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i 392 Management Options of the native chary (Salvelinus fontmalis~. Similar effects are predicted to happen to brown trout (Salmo trutta) in the UK as rainbow trout become more established. In several jurisdictions, a more conservative approach is being used to select species for fisheries management programmes. Many govern- ments have enacted legislation and policies which restrict the movement of fish within their jurisdictions. In cases where waters are shared between nations, such as the Great Lakes in North America, co-operative policies and protocols have been developed to ensure that introductions or range extensions of species are not made without adequate consultation with stakeholders, and that proper assessment of the environmental risks involved is undertaken. Another example of multinational protocols is the Code of Practice adopted by the European Inland Fishery Advisory Committee (EIFAC) in 1987 for the regulation and control of fish introductions. For most stocking applications, only native fish species should be considered. Native species will provide the most predictable results, with the least risk of environmental consequences. How- ever, most species of fish are not homogeneous in terms of their characteristics; fish stocking pro- grammes which use the wrong genetic strain for a specific purpose can be just as damaging to local, native fish communities as if a non-native species were introduced. Genetic strain A fish species may consist of many unique genetic strains which have evolved as a result of distinct geographical, behaviourial or temporal factors. Ignorance of the importance of protecting fish stocks has led to the loss of genetic diversity in many fish populations, causing loss of population fitness. Recent developments in fish culture, such as rotational line crossing of broodstock lines to reduce inbreeding, and the use of large numbers of randomly selected wild brood fish to maximize genetic diversity, can reduce the loss of genetic diversity in fish populations. Selection cannot be eliminated entirely. Nature does not always act randomly, and fish collection tech- niques are often selective. Even if we were able to maintain genetic diversity, environmental factors occur in fish bulture which are fundamentally different to those in a wild environment. Broodstock management The management of broodstocks in a fish culture programme should be aimed not only to ensure an adequate and consistent supply of eggs for rearing and eventual stocking, but also to establish careful breeding programmes, and to maintain the genetic diversity of those stocks over several generations. Genetic variability is important for maintaining maximum hatchery production levels, for disease resistance, and for the ability of progeny to adapt to new environments after stocking. Artificial propagation and rearing procedures used in contemporary fish culture tend to reduce the genetic diversity of captive broodstocks, re- sulting ultimately in inbreeding and associated loss of vigour. The protection afforded by the hatchery environment enables less fit individuals to survive, and because fewer parents produce relatively higher numbers of offspring than in natural conditions, the potential for siblings to be crossed one with another is greater. To avoid-the potential inbreeding effects of fish culture practices a number of principles should be considered in establishing and propagating broodstocks held in fish culture stations. In collections of eggs from the wild to establish a new broodstock, and in propagating captive broodstocks in hatchery: 1 parents should be a random sample from the spawning population with no selection on the basis of size, appearance or other characteristics; 2 select from the entire spawning season or run, preferably with 25% of parents spawned when 15% of females are ripe, 50% spawned when 40% are ripe, and the remaining 25% when 70-80% of females are ripe; 3 a minimum of 50 spawning pairs should be used; 4 coatings should be on a single pair basis, i.e. single males should be used to fertilize the eggs of single females with no pooling of eggs or milt; 5 individual families should be kept separate from fertilization through to incubation;