During the fourth week of my most recent trip we arrived at the southernmost point of the journey, just 130 km from the Isla de los Estados and the famous lighthouse at the end of the world!
As we moved slowly back north, due of low catches in the south, I started testing our trawl mitigation measures; these are designed to keep seabirds away from the danger zone between the trawl warp cables (the cables that hold the net) and the vessel. Testing them is a crucial part of our work as we can compare seabird interactions during the use of mitigation measures against normal fishing operations without these measures.
This is where the offal discards are dumped, attracting albatrosses looking for an easy meal. The problem is that as the cables cut through the water during a trawl, they can push foraging seabirds under the water, or break their wings. Simple mitigation measures can stop this occurring.
I used a tori line for this first test; 25m of rope tied to the stern with an orange buoy at the end and several pairs of orange streamers tied to the rope. These dangle down, scaring the seabirds. The first tests went well: no birds collided with the cables, whereas more than 10 heavy impacts every 30 minutes were recorded without a tori line.
However, in the strong winds of the southern seas I recognised a problem; as the tori line is at the surface, it is subject to buffeting from the wind and waves. These push the tori line in the opposite direction to the cables and they can become entangled. Entanglements can lead to a reduced effectiveness of the tori line and be problematic for the crew.
In order to avoid entanglements, I designed a device using equipment aboard the vessel. With the help of the crew and the ship’s tools, we made a kind of surfboard.
We called this prototype The surfboard. I added this to the tori line to keep it from tangling with the cables. With this simple device the toriline tended to steer away from the cables as the boat moved forward and thus reduced any potential entanglements whilst still keeping seabirds away from the danger area.
After this preliminary testing of The surfboard I found that it works! Eureka! The tori line with the surfboard was separated from the cables. We will continue testing this and refining the mitigation throughout the year, so watch this space!