vrijdag 25 maart 2016

Speaking of the Devil...

A few minutes after posting our first blog entry on Tuesday we observed a welcome sight on the echograms: a dense layer appeared in a depth of around 600 metres, hinting at the occurrence of a large school of Blue Whiting. With excitement we anticipated our first haul. The whole process of setting out the net, fishing through the school and hauling in the net usually takes more than two hours, but we were rewarded with a haul consisting of about 1.6 tons of Blue Whiting, accompanied by some myctophids (Notoscopelus kroyeri) and among others a really nice large flying squid (Todarodes sagittatus).

 A couple of Blue Whiting (Micromesistius poutassou) sorted by size

The myctophid catch, thankfully consisting of only one species this time (Notoscopelus kroyeri)

A nice specimen of Todarodes sagittatus

We followed that up with a second haul at a lesser depth of about 350 metres, catching another 1.5 tons of Blue Whiting with small amounts of bycatch (Argentina silus, hake, various squids).

 The afterdeck of RV Tridens at night during a haul with the pelagic trawl net
On Wednesday, we spent most of the time transitioning between transects north of the Porcupine Bank. The steady clouds of the previous days had given way to actual sunshine, and though there were a lot of white caps on the waves, the sea was rather calm. The weather took a turn for the worse over the course of the day, but it was nevertheless possible to work. In the afternoon, layers of fish were again visible on the echograms during the first north-south transect, so the net was set out. However, while trawling, the net scraped against the seafloor, causing a tear that would prove costly. When it was time to haul in the net, a system failure caused the two winches to operate asynchronously, resulting in a large part of the net getting ripped open completely.

So while the fish lab team was sorting the catch, the replacement trawl net was quickly prepared and tested to ensure that we wouldn’t miss any potential hauls. The species composition was somewhat different from the first two hauls due to getting so close to the seafloor. Although Blue Whiting (2.5 tons) still made up the majority of the catch, we also had about 550 kg of bycatch. A number of large hake (Merluccius merluccius), haddock (Melanogrammus aeglefinus), horse mackerel (Trachurus trachurus) and two yearclasses of mackerel (Scomber scombrus) accounted for most of that. 

 Buckets upon buckets of mackerel (Scomber scombrus)

 Heavy lifting for the fish lab team: Buckets of hake, haddock and mackerel
The rest of the day was spent with a cozy small whiskey tasting while we were steaming westwards towards our next transect.
Thursday brought us even more of the middling weather with a wind speed mostly around 30 knots. The reverbations of the ship hitting the waves can be problematic for the acoustic monitoring especially when heading against the swell, but we were mostly off transect. We started on offshore part of the closely spaced north-south transects in the early evening and are now hoping to find some fish again as we work our way back towards the shelf. Heavy weather is anticipated in the morning hours on Friday, but that won't dissuade us from enjoying the beauty of an evening at sea on the North Atlantic.

 The bow of RV Tridens hitting the waves


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