In Tanzania's Mbezi River basin, threatened Nothobranchius killifish are losing habitat fast. Michael of SHOAL outlines the new conservation efforts that are offering hope for their future.
For many aquarists, annual killifish are among the most fascinating fish on Earth. Their brilliant colours, short lives, and remarkable ability to survive droughts have made them favourites among specialist fishkeepers for decades. Yet in Tanzania's Mbezi River basin, some of these fishes are facing an increasingly uncertain future.
That is what brought Dr David Alila of the University of Dar es Salaam into the wetlands south of Dar es Salaam earlier this year. Supported by SHOAL and The Rufford Foundation, Alila has been leading efforts to assess the status of the basin's highly threatened Nothobranchius species and begin building local support for their conservation.
Searching for Killifish in a small pool - Photo by Dr David Alila
A Centre of Killifish Diversity
Tanzania is the global centre of diversity for Nothobranchius killifish, hosting 47 of the world's 94 recognised species. Within the country, the Mbezi River basin is one of the most important strongholds for these fishes. Surveys carried out under the project confirmed the continued presence of seven threatened species: Nothobranchius geminus, N. albimarginatus, N. lourensi, N. lucius, N. luekei, N. rubripinnis and N. melanospilus. An eighth species, N. ruudwildekampi, was also recorded during fieldwork in the basin.
For killifish fanatics, several of these names will be instantly recognisable and have long attracted attention for their striking colours and fascinating life histories. Like all annual killifish, they inhabit seasonal wetlands that fill during the rains and disappear during the dry season. Adults grow rapidly, breed, and then die within a matter of months, leaving their drought-resistant eggs buried in the mud until the next rains arrive.
N. ruudwildekampi in photo tank by Dr David Alila
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Drained, Filled, and Altered
It is an evolutionary strategy perfectly adapted to an unpredictable environment. The problem is that these wetlands are disappearing. During a seven-day survey of known Nothobranchius sites across the basin, Alila documented extensive habitat degradation. Several seasonal pools that previously supported killifish populations had been converted into agricultural land. Elsewhere, wetlands were affected by water abstraction, pollution, industrial development, and waste disposal.
This pond used to house killifish but is now full of waste glass Photo by Dr David Alila
In some cases, habitats no longer existed. In his field report, Alila warned that several populations may be approaching a critical tipping point as habitat destruction accelerates. The threats are particularly serious because annual killifish depend entirely on these temporary wetlands. If a breeding site is drained, filled, or permanently altered, there is often nowhere else for the fish to go. Entire populations can disappear with the loss of a single pond.
Related article: How do I breed these short-lived fish?
A Positive Future for Killifish
Yet the project has also uncovered reasons for optimism. Following the biological surveys, Alila spent ten days working with communities in the villages of Misufini and Kiparang'anda, as well as local schools. Through meetings, presentations, and discussions, he introduced residents to the unique fish living in their wetlands and explained why these habitats matter.
One of the most important findings was not ecological but social. Most people had never heard of Nothobranchius. Many were unaware that the wetlands around them supported globally important biodiversity. The same knowledge gap extended to local authorities.
Once the fish and their habitats were explained, however, community members showed strong interest in conservation and expressed a willingness to become involved in future monitoring and protection efforts.
For aquarists, that message will sound familiar. The killifish community has long appreciated what makes these fish so special. Hobbyists have maintained and bred many Nothobranchius species for generations, preserving bloodlines and contributing valuable knowledge about their biology.
For those in the UK, the British Killifish Association (BKA) is at the forefront of these efforts, promoting proper care, breeding, and accurate record-keeping within the British killifish hobby.
But despite the hard work of hobbyists, ex situ populations can never replace functioning wild habitats. The remarkable adaptations that make annual killifish so appealing evolved in Tanzania's seasonal wetlands, and those ecosystems remain essential for their long-term survival.
Alila's work represents an important first step towards protecting them. By combining field surveys with community engagement, the project is laying the foundations for a future conservation action plan for the basin. Whether that effort succeeds will depend on continued support, greater awareness, and stronger protection of the wetlands these fishes call home.
For anyone who has ever incubated a bag of peat and watched a tiny Nothobranchius emerge, it is a reminder that some of the hobby's most treasured fishes still depend on a handful of vulnerable pools in coastal Tanzania.
Read more about SHOAL's work: Mini Marvels: The World of Tiny Fishes
SHOAL's Killifish Conservation Programme
Annual killifish are among the most threatened freshwater fish on Earth, with many species restricted to isolated seasonal wetlands that are disappearing under pressure from agriculture, development and climate change.
To help reverse these declines, SHOAL runs a dedicated Killifish Conservation Programme focused entirely on the conservation of annual killifish, particularly species in the genus Nothobranchius. The programme supports field surveys, conservation planning, community engagement, habitat protection, and research across key killifish landscapes.
Dr David Alila's work in Tanzania's Mbezi River basin forms part of this wider effort. By combining scientific surveys with local conservation action, the programme aims to secure a future for some of the world's most remarkable – and most threatened – freshwater fishes.
We regularly feature updates from SHOAL in our monthly magazine, covering not only killifish but a diverse mix of threatened freshwater fishes from around the world. Subscribe today to ensure you never miss an update.