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multiple populations within groups. Only when armed with such knowledge can the manager make informed decisions with respect to preservation of genetic resources. Electrophoretic analysis of all brood stocks should be con- ducted to determine levels of genetic variation, from which all subsequent variation will be derived. Such analysis can be completed without sacrificing individuals: muscle, fin, blood, or even skin mucous (M. H. Smith, personal com- munication) for example, may be obtained for testing with little damage to the fish. Subsequent captive generations should also be sampled periodically (every few generations, if they are retained in captivity for that long) to determine changes in allele frequencies or detect loss of alleles. Such programs have revealed significant genetic deterioration of hatchery salmonid stocks (Ryman and Stahl 1980; Cross and King 1983; Stahl 1983), and could provide the basis for man- agement decisions with respect to genetic welfare of captive endangered fishes. It is only through informed genetic mon- itoring that we can reasonably expect to maintain rare fishes for extended periods of time. In all cases of intervention for management, the largest feasible Ne should be initiated and maintained in a captive breeding program (Table 1). "It is inevitable that some of the natural variability of a species is inadvertently lost when individuals are established as founders of a hatchery stock, and that more and more variability is inadvertently lost in each generation of intensive hatchery production" (Wilkins 1981, p. 217). As a result, the "basic rule of conservation genetics" (Soule 1980) is that a genetically effective popu- lation size of 50 is the minimum requirement for short-term survival (on the order of several generations). This number will result in a 1% AF per generation, which is tolerable for several generations. For long-term genetic health, Franklin (1980) suggests a minimum Ne of at least 500, with an as- sociated inbreeding coefficient of 0.1% and a low rate of genetic drift. Of course, larger populations than this are desirable. Ne in any case may be maximized by maintaining equal sex ratios of breeding adults, insuring even progeny distribution by individual breeding and culling of excess offspring (Frankel and Soule 1981), and avoiding population crashes. Such action will minimize further erosion of quan- titative genetic variation through bottlenecks or drift, and will reduce loss of rare alleles and inbreeding effects. These problems can also be countered by periodic introduction of wild individuals (from the same locality as the original brood stock) into the captive population. If a large population cannot be acquired or maintained in captivity, inbreeding can still be avoided by a controlled selective breeding program that minimizes relatedness of mated individuals (Tave 1984). One example of such a breed- ing scheme is outlined in Fig. 5; many other schemes are possible (e.g., Flesness 1977; Senner 1980). An innovative program that actually utilizes inbreeding to an advantage in cases where few founders are available and others cannot be obtained was successfully applied to the rare Speke's Gazelle (Gazella spekel) by Templeton and Reed (1983). Stocks should be kept in hatchery environments only long enough to accomplish outlined breeding goals such as sci- entific investigation or building a reintroduction stock. Min- imizing time spent under artificial conditions reduces the probability of bottlenecks, drift, inbreeding, artificial selec- tion, domestication, catastrophic losses or disease. By "cir- culating" populations through a hatchery and quickly back P F? F2 Figure 5. One potential scheme for reducing inbreeding in a small captive population, starting with a parental stock of only three males and three females. In each generation, offspring are out- crossed with other lines rather than allowed to freely interbreed as one common stock. The latter practice would result in sib coat- ings and an increase in inbreeding. into the wild, one can avoid most of the pitfalls associated with genetic changes in captivity, and thereby maintain healthier populations of endangered fishes. Smith and Chesser (1981, p. 18) emphasized this point: "To prevent the loss of genetic variability caused by drift and inbreeding, it is important that hatchery and restocking programmes do not maintain spawning stocks as independent units for long periods (Ryman and Stahl 1980). Periodic replacement of hatchery fish with those from natural populations is also advised to prevent possible adaptations of fish to hatchery conditions; these adaptations may not be advantageous in natural environments." Separate stocks of isolated populations (Table 1) will max- imize inter-population variance, maintaining potentially dis- tinct forms and thereby allowing greatest flexibility in man- agement. For example, if a particular field locality is to be stocked with an endangered fish, we have the option of selecting from among several stock populations, and can choose the one whose habitat of origin most closely matches the new site. By not mixing wild populations, we retain the option of experimentally combining portions of these denies in the future, should adverse effects of small populations appear; if initially combined, however, the populations can- not later be separated. A Final Caution I have herein outlined theoretical aspects of genetic perils faced by small populations, supported by appropriate data wherever possible, and have suggested actions that may be taken to minimize these problems. For many species, stated goals simply cannot be met or even closely approximated because facilities or budgets are not adequate, or the number of extant individuals is minimal (e.g., Gambusia gagei, Poe- 20 Fisheries, Vol. 11, No. i