This protocol is from the US FWS in Michigan, which surveys Thunder Bay River in early April through the end of May.  The purpose of this sampling is ruffe removal.

A 30.5 XZ 1.8 m small mesh gill net (3.8 cm stretch mesh monofilament twine) is the primary gear used to remove adult spawning ruffe.  A minimun of 4 nets are set per night (week nights) at four locations during the reduction effort.  Overnight sets are used.  Effort is measured as a lift and catch is measured as catch is measured as catch per lift.  Specifications on the gear and protocol are as follows:

Protocol:

1.  Bridles, anchor lines, anchors, buoy lines, and buoys are attached to the gill net.

2.  The net is deployed at the sampling location perpendicular to shore.

3.  Data sheet is completed.

4.  Fish are removed from the net, placed in a basin of water, and sorted by species.

5.  The net is either reset if during the week or removed for the weekend.

Total lenth (mm), weight (g), and sex are recorded for each ruffe captured.  Aging structures (otoliths, dorsal spines, or scales) are removed from all ruffe captured.  Ruffe are then labeled and frozen for future studies or needs.

The total catch per species is recorded for all non-target species and returned to the water alive when possible.

A minimum of 4 lifts per week night is desired per location.  When four locations are fished each week, the total effort is approximately 16 lifts per week.

Although the 4.9 m trawl is the primary gear used in this sampling programme, alternative gears such as this one are sometimes used when the large trawl is unfeasible.

A 30.5 x 1.8 m small-mesh gillnet (3.81 cm stretch mesh mono-filament) paired with an 37.5 x 1.8 m experimental gillnet (7.5 m panels from 3.8 to 10.1 cm stretch mesh multi-filament) is an alternative gear used iwth un-even bottoms where trawling is not feasible, such as over cobble substrates.  Gillnets are anchored and fished overnight, perpendicular to shore.  Effort is recorded in nights gillnet was fished and would consist of one night each for paired placement of one small-mesh and one experimetnal net at each sampling location.