November 20, 2011 The Epic Catch

  As you may have heard by this point, one of the primary objectives of our work out here is to differentiate the acoustical properties of krill and salps. We’re doing this so that in the future people will be able to more accurately estimate their populations by comparing their acoustical signatures to backscatter in the water column.  For now, the only way to do this is to catch both krill and salps in our nets and perform experiments on them, which in our case entails titrating them to find their density relative to sea water.

Personally, I’m starting to think that this is a bad year for salps. Out of the hundreds of thousands, possibly millions of krill that we have caught in our IKMT tows thus far, we have caught maybe 100 salps.
Last night we had high hopes for finding salps. Paola found that of the salps we’ve caught, most of them were in the upper levels of the water column and were caught in the wee hours of the morning, so we decided to do an extra tow while we transited to our next station.

When we pulled the net in we had the biggest catch of krill I’ve seen. SO MANY KRILL. The cod end was literally overflowing with them, and they were all compacted in together. My first thought when I saw it was that when we flipped it over it was going to look like the cranberry sauce that my dad eats at Thanksgiving that has retained the shape of the can after it’s been poured out.

 Unfortunately, no one had a camera on them at the time to record the epic catch, but this can give you an idea of an average tow for us. In this case, it’s primarily adult E. superba, probably around 2” long, but we often get nets full of juveniles only as long as my thumbnail. Bear in mind, I’ve been told I have very small nails.

We filled something like eight buckets and sorted through whatever made it out of the compacted cod end alive to separate some animals out for titrations. Aside from a few krill, we found some cool amphipods that I was able to take pictures of under the microscope.

 A neat amphipod that we found. From a distance the red ends of his legs look almost feathery

This guy was pretty big for an amphipod at maybe an inch long. In the microscope you can see how pretty this guy actually is. The same is true for most zooplankton. With the naked eye they just look like little bugs swimming around in the water, but when you look at them under a microscope you can see all of the intricate patterns and color variations that make them so visually interesting.

As far as salps go though, I believe we found two. I am beginning to think we’ll never get a respectable catch of those elusive gelatinous goo balls. Our next few stations are in more open water, so many aboard the ship (especially Paola) remain hopeful that they may prove to be the salp promised-land. Stay tuned!

Melissa M (a.k.a Little Melissa, a.k.a. Munchkin, a.k.a. Muffin)