallow water. The standard LTRM set-time for hoop nets is approximately 48 hours (2 days). Like fyke nets, hoop nets are deployed in two standard sizes, large for large fish and small for small fish.


La Crosse Field Station Team Leader
Telephone: (608) 781-6360
Fax: (608) 783-6066

Dipnetting

Day electroshocking (photo 3)

Pike

Mayfly swarm

Day electroshocking is the universal standard gear (fished at all LTRM field stations in all types of aquatic areas). A standardized electric current applied to the water by the long booms that extend in front of the boat temporarily stuns fish so that they are easy to see and capture with dip nets. Fish recover almost immediately from the effect of the electricity and are held in a live well until they can be identified, measured, and released alive back into the river.
(Photos by Mi Ae Lipe-Butterbrodt)
  • Passive gears (the fish come into the gear on their own and are trapped) deployed include hoop nets, fyke nets, mini fyke nets, and tandem (immediately adjacent) sets of the various fyke net and hoop net combinations.
  • Active gears (the fish are actively pursued and captured) deployed include seines, day and night electrofishing, and trawling. Fish captured with either active or passive gears are identified, measured, and released alive back into the river.
  • Data on turtles incidentally trapped in passive gears are also recorded. Turtles are identified, sexed, and measured before being released back into the river.
  • Gears are deployed at randomly assigned sites stratified by five aquatic area (habitat) types (Main Channel [MC], Main Channel Border [MCB—wingdam and unstructured], Side Channel [SC], Contiguous Backwater [BWC], and Impounded [IMP—open water and shoreline]).
  • The LTRMP fisheries field-sampling season is divided into three distinct time periods to allow for comparisons of seasonal differences in fish distribution. The three periods are June 15 through July 31, August 1 through September 15, and September 16 through October 31.
  • Each sampling period contains 150 stratified random sites throughout Pool 8.
  • Several fixed sites in the tailwaters of Dam 7, where fish often congregate at certain times of the year and where certain migratory species not captured elsewhere tend to congregate, are also sampled.
  • Occasionally, day electrofishing is done as funding permits in other areas.
fyke net (photo 1)Fyke nets

Fyke nets are trap nets with leaders that extend to a shoreline or weed bed to guide fish into the net over approximately a 24-hour period. They fish well in relatively shallow areas without little or no current such as backwaters. No bait is used with fyke nets. LTRM crews fish two standard-sized fyke nets--regular fyke nets for larger fish and mini fyke nets scaled to catch young fish and small forage fish in backwaters where weeds are too thick to seine effectively. All nets must be regularly maintained to be effective, including drying them after each use, storing them in a well-ventilated, rodent-free area, and vigilant mending.


Turtle (photo)
Turtles occasionally find their way into fyke and hoop nets because they are attracted by by the fish already caught in the net. LTRM crews identify, measure, sex, and release all turtles caught and record these data available in the fish database. This Blandings Turtle is endangered because of loss of habitat. It is the only one so far caught in Navigation Pool 8 LTRM gears. After photographing it to document identification, we notified appropriate museums and agencies of its occurrence in our area and released it back into the river.

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Page Last Modified: January 29, 2016