Thursday, 4 September 2008

JESRT and some cool beasties

The trawl brought up some pretty neat fishes, and also some sharks, so it was action stations for the Jéssica Escobar Shark Rescue Team (JESRT).

The sharks in the catch were all squaliforms; this means that they have a spiracle on the top of their head, and they're generally quite happy sitting on the bottom, pumping water over their gills; they're not like many pelagic sharks that have to keep swimming to breathe (the latter are termed "obligate ram ventilators"). This also gives them a small chance of surviving the trawl and making it back home - the trick is to minimise stress and get them back into the water as soon as possible. We've come up with the idea of putting them in buckets of water whilst we process them as quickly as possible. After that, they are released back into the water.

The team of people I am not on shift with have dropped hints that they're not happy with the coverage of their activities in this blog, so I shall try to rectify that! On the left, you can see Carel rescusitating a small squaliform shark. The sharks are quickly measured and weighed, and a small tissue sample clipped from the dorsal fin for later genetic analysis.

If you're wondering what spiracles are, take a look at this picture. The half-moon shape behind the eye is a spiracle; you'll notice one on each side of the head. These connect through to the gills (you'll notice the gill slits, where water comes out, a little further down the head).

Here were two of the "fishy" highlights for me:

Malthopsis mitrigera - a rather ridiculously "cute" animal! Yes, those are "legs" you see sticking out of the bottom; they are highly modified pectoral and pelvic fins and many of the fishes in this group walk around on the sea bed using them. Incidentally, the sides of the body are very compressible, I suspect this fish can make itself smaller (less wide) if it wants to.

A deepwater flathead that didn't look quite like the one in Smith's Sea Fishes, from the Family Bembridae. That nice red blotch on the second dorsal fin should help identify it at some stage. They have pretty awesome spines on their heads. The pins you see in the photo are used to keep the fins nicely displayed; for fish photography, one would traditionally pin out the fish like this and then apply a small amount of concentrated formalin to the base of the fins; this fixes the muscles in position after a short while, so you can pull out the pins and the fins stay nicely splayed. You would then put the fish in a photo tank with water in it to reduce the reflections off the moisture on the surface of the fish (you get *much* better photos this way). Unfortunately, because we're taking DNA and stable isotope samples of pretty much everything, we can't use this method (at least not with the formalin) as it ruins the sample for both subsequent investigations.

To the right, you'll see Jéssica's shift team. From left to right, they are John Bemiasa, Irene Rasoamananto, Giselle Bakary and in the back row, Carel Oosthuizen and Jéssica Escobar. Not pictured is Jan Frode Wilhelmsen, part of the Nansen crew who runs the instrumentation such as the CTD during their shifts.

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