Friday, 29 August 2008

Sharks!

In the second trawl, we used a different net and we caught 3 sharks (and a hell of a lot more fish). The first trawl was deployed fairly randomly, but the second one was deployed on a target found with the echosounder equipment during the acoustic survey. Clearly this is a far more efficient way of fishing!

Sharks generally survive being trawled quite well, as they are large, fairly robust, have tough skin and no swim-bladder. This means if you get them back into the water quickly, they have a reasonable chance of surviving. Jéssica (seen left taking a small tissue sample from the dorsal fin of one of them for genetic analysis) spearheads a little campaign to get any sharks back into the water as quickly as possible. Once out of the net, the sharks are quickly measured (more easily said than done when it's thrashing around on deck!) any samples taken, photographed and returned as quickly as possible to the water. We think we caught two Carcharhinus brevipinna and one Carcharhinus limbatus. Carcharhinid sharks are moderately tricky to identify, particularly if you only have them on hand for a short while. Above and to the left you can see Arrie about to return the first shark we measured to the water; above and to the right was Arrie's first attempt to try and move a much bigger shark. We needed a couple of people in the end to lift it up and place it where it would slide down the trawl ramp and back into the sea.

A few minutes ago we were here. The wind has picked up somewhat, being 21 knots, a "strong breeze". The air temperature is a pleasant 22.2°C, the water 21.9°C, with 85% relative humidity, and the air pressure 1014.6hPa. The water under the ship was 1069m deep, and we're making about 11.3 knots.

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