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" It water oses for strategy :ssen tial tat daily gulation :igure 6, the legal led with- j Hauer, ing grids lIe, mod- I utilities wee. The lic desire ,f shallow , all three !Od reser- chanisms le flowing lain point Julations, the other ve speCies m by dams, : critically ically and trategy of areas con- m the core ial supple- this strat- ;). Perhaps I key ques- .0 decades he species ashington, erti et ai" e histories hat loss of ;>eration of cion can be Jgy, While RESTORATION OF REGULATED RIVERS 407 economically important, non-native salmonid and other fisheries have been established from cultured stocks in river segments world-wide, in almost every case this practice has failed miserably to meet its objective of replacing lost fisheries (Lichatowich, in press). Stocking of native and non-native fish has irresponsibly compromised native food-webs around the world and is rightfully called the Frankenstein Effect (Moyle et al., 1986). A large body of literature debates this problem; the bottom line is that culture operations should be avoided unless native biota are clearly headed for extinction as a consequence of habitat loss (Minckley and Deacon, 1991; Hilborn, 1992) Even then, cultured stocks cannot be expected to re-establish if they are simply released back into the same degraded habitats. Ecological bottlenecks that compromised endangered species in the first place have to be rectified, and the only way to do that in large river systems is to restore habitat in a continuum context. Be wary of management actions that attempt to control riverine food webs Perhaps the greatest uncertainty in reregulating river systems to restore hot spot connectivity (Figure 2) is the unexpected consequence of the inexorable proliferation of non-native biota, Wendell Minckley and James Deacon, the sages of fish ecology in the species-rich American Southwest often rightly noted that locally adapted fish of the desert are clearly able to deal with extreme environmental variation, but natives are quickly depressed or driven to extinction by food-web change associated with invasions of non-native species (e.g. Minckley and Douglas, 1991), However, restoration of natural flow and temperature dynamics compromises the ability of non-native species to sustain viable populations and promotes native species (Li et aI., 1987; Meffe and Minckley, 1987; Bain et al., 1988) Even with restoration of the full range of natural flow variation, interactions with non-native plants and animals will most likely continue to be a problem for native biodiversity management and conservation, One alternative is to control non-native populations by aggressive harvest. However, it is very difficult to do this without also affecting natives, and prediction of the influence of the food-web structure is tenuous at best. Moreover, in some cases one or a few native species have become very abundant in regulated rivers along with non-natives, For example, native squawfish (Ptychocheilus oregonensis) in the Columbia River, USA, are thought to be a major source of predation mortality for juvenile salmon, which exist in very depressed populations (Poe et ai" 1991; Rieman et aI., 1991) and a very aggressive control programme has been initiated by paying fishermen a bounty for each squawfish caught. However, food-web structure in the lower Columbia River is poorly known, a wide variety of non-native predators are present and predicting food-web responses as well as influences on salmon mortality is tenuous. A congener (P.lucius) in the Colorado River is listed as endan- gered and a very expensive recovery program has been initiated, For many people these strategies seem at cross- purposes, even though the ecology of the two species is very different. In general, the effectiveness of predator control programmes is minimal or poorly demonstrated even though it is a very popular management strategy, We agree with Goodrich and Buskirk (1995) that popula- tion control of abundant native vertebrates should be a strategy of last resort for conservation of rare natives. Columbia River salmon evolved with squawfish predation and restoration of proper habitats for salmon smolts clearly should reduce smo]t mortality, However, constraining proliferation of non-native plants and animals is an obvious need for conservation of native biodiversity. Again, the preferred approach may be to implement reregulation to restore lost habitat and allow the food-web to adjust as it will. The available body of information suggests that natives will fare better than non-natives. Clearly, it is advisable to document and monitor food-web dynamics carefully from a commu- nity ecology perspective. Use adaptive ecosystem management Any strategy to remediate the effects of large river regulation will require an adaptive approach, Scientists can be relied upon to document ecological problems by research and synthesis of empirical information on cause and effect, but the solution of problems must involve knowledge of human perceptions and desires, which are often different from that inferred by the strict interpretation of the science (Ludwig et ai" 1993), In most cases, inefficient information transfer between science, management, policy makers (govern- ment) and the general public hinders the attainment of common ground.