Sea Sensors: Mapping blast fishing along the coast of East Africa
by Gill Braulik
With carefully packed bags full of dive-gear in the hold , we set sail in a catamaran called Mojo, from the north coast of Zanzibar. . The plan is to sail across the Zanzibar Channel to the Tanga Coast of the African mainland. Tanga has been a hotspot of illegal fishing with explosives in Tanzania for at least 40 years — and the reason I selected it as our first destination to begin the Sea Sensors project. Our goal is to set up a network of underwater acoustic monitoring stations anchored to the seabed along the Tanzanian coast that will log and map each blast as it occurs. The intention is to shine a light on the details of blast fishing — when and where — so that the authorities can target enforcement.
Using explosives for fishing is highly destructive to the environment. Most of the blasting is near shore in shallow waters, and the force of the explosion not only kills all marine creatures in the vicinity of the blast, it also shatters the underlying coral reef which can take decades to recover. Diverse, colourful coral reefs teeming with life have been reduced to colourless rubble fields from the unending blasting. The result is reduced productivity in the ocean and fewer fish for people to eat.
Mojo is heavily loaded with six 50kg concrete blocks and two triangular metal frames each the size of a coffee table, which will be used to mount the hydrophones and keep them firmly attached to the seafloor for at least a year.
Onboard we have our captain Werner Erasmus from South Africa; Jamie Macaulay, a physicist, acoustics specialist and diver from the University of St. Andrews, UK; Jason Rubens, a marine biologist who has been researching the blast fishing issue in Tanzania for several decades; and Hannes Potgieter, the owner-operator of Seabreeze Marine one of the only dive centers on the Tanzania mainland coast.
At each new potential site, the Mojo is safely anchored, and we investigate the conditions to make sure that it is suitable for diving with, and securing expensive equipment. After a few dives and a long time of searching, I select a location on the north coast of Maziwe Island, a big sand bank in the ocean surrounded by coral reef that is protected in an excellent community conservation initiative coordinated by the Friends of Maziwe, based in Ushongo. As we approach the reef we are in the lee of the island and the ocean is flat, calm and blue, blue, blue. Dolphins appear out of nowhere, surface a few times before vanishing into the distance. The conditions look perfect.
The last few days before setting sail we tested the equipment, attaching wires and hydrophones to the frame in different configurations, and finally lowered it into my son Leath’s school swimming pool to make sure all was ready for the final deployment.
As we prepare for deployment, the boat buzzes with action and movement. We shackle together three of the concrete blocks, so that they total 150 kg of weight, and lower them down to the sea bed with a rope. Then wet suits are on, dive gear prepped, masks and fins to the ready. The divers enter the water, which is beautifully warm and clear, we almost don’t need wetsuits. The captain passes us the frame with the hydrophones and recorder zip-tied on tightly, and we inflate lift-bags to keep it steady in the water. On the count of three we submerge, and divers and equipment sink slowly down into the blue.
After just a few minutes the coral below is visible and I search around for the concrete blocks, I see them, and indicate to the others, and our slow procession moves gradually downwards towards them. The triangular frame is placed on an even area of the seabed, and then using my underwater compass we orientate the frame carefully to north.
This is essential so that we can not only detect the acoustic signature of the blast, but we can also record the date, time and the compass bearing to the actual origin of the blast.
Not surprisingly explosions in the ocean can be extremely loud, and as sound travels through water 5 times faster than air, evidence suggests that our recorders will be able to detect blasts up to 30 km away. Where the coastline configuration permits, we will place two of our units 10 km apart and then, using triangulation, the exact location of each blast will be determined and plotted onto an online interactive map for all to see.
After attaching the frame to the weights, and slowly rise up through the water column to the waiting boat. Far beneath me, laid out in a perfect triangle, is our recording system.
We did it! We returned back home, confident in the knowledge that for whole of the next year, this unit, and three others like it in other parts of the coastline, will be recording all blast fishing explosions for miles around.
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About Code for Africa
Code for Africa (CfA) is the continent’s largest federation of data journalism and civic technology laboratories, with labs in four countries and affiliates in a further six countries. CfA manages the $1m/year innovateAFRICA.fund and $500,000/year impactAFRICA.fund, as well as key digital democracy resources such as the openAFRICA data portal and the GotToVote election toolkit. CfA’s labs also incubate a series of trendsetting initiatives, including the PesaCheck fact-checking initiative in East Africa, the continental africanDRONE network, and the African Network of Centres for Investigative Reporting (ANCIR) that spearheaded Panama Papers probes across the continent. CfA is an initiative of the International Center for Journalists (ICFJ).
About SeaSensor Project
The SeaSensor project is funded by Code For Africa and is conducted in association with the University of St. Andrews, UK. Follow more of this work at @GillBraulik, @SeaSensor @Sea_Sensor.Africa, https://seasensors.africa. Environmentally destructive fishing using explosives has been conducted illegally along the coast of Tanzania for decades. Sea Sensors is a project using cutting edge underwater acoustic technology to document and map the occurrence of blasts in hard-to-monitor parts of the country to help understand the scale of the blast fishing problem. The information generated is being used to calibrate and verify the blast fishing incidence recorded from coastal monitors and to explore trend analysis over time. It is also forming the basis for in-depth investigations conducted by media partners and enforcement agencies.
