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<br />liJ24:J7 <br /> <br />The AFS had previously adopted protocols for introducing fish species (Kohler and <br />Courtenay 1986). <br /> <br />There is little doubt that control of nonnative fishes will cause some reduction in <br />recreational fishing opportunities; it is a necessary tradeoff. However, there are ways <br />to mitigate such losses. On the other hand, if no action is taken to control nonnatives, <br />and endangered species are lost, damage to the natural ecosystem cannot be <br />mitigated. Both Federal and State agencies have responsibilities for protecting <br />nongame species and for providing recreational spot fishing opportunities. Both are <br />evaluating solutions. State agencies are working to refine stocking protocols and <br />assisting with identifying potential problem areas. Federal designation of critical <br />habitat (USFWS 1994) included a predator-free environment as a primary constituent <br />element of critical habitat needed for recovery of the endangered Colorado River <br />fishes. All federal agencies are mandated by the ES Act to do everything in their power <br />to assist with those provisions needed in critical habitat, including aiding control <br />measures for nonnative fishes or by assisting in mitigating losses in sportfishing. <br /> <br />Present Technology, Constraints, and New Options <br /> <br />Fish control measures have been so widely used in the US that almost all fish <br />species have been the object of some control program (Wiley and Wydoski 1993). The <br />most commonly controlled fish include herrings, minnows, and sunfishes (54% of <br />effort), suckers (11 %) and bullhead catfishes (11 %). Wiley and Wydoski (1993) <br />provide a comprehensive review of techniques, which fall generally into three <br />categories: mechanical, chemical, and biological. Most of the techniques have been in <br />use for many years and are well understood. Some of the more recent, and exotic, <br />techniques (such as filtration of small life stages or establishment of fish <br />guidance/removal facilities) are costly to implement. <br /> <br />A simple recitation of techniques without context is of little interest, because the <br />choice of techniques is heavily influenced by the target species and the habitat in <br />which the technique will be applied. It is therefore more useful to survey techniques <br />that might be applied for controlling non natives in the UCRB. <br /> <br />There have been several reviews of control techniques that might be applied in <br />the UCRB (Hawkins and Nesler 1991, Nesler 1995, Lentsch et al. 1995). In general, <br />these reviews cover control methods that are well known among fisheries managers. <br />Those authors advocate a cautious approach of establishing test areas and evaluating <br />control effectiveness before applying a technique to other areas. The authors justified <br />their caution by stating that the performance of individual control teChniques has not <br />been adequately studied in the UCRB. Some recommendations provided by Lentsch et <br />al (1995) included: liberalizing fishing regulations to promote higher angler take; <br />mechanical removal by nets, traps and shocking; barriers to keep out nonnative fishes; <br /> <br />20 <br />