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Sunday, March 25, 2012

2012 Blue Whiting Survey Day 4

Location: Rockall Bank. 305 nautical miles from Donegal.

We lose internet access when steaming in certain directions, so I have had to post three days of updates at once now.

Its been a quiet survey so far. We have been on-track since yesterday evening, but so far, no fish. There are four acoustic scientists on board, each working a six hour watch monitoring the equipment and then other time spent cataloguing data. As the scientist on the midnight to 6am shift, I was glad the clocks went forward last night as it saved me an hour.

While on watch the scientists monitor the equipment to make sure everything is recording properly. We also look to see whether there are any fish below us, and if so, whether they look like blue whiting ‘marks’, as they are called. In the event of seeing what looks like blue whiting, the Chief Scientist decides whether to fish on them to collect a sample for age and length measurements. Whether we fish or not depends on where we are in relation to previous fishing tows, and also whether there are any safety risks, e.g, particularly bad weather that might endanger the crew on deck. Ultimately the Captain has the decision on whether to fish or not.

There are also two fish biologists on board. If we get fish they will sample the catch in the wetlab. First they separate the catch into the different species. They will then take the otoliths, the ear bones, from a sample of the blue whiting. Otoliths are like trees, in that they lay down seasonal growth rings. By counting these rings under a microscope, you can tell how old the fish is. Any healthy population of fish should have a mix of young and old fish in it. They will also take length measurements of all the species, and take sex, maturity and stomach contents details from the blue whiting.

Of course all this is theoretical so far as we haven’t caught any blue whiting yet this trip!

A grey day on the Rockall Bank

The weather has not improved over the day. It’s cold wet, windy and foggy. The TV news is showing people on the beaches at home. It's not beach weather here! The forecast is for an improvement tomorrow, but there are no guarantees at Rockall.


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