NOAA Teacher at Sea
Staci DeSchryver
Onboard NOAA Ship Oscar Dyson
July 26 – August 12, 2011
Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska
Location: 57°43.287’N,152°28.867’W
Heading: 242.2° (But we are stationary)
Date: July 26, 2011
Weather Data From the Bridge
Cloudy and Light Drizzle
Air Temperature: 14.0°C
Relative Humidity: approx 79%
Science and Technology Log
Well, I have arrived safely and soundly on the NOAA Ship Oscar Dyson. For the next three weeks, we will be catching, catching, catching as many walleye pollock as we possibly can to determine the health of the stock. How is that done, you ask? Well, they send the Teachers at Sea out to the stern of the ship where we gently call them over for processing.
“Here, Fishy, Fishy…” Just kidding.
First, the scientists use acoustics to find concentrated masses of walleye pollock beneath the surface. The echoes appear on a computer screen for the scientists to evaluate. Once they determine that the acoustic signature is indeed pollock, they take a direct sample of the fish by dropping a large net, called a trawl, down to the location of the fish. The net then captures the fish and they are brought to the surface. The procedure is more like “hunting” rather than “fishing” in that the scientists have sophisticated equipment to detect the locations of the fish – they aren’t just attaching a worm to a hook and hoping for the best. They actively seek out locations where they know pollock exist – this helps preserve the stock populations because if they can “see” the echoes on the screen, they can be sure they are pulling up the right species. In addition, the sample sizes that are taken are quite small in comparison to the commercial fishing industries – we take only what we need to get accurate data.
After the fish are caught, they are sent down a ramp for processing. Unfortunately, most of the fish brought to the surface “donate their bodies to science,” as they don’t survive the trip up from depth to the surface. Why don’t the fish survive? Sometimes, it is simply the stress of being caught. But another contributing factor is stress that is put on a special organ in the fish called a gas bladder. It is easily explained using a reverse example.
Remember the video clip from Mythbusters on the “MeatMan?” In the program, the myth claimed that a person’s body would indeed be crushed by the weight of ocean water at a depth of 300 feet. If you recall, the myth was confirmed when “MeatMan’s” helmet caved in after the Mythbusters removed the pressurizing hose from the back of the diver’s suit after the “diver” was lowered to a depth of 300 feet. With pollock, the reverse happens. The pollock’s body is “conditioned” to being at a particular depth. Inside the pollock is a swim bladder that is filled with air that pushes back on the water at the same pressure that the water pushes in on the fish – much like the pressurized diving suit. As long as the pressure remains constant – both pushing outward on the surrounding water and inward on the swim bladder – the fish is fine. When the fish is forced too quickly above a particular depth, the bladder will expand because the outward pressure is no longer strong enough to push in on the bladder – the exact opposite of what happened to the meat man – the bladder expands too quickly, and it can sometimes cause the fish to die. Pollock do have the ability to regulate their swim bladders, but when the are pulled too quickly to the surface by means of say, a net, for example, they can’t adjust to the pressure changes quickly enough. I’ve shortened this complex idea into to a simple and digestible equation:
Person too deep = squish. Fish too shallow = pop.
Despite the fact that the fish usually perish in their journey, they do so to benefit the overall health of the stocks. Researchers gain a wealth of information from the catch. They measure the size, age, sex, and sometimes the stomach contents of each of the fish! As the data gets collected, it is analyzed to determine the overall health of the population so that fishermen know how much is safe to catch and sell for profit without doing harm to the population.
Personal Log
Well, we haven’t left yet. Some complications on the ship have kept us safely in the comfort of our harbor and will most likely keep us there until Friday afternoon or Saturday morning. So, we’ve been keeping busy with tours of the ship, introductions to the ship’s crew, and trips to town to look around and sample the local fare. We are staying on a Coast Guard base, so it’s a secure location that most civilians can’t access. The base is really interesting.
I especially enjoy hiking around the peninsula that is attached to the base. All along the road are freshly ripened Salmonberries (which coincidentally do not taste like Salmon. They taste like delicious.) Along the opposite side of the road is a rocky shale beach. About a half a mile down the road is a rotting old dock that is commissioned only by grasses and pony-sized seagulls. It is decaying in the most gorgeous manner – to witness an object simultaneously rusting, collapsing, and growing is a delicious paradox for the imagination.
Like an old World War II veteran, I imagine it not as it appears today, but as a majestic and commanding behemoth – an anchor and a doorway home for the ghosts of a time passed bustling about on its intact surface. It’s a good thing there is no possible way to access it, otherwise I may have found myself out there teasing out the details of its surely magnificent story.
When we do leave port, I will be working the night shift. While to some that might seem a bit intimidating, I am actually quite excited. If my shift does not end until 4am, that gives me the luxurious liberty to remain comfortably in my rack until ten am without anyone thinking less of me. Interestingly enough, there are a decent number of people who work nights onboard. This means that there is someone awake at any given hour somewhere on board. It’s hard to feel alone when there is always someone up and about – which is a comfort in the foreign world of a research ship.
For now, there isn’t much to report on other than we are hurrying up and waiting to leave. Hopefully the weather will be friendlier tomorrow for a hike to the top of Mt. Barometer where it is rumored that the view from the top rivals any Hollywood production. Well, maybe except Avatar , but what landscape can compete with an alien land full of glowing trees? I would like to be the judge of that.
