Tag: shark

Posted on

Geoff Goodenow, May 17, 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 17, 2004

Time: 1600

Lat: 18 24 N
Long: 157 47 W
Sky: Stratus cloud layer shielded us from the sun until longline was in then it started to break up by 1030. Sun for awhile then clouded over again by midafternoon. Thinning by evening but still a good blanket on us.

Air temp: 27.3 C
Barometer: 1011.24
Wind: 35 degrees at 7 knots
Relative humidity: 54.5%
Sea temp: 26.8 C
Depth: 4489.2 m

Sea: 2-3 foot swells; no problems

Science and Technical Log

Yesterday after picking up the line we began a westward passage toward Swordfish Seamount. It was a long way off and there was no hope of getting there last night. The line was set along our course at 18 34 N and 156 47 W at no particular oceanographic feature that I am aware of. Perhaps that is why out haul today was none too exciting — a couple escolar, a snake mackeral and two blue sharks. Only one of the blues was brought on board. We will be at Swordfish to set tonight and look forward to a more interesting catch tomorrow.

I have covered each of the areas of research going on by the science teams aboard for this cruise. Today, my focus will be on sharks. We have caught 4 species so far and that has aroused my interest in these animals. I’ll provide some general info as well as some specifics for the species we have caught. For those of you interested in more, my information comes from two sources: Smiths’ Sea Fishes by Margaret Smith and Phillip Heemstra, and Diversity of Life by E.O. Wilson.

Sharks along with skates and rays are among 700-800 species in the subclass Elasmobranchii of the Class Chondrichthyes. Like all members of the class, their skeletons are entirely cartilaginous, but Elasmobranchs are distinguished by an upper jaw that is not fused to the skull and 5-7 pairs of gill slits.

There are about 350 species of sharks ranging in adult size from the 23 cm green lanternshark to whale sharks, the largest of all fishes, which reach 13 meters. Sharks lack a swim bladder, but produce large amounts of lipids which are stored as oils in the liver for buoyancy. The liver can account for up to 25% of the animal’s total weight. Sharks maintain osmotic (water) balance by maintaining a high concentration of urea (so high as to be deadly to most fishes) in their blood and tissues thereby reducing water loss to their salty environment.

All sharks we have caught (except the bigeye thresher, Order Lamniform) belong to the Order Carchariniform. This is the largest group of sharks; it includes about 200 species. These two orders are distinguished from one another in the following ways:

Carchariniforms: purse-like egg cases or live bearing; a movable nictitating membrane (eye covering).

Lamniforms: bear live young with uterine cannibalism (now there’s an interesting bit) evident in some; no movable nictitating membrane. There are also differences between the orders in the internal structure of their intestines — very interesting but I won’t go into description.

Specifics about each species of shark we have taken follow.

Blue sharks: the most fecund of all sharks; viviparous and bear 35-135 pups per litter; 50 cm at birth; attain 3.5 m; widespread in all oceans; favor water 12-16 C.

Oceanic white tip: in all oceans; away from continental shelves; viviparous bearing 6-8 pups usually; 60-65 cm at birth; up to 3 m; abundant in tropical seas.

Silky: widespread, prefer warm water; feeds inshore and in deep water; viviparous bearing 9-14 pups; 80-85 cm at birth; up to 3 m.

Bigeye thresher: widespread in warm ocean waters; ovoviviporous (provides embyo with no nourishment beyond the original yolk); 2 pups per litter; 100-130 cm at birth; attain 4.5 meters.

Personal Log

Well, I guess you can tell what I did today, and I might have a few more tidbits about sharks to add tomorrow. I am completing the log before the line set tonight so as to take in a movie afterwards. Don’t know what’s playing tonight, but it will be free and relaxing.

Tomorrow begins our last week at sea. Little time remains for you to file your questions with me. I’m looking too for suggestions for topics to try to address so if you have ideas, please suggest. I have asked for a tour of the engine room which is a possibility for Tuesday if tickets aren’t sold out. That might give me some interesting goodies to pass along.

Question:

We have seen fish that are rather uniformly dark in color and some that are brightly colored. What are some of the roles of coloration in fishes (as well as other animals)? Describe countershading and how it serves an animal like the blue shark.

Geoff

Posted on

Geoff Goodenow, May 11, 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 11, 2004

Time: 1600

Lat: 18 49 N
Long: 158 03 W
Sky: A gray overcast morning with a couple of showers. Brightened through the late morning and stayed mostly(thin)overcast but enough sun to cast shadows and feel pretty intense. 90% cloud cover through most of daylight hours. Tonight the sky is star-filled — beautiful.

Air temp: 26.3 C
Barometer: 1011.9
Wind: 100 degrees at 8 knots
Relative humidity: 66.9%
Sea temp: 26.7 C
Depth: 3333 m

Sea: A bit of chop especially this morning when wind seemed stronger. There were a couple of splashes onto the deck as we brought in the line this morning. Still some whitecaps this afternoon; well settled this evening.

Salinity: 34.4 (I thought some might be wondering; it has been consistent throughout.)

Scientific and Technical Log

This morning we brought in several escolar (none scoring better than 4 as they belly flopped to the surface), a yellowfin tuna which was tagged and released, and three blue sharks (one was kept and two were returned after blood samples and a couple remoras were secured). Shark wrestling is getting to be routine. Since then we have been steaming northeast beyond Cross Seamount. At 2000 we are at Lat 19 10N and Long 157 45 W as we begin the set.

On minor correction: sharks and other big fish brought on board are hoisted by human muscle using a block and tackle (not a mechanical winch as stated previously)

Kerstin Fritsches from the University of Queensland in Brisbane, Australia is working on vision studies of the fish. Her husband, Steven Evill (often affectionately referred to as Dr. Evil) assists as do three graduate students, Rickard and Eva from Sweden, and Kylie, also from Brisbane. It is for these studies that the eyes are taken from the animals. I will attempt to explain some practical applications of their studies and give you a sense of the kinds of work being done on board. I will do this in several editions of the log — not all at once. So to start —

Fishes, depending on species may use a variety of senses to know their environment. Scent, for example, may allow them to home in on prey.   While research goes on by others to analyze other sensory structures and abilities, Kerstin’s work is about vision. The attempt is being made to find out just what these different fishes are able to see. Do they see differently and, if so, how so? The practical application for longline fisheries, a very indiscriminate practice, is to eliminate by-catch. This can help protect endangered species and make longlining more cost and time efficient by finding ways to attract only economically valued species.

The water column is visually quite a varied environment. Longer wavelengths of red light are essentially filtered out and gone within the first 50 meters below the surface while shorter wavelengths in the blue range penetrate the depths. But imagine hanging out, living, and hunting at 600 meters as some of these fish do, in daytime light levels the equivalent of a starry night at the surface. Some such as swordfish and bigeye tuna come toward the surface at night keeping their exposure to light levels constant. Imagine your life spent in light levels no greater than that of a starlit night. What adaptations do these animals have to accommodate such a lifestyle? What are different parts of the visual apparatus doing in these animals? In order to help uncover answers to these and other questions, three kinds of projects are going on here.

When a live fish of desired species comes aboard, it is first killed then its eyes are taken. Kerstin and Rickard must have living tissue from the retina for their studies. They have about 20 minutes in which to get the tissue they need into a special oxygen-rich solution in which the tissues will be good for 6-8 hours. Steven works with lenses which do tend to cloud over time, but he is able to easily accomplish his work before that happens. For Eva and Kylie there is no rush as their samples, retinas and eyes with only lenses removed, are destined to be preserved for later study at home. I’ll pick up from here tomorrow with details about specific aspects of the work on vision. In preparation you might look up what the retina and lens of the eye do.

Personal Log

I observed our hitchhiking birds in a new feeding maneuver this morning. A bunch of flying fish took to the air and were happily gliding along. Our friends took after them and approaching from the rear snatched them out of the air.

Filling in the non-fishing time gaps: Last night I interviewed Eva about her part of the vision studies and this afternoon Rickard took me through his experiments. At home in Sweden he does vision studies on insects, moths and butterflies in particular. I am also reading Adam’s Navel which I can recommend to those with an interest in human biology written in an interesting non-technical and often humorous style. And it is often nice to find some shade, a comfortable deck chair and with a beverage in hand stare across that wide, blue expanse of water.

The days pass quickly.

Goodenow 5-11-04 sunset
Sunset from NOAA Ship OSCAR ELTON SETTE.

Questions:

I am happy to report that we are eating quite well on our voyage, but that was not the case for early voyagers across the seas. At times they might have had plenty to fill their stomachs, but at the same time lack a balanced diet. Because of this, one condition the mariners suffered was scurvy. What are the symptoms/problems associated with that condition? What can be done to prevent it? See if you can find out when and how the solution to the problem was discovered.

Geoff

Posted on

Geoff Goodenow, May 9, 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 9, 2004

Time: 1600

Lat: 18 39 N
Long: 158 17 W
Sky: A few more cumulus clouds around today (40% cover) but they didn’t seem to get in the way of the sun too often. Some thin stratus and cirrus around too.
Air temp: 26 C
Barometer: 1011.5
Wind: 120 degrees at 3.5 Knots
Relative humidity: 56 %
Sea temp: 27.1 C
Depth: 959.3 m

The sea was very,very smooth throughout the day.

Science and Technology Log

The line last night was put out at Swordfish Seamount (500 meters deep), about 35 miles south of Cross. It was a bit longer than usual. Longline retrieval began 0800 and was not complete until 1130. Both the length and our better fortune accounted for the longer effort. We brought in 7 on the line today including 4 sharks. Species included the following: 1 snakefish (Gempylus serpens – 104 cm long and about 7 cm wide with a big eye, pointy snout and lined with very sharp teeth– dead), oceanic white tipped shark (Carcharhinus longimanus) alive, 157 cm and nasty; a blue shark (Prionace glauca), alive, 132 cm and 32.5 kg, rather docile onboard, very pretty coloration — grayish belly softly blending to a blue dorsally; a big eye thresher shark (Alopias superciliosus — love that name) a bit of life in him but not much, 136 cm + tailfin, 51 kg, its curved tail fin nearly the length of his body; a silky shark (   ?   ) alive; an ono or wahoo, a dolphinfish and an escolar. I took some samples of blue shark and thresher shark teeth. A pretty exciting and busy morning. For most of these fish their fate in our hands was the same as usual.   But the real excitement was bringing on the live sharks. As they are drawn near the ship, netting held in place on a 3 foot by 6 foot rectangular metal frame is lower to the water by a winch. The fish is brought onto it and hoisted aboard. There are a few seconds of near terror as this thrashing animal hits the deck wielding danger at both ends of its body. A mattress like cover is thrown over each end and weighted down by human bodies (mine was not one of them today, but I’ll take my turn eventually; how many people do you know who have ridden a shark?).

The oceanic white and the silky were tagged with the pop ups. To do this a hole is drilled through the base of the dorsal fin. Line looped through that hole attaches the pop up to the animal. Fin clips and blood samples (if possible) are taken as are any remoras attached to the sharks. Then another moment of fear — restraints are withdrawn and animal is sent overboard as quickly as possible. Description of the satellite pop up tags: Each is about 12 inches tall. At the base is a light sensor, above that a cylindrical housing about 1 inch diameter, next a swollen area about 1.75 inch diameter (the pressure sensor) above which is an antenna about 6 inches long.   Each costs about $4000.00 including about $300 satellite time to upload data. Since a signal cannot be sent through seawater to the satellite, the units acquire and store data until a preset pop up date (8 months is about max given battery power of the unit). Then they are released automatically, pop to the surface, find a satellite and dump info to it. The system allows us to track fishes vertical movements (by pressure changes) and horizontal movements by measuring ambient light levels. The latter tells us daylength which can be used to estimate latitude to perhaps within a degree and time of dusk and dawn, which when compared to Greenwich can indicate longitude.

But what if the animal dies before the 8 months are passed? If the animal is headed to the depths, at 1200 meters pressure causes release of the pop up. If no vertical change is detected over 4 days (animal has died in shallow water), they release. Other things can happen that disable the pop ups. They might get broken or eaten by other animals. Only about i in 3 tagged swordfish and big eye thresher sharks are heard from if tagged. Those animals go surface to 600 meters often and rapidly subjecting tags to quick temperature and pressure changes that might disrupt operation of the device. In spite of the obstacles, data is gathered from about 60% of the pop up tags deployed. An alternative is small archival tags that get implanted right onto the animal. These cost only $800 and have much greater storage capacity than pop ups so can provide much more data. However, these must be recovered — the fish have to be recaught in order to get the info from the tag. That’s a tough order in this big ocean and recovery rate is indeed low. Setting longline again tonight in same area. At 2042 we are at lat 18 16 N and long 158 27 W.

Personal Log

Last night was spectacular. Brilliant stars horizon to horizon — a star show above, including the Southern Cross, that was equaled in beauty and wonder by the light show in the water. Bioluminescent organisms were ablaze off stern. It looked like the Milky Way in the water but with the stars turning on and off and swirling about in a frenzy. Some were mere points of light, sometimes things flashed as a light bulb going quickly on and off, and once in a while a ghostly basketball sized sphere tumbled through the view. It was hard to know whether to look up or down for fear of missing the next dazzling event.

And yes, there was a small crowd at the bow to admire the moonrise at about 2345. The ship as always held its position near the longline set. As such we are sort of at the mercy of the sea, just rocking and rolling as it moves beneath us. It is to me a very pleasant motion, one that just rocks you gently to sleep. I have never been on a cruise ship, but friends who have tell me there is no (or little) sense of motion to the ship. Perhaps this is comforting to some, but I like the total experience (within reasonable limits, of course) and these last two nights have been perfect in all respects. I am handing off my duties as brake and bait man to others this evening so that I might digest and organize some of the info passed to me by Kerstin and others in the last couple days.

Questions:

Here are a couple relating to ocean currents. Look at a chart that shows ocean currents along the US east coast (southern and mid-Atlantic states) and for the US west coast (Washington to California). What is the general direction of the flow along each coast? Along which coast, especially in summer, would you expect ocean water to be warmer? Why?

I have given you daily temperature readings for the sea water here at about 18 degrees north. The Galapagos Islands straddle the equator far to the east of here off the west coast of South America. You would most likely expect the water there to be warmer on average than around the Hawaiian Islands. Is it? If not, what accounts for the difference?

Happy Mother’s Day,

Geoff