Fish Faunal Resurgence in Lake Nabugabo, East Africa

Chapman, Lauren J.; Chapman, Colin A.; Schofield, Pamela J.; Olowo, J. P.; Kaufman, Les; Seehausen, Ole; Ogutu‐Ohwayo, R.

doi:10.1046/j.1523-1739.2003.01519.x

Cited by 54 publications

(65 citation statements)

References 38 publications

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“…However, one piscivore, Prognathochromis venator, has never been recovered. Several noncichlids also reappeared or increased in abundance in main Lake Nabugabo (Chapman et al 2003). With respect to species numbers, the Nabugabo cichlid fauna was poor even before Nile perch was introduced; the species richness of the lake and its pattern of faunal recovery are comparable to some turbid inshore areas of Lake Victoria.…”

Section: Conservation Of Biodiversity In the Lake Victoria Regionmentioning

confidence: 72%

See 1 more Smart Citation

Biodiversity and Fishery Sustainability in the Lake Victoria Basin: An Unexpected Marriage?

Balirwa¹,

Chapman²,

Chapman³

et al. 2003

BioScience

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223

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Articles Overfishing, environmental degradation, and redistribution of surface water have placed great stress on inland fisheries throughout the world. Human activities usually shift the balance among fish species, causing the extirpation of many indigenous species and the dominance of a reduced set of often introduced fish species. The result has been a massive reshaping of fish communities in the world's fresh waters over the past few centuries, with the pace of change quickening of late in the tropics.It has been known for some time that fishes react to environmental degradation and fishing pressures with a characteristic series of changes. If too much of the brood stock is caught, fewer and fewer recruits appear in the population in succeeding years. This is called recruitment overfishing. The impact is somewhat different if the large fish in a population are taken first, then smaller ones, and so on. The mean size of individuals drops, and there is selection for individuals that mature at a smaller and less fecund size. This is growth overfishing. Each of these phenomena has a counterpart corresponding to effects that become apparent when more than one species or stock is taken into consideration.Three decades ago, Regier and Loftus (1972) observed a multispecies analog to growth overfishing while they were researching the anthropogenic transformation of fish communities in the Great Lakes of North America. What they described-the successive removal of the largest-bodied species-was later generalized Henderson 1973, Welcomme 1995) and has been called the "fishing-down Uganda, Box 343, Jinja, process." Greater fishing pressure can initially bring about a higher catch, followed by a plateau over a range of increasing exploitation as component fish stocks are serially depleted. First large, and then successively smaller, species are removed and their places taken by even smaller and faster-growing ones, producing an illusion of sustained productivity that conceals deep changes in community and food web structure. Eventually there are no more economically exploitable stocks, and both the fishery and the fish community collapse or are changed beyond recognition (Welcomme 1995(Welcomme , 2003. John S. Balirwa is acting director of the Fisheries Resources Research Institute ofIn Africa, overfishing is a recurrent problem closely tied to environmental conditions. Africa has suffered food crises for decades, exacerbated in the Sahelian zones by prolonged drought through the late 1970s and the 1980s. When severe drought compromises production of livestock, rural communities turn to hunting and fishing to satisfy their protein needs. What worked for a long time when people were relatively few can have quite different impacts on wildlife at the currently very high human population densities. Thus, food crises, together with a political orientation of open access to wild resources such as fish, have led to a rapid increase in fishing pressure. This effect is further compounded by the rapid improvement and disseminat...

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Section: Conservation Of Biodiversity In the Lake Victoria Regionmentioning

confidence: 72%

“…In 1995, haplochromine cichlids were largely confined to inshore areas and were very rare in Nile perch stomachs (Chapman et al 2003). By 2000, haplochromine cichlids had increased dramatically in abundance both in the lake and in Nile perch stomachs (figure 6).…”

Section: Conservation Of Biodiversity In the Lake Victoria Regionmentioning

confidence: 99%

Biodiversity and Fishery Sustainability in the Lake Victoria Basin: An Unexpected Marriage?

Balirwa¹,

Chapman²,

Chapman³

et al. 2003

BioScience

Self Cite

223

220

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show abstract

“…It is tempting to speculate what would have happened if, as Worthington suggested in 1932, an experimental introduction had been made into Lake Nabugabo. What ultimately happened in Lake Nabugabo was similar to what happened in Lake Victoria, with approximately 50 percent of indigenous fishes disappearing from open waters (Chapman et al 2003). This is hardly the "natural balance" that Worthington (1932) was looking for.…”

Section: Discussionmentioning

confidence: 86%

The Origins of the Nile Perch in Lake Victoria

Pringle

2005

BioScience

149

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“…Instead, competition reduces growth and prolongs the period when juvenile least chub are vulnerable to mosquitofish predation. A spatial or temporal refuge from negative interactions would allow the time and/or energy needed for development of characteristics (e.g., rapid growth) that would increase the survival of native species (e.g., Chapman et al 2003). However, this is often not possible, especially when native and invasive species are similar in size and, thus, view the world on similar spatial and temporal scales.…”

Section: Discussionmentioning

confidence: 96%

Complex interactions between native and invasive fish: the simultaneous effects of multiple negative interactions

2004

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We suggest that the ultimate outcome of interactions between native species and invasive species (extinction or coexistence) depends on the number of simultaneous negative interactions (competition and predation), which depends on relative body sizes of the species. Multiple simultaneous interactions may constrain the ability of native species to trade fitness components (i.e., reduced growth for reduced risk of predation) causing a spiral to extinction. We found evidence for five types of interactions between the adults and juveniles of introduced western mosquitofish (Gambusia affinis) and the juveniles of native least chub (Iotichthys phlegethontis). We added ten large (23-28 mm) and seven small (9-13 mm) young-of-the-year (YOY) least chub to replicate enclosures with zero, low, and high densities of mosquitofish in a desert spring ecosystem. Treatments with mosquitofish reduced the average survival of least chub by one-third. No small YOY least chub survived in enclosures with high mosquitofish densities. We also performed two laboratory experiments to determine mortality to predation, aggressiveness, and habitat selection of least chub in the presence of mosquitofish. Mean mortality of least chub due to predation by large mosquitofish was 69.7% over a 3-h trial. Least chub were less aggressive, selected protected habitats (Potamogeton spp.), and were more stationary in the presence of mosquitofish where the dominance hierarchy was large mosquitofish>>large least chub approximately small mosquitofish>>small least chub. Least chub juveniles appear to be figuratively caught in a vice. Rapid growth to a size refuge could reduce the risk of predation, but the simultaneous effects of competition decreased least chub growth and prolonged the period when juveniles were vulnerable to mosquitofish predation.

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Fish Faunal Resurgence in Lake Nabugabo, East Africa

Cited by 54 publications

References 38 publications

Biodiversity and Fishery Sustainability in the Lake Victoria Basin: An Unexpected Marriage?

Biodiversity and Fishery Sustainability in the Lake Victoria Basin: An Unexpected Marriage?

The Origins of the Nile Perch in Lake Victoria

Complex interactions between native and invasive fish: the simultaneous effects of multiple negative interactions

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