HBC comprehensive plan meeting 

Phoenix, AZ 

Feb 12, 2003 

Steve Gloss – HBC data/trends (Powerpoint presentation) 

Discussion about importance of data from 1980’s. Question from AGFD on low 

population estimates in 1980’s – are these reliable? 

Recruitment graph – some desire to use existing HBC specimens to back calculate ages 

of HBC (Persons, Valdez) 

Graph of projected population estimates using assumed 1998 recruitment rate (showing 

decline to 500 >age 4 HBC 

Question about poster displayed at last AMWG meeting that displayed population 

estimates dating from dam closure in 1963, showing sharp decline in HBC immediately 

following dam closure. Steve had not seen this poster prior to the AMWG meeting so 

could not comment. (Need to bring this poster to the next TWG meeting.) 

General sense of the group that the data displayed by Steve should be expanded – some 

felt the data was insufficient on which to base a decision. 

Paul Marsh – need to exercise care in using speculative models, concerned that 

Walters/Coggins weren’t at meeting to explain their work. 

Coggins’ synthesis report in preparation would only address stock assessment model. 

Group felt a need for an overall synthesis, addressing all the HBC data sources. Steve 

felt that it might be possible for a fisheries meeting to be held in conjunction with the 

February TWG meeting. 

Valdez – recommend the stock synthesis report address issue raised today 

Simmons – advised eliminating population estimate other than Kaeding & Zimmerman 

(1983) and recent estimates due to unreliability of other estimates. A 200% change in 

population would have to occur before change could be detected with old sampling 

approaches. 

Marsh – recognized that these types of data quality discussions have been occurring for 

20 years, and that the conclusion of those discussions have never changed. 

Simmons – explained changing confidence intervals of historic population estimate. In 

mid-1980’s intervals were very large since sampling was not designed to produce 

population estimates. Changing sampling techniques produced catch-rate information 

that isn’t comparable throughout time. 
Marsh – historic large magnitude population changes are still unknown as to cause. 

Talbert – convinced that overabundance of trout and cold water are the primary causes of 

HBC mortality 

Group needs to consider whether it will be important to determine cause and effect 

relationships as a result of experimentation. 

Valdez – what hypotheses have been developed by GCMRC? Gloss -> overabundance 

of salmonids have impacted HBC recruitment. Valdez -> predation model of 12 years 

ago indicated that HBC coming into mainstem were being eaten and that recruitment 

came really only in LCR. 

Valdez – questioned the relationship between high LCR flows and strong year class. 

Recruitment model has the problem of waiting for 3 years to determine if there is a 

recruitment failure, intervening period of time could significantly affect recruitment 

sampling results. Gloss -> agree 

Sponholtz – noted last year’s high fall flow in the LCR (20,000 cfs), so future data could 

show if there is a relationship between recruitment and high LCR flows. 

Marsh – in early 1990’s, there was a strong channel catfish population at the mouth of the 

LCR that does not currently exist in those numbers. 

Valdez – are there other hypotheses to explain the decline? Gloss -> referenced all the 

potential threats listed in the outline. 

Johnson/Marsh -> need to take action now, even though we are not as sure what has 

caused the HBC decline 

Randy Peterson – GCD Operations (Powerpoint presentation) 

Discussed current experimental program (2003-2004), resulting in high fluctuating winter 

releases in 2003 and 2004, steady releases during the fall of the autumn sediment inflow 

scenario (possibly 2003), and HMF/ROD flows during fall of next year thereafter that a 

Paria River sediment input occurs. 

Discussion about current and expected dam releases (5-yr outlook). Most probable 

annual releases for next 5 years are between 8.23 and 9 million acre-feet. Minimum 

probable annual releases are 8.23 maf. Expected to take over 10 years of normal inflows 

to refill Lake Powell due to drawn down conditions of both Lakes Powell and Mead. 

Questions about potential for Lake Powell releases to increase in temperature since Lake 

Powell is drawn down, but last year’s data did not indicate such. 
Discussion about current status of TCD, including need for operational scenarios, 

risk/benefits, timing of warm releases to trigger mainstem spawning. Davis -> concerned 

that Powell releases with TCD wouldn’t warm fast enough to be of benefit to non-LCR 

aggregations. Gloss -> release temps wouldn’t be up to 16C until July. Peterson -> 

while that may be true, water of 12C could be released in May which would warm to 16C 

by the time the water got to the LCR. Marsh/Clarkson -> confident that if releases were 

warmed, that mainstem spawning would occur 

Discussion about tribal concerns. Yeatts -> Need to have Navajo approval of any 

proposal that may affect tribal land. Questioned Hualapai beneficial use of removed trout 

as a long-term solution. 

Discussion about NPS issues. Peterson -> some indication that Jeff Cross is receptive to 

the idea of expanding non-native removal to other tributaries. Concern expressed by 

Mark Steffan that we move too quickly to rid the Canyon of trout when we haven’t 

shown the cause/effect proof of predation of Bright Angel trout on LCR HBC. Grand 

Canyon trout fishing is a high priority public use. 

Discussion about Potential Threats to HBC document 

Palmer – Suggested the use of FWS recovery goals as the guiding document for actions 

recommended by this group. Also suggested the creation of a recovery implementation 

program to achieve the recovery goals prepared by FWS. 

Valdez – cited the previous recommendation that a plan be developed that addresses the 

potential for some type of toxic spill in the LCR drainage, both from the Cameron bridge, 

Holbrook sewage plant, and other watershed issues. 

Spiller -> led a discussion on the various threats (see Excel spreadsheet for list of action 

items and assignments) 

Next mtg is March 12, assignments due March 1