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Wednesday, March 28, 2012

2012 Blue Whiting Survey - Day 7

Location: 107 nmi west of Achill island.

We fished again during the night. This time we were fishing on much stronger marks than on the day before.
.Net coming in during the night

We got our sample of blue whiting, along with a mix of several different species of mesopelagic fish. Again, the blue whiting were mature, spawning fish.

Sample from the catch ready in the wetlab.
We are now steaming east towards the Irish coast. The Dutch research vessel, the RV Tridens, is steaming along a parallel course, 20 nmi to the south of us. The Russian research vessel, the RV Fridjof Nansen, is steaming west along a transect  to the north of us.

The weather is sunny, with flat calm seas. You couldn’t ask for better surveying weather, particularly in March. We have carried out this survey in Force 12 winds in the past. This certainly makes a pleasant change.
Sundown on the Celtic Explorer
Fog during the day has made our MMO’s job more difficult, but his patience was rewarded with a sighting of seven common dolphins passing the ship in the late evening.

One final note - As I write, the Norwegian vessel, the FV Brennholm, has arrived and has taken up position to the South, between us and the Dutch.

2012 Blue Whiting Survey Day 6

Location: 230 miles west of Donegal


Early this morning we noted marks of blue whiting on the south-eastern corner of the Rockall Bank at around 550m depth. The presence of blue whiting in this area is a good indication that spawning is still taking place and that the survey timing is correct. Peak spawning time can vary by up to 3 weeks from year to year due to environmental conditions such as temperature but we aim to keep the time of the survey the same each year. One less variable to worry about !

Echogram of small marks of blue whiting.

Big shoals of blue whiting can be 30 miles long, and show up as bright red on the echosounder. Less dense shoals, like these, show up as blue. There is an instrument on the net, the headline transducer, which indicates the density of fish that have entered the net. There were so few fish in these shoals, that it didn’t register any fish going back, so we didn’t know until the net came back if we had caught any or not. Nevertheless, there was enough caught for us to sample.

Work by the two biologists in the wetlab showed that these were all mature, spawning fish. They ranged in age from 3-12 years old.

Blue Whiting Research Fleet:

The Dutch, Russian and Norwegian vessels are now making their way towards a rendezvous point to the north of the Porcupine Bank. The Dutch and Russian vessels began surveying further south, while the C. Explorer covered Rockall. The vessels are due to meet tomorrow and proceed as a coordinated group northwards through the main spawning areas along the shelf edge.  The Norwegian fishing vessel the FV Brennholm has the furthest distance to travel, around the top of Scotland through the Pentland Firth, and will join the survey tomorrow. However, the record for distance travelled stands firmly with the Russian research vessel the Fridjof Nansen which travelled from the Russian Polar research Institute in Murmansk. This journey can take almost 2 weeks…..each way!   

Later this evening, just before dinner, our Marine Mammal Observer finally saw some cetacean activity. A pod of about 10 pilot whales approached the boat and stayed around for a few minutes.

Blog: Graham Johnston & Ciaran O'Donnell

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

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.

2012 Blue Whiting Survey - Day 3

Location: Rockall Bank

We spent 29 hours steaming towards the Rockall Bank and the start of the survey track. The weather is a bit worse than expected, with a 3.5m swell and sustained winds over 25 knots. Things are due to improve on Monday and the outlook looks very encouraging.

There was an emergency muster drill yesterday evening. This is a requirement within 24 hours of departure on every ship. It took at least two scientists by surprise, forcing them to run from the showers!

After lunch this afternoon we had a test shot of the fishing gear. This was just to make sure all the fishing equipment, including the nets, cables and sensors, were working properly.

Shooting the net during gear testing

We passed over several large marks of blue whiting as we left the shelf edge on the steam out to Rockall. We were not officially surveying yet, so they won’t be counted, but hopefully they will still be there when we are back in the area later this week. There have been no sightings of any marine mammals for our observer so far, but there were lots of seabirds, particularly along the cliffs of Donegal Bay. Fulmars, gannets and greater and lesser black-backed gulls are the most prominent species so far.

The ship is on track now. One CTD has been carried out so far. The first transect is 70nmi (nautical miles) long and will take around 7 hours to complete. We have over 2000nmi of transects to complete over the next 18 days.

Friday, March 23, 2012

Blue Whiting Acoustic Survey – Day 2

We left Donegal at 06.00 this morning for the short steam to St John’s Point. When we arrived at St. John’s Point we anchored the ship to keep her stable while we performed the calibration procedure. St John’s Point is the closest deep, yet sheltered, water suitable for our acoustic calibration. The calibration involves lowering a target reference sphere [essentially a copper sphere about the size of an orange] under the boat and “pinging” it with sound waves specific to the frequency we are calibrating. This is repeated one by one for each of the 4 acoustic frequencies we use onboard [18,38,120 and 200 kHz]. Comparing expected and measured values ensures that all the equipment is working properly before we leave.

Each frequency is configured to pick up different target groups such as fish and plankton. The 38 kHz frequency is perfect for blue whiting due to their gas filled swimbladders. These reflected sound waves are how we detect the fish under the vessel as we progress along our survey transects.

One of the copper spheres used in calibration

The reel system used to raise and lower the spheres

Lowering the spheres can be tricky and involves three poles mounted on the sides of the ship. Reels of fishing line are attached to the poles and these lower and raise the spheres through controls in the drylab. Setup was quick this morning, with one minor electrical problem sorted by giving a motor a good shake [precision engineering at its best].

Chief Scientist Ciaran O’Donnell calibrating the acoustic equipment in the drylab.

All four frequencies need to be checked, so calibration is a slow process. However all was done by 13.00 and after a quick check to make sure all the equipment was secure, we started the long steam. Next stop Rockall

Hopefully there will be some interesting birds and mammals on the way.

Blog by Graham Johnston & Ciaran O'Donnell

Thursday, March 22, 2012

2012 Blue Whiting Acoustic Survey - Day 1

The 2012 Blue Whiting Acoustic Survey starts today, and will continue for the next three weeks. This is an annual, co-ordinated, international survey with research vessels from Ireland, the Netherlands, the Faroe Islands, Norway and Russia at sea at the same time. We are looking for blue whiting, Micromesistius poutassou, a pelagic fish species found throughout the North East Atlantic.

Blue whiting is an important commercial species, mainly used for fishmeal, but also for human consumption. Because it is a shoaling species, living high up in the water, we can use an echosounder (acoustics) to count the number of fish beneath the boat. By covering a large area, and comparing and adding our figures to those of the other vessels, we will be able to calculate the blue whiting stock size.

A box of blue whiting, taken on last year's survey

The Celtic Explorer will leave Killybegs before dawn tomorrow. We will then make the short journey to St. John’s Point where there is some sheltered, deep water to calibrate the acoustic equipment. After that we will head towards the Rockall bank. It will take a 30 hour steam to get there, if the good weather holds.

As well as the acoustic surveying, we will be trawling to confirm the species we are seeing on the acoustic equipment. We also have some hydrographic stations to sample, plankton to collect as part of a mackerel egg project, and we have a Marine Mammal Observer (MMO) on board. It should be an interesting three weeks!

Irish blue whiting acoustic survey cruise track, showing hydrographic stations.

Blog by Graham Johnston