Tag: vision study

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Geoff Goodenow, May 15, 2004

NOAA Teacher at Sea
Geoff Goodenow
Onboard NOAA Ship Oscar Elton Sette
May 2 – 25, 2004

Mission: Swordfish Assessment Survey
Geographical Area: Hawaiian Islands
Date: May 15, 2004

Time: 1550

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
Barometer: 1012.72
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.

Personal Log

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.

Question:

Can you find the point on the sea where you would be most distant in any direction from land?

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Geoff Goodenow, May 14, 2004

NOAA Teacher at Sea
Geoff Goodenow
Onboard NOAA Ship Oscar Elton Sette
May 2 – 25, 2004

Mission: Swordfish Assessment Survey
Geographical Area: Hawaiian Islands
Date: May 14, 2004

Time: 1600

Lat: 18 40 N
Long: 158 14 W
Sky: Sunnny with widely scattered cumulus
Air temp: 26.4 C
Barometer: 1011.26
Wind: 172 degrees at 12 knots
Relative humidity: 61.4%
Sea temp: 26.4 C
Depth: 888.5 m

Sea: A few white caps out there; swells in 1-3 foot range — easy going today.

Science and Technology Log

A fairly exciting morning on the longline. Several escolar, a barracuda, and a pomfret (a laterally flattened fish about 30cm long but only 2-3 cm in width with a fine set of sharp teeth). Samples taken from all. We also had a blue shark from which samples were taken and an oceanic white tip shark which was tagged and released. I got to wrestle both. Picked up a few remoras from the sharks. We think we have at least two species of remoras.

This afternoon we passed over Cross Seamount and traversed it several times as we trolled but to no avail. There will be no longline set tonight since we have a date in Kona to drop off one of the current scientific party.

I want to fill in with more of the vision story this evening if I can stay coherent long enough to convey it sensibly. I will touch on the work of Steven, Kerstin, and Rickard.

I have been collecting samples of fish lenses. They vary in size, as you would expect, among different sized fishes. What makes the lenses different from those of most vertebrates is that they are spherical rather than oval in cross section. The cornea of fish is also optically non-functional. Since it has the same refractive index as water, focusing is done by moving the lens back and forth in the eye rather than by changing the shape of the lens as our eye muscles do.

Steven uses laser light to determine the focal point for different colors of light. He suspends lenses in a fluid medium then turns on a laser beam that makes two vertical passes through the diameter of the lens. You can watch light’s path change as the beam migrates. Computer analysis then determines focal point.

Kerstin and Rickard must have live cells from the retina for their studies. Among other things, they are looking at the sensitivity of these cells to different light intensities. Live retina cells convert light to electrical signals which travel via the optical nerve to the brain to produce an image. By attaching electrodes to tissue samples about 1 cm square in size and subjecting the cells to different intensities of light electrical responses of different strengths can be detected and measured. They appear as a wave pattern on a screen. As light intensity is increased, the amplitude of the wave pattern increases. So a flat line (no response) becomes one with small amplitude waves which grow as light intensity increases to a point where more light produces no greater effect.

Lets compare two species, mahi mahi, which stay nearer well lit surface and bigeye tuna which like deeper environs. Which eye would you expect to be more light sensitive? The bigeye. Their cells are stimulated by much lower intensities of light than the mahi’s. They (bigeye) have to be able to detect their prey under minimal light conditions and need the more sensitive eye to do that. Big eyes, big pupils (fish pupil size is fixed) and a “super” sensitive set of retinal cells are adaptations of these fish to their deep environment.

I’ve had enough (as I suppose you have too). I will wrap up the vision story tomorrow or Sunday.

Personal Log

We are headed for Kona. Although we probably will not get any shore time, it has been suggested that there might be an excursion to a place where we can swim/snorkel for awhile. I am hoping very much this it true as are others. A plunge into this element (I guess I should say compound) that we have bobbed around on top of for the past 13 days would be a pleasant change in the routine and scenery.

Reading E.O. Wilson’s The Diversity of Life.

I would like to thank, Ron, a fellow teacher from Michigan who I have never met, for writing a note to tell me that he has been enjoying the logs and also to pose a question. Much appreciated!

Questions:

Sunrise here today is at 6AM and the great yellow ball sets here at 7PM. What time is it rising and setting in your area at this time of year? Find out sunrise and sunset times for the solstices for Honolulu and your area. From that determine A) how much longer the sun is above the horizon for each place in summer vs winter B) which place, Honolulu or your home has more sun time at each solstice? If you find that there are differences explain why they exist.

Geoff

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Geoff Goodenow, May 12, 2004

NOAA Teacher at Sea
Geoff Goodenow
Onboard NOAA Ship Oscar Elton Sette
May 2 – 25, 2004

Mission: Swordfish Assessment Survey
Geographical Area: Hawaiian Islands
Date: May 12, 2004

Time: 1745 (Later than usual due to busy late afternoon fishing)

Lat: 18 33N
Long: 158 20 W
Sky: Somewhat overcast this morning but a nice sunny day overall.
Air temp: 26.5 C
Barometer: 1013.5
Wind: 90 degrees at 10 knots
Relative humidity: 63.5%
Sea temp: 26.3 C
Depth: (forgot to check)
Sea condition: Good sized swells today kept us rocking and rolling pretty good throughout the afternoon and evening. But it wasn’t discomforting at all.

Scientific and Technical Log

Brought up 3 escolar and one wahoo on the longline this morning — not a very exciting time. The set was about 30 miles NE of Cross seamount. After retrieval we steamed south again through/over Cross and back to the area of success around Swordfish seamount to set the line tonight. Along the way we encountered several so called “bird piles”, congregations of birds on the water, indicative of fish below.   Passing over Cross we pulled in 5 mahi mahi, a small yellowfin tuna, and 4 bigeye tunas. It was a busy late afternoon. There’s lots of fish on ice for upcoming meals!

Returning now to the vision studies:

This afternoon Eva gave me the tools and an escolar eye and had me go through the procedures she follows to get what she needs for her studies. (Kylie basically does the same procedure but uses skipjack tunas). I’m not ready for microsurgery yet, but she gave my effort a thumbs up as I successfully secured the materials she needs for later study.

As the eye is taken from the animal marks are made on it with a scalpel to mark its orientation in the animal. After measuring eye cup and pupil size, the cornea and lens are removed and a bit more scraping and cleaning eventually leaves her with optic nerve, retina and vitreous to be preserved. This took me about 45 minutes to do.

Back at her university lab, the retina alone will be used. Sections of the retina will be mounted for microscopic examination. With it she can answer questions such as 1) what do the photoreceptor cells look like? 2) Is there a variety of types of receptors in their eye? 3) What is the density/distribution of receptors across the retina? In another study she makes other preps for microscopic examination to observe density of ganglia in the retina.

Personal Log

I had some ideas for tonight’s entry in this section, but this boat is rocking pretty hard right now and sitting in front of the computer is not particularly pleasant. I’m cutting things short tonight.

Geoff