Lost in Lake Victoria: Cichlid Haplochromis microdon rediscovered after 40 years

For decades, it was considered lost—perhaps even extinct. But now there is new hope for Haplochromis microdon, an endemic cichlid species from Lake Victoria: As reported by the organization SHOAL in an article by Anna Mahulu, the species was detected for the first time since 1985 during targeted research expeditions in 2023 and 2024. A small find with great significance—not only for species conservation, but for understanding one of the most severe biodiversity losses of modern times.

A relic from the vanished world of the furu

Haplochromis microdon, also known by the synonym Lipochromis microdon, is one of the highly specialized cichlid species of Lake Victoria. As a so-called paedophage or fish fry predator, it feeds on the larvae of other—or even its own—cichlid relatives. This unusual feeding strategy reflects the enormous ecological differentiation within the furu, as the cichlids living in the lake are called in East Africa. Besides paedophages, Lake Victoria was home to algae feeders, insect feeders, snail feeders, mud sifters, parasite feeders, scale feeders, and even piscivores—each species perfectly adapted to its own niche.

This extraordinary diversity is the result of an extremely rapid adaptive radiation. Since the lake’s last desiccation approximately 12,000 years ago, an estimated 500 endemic species have evolved from just a few ancestors—nearly all from the genus Haplochromis. The animals differed in body shape, jaw mechanics, dentition, and behavior, occupying the most diverse habitats and dietary niches. Lake Victoria was therefore long regarded as one of the most important natural evolutionary laboratories in the world.

Haplochromis microdon was particularly common in the northern part of the Mwanza Gulf during the 1970s and early 1980s. Bottom trawl samples showed catch frequencies of up to 72% (1978) and 60% (1979–1982) respectively. But from the mid-1980s onward, the population collapsed dramatically. In all subsequent survey periods—such as 1987/88, 1993/95, and 2006/08—not a single specimen was recorded. The species had been considered lost since 1983. The IUCN has listed it as possibly extinct ever since.

The great catastrophe in Lake Victoria

The disappearance of Haplochromis microdon is not an isolated case—it is emblematic of the massive species loss in Lake Victoria. What was once one of the most species-rich freshwater ecosystems in the world became enormously impoverished within just a few decades. It is nearly impossible to determine exactly how many species have disappeared, as no complete survey of the fish fauna was conducted before the profound ecological changes. Conservative estimates suggest more than 200 extinct or severely decimated furu species. Other sources—such as the documentary Darwin’s Nightmare—speak of up to 400 extinguished species, including Haplochromis vonlinnei, which is known only from five specimens caught between 1978 and 1980.

The primary cause of this collapse was the deliberate introduction of the Nile perch (Lates niloticus) by British colonial officials in the 1950s. The predatory fish, growing up to two meters long and weighing 200 kilograms, was intended to make fishing more commercially profitable. But the plan turned into an ecological disaster: the Nile perch spread explosively and devoured the populations of endemic species—especially the piscivorous and predatory furu, which include H. microdon.

The Dutch biologist Tijs Goldschmidt describes the spread of the Nile perch in his book Darwin’s Dreampond (1999) as follows:

“Like the circles around a stone thrown into water, the Nile perch seems to spread in waves from the spot in Uganda where it was introduced.”

Lake Victoria thus became the scene of one of the largest documented mass extinctions in a freshwater ecosystem worldwide—and a cautionary monument to the far-reaching consequences of human interference in complex ecological communities.

The surprising rediscovery

After a multi-year hiatus, the research team led by Swiss evolutionary biologist Ole Seehausen resumed regular surveys of haplochromine species diversity in Lake Victoria in 2023 and 2024. The focus was on rocky reefs in the southern part of the Mwanza Gulf—habitats that were once considered hotspots for specialized cichlids such as Haplochromis microdon.

Success came quickly: in 2023, a male specimen of H. microdon was caught; one year later — again at the exact same location—the researchers discovered another male.

What makes this find so remarkable: the site in question had been sampled multiple times between 1989 and 2015 without H. microdon ever being spotted. In 2023 and 2024, numerous other locations were also surveyed—yet the species appeared only at this one, narrowly confined site. Everything suggests that H. microdon survives only at extremely low density, possibly in a tiny, previously overlooked refuge.

More than just a predatory fish problem

The ecological collapse in Lake Victoria was not a singular event, but the result of a complex interplay of invasive species, environmental pollution, and growing human pressure. The Nile perch may have been the most prominent factor—but it was far from the only one.

• Overfishing: Although Haplochromis microdon was never a targeted catch, it was caught as bycatch like many other furu species. Even before the mass spread of the Nile perch, populations of many species declined sharply—particularly in the shallower, easily accessible shoreline areas with high fishing pressure.
• Eutrophication: Deforestation, intensive agriculture, inadequate sewage disposal, and soil erosion introduced large quantities of nutrients—particularly phosphorus and nitrogen — into the lake. The result: massive algal blooms, reduced light penetration, and oxygen depletion, especially in deeper water layers. Habitats for many specialized species became uninhabitable.
• Hybridization due to water turbidity: The severe clouding of the water had far-reaching consequences for the reproductive behavior of many furu. Females often choose their mates based on specific color patterns. When the water is too turbid, these signals blur—both literally and figuratively. The result: mating between closely related species increased, and rare genetic lineages disappeared through hybridization.
• Water pollution & invasive plants: In addition to nutrient loading, invasive plants such as the water hyacinth (Pontederia crassipes) severely impacted the ecosystem. In the mid-1990s, it temporarily covered up to 90% of the Ugandan shoreline. The dense vegetation not only displaced native aquatic plants but also led to the decline of many fish species through oxygen depletion and habitat loss.

Why the rediscovery is so important

The sighting of Haplochromis microdon after nearly four decades is a rare glimmer of hope—and at the same time a wake-up call. The species apparently survived in a tiny refuge while it was considered lost or even extinct for decades. Its reappearance shows that biodiversity losses are often gradual and invisible, but not always irreversible. Some species disappear from the view of science without actually having disappeared.

But this find is more than a symbol of hope—it is a clear appeal. The causes that led to the disappearance of the furu are still present: habitat loss, overfishing, eutrophication, and invasive species continue to threaten the last survivors. Without measures to protect and restore the ecosystem, they too will soon appear only in old catch statistics.

What needs to be done now

To prevent Haplochromis microdon from vanishing once again—this time for good—decisive action is needed:

• Targeted conservation measures for surviving furu populations
• Long-term monitoring at known and potential refuge sites
• Improved water quality, for example through sustainable agriculture, erosion control, and effective wastewater treatment
• Education and fisheries policy strategies that secure local livelihoods without further endangering the remaining biodiversity

The rediscovery of Haplochromis microdon shows that species can survive even under extreme conditions—but also how narrowly they escape final extinction.

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Source

• Mahulu, A. (2025, March 28). Cichlid species, previously ‘lost’ to science rediscovered in Lake Victoria!. SHOAL Conservation. https://shoalconservation.org/lipochromis-microdon/