WARMALIS 1 - Journal & logbook

French(France) Version Française

alt


>>Access blog latest news<<

SPC, in collaboration with IRD, is engaging in a new series of oceanographic cruises across the Pacific to characterise the western and central Pacific Ocean including the Warm Pool, onboard RV Alis, which gave the name of the cruise series: WARMALIS.

Warmalis 1 is the first cruise that will cross the western Pacific from south to north, departing from Noumea in New Caledonia, finishing in Kosrae in the Federated States of Micronesia, and crossing Solomon Islands and International waters.

Warmalis 2 and Warmalis 3 will be conducted in 2022 and 2023, in the central Pacific (south-north transect from French Polynesia to Kiribati Line Islands), and at the Equator (east-west from French Polynesia to Papua-New Guinea) respectively.

The objective of the project is to understand the functioning of the pelagic ocean ecosystem and determine its influence on tuna resources in the western and central Pacific region. Our project will study the mid-trophic levels (zooplankton and micronekton) of the large pelagic ecosystems of the Pacific where more than 50% of the global tuna catches are produced. Zooplankton and micronekton are components linking the physical/chemical factors of the ocean, which influence their distribution and abundance, with the megafauna (e.g. tuna, marine mammals, seabirds) which are their predators. The aim of our project is to fill the important gap in knowledge on the large pelagic ecosystems of the Pacific. Our goal is to bring scientific knowledge for a sustainable management of the pelagic resources by understanding the functioning of the pelagic ecosystems (from physics to intermediate levels) and by collecting observations to validate and improve ecosystem models used to analyse the tuna resources (SEAPODYM).



Micronekton

Example of micronekton catch with small fish, shrimps and gelatinous organisms
commonly eaten by tuna and other top predators (Photo: V. Allain, SPC).


The Warmalis cruises are multidisciplinary, and we will collect seawater physical and chemical data as well as data on zooplankton and micronekton. To characterise physico-chemical conditions and primary production, we will measure temperature, salinity, oxygen, fluorescence, light, currents, nutrients, photosynthetic pigments, phytoplankton abundance, primary production, phytoplanktonic communities. Secondary production (zooplankton, micronekton) will be measured with acoustic (TAPS, WBAT, S-ADCP, EK60) and net sampling of zooplankton and micronekton.

Starting on 6th of September, the cruise will last 19 days during which 15 sampling stations will be visited, before reaching Kosrae around 24th of September. After a quick stop to refuel but no landing, the vessel will turn back to steam towards Noumea in around 10 days.

Cruise planned track

Scheduled cruise plan for Warmalis 1


This cruise, in the framework of the MICROPAC project, is conducted with the financial support of the French ministry of armed forces (Direction des patrimoines, de la mémoire et des archives), the French ministry of Europe and Foreign Affairs (Pacific Fund), the French oceanographic fleet, the French ministry of studies, research and innocation, the LEFE-INSU, SPC and IRD.




Daily blog

Four days before departure, the scientific team and the crew are busy preparing the vessel for a 1-month trip in complete autonomy. It means embarking a lot of food for 18 people, spare parts for the mechanics, and all the scientific equipment.

It took us the full day to get everything onboard, test all the instruments and making sure they work, and fixating everything no nothing moves when sea gets rough. We feel ready and are looking forward to starting the trip after months of preparation and a lot of uncertainty with the covid pandemic.

We received a lot of help to get prepared and to make sure this cruise gets conducted and we are grateful to everybody.


Alis vessel

The research vessel Alis in Noumea, New Caledonia


Alis scientific crew

The scientific team installing the equipment in the small wet lab.


alt

The acoustic team installing a camera system on one of the probe to try and capture images of deep-sea fish.


Aletier Alis

Our electronician preparing the electronic cable needed to activate the instruments in the water.

We left this morning at 9:30 am as planned and some colleagues and friends came to see us off. We took advantage of the calm waters of the lagoon to do the safety exercises and to steam north. We went out of the lagoon through the Isié pass around 2:30 pm where the damaged wreck of a boat marks the entrance of the pass. The small swell out of the lagoon and our route to the north gave us a rather calm voyage for the moment. The acoustic instruments have been set up as soon as we left to start acquiring data on the micronekton and our first sampling station is planned for tomorrow afternoon.

The team of scientists during departure

The scientific team onboard the RV Alis.


alt

The acoustic team setting up the instruments.


alt

Laure, for her first voyage at sea has tried the survival suit.


alt

The wreck at the entrance of the Isié pass off La Foa in New Caledonia.

After 30 hours of downwind steaming, we arrived at the first sampling station. Most of the team and sailors have already done this work, but the first station allows us to review the sequence of operations.

For this cruise we decided to follow the same protocol, at the same time, every 24 hours. Thus, the work starts around 4 pm with 2 rosette descents to 250 and 600 m depth respectively to collect water for chemistry and phytoplankton and to make profiles of temperature, salinity, light, fluorescence, oxygen etc. Then, as soon as night fell around 6:30 pm, the TAPS was lowered to 200 m, an acoustic instrument for zooplankton, and zooplankton sampling was carried out at depths of up to 600 m with the hydrobios multinet, which allows the collection of organisms at 5 different depths. Finally, the last part of the evening was devoted to micronekton with a descent of the WBAT, an acoustic instrument, and the collection of organisms by pelagic trawling at different depths.

For this first station there was a small problem on the zooplankton multinet, and we cancelled this operation. As the wind increased with gusts to 30 knots and an average wind of more than 25 knots, the manoeuvres were complicated, and we shipped a few packs of sea. We also did only one micronekton trawl between 0 and 200 m depth, the weather conditions being too bad to attempt a trawl at 500 m. We did not collect many organisms, but it was very diversified with fish and shrimps.

This first station was very difficult for all of us with bad weather conditions and several of us suffered from sea sickness. We were happy to finish the work around 11:30 pm after a very busy day.

Collecting sea water

Collecting sea water

Collecting sea water sampled between 600m depth and the surface with the rosette.


alt

The sea is rough, packets of sea invade the deck.


alt

Zoom in on some micronekton organisms.


alt

In the scientific dry lab, monitoring of the acoustic screens.


alt

All the manoeuvres are recorded in the logbook, here by the lieutenant.

After sampling station 1 we continued our route north but with winds averaging over 25 knots and gusts over 30 knots, we decided to find shelter and anchor. Indeed, the manoeuvres become dangerous and the quality of the data poor when the weather conditions are so bad.

We take advantage of this forced stop to make a number of repairs and adjustments to our instruments after the first station. This also gives us time to review and optimize our procedures for the next stations. The crew also has some work to do with various devices to repair such as the osmosis unit that provides us with fresh water. We took the opportunity to make a first processing of the few data collected. We are collecting measurements by continuous active acoustics (day and night) with the calibrated SIMRAD EK60 hull sounders. Four frequencies are used simultaneously: 38, 70, 120 and 200kHz, allowing to probe the water column up to 800, 400, 250 and 120m depth respectively. A measurement (a ping) is made every 3 seconds.

We hope the weather will allow us to resume operations on Friday.


alt

Echogram recorded at 38 kHz, the frequency most commonly used to study micronekton, showing the density of marine organisms in the water column between the surface and 800m depth (yellow-green for high densities, blue-white for low densities). This record corresponds to the 24 hours of 7th September 2021 from 0h00 to midnight. The horizontal bar under the echogram represents in black the night, in orange the dawn, in white the day and in blue the twilight. We can observe that micronekton organisms (1 to 20 cm) are mostly close to the surface at night and at depth (500-700m) during the day. They perform a vertical migration at sunrise and sunset.


alt

The team is working to repair the zooplankton net.


alt

The brown boobies are watching us.

We took advantage of the morning to finish adjusting our instruments and especially the zooplankton net. The chief mechanic and one of the sailors spent a lot of time to re-fabricate a broken part and to re-weld it to the device and it also took us some time with the electronic technician to make the net functional. The crew also took advantage of the quiet morning to do some first aid exercises.

We finally left our mooring at 12:30 to be on the sampling station number 2 at about 15:30. We were able to carry out all the operations with however a 2m swell which made the work difficult. The trawling at the end of the day brought us a nice diversity of species, including a small cookie cutter shark (Isistius brasilensis) of about 20 cm that we released alive after having measured it.


alt

Reassembling the zooplankton net.


alt

The devices on the deck.


alt

The first mate gives a first aid training session to the crew while we are at anchor.


alt

Taking water samples to measure the amount of oxygen in the water.


alt

The catch of the day with on the left the small shark Isistius brasilensis and in the centre a beautiful squid among shrimps and fish caught between the surface and 200 m depth.

We continue our way north with a side swell that makes navigation difficult with sometimes big rolls that surprise us and cause damages in the boat even when everything is planned to face the movements. One of the showers came off the wall, but it was quickly fixed by the mechanics. The books ended up on the floor in the dining room. Disaster in the kitchen, the 2 appetizer dishes of midday found themselves on the floor and there was a lot of broken plates.

Arrived at the station 3 at 4 pm we decided to cancel the operations, the sea was too strong with more than 25 knots of wind and the manoeuvres become dangerous for the sailors and the risk to damage the electronic equipment if it hits the side of the boat during the launching is too important. So, we continue our way north at a slow pace to reach station 4. We leave the waters of New Caledonia to enter the waters of the Solomon Islands.


alt

The shower broken by the roll.


alt

The books scattered in the dining room by the bad weather.


alt

The vessel rolls.

It is easy to lose track of time when you are at sea. We work every day, and every day is the same, but on board the RV Alis we always know when it's Sunday because that's the day we have croissants and pains au chocolat for breakfast, a festive dish at noon, it was couscous this Sunday, and a cheese plate for dessert in the evening. This allows us to reboot for another week and enjoy our meal. All the sailors will tell you that the most important person on board is not the captain, but the cook and we are lucky to have a very good cook on board who prepares us food whatever the weather with his assistant cook.

The weather is slightly better with winds of 18-20 knots and a swell of 2.5m and we start the work sequence at 4pm at sampling station 4. With the better weather and with a better run-in of the sequences, we are faster to do the manoeuvres which allows us for the first time to do 2 trawls at the end of the day instead of one. After the oblique trawl between the surface and 200m, we did a horizontal deep trawl at 500m which brought back some unusual fish and shrimps. The day of the sailors ends just after midnight and for the scientists it will take an extra hour to sort the specimens, to take them down to the freezer and to clean the equipment and the lab in preparation for the next day.


alt

The kitchen team in full preparation for a pear-almond bourdalou pie.


alt

The recovery of the micronekton pelagic net.


alt

A fish caught at 500m depth and that we called the rainbow fish until we could identify it.

We had hoped for better weather in the Solomon Islands, but the cross swell makes the transits between stations very difficult, and it is always so difficult for the few who are seasick.

Station 6 went well, and we were able to do all the work planned between 3:45 and 11:55 pm. A big surprise when the first trawl was hauled up, a shark of about 1.5 m was in the net. This is the first time in the 10 years that we have been trawling (262 trawls to date), that we have caught a fish of more than 50 cm. It was an oceanic white-tip shark Carcharhinus longimanus which had a hook in the corner of its mouth with a piece of longline. It was alive and well and we put it back in the water immediately. For the second trawl, same scenario, another oceanic white-tip shark, of similar size, but another individual without a hook, it also went back into the water quite alive. It seems that these sharks follow the boat and get caught in the trawl as the net is being brought back on board. We hope that this does not happen again, because it is always dangerous for the sailors to handle a shark, and it is probably not a good experience for the shark, and the presence of this big fish spoils the whole content of our trawl.


alt

The shark in the codend.

alt

The shark on the deck before its release. You can see the piece of line at the end of the hook hanging from the corner of its mouth.

Back to the oceanic whitetip shark episode!

To try to identify micronektonic organisms detected by acoustics, we test a camera coupled with a projector (circled in yellow on the picture) that we lower to 500m. The camera is oriented downwards with an estimated range of 4-5m.

Today, while viewing the images taken yesterday before the trawl, we noticed that the famous oceanic whitetip shark passed in front of our camera! Proof that we were followed for at least two good hours.


alt

In the yellow circle, the camera system installed on one of the acoustic instruments.


alt

A very clear shot of the oceanic whitetip shark Carcharinus longimanus with its dorsal and pectoral fins with rounded ends.


Acoustics allows us to study predator-prey relationships such as tuna feeding on micronekton.

With the hull acoustic sounders, we believe that we detected today before station 7 schools of tuna between the surface and 200 m at about 3 p.m. over a distance of 5 kilometers. The schools of tuna form characteristic spots on the acoustic sounder.

It seems that the tunas have eaten the micronekton present in the area at these depths: on the left of the school we see micronekton/zooplankton in blue between 100 and 200 m, and on the right it has disappeared.


alt

Acoustic detections at 38kHz between the surface and 800m depth (from top to bottom of the figure) during 1h30 (from left to right of the figure).


alt

Zoom on tuna school detections at 38kHz in yellow/orange.

We present today the physical data of temperature, salinity and fluorescence taken by what is called a CTD-rosette, (Conductivity, Temperature, Depth). This probe allows to measure physical data, but also to collect water at different depths using the sampling bottles, also called "rosette", present on the figure below:


alt

We show here the location of the temperature sensor in blue, the conductivity sensor in red, the latter allows us to extract salinity data, and finally the fluorescence sensor in green, located in the centre of the CTD

The fluorescence data allow us to highlight what is called the DCM, (Deep Chlorophyll Maximum), thus the depth where the maximum of chlorophyll present in the phytoplankton is located. This gives us an idea of the distribution of the latter but also of the zooplankton which feeds on the phytoplankton but also of a part of the micronecton which feeds in part on the zooplankton.


alt

This graph shows the fluorescence (green), temperature (blue) and salinity (red) between 0 and 200m depth (from top to bottom) on a profile carried out at the start of the cruise in the north of New Caledonia, at station 2; it shows the DCM at about 85 m, a salinity at 35.1 at the surface, which increases with depth, and the temperature is stable from the surface down to 80 m depth at 25 °C before decreasing to 20°C at 200 m.


alt

The profile of the day, at station 8, east of the Solomon Islands, shows a DCM at about 100 m, a salinity of 35.2 at the surface and a temperature of about 30°C from the surface to 80 m depth, which drops to 22°C at 200 m.

We thus note a significant warming of the surface water temperature as we go north towards the equator, since we passed between these two profiles, from about 25°C to 30°C.


alt

We caught our first juvenile tuna today.

We have left the waters of the Solomon Islands and are now in international waters.

The engine crew has had a lot to do so far. They are of course in charge of the main engine, but also of all the equipment on board, whether it is engine, electricity or small jobs. Besides the classical maintenance of the machine, they had to intervene to repair the showers, cabin doors, the kitchen fridge and many other things. They also provide great support to the scientific team by reworking broken mechanical parts, helping us to glue broken equipment and proposing all sorts of innovative solutions such as the use of curtains, and all this in a good mood. We are very grateful for their help.


alt

The chief mechanic and his second in the kitchen to repair the fridge until midnight.

On the scientific side, it seems that we will unfortunately have to do without the zooplankton net. Indeed, after a whole morning spent changing cables, batteries, testing and dismantling it, we still can't make it work.


alt

Sewing session to repair one of the zooplankton nets, with the help of one of the sailors.

After almost 2 weeks of campaign we can already start to observe differences between the different geographical areas we are crossing. The acoustics in particular, which allow us to study the density of marine organisms such as micronekton and zooplankton, gives a first idea of the visible differences between the southern and northern latitudes through which we pass.

We look at the acoustic data in the form of echograms of 2 different days: on September 7 in New Caledonian waters, after leaving the lagoon at the beginning of the campaign and on September 16 at 6°S latitude north of the Solomon Islands.

In the north of New Caledonia, the density of organisms is quite high during the day and night. On the contrary, on the 2nd echogram in the north of the Solomon Islands, the density of organisms is much lower, particularly during the day below 400 m.This comparison shows that, depending on the ocean area, marine organisms are not organized in the same way according to depth and are not found in the same quantity. Some areas are poorer in micronekton and zooplankton than others.


alt

Echogram recorded at 38 kHz, between the surface and 800 m (from top to bottom of the figure) for the 24 hours of September 7 (the horizontal bar below the echogram represents night in brown, dawn in pink, day in white and dusk in blue), in Caledonian waters. High densities of organisms are shown in yellow-green and low densities in blue-white.


alt

Echogram recorded at 38 kHz on September 16 at 6°S latitude, north of the Solomon Islands.

The continuation of our work on this cruise will use all other data: physical and environmental (temperature, salinity, chlorophyll...), biological (organisms caught by trawl) to try to understand and explain these geographical differences.

To finish this section of the day, one of the crew members wanted to share the fact that the navigation lieutenant is really an exceptional person, and with the second mechanic they ensure a good mood and the good functioning of the vessel.

Today was a great day on board the Alis!

Like every Sunday, the kitchen spoiled us and this time we had a delicious paella! Enough to give energy to the whole team for the rest of the mission! (Note the devastating smile of the ALIS officers).


alt

La paella del domingo, buen provecho y salud!

*Translation: Sunday paella, good appetite and health!

At 4pm, we reached the equator, in other words the 0 latitude! This fictitious line being of course not visible, we created a nice sign especially for the occasion!


alt

The GPS showing the 0 latitude on which we made the station 11.


alt

The scientific team has arrived in the Northern Hemisphere by crossing the equator line.

The Northern Hemisphere can remind us of the Canadian cold or the polar bears... On the Alis, what is closest to the ice pack are the cold rooms at -20°C. There is one to store the food, but also a cold room dedicated to our precious samples while waiting for the return on the land! For each station, the micronekton specimens collected in the trawls are sorted by groups (jellyfish, crustaceans, fish, molluscs). They are preserved in plastic bags filled with sea water, then frozen flat in trays so that they are not damaged during the journey. Once on land, we will thaw these specimens carefully to analyse them in the laboratory.


alt alt

The cold room at -20°C, the specimens frozen in bags filled with sea water.

Today is a special day for several reasons.

Indeed, today is our last sampling station. On this occasion, we will take the opportunity to introduce you to the entire crew of this incredible mission WARMALIS 1.

The one without whom all this would not have been possible, and who, despite the postponements, cancellations, all kinds of bad weather, leads this team with a master hand, I present to you our wonderful scientific cruise leader, Valérie.

alt


We are 18 people on board for this cruise. 6 people for the science team and 12 sailors to ensure the smooth running of the boat, operations and navigation.

For more clarity, we will separate the sailors into teams, to start with, we have the bridge team, which is made up of 3 people. At its head, here is our captain Jeff "Oh yeah! In addition to the navigation, he ensured every evening the smooth running of the trawling operations. Again, a big thank you for these hours on the bridge telling us great stories of incredible life in the four corners of the world, it was EXCELLENT!

alt


To assist him, here is Titouan the second mate, who also assures the functions of sports coach of the science team and our exceptional favourite lieutenant, Guillaume alias doudou-bridge who strives every day to maintain the good mood.

alt alt


It would be impossible to steam this boat without our mechanics team, made up of outstanding mechanics who are often referred to as magicians. Here are Jeff, Gwen, Xavier alias doudouh-mechanic. During this mission we learned a lot of things, especially that it is possible to repair everything with a curtain and some sika.

alt


And to sustain all this crew, those who treat our taste buds and therefore our morale, who provide us with a remarkable service despite the sometimes difficult sea conditions, a thunderous applause for Jacques and Mateo. Oleti atraqatr mama Jacques!

alt alt


Every day when we are on station, we have to take water samples, specimens, physical measurements. It is thanks to our deck team that all these machines are deployed, a difficult and technical work that is done every day of this mission, on the picture, from left to right with the red helmets, Ronald, Jean, Steeve and Vincent. A huge thank you to all for their work and their kindness.

alt


On this picture you will notice two intruders of the science team, Elodie, alias Leodi and Annie alias Annie-chou, our two staff in charge of micronekton sorting, filtrations... These two professional taxonomists delight us every day with their good mood and their joy of living and we are lucky to share all these beautiful scientific and human moments with them.

alt


Laure and Jérémie, alias the jaguar, and more recently alias Miguel, are our two acousticians. Indeed, they are the ones who ensure with great professionalism the acoustic follow-up, but not only, they also passed their grades which earned them an orange belt in taxonomy. We would like to congratulate our padawans.

alt


And finally, we saved the best for last on this day, here is Céline, our heroine of the day, our favorite electronics engineer, undisputed champion of splicing. At the same time mother, singer and engineer, it is thanks to her incredible multidisciplinarity and her unequalled sense of humor that this mission could be carried out successfully.

alt alt

We all wish her a very happy birthday!

Last night we completed the last sampling station of the mission. This does not mean that the field work is over.

Indeed, one of the experiments is carried out over 24 hours. It is to determine the production of phytoplankton, that is to say, to estimate the rate of growth and multiplication of these small, microscopic marine algae.

Phytoplankton is the basis of the food web and knowing its quantities allows us to estimate if the waters are rich or poor and if they can potentially provide enough food for larger marine organisms.

Phytoplankton is not visible to the naked eye, it is necessary to look at a drop of water under a microscope to see it, but it can also be observed by satellite since the chlorophyll and other pigments contained in phytoplankton colour the surface water.

We study the production of phytoplankton by putting 2 litres of water in transparent bottles in which we inject nitrogen and carbon that act as fertilizers and that will be absorbed by the phytoplankton cells contained in the water of the bottles. We let the phytoplankton in the bottles grow and multiply for 24 hours in an incubator placed on the rear deck of the boat under natural light with 6 compartments that have lids covered with blue filters of different intensities simulating 6 different depths between 3 and 120m deep.

At the end of the 24 hours of incubation, we filter the bottles and collect the phytoplankton on small filters that are kept in the freezer and will be analysed later in the laboratory to determine the amount of phytoplankton that grew in 24 hours. This way we can estimate the production of this area at different depths.


alt

Collection of water from the rosette into the clear bottles for production.


alt

Injection of nitrogen into the bottles of seawater for production.


alt

The bottles are placed in the incubator.


alt

The incubator to determine the production of phytoplankton, with 6 compartments simulating different depths, and with a water circulation system, all ingeniously installed by the crew.


alt

Blue filter of the incubator which intensity simulates the depth of 75m.


alt

The system of racks and filtration with the 6 bottles of sea water used to estimate the production of phytoplankton after the 24h of incubation.


alt

Recovery of the filter on which the phytoplankton was deposited for later analysis in the laboratory.

We were fortunate to have very good weather for our transit from the last sampling station to Rabaul in Papua New Guinea with favorable currents and swell allowing us to steam at more than 10 knots with little movement of the boat.

We took the opportunity to clean and store the equipment and start reviewing the data collected and writing the mission reports.

While during the sampling stations our work went from 4pm to midnight, we now have our afternoons free and enjoy beautiful sunsets on the front deck, more commonly known as "the beach".


alt

Cleaning the zooplankton nets.


alt

Drying the zooplankton nets, like curtains in the wind.


alt

Late afternoon relaxation.


alt

Sunset towards the equator.

After 4 days of transit, we see this morning the first lands after 20 days spent at sea. It is a great pleasure to see the hilly coasts of New Ireland and New Britain in Papua New Guinea. The air is saturated with humidity and the landscapes give us to see only forests and coconut groves as far as the eye can see.

The navigation is calm, and Annie and Jacques take the opportunity to prepare pancakes.

We have an appointment at 2 pm at the entrance of Rabaul Bay, just in front of the majestic volcanoes and we are accompanied by dolphins. But in spite of this idyllic image, the hard reality catches up with us because the authorities are going to board the boat, so we have to set up a Covid protocol with, notably, the wearing of a mask.

We docked at the marine gas station to fill up with fuel and some food. We are not allowed to go ashore, but it is a pleasure to see the land from close.

We also had the opportunity to see a Philippine longliner and a purse seiner leaving, and a purse seiner registered in Port Vila in Vanuatu was anchored in the bay with its helicopter to spot the schools of tuna. Tuna fishing is still in full swing in the area.


alt

The preparation of pancakes.


alt

Dolphins in front of the active volcano of Rabaul.


alt

The Alis with the flag of Papua New Guinea.


alt

The volcanoes at the entrance of Rabaul bay.


alt

The gas station of Rabaul.


alt

A seiner carrying a helicopter on the bow to spot schools of tuna.


alt

A longliner leaving Rabaul Bay.

To review our work during the sampling stations, we present today in detail the trawling.

At each station, we carried out one to two fishing operations for micronekton using a trawl net. This is a large net of about 50 m in length, which can open horizontally and vertically by about ten meters. At its end, there is a part that is called the "codend" and its mesh is 10mm, it ends in turn with a waterproof canvas bag that allows to concentrate in sea water the specimens caught, so that they are not crushed against the net, this codend is called the pool codend.


alt

Figure 1: Photo of the trawl net rolled up on board the boat

The operation to launch and retrieve the trawl was delicate and very complicated. 4 sailors are in charge of deploying the trawl, and the captain is on the bridge to command the operations.


alt

Figure 2: Launching of the trawl by the deckhands

On each station, two trawls were carried out, the first oblique from 0 to 200 m and the second, deep, to 500 m. For the first one, the fishing period starts from the surface until the trawl reaches 200 m depth, which corresponds most often to 30 minutes. Once the depth is reached, the net is brought back on board the boat. While for the second, the net is sent to a depth of 500 m, once this depth is reached, the boat starts fishing and pulls the net at about 3 knots for 30 min and then is brought back on board. Generally, the whole maneuver takes 2 hours.

Once the net has been hauled up in its entirety, we recover the codend in a trash can. We then take two tubes of water for later genetic analysis of environmental DNA. Very briefly, it will be a question later of knowing thanks to this molecular tool which large families, which genera or if possible which species of micronekton passed in this water.


alt alt

Figure 3 and 4: Recovery of the codend on board the vessel and Trawl water sampling

We then pour the contents of this garbage can onto a sieve and sort the organisms in the boat's wet lab.


alt

alt

Figure 5 and 6: Photos of sieves before sorting specimens from an oblique trawl

The specimens are roughly sorted into large groups and then packed in plastic bags containing seawater. We also take the liquid present in the bottom of the tray, which was rejected by the sieve organisms. We will later perform genetic analyses, which we will compare with our results of sorting and morphological identification of the organisms.


alt

alt

Figure 7 and 8: Sorting of specimens in the wet lab

All these samples, trawl water, tray juice and specimens in plastic bags are placed in the -20°C freezer of the boat (see blog station 11).


alt

Figure 9: Specimens sorted and packaged in plastic bags


alt

Figure 10: Tubes containing trawl water and tray juice before freezing. The content of the tray juice tube is black because a squid has expelled its ink.



alt alt


alt alt alt


alt

Last Updated on Tuesday, 28 September 2021 18:44
 
Copyright © 2021 Oceanic Fisheries Programme. All Rights Reserved.
Joomla! is Free Software released under the GNU/GPL License.
 
   SPC Homepage | About SPC | Copyright © SPC 2010