Fish in Tomichi and Cochetopa creeks travel great distances despite drought conditions and higher temperatures. That’s according to recent research comprising two separate studies spanning 2015-2018.
Rather than pursuing fish with rod in hand, biologists have conducted research in the Gunnison Valley utilizing transmitters and antennas — a project that began with the Adopt-A-Trout program, which used radio telemetry to track fish movement.
Adopt-A-Trout is a conservation and education project launched by Trout Unlimited which included a local component focused on Tomichi Creek. Beginning in 2015, Colorado Parks and Wildlife (CPW) partnered with students and community members to implement the study.
Initially, a total of 15 trout — including 14 browns and one rainbow — were tracked using radio tags — or small transmitters installed under a fish’s dorsal fin — over the course of two years. Two of the 15 fish were believed to have died after the tags were implemented, two were found near irrigation diversions and another two were found at the bottom of a heron rookery.
Dan Brauch of CPW and Russell Japuntich with the Bureau of Land Management (BLM) noted the study’s findings — including a surprising discovery which revealed that migration patterns are larger than previously thought.
Of the original 15 fish, nine moved significant distances — averaging 10 miles of travel with some even moving 20 miles upstream.
“What always baffles me is that fish made it during high spring flows,” said Japuntich of trout migration. “It would be like you getting on a bike in Kansas and leaving late in the afternoon to get to the West Coast.”
However, the study itself had limits — such as a relatively small sample size and restraints associated with the types of tags. Each tag weighed 9.5 grams and could only be inserted in a fish that was 15 inches or larger, leaving a large portion of the population omitted from the study, said Brauch.
That led CPW and the BLM to conduct a similar study on a larger scale. Following the end of the Adopt-A-Trout program in late 2017, the agencies developed new ways to analyze the habits of fish.
The study focused on 20 miles of Tomichi Creek and 25 miles of Cochetopa Creek. The environment includes both private and public lands, upwards of 40 irrigation diversions and significant beaver activity.
Additionally, each fish was tracked using a passive integrated transponder, or PIT tag, a tracking device that differs from the radio tags used in the Adopt-A-Trout program. The smaller size of the PIT tag allowed a larger pool of fish — starting at five inches in length — to be tracked within the water system.
As a result, a total of 1,715 fish were tagged between May and June of last year with another 930 tagged between September and October.
Once again, the findings indicated significant local movement among fish, with the majority of fish from Tomichi Creek making movements of 2 miles or more.
“We didn't see near as much movement on Cochetopa Creek,” explained Japuntich, who surmised the lack of activity may have had to do with cooler temperatures.
Japuntich also pointed out the results are representative of a drought year — meaning low flows and higher water temperatures, factors which affect how much a fish may move.
“Tomichi Creek gets fairly warm and during drought years can see pretty low flows and that can impact the fishery,” said Japuntich.
Both Brauch and Japuntich plan to continue the study again this year, gathering data in a year with regular runoff to compare movement during higher flows.
“Using these antennas really has been a good way to try and detect what sizes of fish are moving larger distances,” said Brauch. “It’s also allowed us to look at the population as a whole.”
(Kate Gienapp can be reached at 970.641.1414 or firstname.lastname@example.org.)