Aggregations Projects

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Aggregation:

“A consistent and disjunct group of fish with no significant exchange of individuals with other aggregations, as indicated by recapture of PIT‐tagged juveniles and adults and movement of radio‐tagged adults.” (Valdez and Ryel 1995)

There are six recognized aggregations below Glen Canyon Dam: [1]

  • 30 Mile (RM 29.8-36.3)
  • Little Colorado River inflow (RM 57.0-77.2)
  • Shinumo Creek inflow (RM 107.8-110.0)
  • Middle Granite Gorge (RM 125.0-129.7)
  • Havasu Creek inflow (RM 155.8-159.2)
  • Pumpkin Spring (RM 212.5-216.0)

Humpback chub are also caught outside of the aggregations. Samples are also being collected at:

  • Fern Glen - Stairway (RM 168.5-172.9)
  • Froggy Fault (RM 196-198.5)
  • Fall Canyon (RM 210-212)
  • Bridge City (RM 237-244)
  • Spencer & Surprise (RM 245-249.5) [2]
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Updates

There have been substantial increases in the captures of humpback chub in aggregation sampling since 2014, particularly at the LCR, Havasu, Pumpkin Spring, and in Western Grand Canyon. [3] [4]

AggregationsCPUE.jpg
[5]
WGC CPUE.jpg
[6]
SWEF hoopnetting.jpg
[7]

Possible drivers for the increases of humpback chub in Western Grand Canyon

Immigration

2016 Aggregation sampling
Of 79 recaptures, Havasu & below (2014-2016):

  • 8 moved down from Havasu (3 Pumpkin; 5 Fern Glen)
  • 5 moved up from Pumpkin (3 Froggy; 2 Fall Canyon) [8]

Temperature: consistently >19C in Western Grand Canyon [9]

Local Recruitment

2016 System Wide Electrofishing (and hoopnetting)
Above RM 220: 21/37 recaptures (57%)

  • At Little Colorado River confluence ~80% recaptures

Below RM 220: 3/146 recaptures (2%)

  • 3 were tagged recently and at RM 238-239 [11]

Translocations: Population may be reaching a critical mass

Links and Information

The Humpback Chub Page

Projects

  • Aggregation Sampling: Electrofishing at the 6 aggregation sites specified above since 2010. 1 trip/year (reduced from two trips/year in FY13-14). Lead by USFWS.
  • System Wide Electrofishing: Collect longterm monitoring data of native and nonnative fish outside of the LCR/NO reaches. 3 trips: 2 spring/summer, 1 in fall since 2000. Near shore electrofishing. New in 2016: Baited hoop nets and extended below Diamond to Pierce. Lead by AZDGF.
  • Otolith Microchemistry: Determine sources of humpback chub recruitment.
  • Portable PIT-tag antennas: Locate additional aggregations.

Presentations and Papers

2020

2019

2017

2016

2015

2014

2013

Other Stuff