Capturing kelp with kayaks, camera and acoustics

Chris Yesson

Did you know that sea kelps are hugely important marine habitats? Or that there may be as much kelp forests in the UK oceans as there is native woodland?

Dr Chris Yesson, Research Fellow at ZSL's Institute of Zoology, blogs about his first attempt to survey UK kelp habitat using video and sonar devices mounted on a sea kayak. 

Kelp emerging from the water
Kelp emerging from the water at low tide

Recently, I joined a team from the Natural History Museum and University of Bristol to try out a kayak-based kelp monitoring system. Finding out what is going on under the water is always challenging. We want to find a cheap and quick method for monitoring kelp beds in areas of high conservation value, such as marine conservation zones, or areas where there is wild harvesting.

Kelp are large brown seaweeds, which can create dense 'forests' all around our rocky shores. We estimate there is as much kelp forest around the UK as there is native woodland. Kelp beds are important habitats for fish, crustaceans and many other species. There is increasing interest to use these fast growing algae for a range of commercial purposes, including biofuels, cosmetics, pharmaceuticals and foods.

Our project, led by seaweed expert Juliet Brodie of NHM, and funded by the Crown Estate, is to develop and trial methods to monitor kelp beds around the UK.

On our first experimental field trip in Pembrokeshire we performed seabed surveys with kayaks. One kayak was fitted with a chirp sonar device, which uses sound to profile the seabed. Gary Barker and Chris Belas from University of Bristol had designed a waterproofing system for the batteries and monitor, basically a lunchbox with a hole for cable, sealed to be waterproof.

I was in an inflatable kayak, where my role was to film the kelp underwater. IoZ intern Jess Fisher had put together our camera system, which was a small waterproof 'gopro' video camera, along with some dive torches, stuck onto an extendible pole, which I could lower over the side to take images of the sea bed.

GoPro Camera for Kayak Survey of Kelp
GoPro Camera for Kayak Survey of Kelp

Chris Yesson & Gary Barker on a kayak survey
Chris Yesson and Gary Barker on a kayak survey

Within a short period of time it was apparent there were a number of teething problems, requiring rapid repair. Using my coat as an impromptu rain cover we fixed the sonar without it getting too wet, and all was well. The kelp showed up on the sonar image as 1-2 metre high 'tufts' sticking up from the sea bed. We used this to record the extent of kelp habitat in the area.

Display from sonar device showing kelp habitat
Picture of sonar display showing kelp habitat

Eventually, the rain stopped, and the afternoon survey captured some great footage of kelp on our video, which we will use to validate our interpretations of the acoustic survey.

We received some curious stares from the local fishermen, and we quickly realised that they were strategically placing their pots just outside the kelp zones, apparently to lure the crustaceans out and into their pots while avoiding rope entanglement. This behaviour highlights the importance of the kelp habitat and its integration with humans in the seascape.

We also saw many barrel jellyfish, this bay is known for this species, which is also aptly called the dustbin lid jellyfish or the frilly mouthed jellyfish (Rhizostoma pulmo), and we took some nice footage of a large specimen almost a metre in size 

Our project proved to be a successful pilot of the acoustic monitoring method. It is important that we find practical and cost effective methods for monitoring kelp, particularly given our observations of changes in kelp abundance that may be linked to climate change.

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