Tuesday, August 7, 2012

06 Aug 2012 - Lots of krill

So our luck in catching squid and hake appears to have run out, however we still are catching lots of stuff in our net tows.

By far the most common critters we catch are krill.  Krill are always described as "shrimp-like" animals, but they aren't shrimp (although they do look similar). We've been catching Euphausia pacifica, an animal that's between 1-3 cm in length and serves as the base of the food chain out here with fish and higher predators (whales, seabirds, etc) eating lots and lots of krill.

This catch contains probably more than 100,000 individual krill.

These krill have been eating pretty well as you can tell by their green/brown stomachs which indicate that there's lots of phytoplankton (small ocean plants) in the water column.

The team (Kaylyn, Stephanie, and Emily) have been titrating a lot of animals on this trip (when I say titrate, I mean measuring the density of the animal relative to the density of seawater).  This is an important property which helps us estimate how much sound these animals scatter.  Despite the loss of all our gear before the cruise and only having one working titration set-up (we'd packed two), they've set a new record (for my lab) in number of individuals measured. We're currently at ~ 1100 individuals, although we've got several more tows to come so who knows how many we'll end up with.  Despite this huge number of measurements, Kaylyn is still smiling.

Titration is fun !

The other animal we've caught a lot of in our nets are myctophids.  We've been doing a lot of different measurements on these guys, measuring their lengths, heights, and widths. Dissecting them to locate and measure their swim bladders (an air or wax filled organ in the animal that helps it control its buoyancy), and even dissecting out the myctophids otoliths (very very tiny ear bones that help identify the animal (when they're found in predator scat) or identifying where the animals live via isotope chemistry (not something we're doing).  The OSU group has very adeptly shifted from rod and reel fishing for larger fish and squid, to taking apart small fish.

Who knew junior high cafeteria trays were so useful on a research cruise.  Dave, Neal, and Aaron (top to bottom) and the remnants of one of the tows.

We're on the home stretch now.  Back on shore on friday.
Joe

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