BRUV: new insight into offshore reef marine life

A black musselcracker approaches the bait box attached to a baited remote underwater video (BRUV) system, used to study marine fish on offshore reefs

Baited remote underwater video (BRUV) systems offer a relatively new method to study marine fish on offshore reefs. Using a lightweight steel frame, a camera is mounted in front of a bait canister, which is filled with about 1kg of chopped sardines.

The BRUV system is lowered from a boat down to the seafloor on a thin rope. A bright orange surface marker buoy is attached to the rope and is used to mark the location of the BRUV unit. For one hour, the camera records all marine life that is attracted to the smell coming from the bait canister. The boat then returns to the buoy, the BRUV unit is lifted back to the surface and the video footage is stored for later analysis.

BRUV was originally developed in Australia, but quickly gained popularity and is now being used widely to gather abundance, biomass, diversity and even behavioural data. More recently, South African scientists have also adopted this approach, using relatively inexpensive GoPro cameras. In the past year (2012-2013), ORI scientists Jade Maggs and Bruce Mann have been developing a BRUV system that can withstand the strong currents found along the east coast of South Africa.

BRUV is not necessarily a complete replacement for other established marine biological sampling methods, such as diving and fishing. Instead, it offers an additional method with numerous benefits.

BRUV can be used to collect data with as little as two people using only a small boat. BRUV can also be used in low-visibility water, which may pose certain risks for divers. Many of ORI’s projects are within marine-protected areas, and BRUV has a low environmental impact, which is especially suitable for working in such sensitive areas. BRUV units can also be used to collect data in multiple places simultaneously, saving time and money. Video footage is also very useful for educational purposes, and for spreading a conservation message.

Video 1 (November 2012): Is the Pondoland Marine Protected Area working?

In 2012 we experimented with a prototype BRUV unit in the Pondoland Marine Protected Area (MPA). This MPA was established in June 2004 on the Eastern Cape coast of South Africa. The MPA is an 800km2 patch of ocean environment with areas that allow some forms of fishing. One area or zone is strictly no-take, meaning that no fishing is allowed. We used our BRUV system to film in the no-take zone and in the adjacent fished zone. As expected, footage from the fished area was not very exciting with not much fish activity. When watching the video from the no-take zone, however, we all sat up, put our coffee down and were amazed by the abundance and size of fish. Some of the species in the video have been exploited heavily in the past, with mostly small individuals occurring in low numbers in fished areas. However, in the no-take zone they were large and abundant.

February 2013: Prototype BRUV unit lost in strong current

We experienced problems with the first prototype BRUV unit, which tended to get snagged on the bottom from time to time. The first prototype was eventually lost at sea in February 2013, when it snagged on the bottom and a strong current pulled the surface-marker-buoy underwater. The original design needed to be modified to reduce the chances of the BRUV system being snagged.

May 2013: New BRUV design

A new BRUV system has been designed, which will hopefully land upright when deployed and be less likely to get snagged on the seafloor. The original prototype was made of mild steel flatbar, and had many protruding ends that could get snagged on reefs. The original unit was also attached at one end to a line, which linked the unit to the surface. When retrieving the unit, it always turned upside-down and tended to act like an anchor. The new system, made of stainless steel round tubing, is square and with hardly any metal protrusions. The surface marker buoy will also now be attached to the centre of the unit. This will hopefully stabilise the unit, so that it always lands upright and will reduce snagging on the reef.

Video 2 (July 2013): Collateral damage: black musselcracker breaks our bait box

 

The bait container was originally made out of rigid plastic pipe, but was not able to withstand the teeth of a big black musselcracker, as seen in the video. The rigid plastic pipe will be replaced with a mesh bag, which will be more pliable and hopefully more resistant to fish teeth. Big fish and sharks tend to be shy around a foreign object, but as you can see from the video, collateral damage is sometimes unavoidable.

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