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Tuesday, March 27, 2012

2012 Blue Whiting Survey Day 5


Location: 255 miles west of Donegal Bay

It has been another quiet day. Thankfully the weather is improving and the swell is dropping away. There was even some blue sky for a while!

We saw six Russian fishing boats during the night. There was no sign of blue whiting in the area, so they are also trying to find these fish.

While we have not seen any blue whiting, we are seeing other types of fish on the echosounder. We have most frequently encountered mesoeplagic fish  Mesopleagic fish are made up of many species including lantern fish, hatchet fish and pearlsides. These generally small fish, are often less than 15cm for many species, occur over vast areas in the Atlantic and inhabit the pelagic region between 0-180m in the open ocean. 

During daylight hours many mesopelagic fish spend their time at depth (120-180m) and at night they migrate to surface waters (0-50m) to feed on the myriad of other organisms that also migrated to the surface to feed.
Echogram of Mesopelagic migration
    




This vertical movement accounts for one of the largest migrations of biomass on the planet and it happens twice a day, every day !

We are now heading in a generally easterly direction, back towards the shelf edge. We know there are blue whiting there, as we passed over them on the way west last week. That should mean we'll be fishing soon.

 Blog: Ciaran O’Donnell & Graham Johnston

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