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NEST-SPECIFIC BASS DNA FINGERPRINTS 457 tion, thus increasing the probability of matings between close relatives, It is not clear whether in- breeding results from a species being philopatric or philopatry evolved to facilitate inbreeding (Shields 1982), Our DNA fingerprinting data provide support for the hypothesis that smallmouth bass in Lake Opeongo are philopatric, resulting in some level of inbreeding, Reeve et al. (1990) found that full siblings of inbred colonies of naked mole-rats Hel- erocephalus glaber had an average SI of95,O, and Schartl et al. (1991) calculated a similar value for a clonal fish, the amazon molly Poeciliaformosa, Lehman et al. (1992), working with gray wolves Canis lupus, found that full siblings with inbred parents had an average SI of 78,7, On the other hand, average SI values calculated for outbred full siblings oflargemouth bass Microplerus salmoides and threespine stickleback Gaslerosleus aculealus were 66,0 (Whitmore et al. 1990) and 56,0 (Rico et al. 1991), respectively. Therefore, the SI of87.2 for full-sibling smallmouth bass in Lake Opeongo probably represents an inbred population, Limited evidence for inbreeding also comes from comparisons of banding patterns between the male and female mates in two pairs of smallmouth bass captured while spawning, which had an average SI value of69.5 (fingerprint data not shown), This value is higher than the population SI value of 52,5, suggesting that these two spawning pairs were inbreeding (rather than randomly mating) because they are more closely related to each other than to the population in general (the SI value increases with increasing relatedness; Lynch 1988), More extensive sampling of spawning pairs is needed to confirm the generality of this finding for the Lake Opeongo population. Evidence of philopatry for the Lake Opeongo smallmouth bass is supported by the higher av- erage 51 value for fry from closely spaced nests (67,2) than for fry from nests distributed through- out Jones Bay (52.5), This results suggests that fry from nests clustered together are more closely re- lated to each other than are Jones Bay fry in gen- eral. If nest site selection were random (no occur- rence of philo patry), an SI value ofapproximately 52 would be expected for fry from closely spaced nests, Although philopatry has not been explicitly demonstrated for small mouth bass, the species is capable of homing (Larimore 1952) and adults have high nest site fidelity (Ridgway et al. 1991). Preliminary telemetry data for Lake Opeongo smallmouth bass indicate that the fish set up sum- mer home ranges that can be very distant (several kilometers) from where they spawn (Mark Ridg- way, Ontario Ministry of Natural Resources, per- sonal communication), These observations sug- gest that adult fish move throughout the lake and are aware of other spawning sites, but still return to their previous spawning area, An additional explanation for the observed high levels of homozygosity within nests, which form the basis of the observed nest-specific DNA fin- gerprints, may be that they are the result of a pop- ulation bottleneck, a phenomenon that may have occurred when smallmouth bass were initially stocked into Lake Opeongo in the 1920s. A pop- ulation bottleneck is defined as a severe temporary reduction in population size (Hartl and Clark 1989), Population bottlenecks increase the ho- mozygosity of a population because a dramatic reduction in population size increases the likeli- hood of inbreeding, In our opinion, such a bottle- neck is an unlikely cause of the relatively high homozygosities within nest cohorts. If a bottle- neck had occurred, one would expect the popu- lation as a whole to have increased homozygosity and very similar DNA fingerprints among nest cohorts, thus precluding nest-specific fingerprints. In conclusion, we have observed an unexpected pattern of nest-specific DNA fingerprints in one lake population of smallmouth bass. The gener- ality of this phenomenon for lake and river pop- ulations of this species is currently unknown and requires additional research. These results raise intriguing questions about the roles of philopatry and inbreeding in the life history strategy of this Lake Opeongo population, Nest-specific DNA fin- gerprints could become a powerful tool for man- agement of fisheries populations in which they oc- cur because they would allow monitoring of individual reproductive success to any life stage, This would make it possible to determine patterns of temporal and spatial variability in individual reproductive success and to elucidate roles of myr- iad factors in control of reproductive success, Un- derstanding these patterns and the factors that drive them will help managers to improve harvest regulation and direct habitat management so as to prevent diminution of individual reproductive success, Acknowledgments We thank the Ontario Ministry of Natural Re- sources, particularly M. Ridgway, L. King, and the staff at the Harkness Laboratory of Fisheries Re- search, for help in collection of samples, We would