Thursday, August 2, 2012

02 August 2012 - Meet the Humboldt Squid !

One of the target species we're looking for out here is the Humboldt squid.  They can be tricky to catch, particularly from an oceanographic research vessel which isn't designed to trawl large nets or long-line fish.  However, last night we had success with rod-and-reel fishing (albeit really fancy reels) targeting fish that were somewhere between 70-100 m depth.  We've been fishing like this as part of our regular station operations trying to catch hake or squid (depending on where we are and what time of the day it is).

We (the royal "we" meaning Kelly Benoit-Bird's group from Oregon State)  have three fishing stations on the port side of the back deck.

They use a lure/jig with a series of sharp hooks such that if the squid encounters it, it gets hooked on the barbs and as the reel pulls the squid back to the surface, it can't escape.

This animal still has lots of energy even out of water. When we first pulled it out, it was inking/squirting everywhere.
The Humboldt squid we caught last night is on the small side (they can be 5' long).  Kelly's past research has measured how much sound these animals scatter, but we don't know exactly what part(s) of the animal cause the acoustic scattering. If we can figure that out, then we (scientists) would be better able to measure their presence and abundance in the ocean.  These animals have started to show up along the Western coast of the United States more regularly (and over larger areas) over the past decade. The change in their distribution may be related to environmental factors such as changes in water temperature or oxygen levels which may expand or reduce their preferred habitat areas.
Various parts of the squid that we are measuring.
Our group is responsible for measuring the material properties of the different parts of the squid which will help us to better understand their acoustic scattering characteristics. We measure the density and the soundspeed of the various tissues and organs.  In order to get these pieces, we dissect the animal and then measure different parts of it. For this squid, we did measurements on its mantle (body tissue), arms, eye, brain case (i.e. the cartilaginous skull), the pen (which helps make the animal rigid), and the beak.
A dissected myctophid, the balloon-like structure in its body cavity is its swimbladder (probably over-inflated due to us bringing it up from depth). Other internal organs have been removed so we can measure the swimbladder.

In addition to the squid, we've been examining other animals we catch in the net (as you've seen previously). One of the most interesting animals we catch regularly are myctophids which are small fish that spend most of their time in the middle of the ocean (i.e. hundreds of meters deep). These animals were first observed (acoustically) over 60 years ago, and we still know very little about them. They have a swim-bladder (an air or wax filled organ) inside of them which 1) helps them maintain their buoyancy in the water column and 2) scatters a lot of acoustic energy. We've been dissecting the animals that we catch and measuring their swim bladders to better understand our acoustic backscatter data.

We've been busy the past few days with lots of measurements and Chad just caught a hake (on a squid jig) so it's back to the wet lab.