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<br />go through and pass a testing phase with surrogate species before the first humpback
<br />chub arrives.
<br />
<br />Should a facility be selected for captive propagation and fully equipped to ensure
<br />compliance with health and genetic protocols, we suggest capturing fish in the age-O
<br />cohort to minimize impacting the wild population. In June, it may be possible to capture
<br />large numbers of age-O fish, but most will likely be < 50 mm (Gorman 1994, Van
<br />Haverbeke 2001 a). The modal length of age-O humpback chub reached> 50 mm in
<br />late July and early August during 1993 and 1994 (Gorman 1994). Humpback chub
<br />within the 50 to 75 mm size class can be captured relatively easily with seines, and
<br />transported with minimum mortality (D. Van Haverbeke, pers. obs.). It is possible to
<br />capture this size class of fish between June and November (USFWS 2000, Van
<br />Haverbeke 2001 b), but the optimal months are probably from mid July through the end
<br />of August (D. Stone, USFWS, pers. com., D. Van Haverbeke, pers. obs.).
<br />
<br />In addition, the logistics of capturing a sufficient number of age-O fish can be
<br />complicated by the hydrograph of the LCR (Figure 2). It may seem that June would be
<br />the optimal month for capturing fish, when the LCR is most likely to be running at base
<br />flow. However, during spates, age-O fish >50 mm appear to concentrate in zero velocity
<br />near shore habitat, and can easily be seined (D. Van Haverbeke, pers. obs.). For
<br />example, during late July 1998, about 450 age-O humpback chub were seined in a half-
<br />day under turbid water conditions between 10 and 12 km in the LCR, and transported
<br />via helicopter to Willow Beach NFH (Gorman and VanHoosen 2000, D. Van Haverbeke,
<br />pers. obs.). Thus, flood conditions can actually facilitate capture, since fish appear to
<br />be concentrated, and will not "see" the capture gear.
<br />
<br />By late summer and fall, many age-O fish are transported out of LCR by flood events
<br />(Valdez and RyeI1995). As flood conditions become more extreme (or more time
<br />passes under erratic flood regimes), progressively more age-O fish may drift into the
<br />mainstem, making capture more difficult. Flows in the LCR generally return to base flow
<br />conditions during November; however, by then much of the age-O cohort has undergone
<br />mortality (e.g., transported to the mainstem), or grown> 75 mm. Again, flexibility will be
<br />required to accommodate an appropriate temporal scale for collection.
<br />
<br />Streamside spawning could be initiated as another option, and entails capturing adult
<br />fish during the spawning season. Ripe males are easy to capture, but capture of ripe
<br />females is much less frequent (Gorman and Stone 1999, Van Haverbeke 2004). As a
<br />result, large females must usually be held in a holding pen and injected with carp
<br />pituitary hormone to induce ovulation (Hamman 1982). Once ovulation occurs, the
<br />extruded eggs can be fertilized with ripe males, much easier to capture. However, the
<br />logistics of such an endeavor can be enormous (R. Hammon, USFWS, DNFH&TC, pers
<br />com; B. Persons, AGFD, pers. com.; C.O. Minckley, USFWS, pers. com.; D. Van
<br />Haverbeke, pers. obs.). Difficulties inevitably occur in capturing a sufficient number of
<br />ripe females at the right time, in holding fish in pens without stress if hormones are
<br />used, in egg survivorship, transport out of the Grand Canyon, etc. All of these
<br />difficulties and more have been present in past efforts to collect eggs from Grand
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