Rockfish Recompression

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Images of a bocaccio with severe barotrauma at the surface and in a basket being sent to the bottom for recompression.  Image from NOAA SWFSC

Here is a great PSA put out by NOAA Southwest Fisheries Science Center, all about the effects of barotrauma on rockfish and how to help recompress rockfish once you’ve caught them.  We use the inverted basket method to send our fish back down after we catch them for diet analysis.

The bulging eyes and stomach forced out through the mouth are the result of increased pressure on the internal organs from the swim bladder.

Boyle’s gas law says that as the pressure on a unit of gas decreases, the volume of that gas increases proportionally.  That is, when the pressure is cut in half, the volume doubles.

Rockfish live in deep water, typically 20m or deeper, and often several hundred meters deep.  Standing at sea level, you have all the weight of the gaseous atmosphere pressing down on you.  When you dive into the water, the weight of the water is added to that, at a rate of the equivalent of one atmosphere every 10m you descend.  The pressure at 20m is 3atm.  If a rockfish is brought from 20m to the surface, the pressure on it decreases to 1/3 the original pressure, which means the volume of its swim bladder increases 3-fold.

Unlike salmon and other surface-oriented fishes, the swim bladder of rockfish is not connected to the esophagus.  Salmon add gas to their swim bladder by swallowing gulps of air from the surface.  This limits them to staying near the surface.  Rockfish use a capillary system like that surrounding our lungs to deliver gas to the swim bladder.  The benefit of this system is that rockfish are not tied to the surface, and can colonize deeper habitats.  However, it also prevents them from being able to quickly vent gas as the surrounding pressure decreases.

Since rockfish can’t burp, when they are brought to the surface the swim bladder swells and causes the stomach and eyes to bulge out.

Year of the Serpent

Today marks the beginning of the Chinese New Year – the Year of the Snake.

A few snakey photos from my research were featured in a post about snakes and serpents on the UW Biology Department graduate students’ blog, Science Positive.

Serpula columbiana tube worms are sessile invertebrates that secrete a calcareous tube (Serpula means “serpent”).  There are also brittle star arms snaking out from the crack in the rock (brittle stars are in a group called the ophiuroids, which means “snake-like”).

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The scientific name for lingcod is Ophiodon elongatus (Ophiodon means “snake-tooth”).

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Greenling Eggs

In the fall we frequently see small clutches of fish eggs.  We typically see them laid inside empty giant barnacle shells, and sometimes even in the holes in the bricks we use in our clod card work.This egg mass is different for two reasons.  First, it’s not laid inside any protective shell or brick, and second, the developing fish can be seen inside their eggs – usually the eggs we see are either opaque or don’t have any clear differentiation inside them.

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If you look close you can see eyes and even the coiled body of the embryos.

We think these are the eggs of a greenling, mostly because they don’t look like lingcod or red irish lord egg masses.  If they are greenling, they’re likely kelp greenling, the most common species of greenling.

Greenling are relatives of lingcod (note the “ling”).  However, greenling don’t get nearly as large as lingcod, and are much more active.  Greenling are commonly seen by divers, and even seem to follow us around on our dives.  Here are some photos of adults (not my photos):

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This is a female.  Key characteristics to look for: gold fins and lots of small dark spots on a light background.

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This is a male.  Note the blue-grey fins and few large light spots concentrated near the head on a dark background.

I remember the two genders with the color of their fins: boys are blue and girls are gold.

Last Transect Complete!

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Tim Dwyer and me through the camera framer, just after finishing the last transect dive of 2012

After a long autumn quarter, we finally finished our annual fall surveys.  This enormous body of work (95 transects in about 75 dives) could not have been accomplished without the help of a small army of volunteers and interns.

Thanks to Annie Thomson, Aaron Galloway, Derek Smith, Noel Larson, Rhoda Green, Autumn Turner, Gavin Brackett, Ryan McLaughlin, Ryan Knowles, Jackie O’Mara, Megan Cook, Pema Kitaeff and Alex Lowe.

And thanks especially to Tim Dwyer, inexhaustible dive buddy extraordinaire.

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That’s our planning whiteboard.  All those purple boxes are transects that needed doing, and the green text are the dates we completed the transects.  They’re finally all full – whew!

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Tim and me collapsed under the weight of all the equipment it takes to get the science done.

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My face seconds after finishing the last transect.

Sunset Diving

Derek Smith and I finished up a transect dive at Shady Cove just as the sun set over Friday Harbor.  Derek snapped this photo with our photoquadrat camera setup.

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This is definitely one of the benefits of trying to dive every available slack between October and January every year!

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Split Arms

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This Pisaster brevispinus has a pretty dramatic split arm.  I wonder how they control the regrowth of limbs to reach the same length as the others.  This photo is from Neck Point in October 2010.

Seastars can drop their arms if they feel threatened, a process called autotomy (“self-sever”), and regrow the arm later on.  But sometimes things go screwy and they don’t regrow quite right.  Seeing six arms on a star that should have only 5 is fairly common.  These photos are from one of the more unique examples I’ve encountered.

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Can you see the little nub on the Pycnopodia helianthoides arm?

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And yes, there are tube feet on the bottom, just like any proper seastar arm.

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Pycnopodia helianthoides is my favorite example to use when students complain about having to learn the scientific names for organisms.  As long as the describer didn’t name the organism after a person or a place, the scientific name can be very descriptive.  “Dense-feet sun-flower-ish” is a very accurate description of this star.

Octopus

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Enteroctopus dofleini arm sliding out of its den.  We typically find octopus by looking for midden heaps, piles of shells leftover from the octopus’ meals.

Octopus sightings seem to be getting more and more common.  This one hangs out under a boulder at Neck Point.  Megan Cook, the 2012 North American Rolex Scholar, joined us for a few days of diving and snapped these photos.

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The giant pacific octopus feeds on all kinds of prey, from the red rock crabs and clams seen in these photos, to dogfish sharks and seagulls.

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Octopus are well known for their ability to change colors.  This one is showing a lot of white, which may mean that it’s scared or upset at our presence or the flash of the camera.

This octopus (or at least the den) has been here for some time.  Tim Dwyer got this excellent video in September 2011.  Near the end of the video watch for a rapid skin color and texture change as it leaps into its den.

For as large as they are, giant pacific octopus do not live very long – only 3-5 years.  After mating, females lay a cluster of eggs in their den and stop feeding.  They spend all of their time guarding the eggs and pumping water through them to keep the developing larvae oxygenated.  By the time the larvae hatch the female has used up all of her energy reserves, and dies.

800th Dive

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Today marks a major milestone – 800 dives since starting graduate school.  That’s 57,065 feet down (and back) and over 417 hours underwater.  I wonder if I can make it to 900 before I graduate…  Should I even be trying to make it that many?

Photoquadrats

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Epilithic organisms in a photoquadrat at Minnesota Reef, 21m depth.  You can see cup corals, several bryozoans, hydroids, sponges, encrusting algae and a creeping sea cucumber.

A lot of the work our lab does involves taking photos of quadrats underwater.  We take photos because the depth we work at (up to 27m) prevents us from spending enough time to quantify epifauna along our transects.

Our camera setup consists of an Olympus C-8080 in an underwater housing, a strobe slave, and an Ikelite strobe, all mounted on an aluminum frame.

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Photo by Megan Cook

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Photo by Megan Cook, Ryan Knowles diving

The business end of the framer measures 35x25cm.  When we take photos we rest this rectangle flat against the bottom, and use the rulers to set an accurate scale for measuring mobile fauna on the computer.  We quantify percent cover of sessile organisms by dividing the photo into 24 blocks and estimating basal and canopy cover in each block.

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