Volunteers Help CPW Biologists Survey John Martin Reservoir Fish Population

HASTY, Colo. – The shop behind the John Martin Reservoir State Park dam resembled a fish market recently when Colorado Parks and Wildlife aquatic biologists, staff and volunteers assembled to survey fish in the lake.

To get a snapshot of the fish population in John Martin Reservoir, crews deployed gillnets overnight, pulled them in the morning and then went to work weighing, measuring and documenting each species. It’s an annual project at many of the reservoirs in southeast Colorado and this year it went on Oct 1-16.

After the catch was processed and data collected, all the edible game fish were filleted on site and given to the volunteers.

“This data is vital to help us determine future fish stocking and for setting fishing limits,” said Jim Ramsay, CPW aquatic biologist in Lamar. “Since we can’t observe the aquatic wildlife in its natural habitat, we must do the next best thing by collecting samples.” 

Biologists use a variety of methods to get a snapshot of the population. One of the better sampling methods is the experimental gillnet. 

The nets have a range of mesh sizes so they can capture fish from juvenile to adult sizes. Usually, these nets are set in the evening and pulled in the following morning.  

Unfortunately, gillnetting often is lethal to the fish. But the number caught in the nets is a tiny fraction of the actual lake population and the data collected provides valuable insight to the fishery as a whole. 

Ramsay praised the two dozen or so volunteers who help pull in the nets, free them for processing and then weigh and measure them to collect the data. 

“Without the help of dedicated individuals who understand the importance of this work, aquatic sampling could not be done effectively,” Ramsay said. “CPW and the fishing public are in their debt for all their work helping us maintain healthy fisheries in John Martin, all our reservoirs and rivers in Colorado.” 

PHOTOS are Courtesy Colorado Parks and Wildlife