Northern Pike Esox lucius are native to the mid-western United States, parts of Alaska, and the Saskatchewan River drainage in Montana (Wydoski and Whitney 2003). Northern Pike are a highly invasive fish species that have been shown to significantly reduce prey fish densities and have the potential to cause large-scale changes in fish communities, even resulting in species elimination (He and Kitchell 1990; McMahon and Bennett 1996).  Northern Pike pose significant threats to the Columbia River ecosystem including predation of native species, introductions of wide variety of parasites and disease, and competition with other species for food resources (Baxter and Neufeld 2015).

Northern Pike spawn in shallow water (<0.3 m) in the late winter or early spring when water temperatures reach 8.9 °C (48 °F).  Northern Pike grow rapidly within the first two years and reach sexual maturity between ages 3 and 5. Pike prefer marshy habitats with dense vegetation in streams, lakes and large rivers.  They occupy littoral habitats, but prefer cool water which causes them to head to deeper water in the summer.  Northern Pike are considered an ambush predator and will feed on a variety of organisms up to 75% of their body length.

Northern Pike were first collected in the Pend Oreille River system in 2004.  The unchecked population exploded and increased from 665 in 2006 to >10,000 in 2011 (Bean et al. 2011; Bean 2014; King and Lee 2016) (Connor and Black 2010; King and Lee 2016).  Aggressive mechanical removal in the Box Canyon Reservoir reach of the Pend Oreille River was implemented by the Kalispel Tribe and Washington Department of Fish and Wildlife (WDFW) in 2012. The Box Canyon Reservoir Northern Pike removal effort has been successful.  Catch rates and abundance have been reduced from a high of 12.2 pike/net night in the initial year to 0.18 pike/net night in 2015 (Bean 2014; Harvey and Bean 2016).

Despite the removal efforts in the Pend Oreille River drainage, the distribution of Northern Pike expanded downstream to the Columbia River.  Northern Pike have been detected in the Columbia River both upstream and downstream of the confluence with the Pend Oreille River.  Northern Pike were detected in 2009 below Hugh Keenleyside Dam, and have colonized a significant portion of the Canadian Columbia River near Castlegar, British Columbia (Baxter and Neufeld 2015).  In 2014, the Ministry of Forest Land and Natural Resources Operations (MFLNRO) recognized the threats associated with Northern Pike and initiated a gill net removal program, liberalized angling regulations (unlimited), and implemented an incentive program aimed at encouraging anglers to remove Northern Pike (Baxter and Neufeld 2015).  

The first Northern Pike were first documented in upper reach of US portion of the Columbia River (Lake Roosevelt) in 2007 at Alder Creek (near Hunters, WA) (Lee et al. 2007).  Since then, Northern Pike have been increasing in observance during the Fall Walleye Index Netting (King and Lee 2016) and in White Sturgeon surveys (Seibert et al. 2015; King and Lee 2016).  Northern Pike were first observed in the fishery in 2014 and are now routinely captured by anglers (King and Lee 2016; Spokane Tribe of Indians unpublished data).

In 2014 the Spokane Tribe of Indians (STOI), in collaboration with WDFW and the Colville Confederated Tribes (CCT), submitted a request for funding to the Northwest Power and Conservation Council to support Northern Pike monitoring and suppression in Lake Roosevelt.  In 2015, the Council provided limited funding to monitor and suppress Northern Pike in three annual installments of $69,629, $40,000 and $40,000.

The WDFW, STOI, and CCT implemented a standardized Northern Pike survey in the Kettle Falls area of Lake Roosevelt in June of 2015.  The catch rate of Northern Pike was 0.08 pike/hr in gill nets (n = 21).  During a follow up survey in February 2016 the catch rate had increased to 0.38 pike/hr (n = 71) (Lee and King 2015; King and Lee 2016).  However, the June 2016 catch rate decreased to 0.12 pike/hr (n = 4) (C. Lee, WDWF, personal communication).  The decrease in adult catch rate was promising, until periodic boat electrofishing surveys in August found a substantial number of juvenile Northern Pike (n=100) in shallow bays of the Kettle River (12.3 pike/hr; CCT unpublished data).  Additional juvenile sampling by the STOI further documented high abundance with an additional 797 juvenile Northern Pike captured during 16.5 hrs of boat electrofishing (48.3 pike/hr) and 152 were captured during juvenile White Sturgeon sampling in October (STOI unpublished data).

Northern Pike are a severe threat to the Lake Roosevelt ecosystem.  The lake supports native Redband Trout Oncorhynchus mykiss, kokanee O. nerka, Burbot Lota lota, White Sturgeon Acipenser transmontanus, and other native minnows and suckers.  The ecological consequences, both to fish and other animals, have the potential to be devastating.

The co-managers of Lake Roosevelt mutually agree that an aggressive removal effort, similar to those that have been implemented by the Kalispel Tribe and WDFW in the Pend Oreille system and the MFLNRO in the Columbia River in Canada, is necessary to curb the expansion of the Northern Pike population in Lake Roosevelt and prevent them from expanding downstream into areas of the Columbia River with anadromous fish populations.

Aggressive fish removal techniques can all be employed during various times of the year to maximize catch rates of Northern Pike and to limit mortality of by-catch.  The co-managers of Lake Roosevelt wish to pool resources and attack the problem using a multi-faceted approach.  It is our goal to stop the spread of Northern Pike and eliminated them from Lake Roosevelt.

Work Plan Outline
The Colville Confederated Tribes wished to use coordinate with the co-managers of Lake Roosevelt and:  
1.  Assist with the Northern Pike adult abundance surveys led by WDFW
2.  Conduct adult Northern Pike suppression surveys in cooperation with the Spokane Tribe

Combined, these monitoring and suppression efforts will limit the spread of Northern Pike and provide managers with information to further reduce the impacts within Lake Roosevelt.