7166

• UCREFRP Catalog Number: 7166
• Author: Miller, W. H., et al.
• Title: Yampa River Fishes Study
• USFW Year: 1982.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

Spawning - Spawning habitat of Colorado squawfish was never documented
until 1981 when eight Colorado squawfish were radiotracked,nfrom the
upper Yampa and lower Green rivers to spawning grounds in the lower.20
mi (32 km) of the Yampa River. Seven Colorado squawfish migrated from
128 mi (205 km) to 100 mi (160 km) downstream in the Yampa. River and one
migrated 96.2 mi (154 km) upstream from the Green River to the, spawning
grounds. Radiotagged fish remained in the lower Yampa from 26 June to
10 July. Three Colorado squawfish originally tagged with dangler-tags
in the upper Yampa River in 1978 and 1980 and in the upper Green River Y
in 1981 were recaptured on the spawning grounds from 18 June to 9July.
On 1 July 1981 a radiotagged Colorado squawfish was followed to a
potential spawning area at RM 18.5 (km 29.6). Collections in this area
produced two ripe male Colorado squawfish. Efforts to locate `,spawning
fish were increased and on 5 July 1981 three radiotagged Colorado squaw-
fish were located at RM 16.5 (km 26.4) in the same general area of the
Yampa River.. These fish were moving between a deep pool (Figure 14) and
a shallow cobble-rubble bar. This behavior appeared to be associated
with spawning, and was similar to that reported by Beamsderfer and
Bjornn (1981) for spawning northern squawfish (P. oregonensis)., A
floating trammel net was fished over the bar; 13 ripe Colorado squawfish
were captured in one net haul, and 2 ripe fish were collected in.the
second haul. One of these was a recapture (No. 1537B) (Table 19).. All
of these Colorado squawfish were ripe males except one, a large .(779,mm)
spent female. All were heavily tuberculated.
The discovery of these 13 ripe Colorado squawfish at RM 16.5"(km
26.4) prompted an intensive survey of the lower 20 mi (32 km) of the
Yampa River within Stratum 1. Between 1 and 9 July, a total of 35 ripe
or spent adults was captured, of which one (No. 1313) was a local
recapture and one (No. 1537B) was a recapture from 1979 (Table 20).,'It
is important to note that at least 43 adult Colorado squawf ish were
present in Stratum 1 (Table 21) between 5 June and 9 July (36 collected,
7 radiotagged). Although repeatedly sampled, no adults were collected
after July in 1980 or 1981 from Stratum 1. It was concluded that this
represented a major spawning congregation and the five adults captured
before 19 June possibly were early arrivals. It is likely that the
observed spawning congregation is repeated periodically since. Holden and
Stalnaker (1975b) reported increased numbers of ripe Colorado squawfish
in the lower Yampa River in July 1968-1970. Collections made by,
Seethaler (1978) also indicated increased numbers of Colorado squawfish
in the lower Yampa River in July 1974-75. Therefore, it is important to
consider the results of larval fish collections in DW conducted by CDOW
in August, 1980, and the more intensive sampling by the CDOW and FWS in
July-August 1981. 1980 collections produced larval Colorado squawfish
in the lower 10 mi (16 km) of the Yampa River. Although,the lower 119
mi (190 km) of the Yampa River were intensively sampled in 1981, larval
Colorado squawfish (9-13 mm) were collected only in the lower 12.5 mi
(20 km). This is conclusive proof that spawning occurred in the Yampa
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