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iy KS ie es ig ys 3y :k al e, ut c- io le is z. ~n ~e it s, ~o ~s ~r -g is ae es ;n ~s le c- ~s es ~r- es c- or :n es is D~~rect Control of Fauna of fish species was to maintain or increase yields and harvests. Some introductions met this pur- posebut others may have compromised long-term sustainable harvests, in part by altering the aquatic environment and competing with native species. The short-term benefits have .increased the fish protein supply in these countries but more reseazch and assessment aze necessary to understand how introductions serve the reaching of long-term objectives (Ogutu-Ohwayo 8t Hecky 1'991 ~. Holcik (1991 ] identified at least 134 fish species that had been introduced or relocated within 29 European countries, especially Central and Eastern Europe. He noted that poor success was recorded for most cases, as well as measurable ill-effects on native fish and their habitat. For further reading, especially for analyses about the implications to fish genc;tics and aquaculture from introductions, the publication by Billington and Hebert (1991) is an excellent reference. It is imperative that fisheries managers use some disciplined decision-making when con- sidering introductions as a means to re-establish a fishery. One approach applied by the. Province of Ontario (Canada) as a procedure to evaluate proposals to stock species beyond their current range in Ontario waters is a sequential decision model adapted from Kohler and Stanley (1984]. Using this model, the decision process continues until the fast `REJECT' decision is reached. Successful completion of the decision model would lead to a decision to approve the stocking (see also Fig. 20.1]. 1 (aj Are reasons for introduction valid (includ- ingdemonstrated need which cannot be met by other management actions[? [No-REJECT] (bj Would adequate precautions be taken to safeguard against introduction of disease and parasites? ]No-REJECT] 2 (aj Would the species be able to survive in the range of habitats that would be available? [No -REJECT] 3 (aj Would the species have adverse ecological impacts? [Yes- REJECT] (bj Would the species potentially be hazazdous to humans? (Yes- REJECT] (c) Is the species endangered, threatened or rare in its native range? (Yes-- REJECT] 389 Unless: (i) purpose is to create a refuge, to prevent species extinction, and/or (iij source of fish is a hatchery stock or na- turalized population(s) which is (are] not threatened in any fashion. (aj Was database adequate to develop a com- plete species synopsis? [No-FURTHER RESEARCH] Based on all available information, do the ben- efits of the fish introduction outweigh the risks? (No-REJECT; Yes- APPROVE; Unclear - FURTHER RESEARCH] Hatchery-dependent fisheries Stocking is also used to provide a fishery in water bodies where natural reproduction cannot occur. These hatchery-dependent fisheries often provide important social and economic benefits, and the lack of natural reproduction may actually be ben- eficial since it may limit the damage caused by bad stocking decisions. However, hatchery-dependent fisheries have often been used without adequate consideration of biological, social or economic implications. For example, the adaptability of introduced species to reproduce naturally in water bodies where they `couldn't' has tested the credibility of many respected fisheries biologists. An example of casual approaches to a potential disaster is the treatment of the spread of the wide-ranging cyprinid, the rudd (Scardinius erythrophthalmus), throughout North America. Although the species arrived in the USA in 1916 (Cahn 1927], Courtenay et al [ 1986) considered the species as part of a group of non-native fish whose populations were in decline, as if there were unlikely now to be any effects. However, the rudd was being cultured in ponds in central USA and distributed extensively to anglers, who preferred it as bait to catch bass. Now Burkhead and Williams (1991) report that the rudd has interbred with the native cyprinid golden shiner (Notemigonus crysoleucas] to pro- duce the first non-salmonid intergenic hybrid in North America. The potential effects on any fish community where golden shiner is the major forage species may be horrific; the loss of the genetic pool called golden shiner is immoral.