Monthly Archives: May 2004

Geoff Goodenow, May 24, 2004

Posted on by Teacher at Sea

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 24, 2004

Time: 1615

Lat: 20 09 N
Long: 156 15 W
Sky: Bright and sunny
Air temp: 26.5 C
Barometer: 1014.3
Relative humidity: 57%
Wind: 60 degrees at 28 knots gusting to 35
Sea temp: 26.3 C
Depth: 1227.6 m
Sea: Its really rocking at the moment!

Science and Technology Log

This was the last roundup — and a rather disappointing finish. Four barracuda came up, an escolar and half of an escolar cleanly bitten in half by a shark. A blue shark and a blue marlin were on the line also but, unfortunately, dead. Trolling through early afternoon brought in a yellowfin tuna and a wahoo.

The main mission for the rest of the day is to make way for Honolulu.

In case some of you might be thinking about a Teacher at Sea experience, but wondering if longlining is for you, I thought I’d give you a bit of info related to other missions of the SETTE. Perhaps one of those operations would be of more interest to you. (Of course, there are other ships in other places doing other things for different lengths of time.)

The next cruise for the SETTE is a Protected Species Investigations cruise which takes the crew to the northwestern Hawaiian Islands. These are primarily resupply trips to take scientists and materials to and from temporary camps set up on these remote islands for the study of monk seals and bird populations. I read about these camps and found them quite interesting. For example, in an effort to prevent invasion of (more) exotics to these islands items going assure are placed in a freezer for a time to kill hitchhiking critters.

Debris cruises are another NOAA mission. Yep, that’s right, picking up trash from the island beaches and off of coral reefs. A crewman, John, related to me that the stomach contents of dead chicks are often clogged with plastics fed to them by their parents. He has even found plastic lighters, which to the birds might look like squids, in the stomach remains of these birds. It’s nice to know an effort is being made to reduce the hazards, but sad to note that the negative impact of humans strikes even in the most remote places.

Coral reef surveys are done to monitor health of those systems. Studies of benthic habitats are conducted as well as investigations of planktonic life. Later this year the SETTE will do a lobster cruise to assess those populations. John, our electronics technician, described to me that overharvesting of spiny lobsters which like relatively shallow water opened up their habitat to invasion by the slipper lobster. Slippers typically stayed deep to avoid the spiny, but now that the species are encountering each other a hybrid has developed.

John also pointed out that regardless of the mission of the science teams aboard, the SETTE is constantly collecting and filing data. Wherever the ship is, it is recording weather information and physical characteristics of the seawater and the seafloor. Perhaps you get the idea that this is a busy little platform sailing out here in the big blue sea.

Personal Log

At the time of my weather report we were passing through the channel between Hawaii and Maui. This is where we got blasted by heavy (much more so than today) seas on our first night out. I’m handling this well and would like to boast that I am now seaworthy enough to handle with ease forces as encountered on day 1. But then I don’t want to tempt the sea gods to challenge me with a new test of my endurance. The sea is very pretty in this state (something I was in no condition to say 3 weeks ago). White-capped waves, snow white on a navy blue backdrop and fleeting rainbows of color as wind blown spray catches the light just right fill the gap between the island masses.

The sea calms dramatically as we pass between Maui and islands to its west. We are close enough now to Maui to see the green of the land with its black lava scars and the observatories perched atop 10,000 foot Haleakala glistening white in the late afternoon sun. To our southwest the surf crashes against the shear walls of the neighboring island, Kanoolaweu. Lenai and Molokai lie ahead and frame a beautiful sunset for our last night at sea as several of us enjoy it from the bow.

I will be doing my last edition of the log tomorrow (Tuesday). I think I lose my NOAA address as of tomorrow also. If you have any questions perhaps they will be forwarded to me through the Teacher at Sea website. I look forward to hearing from you.

Geoff

Geoff Goodenow, May 23, 2004

Posted on by Teacher at Sea

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 23, 2004

Time: 1600

Lat: 19 35 N
Long: 156 08 W
Sky: Hazy, bright sunshine; mostly cloudy by evening. No green flash or stars tonight.
Air temp: 26.8 C
Barometer: 1014.4
Relative humidity: 53.7%
Wind: 282 degrees at 6 knots
Sea temp: 27.3 C
Depth: 2611.9 m
Sea: Very gentle today. Not quite glassy but quite smooth.

Science and Technology Log

Eight fish on the longline this morning including a striped marlin (Tetrapturus audax) which was tagged and released. We had 2 representatives of a species, crocodile shark (Pseudocharcharius kamoharai) not previously caught. Also on the line were an oceanic white tip, a large barracuda, a mahi mahi, a swordfish and (you guessed it) an escolar.

Here are a few facts related to some species new since I reported on fish types previously. My source is the same. Please note that it was published in the 1980’s and that some info could be out of date, but it’s the best I have for you.

Crocodile sharks: There is only one genus and one species in the family. These are not very large sharks attaining about 110cm. Their teeth are long, curved and slender, very sharp (and, I thought, very impressive).

Striped marlin attain 2.9 m.

Blue marlin (Makaira mazara): Males reach about 150 kg but females can grow to 5 meters and weigh over 800 kg.

Tonight is out last set of the longline. Again we are off the coast of Kona.

I asked our electronics technician, John, to tells me about some of the safety systems on the ship. This would have been good to report first thing so as to put my mother’s mind at ease. Anyway, here’s a bit about how we are protected in case our ship encounters some sort of distress. These are all part of the global Maritime Distress Signal System.

We are capable of sending radio distress signals indicating our position. A VHF signal has a range of about 50 miles, and HF signal up to 1500 miles. A satellite connection for the “All Pacific Region” alerts stations from northern Alaska to the tip of South Anmerica and east to west across the Pacific.

Emergency Position Indicating Radio Beacon (EPIRB): This can be activated manually, but is activated automatically if it contacts saltwater. It sends a keycode to a satellite which alerts NOAA where the ship can be identified, its most recent position marked, and direct nearby ships to assist.

Search and Rescue Transponders (SARTs): Our ship as well as others are constantly sending out a signal at a certain frequency. Assume we have lost the ship and are in a boat/raft with our SART. When it detects the signal from a ship in the area it lights up. We would then turn on our SART which sends a signal to that ship’s radar indicating our direction and distance.

I feel pretty confident that someone always knows where we are! John also showed a couple of other pieces of gear on the ship. One is an Accoustic Doppler Current Profiler used to determine current speed and direction at various depths. In another, transducers on the bottom of the ship “ping” the bottom at low and high frequencies. Lower frequency signals travel farther and can give us a profile of the bottom. Higher frequency signals can actually detect schools of fish or concentrations of plankton.

Personal Log

Still on the finger soaks and antibiotics, but finger infection is clearing up. The crocodile shark teeth were so impressive to me and make a great contrast to the blue shark’s jaw that I decided to risk further pain, discomfort and more infection in another jaw cleaning exercise. Small size and previous experience combined to make this a much shorter effort than that with the blue, but nonetheless painful as those needle sharp teeth penetrated gloved hand and found their mark in human epidermis.

Then it was to work on a eye cup from the blue marlin pulled in yesterday. Kylie made the official presentation to me last evening as Kerstin and Eva listened on. I had to finish the cleaning job then apply Kerstin’s newly found hot water bath treatment to complete the removal of the flesh. I feel like a real, official Junior Eye Scientist Club member now that I’ve been awarded my first “medal”.

Questions:

I’m drained; I can’t think of any.

Geoff

Geoff Goodenow, May 22, 2004

Posted on by Teacher at Sea

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 22, 2004

Time: 1600

Lat: 19 24 N
Long: 156 53 W
Sky: Sunny this morning, but brightly overcast at the moment. Clear this evening.
Air temp: 26.5 C
Barometer: 1015.1
Relative humidity: 59.9%
Wind: 144 degrees at 6 knots
Sea temp: 26.7 C
Depth: 3810.4 m
Sea:

Science and Technology Log

Even with our normal start time today we were able to get to our one broadbill swordfish in time to tag and release it. we had a new species on — a 176 cm blue marlin (   ). It looked as though it had been attacked by sharks while on the line. We were also able to tag an oceanic whitetip shark. Also for the first time on the longline we had a shortbill spearfish. The rest of the catch was rounded out by the regular cast of characters: 3 escolar, a snake mackeral, one great barracuda and one mahi mahi.

We trolled lines up to 40 miles away from the big island today but nothing grabbed the lures. Tonight we are setting again offshore of Kona, perhaps 25 miles out (not sure).

A chapter in Wilson’s book and some comments made by Kirsten and Mike a couple days ago are the motivation for this part of today’s log. Should we be looking for ways of expanding aquaculture and reducing our dependence on wild stocks to provide fish protein? Wilson in Diversity of Life (1992) states that 90% of fish consumed worldwide is taken from wild stocks. He further states that while about 300 finfish species are cultured throughout the world, 85% of the yield comes from just a few species, talapias, for example.

Kerstin told me of the southern blue fin tuna, a highly prized species, whose numbers crashed due to overfishing in the 1950’s and 60’s. A moratorium on taking the species was imposed and resulted in an increase in the wild stocks. Now quotas are set to protect the species. Australia meets its quota by capturing animals then towing them live to ocean pens at Port Lincoln. The pens are roughly 40 meters in diameter and 15-20 meters deep with about 2000 fish per enclosure. There the animals are fed a diet of fish over 3-4 months that brings their flesh to a desired quality. Of course, this demands harvesting many tons of feeder fish (from the wild) to support the pen raised stock.

In America and elsewhere we have turned from wild stocks of animals to support our numbers. We raise chickens, pigs, cattle and sheep to provide most of our meat. Hunting of wild game is reduced to controlled recreational seasons designed to protect those resources. Should we be doing much the same for more species of ocean fishes, that is, develop methods to economically raise several desired species and greatly reduce our take from wild stocks? Should some receive total protection?

Check out the question section below for some reading about certain aspects of the issues then decide what you think about the concerns raised.

Personal Log

The doc lanced my finger today and I’m still on the antibiotic and hot water soak routine. Feeling kind of sluggish today and appetite is not quite up to my norm; probably effects of antibiotic.

Sky cleared nicely before sunset providing a clear horizon and our first green flash in many days.

Hope to sit out the line set tonight and perhaps just take in a movie.

Question:

In the June 9, 2003 issue of U.S. News and World Report is an article titled “Fished Out” in which the state of oceanic fish populations is discussed. What is you reaction to the article?

On page 40, there is a reference to a report by scientists Myers and Worm. Rich and Mike have told me that there have been several rebuttals to the Myers and Worm report noting flaws in their methods and conclusions. Find such an article then rethink your attitude toward the US news and World Report article and issues raised above.

Geoff

Geoff Goodenow, May 21, 2004

Posted on by Teacher at Sea

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 21, 2004

Time: 1600

Lat: 19 25 N
Long: 156 54 W
Sky: Overcast today. A bright unthreatening sky but clouds thick enough to prevent casting of shadows.
Air temp: 26.3 C
Relative humidity: 70%
Barometer: 1015.7
Wind: 146 degrees at 14 knots
Sea temp: 26.5 C
Depth: 4738 m (at 1645 hrs)
Sea: Rolling today with 3-5 foot swells but not uncomfortable. Much calmer this evening now that we are nearer the Kona coast.

Science and Technology Log

We began our retrieval of the longline at 0600 today; usually we begin at 0800. This change was made in light of the fact that we have been catching swordfish in this area and that they are dead when we get to them. These are animals (when alive) that we would like to tag. The thought is that if we get to them sooner we will have live animals to work with. I hate to see any of them dead, but it was especially hard to accept the loss of that big guy yesterday.

Did it work? Well, we didn’t lose any swordfish today, but then we didn’t catch any either. It was a very poor catch — several escolar (apparently the most abundant fish in the sea), one snakemackeral, and, the only thing worth getting up for (personal commentary), a bigeye thresher shark. This one was tagged by Rich who harpooned the pop up into its back with one swift and well aimed lunge. He was then cut free of the line — another mobile laboratory.

Tonight we are again off the Kona coast for the line set. I don’t know why the decision was made to come here as opposed to staying over one of the seamounts.

Yesterday I had a tour of the engine room. I thought I’d mention a couple things going on below deck and perhaps a few other tidbits about our floating city of 30-40 people. In an earlier log, I think I mentioned that we make our own fresh water. Waste heat from the engine cooling water heats sea water held in a partial vacuum where it can boil at less than 100 degrees C. then be recondensed to yield our water supply.

Our waste water treatment system is a Class 2 type according to chief engineer, Frank. All human waste and gray water goes to a holding tank. From there it is pumped through a unit to macerated solids. The slurry then passes through an electrical cell that completes the purification process before discharge to the sea.

Our little city generates its share of trash as well. Bins around the ship are marked as to the specific kinds of refuse we may put into each. Here’s is what I understand concerning disposal of sewage and trash. Within 3 miles of shore everything must be held although I think if sewage is treated, as ours is, it is OK to let it go even there. Plastics are never to be dumped. From 3-12 miles out, we can dump trash and food waste ground to less than an inch, but no packaging and such that floats. At 12-25 miles, food wastes can go but again the floating debris is prohibited. Beyond 25 miles, I think all can go but the plastics. Cardboard boxes and paper trash go over the side out here and untreated sewage can be flushed.

And, of course, we have to eat. Todd and Susan are our stewards. Todd insisted that I write that “the second cook (in this case Susan) has the hardest job on the ship.” Susan agrees. For a typical 24 day cruise, Todd (chief steward) spends $5000-$6000. To mention just a few of his purchases for this trip he packed on 48 gallons of milk, six cases of juices, a case being containing 4 three-liter bottles of 4-1 concentrate, and over 80 loaves of bread. Whatever he buys is supplemented by our catch. He noted too that in different areas, crews have different likes. For example, in Hawaii he packs on lots of fruits. In cold Alaska, crews like to have soup everyday whereas here it’s not as welcome because of the heat.

Well, that diversion got me (and you) away from fish science for today. Sorry if anyone is disappointed.

Personal Log

I think the early start jolted everyone’s biorhythms or perhaps just mine. I liked being done with the line by 0830, but I did feel kind of lazy all day afterwards. Perhaps that along with the humid, overcast sky and an antibiotic the doc gave me for an infected finger combined to make napping the desired task of the day for me. So aside doing this log, soaking my finger and a bit of reading that’s about all that happened for me today.

Questions:

Perhaps this should have preceded yesterday’s questions. The Hawaiian Islands are some of the most remote island in the world. How did they originally (before the hands of humans) become inhabited by plants, animals, fungi? What are some of the mechanisms that permit dispersal of life to such isolated places as these?

Geoff

Geoff Goodenow, May 20, 2004

Posted on by Teacher at Sea

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 20, 2004

Time: 1600

Lat: 19 15 N
Long: 157 06 W
Sky: Beautiful day; lots of sunshine with scattered cumulus clouds
Air temp: 26.6 C
Barometer: 1015.2
Wind: 132 degrees at 15 knots
Relative humidity: 62%
Sea temp: 26.7 C
Depth: 3116.6 m
Sea: Swells less than a meter offering up a very smooth and pleasant ride.

Science and Technology Log

Several escolar, 2 snake mackeral, 2 sharks and 2 swordfish on the line today. The sharks were both silky sharks. One was tagged and released. The same treatment was intended for the other but it broke free of the hook before we got it on board. Both swordfish were dead.

The last of the swordfish was the biggest we have seen: 185 cm plus a sword of over 60cm and weighing in at 90kg. A couple skipjack tunas were landed with troll lines.

We are staying in the same area for the longline set tonight. We didn’t even bother to check Cross seamount as things are pretty good here and we would probably have had to turn away from there out of respect for others’ presence.

In reviewing Kylie’s presentation (see personal log), Rich commented that we know what the movements of the animals are, but we don’t know so well why they make various vertical movements nor how they are able to deal with the stresses imposed by those movements. The temperature/cardiac function relationship described yesterday adds a bit to the puzzle as do studies of tolerance to oxygen reduction. I found this quite interesting and hope I can condense the story to something meaningful for you.

At depths reached by bigeye tuna oxygen levels are far lower than levels experienced by skipjack and yellowfin tunas at the depths they are normally found. Tunas characteristically have high metabolic rates which might seem impossible to maintain at low ambient oxygen levels experienced by the bigeye. Fishes tolerant of low oxygen levels are typically very sluggish, have low metabolic rates and have blood with a higher affinity for oxygen than less tolerant species. In exchange for that high oxygen affinity (a benefit at the gills), they sacrifice maximum delivery of that oxygen to their tissues; their blood just doesn’t want to let go of it.

Bigeyes then, as you would expect, have blood that grabs oxygen more readily than blood of skipjacks and yellowfin. So how are bigeyes able to remain so active when their fellow fishes with high oxygen affinities just can’t keep the pace? Recall those heat exchange units we’ve mentioned before??? Bigeyes’ blood loses much of its grasp on the vital gas as it is warmed by those heat exchange units. And remember that at the gills the blood is “cold” again. What a great system — readily grab and hold oxygen at the gills even in low ambient oxygen environments, and readily release it in the muscles. Pretty cool, I think.

To conclude, I quote from the summary section of my source as to the value of these studies. I presume that what is stated here specifically with respect to bigeye applies more broadly. “Understanding the vertical movements and depth distribution of bigeye tuna, as well as the physiological abilities/tolerances and oceanographic conditions controlling them, has been shown to be critical to improve longline catch-per-unit effort analysis and long term population assessments in the Pacific.”

Goodenow 5-20-04 oceanic white tip

Geoff with a small oceanic white tip shark

Personal Log

Following the line retrieval, I managed to get some time on the upper deck in my favorite shady spot with my book. Reading, snoozing and enjoying the view passed the afternoon along with an interruption to assist with a troll line catch. This was very nice after such a gloomy yesterday that was topped off with another late night at the movies (Pirates of the Caribbean).

Just before supper Kylie did a rehearsal of a presentation she will be making in Australia about her vision studies. Rich and Kerstin made comments and suggestions to help her polish the presentation. It was interesting to hear them address content and presentation issues much as I do with my own students.

Kerstin asked me today if it is getting tough coming up with material for the log. I suggested that indeed it is becoming more of a challenge. Perhaps out of sympathy, she called me to her lab early this evening to share with me some details related to the eye socket of a swordfish. Thanks, Kerstin, and keep ’em coming!

Questions:

Many native plants and animals of the Hawaiian Islands have suffered due to the introduction of non-native species to their environment. The green cover of the islands is very different in most places than what Polynesian settlers saw. Mongooses and ginger are two introduced species. See if you can find out how they got here, why they were introduced and specific impacts they have had on native species. (There are others for which you could do the same investigation including many in your home area).

Geoff

Geoff Goodenow, May 19, 2004

Posted on by Teacher at Sea

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 19, 2004

Time: 1615

Lat: 19 15 N
Long: 157 14 W
Sky: Cloudy all day with light to moderate rain showers throughout the day after longline retrieval. Ended by supper time, but the sky remained overcast.

Air temp: 23.6 C
Barometer: 1012.5
Wind: 106 degrees 16 at knots
Relative humidity: 73.4%
Sea temp: 26.2 C
Depth: 3959.8 m
Sea: Swells less than a meter.

Science and Technology Log

Not a big catch today, but everything we did catch came at once resulting in a flurry of activity for a short time. A blue shark was kept, and our largest swordfish so far came up dead. Too bad as it would have been an excellent one to tag.

For today’s in depth science report, I will refer to a couple of papers both coauthored by our chief scientist, Rich, relating to vertical movements of some of the species we have seen. Some fish tend to stay within particular vertical realms while others traverse them. What factors influence the animals’ movements?

One seems to be temperature. In a study of yellowfin tuna, blue marlin and striped marlins, all three were found to descend to depths where water is no more than 8C below surface temperature. Where oxygen levels in the water are not a factor, all three of these species seem to be restricted by the effects of water temperature on cardiac muscle function.

Bigeye tuna as you will recall stay deep (500m) by day and rise to the surface waters at night. At depth the animals are exposing themselves to ambient temperatures that are up to 20C colder and oxygen levels much lower than in the upper layers. Swordfish and bigeye thresher sharks exhibit patterns similar to those of the bigeye tuna.

What about those heat exchange mechanisms described in earlier issues of my log? Shouldn’t they, if present, allow a fish to tolerate a wide temperature range? While indeed they are present in some species, they are not working to keep blood warm as it goes to and through the heart. Any heat left in the blood on its return to the heart is lost as it passes through the gills. Since the heart is “downstream” of the gills, cardiac muscle remains within 1C of ambient temp. Studies show that temp. reductions cause heart rate and output to decrease.

Yellowfin tuna and the marlins seem to have no ability to increase heart rate or cardiac output following sudden temperature reductions. Consequently, they stay within that 8C window of surface temp.

So how do the bigeye tunas and others manage to negotiate these temperature realms with apparent ease? The question remains, the full story unknown so untold. Perhaps by the time you are here as a teacher at sea you can fill us in with the details. I’ll be waiting!

I’ll complete this look at physiology tomorrow with a bit more to relay about the oxygen issue.

Goodenow 5-19-04 bite marks

This was taken to show countershading and nuptial bites. The large bite is obvious but also note the smaller teeth marks below. The bites are made by the males on the females.

Personal Log

I usually have a good start on the log by supper time but not today. In the quiet following the period of intense longline activity, I began the process of securing the jaws of the blue shark for display. This was a female of good size (165cm, 45kg) and with a nice set of choppers. I was being pelted with rain as I worked through lunch and beyond. I thought if I stopped I wouldn’t go back out to deal with it any more so I just kept peeling away the flesh to expose the teeth and reduce future odor issues. Had it pretty well done as chill started to get to me. I headed for the warmth of a stairwell over the engine room pausing momentarily to enjoy the (usually) stifling heat before finishing my route to room and warm shower. I did return to inspect my work. In comparing it to Eva’s similar effort I felt more had to be done to match her high standard. But now it’s done and jaws are held wide apart with crossed chopsticks as nature tends to the final phase.

No longline duties at the start of tonight’s set which I think is in last night’s neighborhood. Perhaps I will be in there as a reliever a bit later.

Question:

For something completely different and to address the history buffs among you:

How long ago is it estimated that Polynesians discovered and settled in the Hawaiian Islands?   When were the islands discovered by European explorers? Why was captain Cook first welcomed by the native people, but not received so well (and eventually killed) when he returned shortly after his departure?

Any subject areas I’ve not touched on yet?

Geoff

Geoff Goodenow, May 17, 2004

Posted on by Teacher at Sea

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