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Our first night trawl

“On the morning of 11th June we decided to do our first night trawl and deploy SaManta at 04:00! She plunged into and sifted through the calm, tropical, surface waters for approximately 1 hour. The difference with this specific trawl was that we used a solid cylindrical cod-end specifically for sampling plankton, as opposed to the mesh cod-end we’ve been using for sampling plastic (a “cod-end” is the end of the net that collects what has just been filtered).
   
Just as we recovered the net and got it safely on board, it started 
to thrash around which took us all totally by surprise and certainly increased our heart rates! I donned some rubber gloves and removed the cod-end with caution… once safely off, out poured a multitude of fish – most of which were small, but one large fish approximately 30cm long! It was a flying fish that had got stuck head-first in the cod-end and was trapped by its 6cm-long spines coming off the operculum (plate covering and protecting the gills). Also preventing its exit were the pelvic
fins, but eventually I managed to carefully ease it out… We got another fright however when we shone a torch on its head because the eyes were red and bloodshot! It really looked like it had been drawn up from the depths of the abyss… slightly taken aback by this scary specimen, we waited until daybreak to look at it more closely.
   
After breakfast I got out my dissection tools and started the 
operation. However deadly it was in appearance, it was very beautiful– almost black in colour on its dorsal side with blue spots, and then
pearly white on its ventral side (this difference in colour is known as ‘counter-shading’). It had a boxed head, wings less robust than those seen on other flying fish, huge eyes (which explains why it was feeding at night) and as already mentioned: spines – 4 large at the head-end and then rows of much smaller spines running laterally from its pectoral fin region to just before the tail. The dissection began and the aim was to find out what it ate and whether or not there was any plastic in its digestive system. I am pleased to announce that there was no plastic to
be found!
Instead there were several juvenile flying fish, plus an 
entire fish roughly 10cm long in its stomach covered in shimmery, silvered scales. On the exterior of this handsome flying fish there were
unfortunately many parasites penetrating the skin and the wings; one had gone all the way through its right wing from underneath and was hooked onto its host using three incredibly effective but terrifying barbs - piercing the skin and clamping it into position. Despite the fact that the fish was no longer of this life, I felt a great deal of relief upon removal of that parasite from its wing. The appearance of this peculiar flying fish surprised many of us, as we were so used to just seeing the slender pale blue flying fish by day (I have yet to identify it). An interesting find!
    
So overall we’ve seen a great change in the sea life whilst 
trawling at night compared to during the day: larger fish species and fewer smaller planktonic organisms. The sea temperature saw its peak of the trip earlier this week of 28.8°C! We have also come across huge clumps and mats of Sargassum (Sargasso weed) since entering warmer waters that are oases for marine life, where I’ve found beautifully camouflaged crabs and shrimps. The other day we also spotted a sperm whale, turtle and a hammerhead shark!! Bioluminescence continues to embellish the ocean surface, the moon evolving from New to First Quarter and the stars are gradually shifting position as we sail and increase our latitude northwards. Life at sea is a true gift.
   
Having now crossed the equator we expect to see (and are seeing) an 
increase in the marine life and plastic abundance/distribution as we progress further into the North Atlantic. On 12th June we had our Equator Crossing ceremony when, only after trial, punishment and cleansing of our salty souls, all Pollywogs (those who haven’t crossed the equator on a ship) were found worthy by King Neptune’s Court and initiated into the solemn mysteries of the Ancient Order of the Deep. An utterly brilliant occasion!
   

The last couple of days have seen some of the heaviest rain I’ve experienced so far; We entered into the Doldrums where the wind dropped significantly, but it wasn’t long before that changed and we were inundated with unpredictable winds, squalls and rain, so torrential that the pounding water flattened the persistent, stormy waves – the wind so variable that it had 180° shifts! I was on the midnight-0400 watch that morning and the atmosphere was incredible – driving rain, hammering squalls and relentless seas that looked as if they were being haunted by the storms of the past. However, as with everything: “every cloud has a silver lining”, which was that the rain was warm and that it really was worth me bringing my bulky foul weather gear along!
   
SST has seen a decrease in approximately 3°C over the last few days 
– as of this morning it was down to 25.8°C.
Keep an eye on the Bark EUROPA page for more updates on marine life and plastics!

Jess Fox (marine biology with oceanography, Bangor University)

Written by:
Jess Fox | scientist in residence

1

Comments

A wonderful log entry ...I felt i was part of the experience on board the Europa bon voyage


Emile Morel  |  23-06-2018 08:50 uur

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