NOAA Teacher at Sea
Onboard NOAA Ship Oscar Elton Sette
May 2 – 25, 2004
Mission: Swordfish Assessment Survey
Geographical Area: Hawaiian Islands
Date: May 15, 2004
Lat: 18 52 N
Long: 155 47 W
Sky: Bright and sunny over us but the island has a layer of stratus obscuring views to top
Air temp: 26.3 C
Wind: 202 degrees at 12 knots
Relative humidity: 62.4
Sea temp: 26.2 C
Depth: 2015.4 m
Sea: Rolling along with 2-3 foot swells; no big deal.
Scientific and Technical Log
Scientific name for the pomfret we caught yesterday is Brama brama and for the silky shark (caught a week or so ago) it is Carcharhinus falciformis.
Today as we trolled just off the Hawaii shoreline as we steamed south to our longline set position. Mike and Chris teamed up again to land a shortbilled spearfish (Tetraturus angustirostris) 161 cm and 17 kg, silvery body with a deep blue dorsal fin — beautiful fish. This one was kept for eye studies and other tissue samples. We pulled a nearly intact fish about 20 cm long from its stomach. The 2 man team of Chris and Mike is working smoothly and efficiently; no fish has a chance against them now.
We will set the longline tonight southeast of the southern tip of Hawaii at Apuupuu Seamount, 929 m below. (18 31N, 155.24 W). Following the set we will be doing a plankton tow.
Vision (one more time):
Another aspect of the vision studies is trying to assess the animal’s speed of vision. Electroretinography measures the response of an eye to light pulses from a flickering source. So called flicker fusion (FF) is reached when the eye loses its ability to perceive individual pulses of light. A relatively high FF value is characteristic of shallow living species compared to deeper dwellers. In the dim light the speed of light gathering is slowed similar to the need to slow a camera’s shutter speed to gather sufficient light.
In concluding this abbreviated look at the vision studies, I’ll try to draw some of the pieces together. Pop up tags show where these animals spend their time in terms of depth, light and temperature realms. We can tell how sensitive an eye is to light and how fast it works. As you will recall, some of these fishes deep dwelling fishes have heat a exchange system located in the eye which keep it warm. It has been shown that speed of vision is affected by temperature change — a warm (above ambient) eye functions more effectively. Much more goes on, but perhaps you get a sense of how different areas of study contribute to a better picture of this function in these pelagic fishes.
To other (non-vision) studies tomorrow.
We steamed toward Kona through the night so that we could ferry Steven to shore and flights to other places. It was great to have met him; I’m sorry he had to jump ship. I got up at 5:30 to experience sunrise (around 6 o’clock). I thought it would be nice to see it rise over the island, but didn’t count on the clouds hanging over the mountains to obscure anything that might have been spectacular; it wasn’t even good from our perspective. But it was nice to see a color that I haven’t seen (except as a flash) in over a week — green. We have been wrapped in a beautiful blue and white world (which I am sure would excite fans of the Penn State Nittany Lions and the Mifflinburg HS Wildcats), but I tend to favor green fields and forests in the mix.
Unfortunately, we didn’t get to touch the green or for that matter the briny deep as snorkeling was denied us. So it was a day of leisure on board. I spent time reading (Diversity of Life), making some journal entries and enjoying the sight of land — perhaps the last for another 9 days (not complaining). I tried to ignore the typical signatures of human presence at Kona: autos, the Big K-Mart and Lowes perched to give exiting customers a grand view across the sea, a cruise ship at anchor, shore front hotels and homes dotting the mountainside. I directed my focus on the crashing surf, blankets of exposed black lava rock interrupting the predominant green, and shear black cliffs dropping to the sea — the natural stuff. It got better the further south we moved along the coast.
Dan guided Kylie and me through filleting of the spearfish this afternoon. Between the three of us (and the catch team, of course) we secured a good bit of food for the crew. This evening I split spool duty with Kerstin then took a chair from which to watch the rest of the set, read and talk with super fisherman Chris.
It’s a great night back in the world of blue and white.
Can you find the point on the sea where you would be most distant in any direction from land?