SILVER CITY, NM — Gila trout (Oncorhynchus gilae gilae) is endemic to mountain streams in the Gila, San Francisco, Agua Fria, and Verde river drainages in New Mexico and Arizona. Gila trout was originally recognized as endangered under the Federal Endangered Species Preservation Act of 1966 (US Fish and Wildlife Service, 1967). Federal-designated status of the fish as endangered was continued under the Endangered Species Act of 1973. Gila trout was reclassified, or down listed, from endangered to threatened in 2006 (US Fish and Wildlife Service, 2006).
The distribution of Gila trout has fluctuated since 1975 when only five populations of the species were known in Main Diamond Creek, South Diamond Creek, Whiskey Creek, and Spruce Creek. Range expansions resulted from establishing new populations through stocking by resource management agencies. Range fluctuations occurred from local extirpations (local extinction) caused by a high-severity forest fire, stream drying due to drought, and hybridization with rainbow trout.
The watersheds containing two of the remnant populations, Main and South Diamond creeks, and one replicated population in Black Canyon Creek were burned in the 2022 Black Fire. Over 50% of the burned areas in the Main and South Diamond Creeks are classified as moderate or high soil burn which makes it likely that the fish populations will be negatively affected by post-fire increased water flows containing ash and other debris.
Thirtythree percent of the headwaters of Black Canyon watershed burned with moderate and high soil burn intensity which makes it likely that the Gila National Forest managers made the decision to rescue the Gila trout in Main Diamond Creek prior to upcoming rainstorm events and transport the fish to the US Fish & Wildlife Service’s (FWS) Mora National Fish Hatchery.
Crucial coordination and assistance from Forest Service Southwest Regional Fisheries Program Leader Yvette Paroz and USFWS Assistant Project Leader Tom Tighe were instrumental in helping to transport the fish and set up separate isolation systems at the hatchery for these relocated Gila trout. (For more information about this fish hatchery, see Mora National Fish Hatchery|US Fish & Wildlife Service (fws.gov).
After the logistics were finalized with the USFWS, Forest Service (USFS) specialists (Dustin Myers, Jim Apodaca, Tony Ybarra, and Kenny Capps) hiked into Main Diamond drainage on June 8, 2022, and electro-fished the stream to be able to collect the fish. Water conditions were very low, and temperatures were hot, which is not ideal for the trout.
The collected Gila trout were held in instream net pens temporarily and the plan was to use a helicopter with a long line and fly the fish out in a specially designed fish tank. However, weather cells came in and the helicopter was not able to get to the site.
The fish were released back into the stream in the largest pool. A total of 89 Main Diamond Gila trout were rescued and taken to Mora National Fish Hatchery.
These fish will be used for breeding and to repopulate other streams with Gila trout. Depending on how the upcoming rainstorm events and predicted increased water flows affect the stream, it may be several years before the habitat in Main Diamond Creek is able to support Gila trout and can be restocked.
The Gila trout interagency management group is currently discussing priorities and logistics for additional Gila trout fish salvage in the South Diamond and Black Canyon creeks based on safety, recovery needs, and the likelihood of success prior to rain events. There were several Gila trout streams that were affected by the 2021 fires that have not been assessed yet to see if fish still occupy them.
Between the 2021 and 2022 fires, over 35% of the occupied stream miles have been negatively affected by fire. In addition, persistent drought and low water flow conditions have decreased the amount of cold-water habitat in other Gila trout streams, demonstrating the need to actively protect and improve stream habitat within the range of Gila trout.