9556 - Laserfiche WebLink

Home Browse Search

Non-native fishes.In general, non-native fish distribution in the study area increased between the period 1994-1996 and 2002-2004. In 2005 and 2006, distribution of smallmouth bass and northern pike further increased upstream into Browns Park. In 2005 and 2006, species abundances appeared to stabilize for the most part where they were previously established (e.g., trout, northern pike, red shiner in Lodore Canyon) or even decline slightly (smallmouth bass), although white sucker may have increased. Northern pike were found sporadically throughout the study area from the upstream reaches of Browns Park (only since 2005) downstream through Whirlpool Canyon. Northern pike are increasing in distribution and abundance in upstream reaches of the Green River in Browns Park. This was based on the finding pike, all age-0 specimens (190-280 mm TL in 2006), in Browns Park in autumn 2005 (n = 10) and summer 2006 (n = 11). The 2005 fish were captured in regular autumn seine sampling conducted in backwaters and 2006 sampling was seining plus a special effort with an electric seine devoted to obtaining a better understanding of pike distribution in Browns Park (more discussion on that effort below). Northern pike capture rates have been relatively low and static in the Green River downstream of Browns Park in Lodore and Whirlpool canyons in the 1994-2006 period. In all electrofishing sampling conducted from 1994-2006 (no Whirlpool Canyon sampling in 1994- 1996) 7 pike were captured in reach LD3, 39 in LD4, 2 in WH1 and two in WH2. Most LD4 reach pike were captured within 1 km of the confluence of the Yampa and Green rivers. Electrofishing capture rates of northern pike in the 1994-1996 and 2002-2004 period were constant at 0.2 fish/hr, even though number of fish captured by electrofishing in each study increased over time (8 and 18, respectively). In 2005, electrofishing capture rate for northern pike remained constant at 0.2 fish/hr (N = 16 total fish), but declined to 0.09 (n = 8) in 2006. Reduced capture rates in 2006 may reflect continued upstream removal in the Yampa River, increased effort in lower Lodore Canyon where pike appear concentrated, or variation in abundance or sampling efficiency. Several captured pike had been previously tagged and had dispersed downstream from the middle Yampa River. For example, in 2003, all four recaptured pike were from the middle portion of the Yampa River (Bestgen et al. 2006). Northern pike 25