July 02, 2018
Anglers, guides and trout in Southern Colorado are all toughing it out this season in an exceptional drought. A combination of low snowpack at higher elevations and unseasonably warm weather has created conditions that are now putting fish at risk.
The San Luis Valley chapter of Trout Unlimited issued a statement last week requesting anglers comply with voluntary limits on fishing in the afternoons, owing to high water temperatures stressing cold water species of fish. Both personal thermometers and Division of Water Resources gauging stations are all telling the same story -- that river temperatures are now hitting a cutoff point of 67 degrees Fahrenheit, which is the event horizon where dissolved oxygen and a trout's metabolism cross a threshold and become unsustainable.
Temperature is a primary factor in the ability of water to bind and carry oxygen, with colder, denser water near the freezing point of 32F degrees having the highest capacity. Water at the boiling point of 212F begins to shed all its bound constituents, and begins to revert to a gaseous state. In between, most trout have a happy zone for activity, with species like Rainbows becoming active at about 45F, and then getting cranky when things creep up above 60F. Brown Trout seem to like things a little warmer by five degrees overall, with Brook Trout and full-blooded Cutthroats seeming to prefer things on the cooler side. But with the exception of outlier warm water adaptations like the Gila Trout of southern New Mexico, it's probably accurate to say that Trout in general are a delicate organism with very specific temperature requirements needed to thrive.
Guides on the Upper Rio Grande are acutely aware of the issue, and while their livelihoods are dependent on squeezing the most out of seasonal business, they also recognize that thrashing the resource isn't in anybody's best interest. Local guides typically float hard sided boats like Dories in the larger volume water of the main river below the major tributaries, and inflatables upriver in a season that for most years runs June through the end of August. Joel Condren, lead guide and owner of 8200 Sports in South Fork, supports the effort and plans to take the high road should conditions become even more difficult.
"We've had an awesome spring season, with what little amount of runoff there was peaking a month early and allowing what's honestly been fantastic fishing for us all through May and early June. But now the river is too low to even float rafts downriver, and we're seeing afternoon water temperatures that we know are just too hard on the fish. We've stopped booking full-day trips and are only offering half days, pulling people off the water by noon. If those overnight water temperatures start bumping up against that 67F mark in the mornings, it will be best to just stop doing business until conditions rebound. We're here for the long haul, and think the professional guiding community should be the first to set an example -- these fish are what everybody is here for."
Southern Colorado usually enjoys a summer monsoon season, with moisture from the Gulf of Mexico pushing up in midsummer and colliding with cool air at high altitude. The result is strong afternoon thunderstorms that can dump prodigious amounts of cool rain onto the huge catch basins feeding the Rio Grande and other rivers like the Animas near Durango. Until that happens, however, the trout of southern Colorado are hunkered down in the deepest pools, waiting it out.
Unusual weather conditions in the last few years seem to be becoming the norm lately, and for anglers nationwide, developing an understanding of the stresses that fish deal with will help with protecting your personal fishing experience. Broader awareness among fishermen of how changing dynamics affect resources should drive public policy, with advocate organizations and professional groups pointing the way.
Colorado Trout Unlimited's top five recommendations for responsible fishing in high temperatures are as follows:
1. Respect the Fishery - When conditions become too extreme for fish, consider putting the rods away or fishing somewhere else. This could be a good time to explore another part of the state. Rivers in northern Colorado are in much better shape including the Arkansas. There is no need to over-stress and kill the fish we all love. Help the fish make it through a tough year by limiting the times you catch them.
2. Keep the Fight Short - Land and release the fish as quickly as possible so the fish don't expend too much energy. Use heavier tippet and do not handle the fish any more than possible. Make sure they are revived enough to swim away from you before releasing them. Using barbless hooks or flattening the barbs on your hooks will also reduce stress to the fish significantly. Consider carrying a small pocket thermometer if you are unsure about the water temperature, they are inexpensive and available at any local fly shop.
3. Fish Early - Fish earlier in the morning when the ambient air temperatures are lower. Fishing the cooler times will reduce stress on the fish and the fishing can be better too!
4. Fish Higher Up - Consider fishing higher up in mountains in some of the tributaries and alpine lakes. This will reduce stress on lower level streams and you can still have a great time fishing, you might even discover a new place with great fishing!
5. It's Not All Bad - Colorado is experiencing a tough water year but many of the fish can adapt and survive these conditions if we do our part by following these few guidelines. If you have questions about when and where to fish please call or visit one of your local fly shops.