March 5, 2018 Marble Canyon, AZ – In concert with the National Park Service, the Arizona Game and Fish Department provided a 2 year and 20 year plan to approximately 35 citizens on the plan to maintain a viable population of Rainbow Trout in a 30 mile stretch of the Colorado River. These efforts include the concerns of Humpback Chubs, loss of aquatic insects, growth of aquatic vegetation and High Flow Events (HFEs) from Glen Canyon Dam.
For the past 18-24 months the AZGFD has been conducting research after hiring scientists to determine what is required to bring back the wild Rainbow Trout, that over time this section of the Colorado River will return to its previous status as a Blue Ribbon Fishery.
Jim Devos opened the meeting by describing the efforts of the AZGFD to return this fishery to blue ribbon status but efforts are required to maintain this fishery for the local economy. To accomplish this task, the Fisheries Branch conducts surveys through creel counts and electro fishing.
In summary, the AZGFD works in tandem with the National Park Service and the U.S. Fish and Wildlife Service to cooperatively attack the problem through stocking triploid Rainbow Trout until the wild trout return in acceptable numbers.
The Plan Approach
Glen Canyon Reach Rainbow Trout Experimental Stocking Criteria
NPS – Recruitment (wild young fish) is low for multiple years: rainbow trout recruits (fish less than six inches) comprise less than 20% of the fish community during AZGFD fall monitoring events for more than three (3) consecutive years; or
AZGFD – electro-fishing estimates of relative abundance are less than one (1) fish/minute for two consecutive years; or
NPS – If angler catch rates in Glen Canyon Reach decline to less than or equal to 0.5 rainbow trout/hour, and average size less than 14 inches for two consecutive years; in other words, if trout density and angler catch rates are very low, but average fish size is very large, then goals for the fishery would have been met and no sterile triploid trout stocking would be necessary.
AZGFD – Implementing a restocking based on catch rates of one (1) fish per hour or lower.
Current AZGFD/USFWS Plan Approach
2018/2019 – Two year cooperative agreement with USFWS.
20 Year Agreement – Nonnative stocking procedures manual consistent with Upper Basin Program (final agreement not reached)
Facts on Triploid Rainbow Trout Survivability
Triploid Rainbow Trout: Rainbow that cannot reproduce
Survivability of Rainbow Trout stocked into Lee’s Ferry : estimated 95% mortality over 90 days
Number of Rainbow Trout to out-migrate to habitats occupied by Humpback Chubs: .11%
Number of Humpback Chubs ingested by Rainbow Trout: 3.12 and 7.8 fish ingested per Rainbow. Of those fish, 27.3% are assumed to be Humpback Chubs.
Humpback Chub population: Exceeds 10,000 adults and adding 1.6% triploid Rainbows to the existing Rainbow population does not constitute a habitat modification to the environmental baseline or population level effect.
1. AGFD will host annual reporting meeting
2. AGFD will not stock more than 5,000 Rainbow Trout per month.
3. All stocked trout will be right pelvic fin clipped. If funding and compliance is available PIT tags and Pit tag antenna will be placed in the Grand Canyon.
4. AGFD will assist the USFWS in monitoring 30 mile spring for Humpback Chub.
5. Trout stockings halted when Humpback Chub population between 8000-9500 individuals (rates TBD)
6. Monitor Lees Ferry Rainbow Objectives via creel and electro fishing surveys.
7. Monitor downstream under existing planned surveys – any suspected stocked trout will be evaluated for triploidy or PIT tags.
1. Finalize Cooperative Agreement with USFWS for 2018.
2. USFWS will finalize compliance for 2018.
3. Stocking for 2018 to begin in spring.
4. Begin nonnative stocking procedures manual for the State of Arizona.
5. Initiate EA and Section 7 on Arizona specific nonnative stocking procedures manual.
6. Execute MOU on Arizona specific nonnative stocking procedures manual.