Apex Predators and their Importance to Ecosystems
Apex predators sit at the top of the food chain and generally have no natural predators. They play critical roles in maintaining healthy ecosystems as they have significant impacts on the population dynamics of prey species as well as other predators. When apex predators, such as sharks or lions disappear, ecosystems start to unravel as repercussions are felt all the way through the food chain.
Recent scientific research suggests healthy shark populations are linked to coral cover and the health of coral reefs. In a study that assessed the removal of grey reef sharks from a coral reef system, an increase of smaller predators and a decrease in herbivorous or algae-eating fishes was observed. Herbivorous fish are critically important to coral reefs because they eat algae that otherwise smother young corals. Their demise in turn reduces the resilience of coral reefs to recover from disturbance such as from cyclones or bleaching – two impacts that are predicted to increase with climate change.
Vulnerability of Apex Predators
Predators near the top of the food chain are naturally rare as they tend to grow slowly, are late to reach sexual maturity and have relatively low rates of reproduction. These traits also make them especially vulnerable to threats including persecution, overfishing and habitat loss. Recent estimates suggest that around 100 million, and possibly as many as 270 million sharks, are killed around the world each year, with many species removed faster than they can reproduce. Much of this over-exploitation is driven by rapidly growing demand for shark fins, with coral reefs once known for their abundance of sharks targeted and showing drastically reduced shark populations.
Conservation of Flagship Species
Our conservation and research projects currently focus on two important marine predators found at our island sites in Mozambique – the grey reef shark and giant trevally. Targeting these ‘flagship’ species for protection not only helps maintain their populations but has the additional benefit of acting as an umbrella for the protection of many others.
The reefs of the northern Quirimbas Archipelago in Mozambique are critically important breeding aggregation sites for several fish species and a nursery ground for grey reef sharks – one of very few such sites known in East Africa and the Western Indian Ocean.
By conducting regular surveys of sites and employing the latest in satellite tracking technology including a network of underwater acoustic receivers that ‘listen in’ on sharks fitted with special transmitters, our conservation and research project aims to improve our knowledge of the habitat needs, movements and population status of top-end predator species to inform the establishment and management of marine protected areas in the region.
An important component of this work includes collaboration with other marine research organisations that do similar work. By working closely and sharing access to each other’s arrays of acoustic receivers we are more effectively able to track the movements of animals that we have individually tagged, thereby building the picture of how marine fauna move across broad scales both in time and space.
Giant trevally (GT) are one of many fish species that gather in large spawning aggregations to breed. Many individuals often come from far and wide to meet at the same time and place each year. The predictability of these mass gatherings means they can be readily exploited by harvesting large numbers of fish with little effort. For this reason, spawning aggregations are the basis of many of the most productive commercial and subsistence fisheries.
However, despite their importance to global fisheries, food security and ecosystem health, such aggregations are seldom managed or protected well enough to ensure the long-term sustainability of many fish stocks. Of such aggregations that have been studied around the world, more than half are declining and 1 in 10 have disappeared altogether.
Our giant trevally conservation and research projects in the Bazaruto and Quirimbas Archipelagos in Mozambique aim to shed light on the movements, habitat use and breeding biology of the species. By identifying and managing important breeding aggregations, and knowing where the fish move to, we stand a chance at protecting them and ensuring they remain vital pillars of marine ecosystems and important source areas for fish stocks for the many coastal communities of the region that depend on them.
Access a research paper we co-authored about a giant trevally spawning aggregation and the importance of community fisheries management off Vamizi Island in Mozambique.
Learn more about our other projects…
Explore our activities at each of our different sites
Working in close partnership with coastal communities to build capacity, develop sustainable livelihoods, promote marine conservation education and train & employ Marine Community & Conservation Rangers.
Coral Reef Diversity
With some of our sites hosting among the highest coral diversity outside the Coral Triangle, coral reef studies are a major focus of our work including documenting & monitoring coral, fish & invertebrate health, diversity & abundance.
Fisheries & Food Security
Many millions of people depend directly on marine resources in East Africa. Our work contributes to fisheries monitoring, promoting sustainable fishing practices & assessing the nutritional value of fish to people as reef ecosystems change.
Listening in on ocean soundscapes using underwater microphones enables us to monitor the health of coral reef ecosystems, study the behaviour of iconic marine animals and assess the impacts of noise pollution.
Five species of sea turtles occur in the Western Indian Ocean, with our sites supporting important nesting areas for four of these. Our sea turtle nest monitoring projects on Mnemba and Vamizi Islands are amongst the longest continuously running programs in East Africa.
Seascape Mapping & Monitoring
Mapping habitats & multiple use zones & deploying environmental sensors at our sites provides vital information for marine scientists, & informs marine spatial planning and the establishment & management of marine protected areas.
Islands have high conservation value for threatened & endemic plants & animals. Our work focuses on plants, birds, reptiles & mammals, including a unique sub-species of the Samango monkey and the Endangered Ader’s duiker.
Whales and Dolphins
Numerous whale & dolphin species occur at out sites in East Africa with our focus on regular surveys and monitoring & research of resident and migrating populations, including Humpback Whales, using passive acoustic monitoring (underwater microphones).