Reef survey of entire East African coast

The east coast of Africa is an important marine region that provides subsistence and economic resources to over 22 million people in Kenya, Tanzania and Mozambique

The east coast of Africa is an important marine region that provides subsistence and economic resources to over 22 million people in Kenya, Tanzania and Mozambique

An ambitious project to collect data on the reef fish community structure along the whole of East Africa’s coast aims to provide a baseline understanding to underpin and inform future conservation efforts.

There is a global push for networks of marine protected areas (MPAs) as one ecosystem based mechanism of protecting marine biodiversity, reducing the impacts of overfishing, and to mitigate the effects of climate change. Early marine protected areas were placed largely in response to social or political pressures or knowledge of areas of high biodiversity or habitat complexity.

More recently, biological considerations have played a greater role, and systematic planning tools are frequently used to plan MPA networks (eg Great Barrier Reef Marine Park). Nonetheless, MPAs are generally a local-scale management tool irrespective of the conservation goal (an increase in biodiversity, biomass, fisheries via spill-over etc).

With the call to develop global, or continental scale networks of marine protected areas, very little consideration has been given to understanding the patterns and dynamics of communities at these large scales. However, it is the influence of biogeography and evolution and large-scale physical processes such as temperature and currents that determine species ranges, distribution, and abundance that essentially dictate the composition and structure of communities at local scales.

Given this, building a baseline understanding of the structure of communities along continental margins should be the first priority in pursuing large-scale networks of marine protected areas. Otherwise, for example, without these data, MPAs may fail to offer protection for restricted-range endemic species, or to protect areas of high biomass and low fishing effort that may offer some of the last refuges of spawning stock to prevent fisheries from collapsing.

East Africa

Marine biologist film the reef using stereo-vidoe cameras

Underwater stereo-video cameras are being used to collect data on diversity, abundance and size-structure of reef fishes that are unbiased and free of observer bias

The east coast of Africa is an important marine region that provides subsistence and economic resources to over 22 million people in Kenya, Tanzania and Mozambique. Here, reef fish resources are an important component of the economy and subsistence, and over the last 20 years some sites have shown a 40 % decline in reef fish resources. Yet the ecology of these reef fish communities along this coast are some of the least understood in the world, despite being some of the richest.

Governments have shown the foresight to protect marine biodiversity and conserve fisheries resources for future generations by establishing MPAs throughout the region, although improvements in management and the size and number of MPAs are needed.

To facilitate future MPA planning to protect reef fish resources, and to assess how current MPAs are performing in the context of a continental network, large-scale data on reef fish community dynamics and structure is required.

A multi-, large-scale approach is required for two reasons: 1) There are natural trends in the structure of marine fish assemblages along coastal/ latitudinal gradients; 2) the history and pattern of human exploitation of coastal resources will differ within and between national boundaries.

Therefore, the goals of the research are to collect rigorous and unbiased data on reef fish community structure (abundance, diversity, size structure and biomass) along the entire east coast of Africa, focusing on multi-scale sampling régime that surveys reefs at regular intervals (100-200km, guided by satellite imagery from www.asclme.org, and local knowledge) and both inside and outside MPAs.

This will provide the means to comprehensively assess the status of these resources and human impacts and provide a basis for establishing an understanding influence of climate change along this coast. This cannot be achieved with the current knowledge base, or sampling programmes that are in place.

Collecting data

Copyright Caine Delacy 2012-2809We are using underwater stereo-video to collect data on diversity, abundance and size-structure of reef fishes that are unbiased and free of observer bias. These data are collected using scuba divers to collect twelve 25 m transects that are stratified by depth to a maximum depth of 25 m. At each sampling site benthic photoquadrats (for % cover) is also collected simultaneously. And the survey design is based around a hierarchical design of multiple sites nested within locations at each point along the coast.

The proposed sampling region will cover ~27o of latitude and will be expected to show significant variation in fish abundance patterns and species composition over this range driven by latitudinal temperate profiles, coastal geomorphology, biogeography and anthropogenic influences.

This variation will be enhanced by the action of the southwards flowing Agulhas current which will have the effect of extending the range of tropical species into the southern regions of the latitudinal gradient.

Importantly, capturing the range boundaries of tropical and endemic species, the location of such range boundaries and understanding the role of temperature in their determination will be an important aspect of the future response of coastal fish species to fishing pressure and climatic shifts.

The resultant database will provide a means to not only assess MPA performance and design, but can also be interrogated for biogeographic studies, and provide local and national governments with tools for planning at a local and national scale. These data sets are extremely rare or non-existent in marine conservation, and such data will be an invaluable resource.

We have just completed our journey and returned to our respective homes. A great and resounding success by the team to survey coral reefs along the entire east african coastline to Northern Kenya. Now begins the major task of video analysis, and data collection. We have lots to do, and are seeking support for this. Please check out the website for more information.

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