Biology in History

780 BioScience • September 2005 / Vol. 55 No. 9 M ecologists and evolutionary biologists are familiar with the saga of the introduced Nile perch (Lates niloticus) in Lake Victoria. The explosion of the lake’s Nile perch population in the 1980s was monitored closely, because it coincided both with a fivefold increase in the economic value of the fishery (Reynolds et al. 1995) and with a halving of the lake’s 500-species haplochromine cichlid flock (OgutuOhwayo 1990). This reduction in species and functional diversity restructured the lake’s ecology; for example, the disappearance of zooplanktivorous haplochromines coincided with a dramatic sixfold increase in biomass of the zooplanktivorous cyprinid Rastrineobola argentea (Wanink 1999). By the early 1990s, what had been a diverse multispecies fishery rested on only three species: the nonindigenous Nile perch, the nonindigenous Nile tilapia Oreochromis niloticus, and the diminutive R. argentea. Although some of the blame for the cichlid extinction spasm has been shifted from the Nile perch to other anthropogenic factors, such as overfishing and eutrophication (Seehausen et al. 1997), the Nile perch was certainly a major contributor. The lucrative fishery that developed for Nile perch has itself had diverse impacts. Around the lakeshore, enthusiasm over the increase in the value of the fishery has been tempered by concerns about species loss, increased economic stratification, and the fact that most Nile perch is exported and locally unaffordable (Pringle 2005). Ecologically, the intense fishing pressure on Nile perch has depressed its populations to the extent that certain species of the remnant cichlid fauna are resurging (Witte et al. 2000). These events have spawned hundreds of publications, making the Nile perch in Lake Victoria one of the beststudied invasive species in history (for a recent review, see Balirwa et al. 2003).Yet despite this wealth of knowledge, there remains confusion about exactly when, why, and by whom the Nile perch was introduced into Lake Victoria. The literature offers a range of dates for the introduction, from the 1920s to the 1960s; tracing the tortuous citation chain to the origins of these dates reveals a fundamental uncertainty about when the Nile perch was first introduced. Likewise, the motivations for this anthropogenic introduction, often ambiguously ascribed to a desire to “increase productivity,” have not been thoroughly explored. Unlike many introductions, which occur by accident or are made quietly by private citizens, the introduction of Nile perch into Lake Victoria was hotly debated at the highest levels of the British administration in colonial East Africa. As today’s ecologists often note, colonial ecologists opposed the proposal (Fryer 1960). The eventual introduction of the Nile perch therefore represents the failure of ecologists to communicate and implement their vision for Lake Victoria. Although this failure was at least partially due to the familiar problem of trying to regulate a common resource, I suggest that there were two additional factors at play.