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it ~e i- :s ~e ~- d d ~- d h y :r e i- Direct Control of Fauna reproducing native fish populations. Hatchery fish are a means to achieve this kind of goal, but ark not by themselves the raison d'etre for fish management. Obviously we aze advocating re- habilitation over mitigation as the first choice for managers of riverine fisheries. However, there will be many situations where mitigation using hatchery fish is the only means available for river management, e.g. where spawning habitat is permanently lost or water quality changes prevent self-sustained populations. The demand for high- quality, inexpensive and readily available protein may eliminate most if not all options except the use of hatchery fish for aput-grow-and-take fisheries management system. In the Orient, and in' many European and African river systems, fish communities necessary for human survival would fail without the support of stocking. Our examples focus on multi-agency experi- ences derived from nearly 150 yeazs of managing fish communities and their fisheries in the Laurentian Great Lakes Region and other parts of North America. On the one hand, this chapter may not serve managers from Europe and Asia who are working with rivers with longer manage- ment experiences and already altered fish com- munities. However, we feel the North American experience is relevant for river managers in de- veloping countries facing major demands for increased fish extraction from severely-stressed native fish communities, and who are trying to develop a place and purpose for fish culture to maintain some form of sustainability. North Americans made horrendous decisions in the mid-1800s that continue to this day to thwart sustainability of fish communities in the Great lakes ~e.g. introduction of the smelt, Osmerus mordax~. These lessons, and the 1990's approach to managing the Great Lakes ecosystem with hatcheries as a major component, can help river managers throughout the world. For the purposes of this chapter, we have con- fined our discussion to the intentional release of chosen species. There is no doubt that similar and often more disastrous effects can be traced to introductions of new species that have escaped confinement or that were accidentally introduced by an unsuspected vector. One hundred years of rainbow trout ~Oncorynchus mykiss~ culture and 387 stocking worldwide have created naturalized, often self-sustaining, populations which have already caused most of their potential effects. However, rainbow trout escapes from intensive pond culture (e.g. in southern England) threaten native brown trout (Salmo trutta~. Similarly, the introduction of ruffe (Gymnocephalus cemus) into Lake Superior from ballast water taken at a European port carries the potential for an eco- logical disaster for native Great Lakes percid communities ~e.g. Stizostedian vitreum, Percn flavescens~. All this points up the importance of planning, of understanding the needs of the fish being cul- tured (or being considered for culture and intro- duction) and of assessing the potential effects on endemic fish communities from the stocked fish before one puts great reliance on a fish culture system to sustain a fishery. This chapter is divided into sections that ex- amine first the basic principles of fish culture and the product desired; secondly, the factors that influence the survival and growth of the fish; and finally the role of regulations. 20.2 HATCHERIES AND FISH STOCKING History of stocking The art and science of fish culture are ancient pursuits. The Chinese cultured carp (Cyprinus carpio~ and goldfish (C. crassus~ for food and ornamentation as early as 4000 s.P. ~MacCrimmon 1968; Balon 1974. Although little evidence is available showing that these and other species were purposely introduced into 'wild' environ- ments, there is no doubt that ponds and raceways failed as frequently then as they have in modern times so that cultured fish were released to new environments to start new populations. Despite a common misconception, trout and salmon culture is a relatively young industry. In the mid-1700s, Stephen Jacobi successfully stripped and fertilized trout eggs and noted the effects of light and temperature on the developing embryos. Although his successes in Germany were well publicized, a Frenchman, Joseph Remy,