Our Liviiii^ Rfsourcc.'i — Fishes 



1^5 



inipoLindments with low suslainable harvest 

 levels. 



While sturgeon populations in Iree-llowing 

 and inundated reaches of the Columbia River 

 Basin have been negatively affected by the abun- 

 dant hydropower dams in most of the mainstem 

 Columbia and Snake rivers (Rieman and 

 Beamesderfer 1990). These dams have altered 

 the magnitude and timing of discharge, water 

 depths, velocities, temperatures, turbidities, and 

 substrates, and have restricted sturgeon move- 

 ment within the basin. Sturgeons in other river 

 basins have declined in response to dam-induced 

 habitat alterations (Artyukhin et al. 1978). 



Mainstem Columbia River 



Abundance and growth of white sturgeon are 

 greatest in the lower Columbia River (Figure). 

 These tlsh use estuarine and marine habitats as 

 well as riverine habitats, allowing them to feed 

 on anadromous prey fishes (those fishes travel- 

 ing upriver from the sea to spawn; Tracy 1993). 

 Although the lower Columbia River population 

 may be the only one in this basin that is abun- 

 dant and stable, even it is at some risk of col- 

 lapse (Rieman and Beamesderfer 1990). Of the 

 1 1 populations isolated between dams 

 upstream, white sturgeon are known to be rela- 

 tively abundant in only 3 (Figure). White stur- 

 geon densities in three of the remaining eight 

 populations are much lower than in the abun- 

 dant populations. Data are sparse for the 

 remaining five populations, although Zinicola 

 and Hoines (1988) reported that in 1988 fewer 

 than 10 white sturgeon were harvested in each 

 of four of these impoundments and only 34 in 

 another. 



Although the lower Columbia River popula- 

 tion probably declined during the 1980's, adop- 

 tion of more restrictive harvest regulations 

 appears to have stabilized the population (Tracy 

 1993). Successful spawning occurs each year in 

 this reach (McCabe and Tracy 1993). Catch- 

 per-unit-effort of most size groups in the three 

 populations for which data are available 

 declined considerably from 1987 to 1991; fish- 

 eries there have collapsed and the populations 

 are at risk of collap.se (Beamesderfer and Rien 

 1993). Recruitment in some populations 

 appears limited to years with high river dis- 

 charges in spring (Miller and Beckman 1993). 

 Although most of the mainstem populations 

 appear unstable, their genetic similarity to the 

 stable lower Columbia River population has 

 excluded them from consideration for listing 

 under the federal Endangered Species Act. 



Overexploitation and poaching have reduced 

 population size (Beamesderfer and Rien 1993), 

 and impoundments and altered hydrographs 

 caused by development of the hydropower sys- 



\^^^/ 



7 



Lower 

 Monumental 

 Dam ^ 



^> ^ 



' I ce Goose 

 J Harbor Dam 

 McNary Dam 

 Dam 



Lower Granite Dam 



Little 



Abundant but below 

 historical levels 



Sparse 



Endangered (ESA) 



Extirpated 



Unknown 



Hells Canyon Dam 



Montana 



Oxbow Dam 

 CO ^ Browniee Dam 



Oregon 



^"^l 



tem have altered critical spawning habitat 

 (Parsley et al. 1993). Because the factors identi- 

 fied as causing declines in other white sturgeon 

 populations are present to varying degrees in 

 each of the other eight upstream impoundments, 

 these populations are likely declining as well. 



Kootenai River 



Current research on white sturgeon in the 

 Kootenai River indicates that this population is 

 unstable and declining. The U.S. Fish and 

 Wildlife Service listed the Kootenai River pop- 

 ulation as endangered in 1994. 



This population has declined to fewer than 

 1 ,000 fish, about 80% of which are more than 20 

 years old. Apperson and Anders (1990) conclud- 

 ed that virtually no recruitment has occurred 

 since 1974. soon after Libby Dam began regu- 

 lating flows, thereby altering historical dis- 

 charge patterns of the river. This altering of dis- 

 charge patterns is thought to be a major causal 

 factor limiting recruitment into this unique stur- 

 geon population. Research on the Kootenai 

 River is examining the effects of increased dis- 

 charge on the spawning behavior of white stur- 

 geon. During 1993 increased discharges resulted 

 in the collection of only three white sturgeon 

 eggs despite intensive effoils to collect early 

 lifestages of white sturgeon (Marcuson 1994). 



Fishing for white sturgeon in the Kootenai 

 River has been regulated in Idaho since 1944. in 

 Montana since 1957, and in British Columbia 

 since 1952, indicating that overharvesting may 

 have been affecting population size. Fishing for 

 white sturgeon has been closed in Montana 

 since 1979, and catch and release angling 



Figure. Distribution and status of 

 white sturgeon in the U.S. portion 

 of the Columhia River Basin. 



