Tracking Bluefin Tuna
Tracking Bluefin Tuna
NPR/NGS Radio Expeditions
17 Mar 1997
North CarolinaDare County
- Cape Hatteras National Seashore
- 35.25278 -75.03333
Stereo=1; Decoded MS stereo; Dual-Channel Mono
NPR/NGS RADIO EXPEDITIONS
TUNA DAT 4
1:17 (some ambi before, but cj and Linda are talking in bg)
CJ -how did you conceive of doing this rather strange thing with bluefin tuna?
1:21 BB -well, i think we have been on the path for doing now for quite a long time. i have studied where pelagic fish go using acoustics under the best scientists in our nation and have been ...1:39 we have been using techniques to study fish remotely through acoustics and now archival and now sat. tags for over 15 yrs and it is a tradition that has been passed on to me by my mentors and one that i believe that will help us understand what these animals do in what is a relatively difficult environment to study them in -the open ocean, far from shore where most of us have very little understanding of how things work
CJ -diff tags -and what they say about the fish -
BB -we use 3 diff kinds of tags in this project. acoustic tags which send us data via sound, give us high resolution but short term data. so we get where the fish is going in second by second bits of information, and it tells us a lot about the behavior of the animal, but for short periods -2 to 5 days. archival tags are taking data every 2 minutes so the tags sleeps it then wakes up sample the en ....AGAIN: archival tags are taking data every 2 mins and what they do is they have a microprocessor that is in a sleep state it wakes up samples 4 variables [cj -which are] temperature of the body, temperature of the ambient environment, light and pressure. it then goes back to sleep and we are then able to construct a plot of these 2 variables that give us relatively highly accurate information over the day and night time period. what's is great about archival tags is that we get long term data, data that for up ......AGAIN: 3:31 archival tags take data every 2 mins from 4 sensors: light, pressure or depth, ambient temp. and body temp. and from those every 2 min samplings the microprocessors wakes up and does we are able to reconstruct daily what the fish is doing during the daytime and nighttime and also get a light plot that allows us to calculate geolocation of the fish on earth. 3:58
CJ -you can tell where the fish is bc of -describe how that
4:03 BB-similar to the techniques used by ancient mariners, and mariners today, we can calculate a local noon from sunrise and sunset data and AGAIN: 4:16 similar to ancient mariners that were able to locate by using the local apparent noon, what the fish is doing is measuring light every 2 mins and gives us a sunrise, a plateau of light everyday and a sunset event and from that data we are able to calculate a midpoint which is local noon for the fish and it has a very accurate clock in the microprocessor that's in the tag and we can use the clock time and the local noon to calculate longitude -where we are in relation to Greenwich. Latitude we get by knowing the day length, so when the sun came up and when the sun came down. and what makes this tricky is that this is al in a fish that is moving up and down rapidly from the surface down to about 700 feet down in the water column. 4:58
CJ could you do anything like this kind of research w/o these tags?
5:03 BB-no i think it has been a mystery up until now where do these animals go. the open ocean environment is a challenging environment for humans to work in. we have very little concept of how an animal chooses to move in this environment and w/o the technology that we are using in this project we wouldn't know anything about what these animals are doing bc it is too difficult an environment to access the animals in and he reason an animal as large as a bluefin and as majestic has remained somewhat of a mystery for biologists for so long is that there has not been the technology available to study them. 5:36
CJ -do you know -do scientists know -enough about the bluefin to determine whether it is endangered or whether it is threatened, and do they know enough to do anything about it?
5:48 BB -i think what we know is that these fish are being landed (?) for the species in the entire atlantic basin in record numbers over the past few yrs. what we realize is that we don't have that much knowledge about this animal we barely know anything about its habits. we know a little bit about where it is reproducing, but we don't know a fish that reproduces in more than one area can actually move ...AGAIN: (cj asks question again -good) 6: 23 All we know is that the bluefin tuna is being landed as a species in record numbers in the atlantic right now and there's too many questions remaining about its biology, its ecology and its population structure to assess whether the management practices that we have-put in place as an international community are correct for the current levels of take that are occurring in the ocean. so what we are up to is trying to get answers to some of the key questions. whether there is one stock of atlantic bluefin tuna or whether there are 2 stocks to better understand as to how we should manage the fishery in this time of over-exploitation. 6:59
CJ -now that we know what it is like to be out there, 12 hours on a rocking boat in heavy seas, a 350 lb animal up on the deck doing surgery with sharp instruments allover the place. this is really really hard work and rather dangerous work. do you have to be a little obsessed to do this?
7:19 BB well i think that we are certainly on a mission and we understand all of the folks on my team understand that this is a fish that deserves attention right now as a nation as scientists and as human beings. it is a majestic animal, perfectly capable of swimming across the atlantic basin in less than 50 days. to work on this animals under these conditions makes us a little humble. it teaches us why no one before us has gotten much information of what bluefin tuna do and how they work.
CJ -what is it about bluefin tuna that sets them apart not only from other fish but other animals of -
7:56 BB -well, it is rare amongst fish to be warm, and what i like to think about when i think about bluefin tuna is that they are actually like whales with gills. so bluefin tuna is amongst the warmest of fish in the sea and there are only about 2 dozen fish that are warm in the ocean. it can take that warmth that it generates in its muscles and move at relatively fast sustained speeds and access polar seas as well as tropical seas in very short periods of time. and there are very few fish that travel the distances that this highly migratory fish travels ...AGAIN!
8:39 what makes the bluefin tuna separate from most other fishes is one its large size, but most importantly is the fact that it is a warm bodied fish. so much like a mammal or a bird it generates heat in its muscles as well as its cranial cavity and its viscera and it uses its advantage of warming up its tissues to go faster and perhaps digest their meals quicker and access other water temperatures that other fish might not access. so what these animals can do is go to subpolar seas to feed in the wintertime -excuse me (SNIFF!) -summertime, much like a cetacean would do and then come back to warm temperate waters to breed. 9:18
CJ -what is special about hatteras, what is special about this place?
9:25 BB -well beyond the physical beauty of the outer banks, the hatteras community is like no other fishing community i have worked with in the fishing world. the captains of the fishing boats here have cooperatively interacted with the scientists of our project. and what we are doing here would not be possible if it wasn't for the captains that we are working with on the boats as well as the entire fleet passing us giant bluefin tuna which in a different location in a different time could be worth as much as $50,000 to the individual captains 9:54
CJ -it's hard enough to get these tags inserted or placed in tne fish. what do you need down the line to make this sort of thing work?
10:12 BB -well with archival tags it requires an entire international community coop. on this project. so what we did for a pilot project last year was we put a few archival tags out there and then spent most of the time advertising around the atlantic basin all the way through europe and the medit. as well as in the western atlantic to tell people that these tags are in fish so that if they see a fish wearing one of our marker green tags to take the fish to get the tag back. so what we need is the community of fishermen fishing on atlantic bluefin tuna to recognized a tagged fish and to know what to do when they see one
CJ -is anyone else ln the world doing this kind of work?
10:48 BB-there are scientists in australia and japan who are working on other species of bluefin tuna, the souther bluefin and the pacific bluefin, each heavily exploited in their own areas to see if archival tape can teach them about where they go. to help us understand better the population structure and the stock structure that is needed to better set better set up management practices for these fishes. 11:11
CJ-do you think you are going to do this the rest of your life with tuna?
11:30 BB-i think the opportunity at cape hateras is .....AGAIN!
11:37 i think the opportunity i have as a scientist to work on bluefin tuna right now, as well as our nation of AGAIN 11:43 i think the opportunity that we have right now to work on bluefin tuna is unparallel. never before have we had this access point to bluefin tuna, about 18 miles from shore we can go on a daily basis, not stay out on a ship, and do the types of scientific work that we are doing right now. so i think that the next decade bodes well for learning about bluefin tuna bc of whats happened here in cape hatteras 12:08
CJ -and this technology allows you to do things with fish that no one imagined you to do?
12:13 BB yeah i think it is the golden age of fisheries science. i think btwn the uses of remote technologies through satellites through microprocessors, through molecular genetics too that we have the capacity to solve issues related to understanding where these fish go, how they are utilizing their environment and how they set up their population structures in a way that we have never had before 12:37
CJ -where does the bluefin stand in an evolutionary stance?
BB -hard question .........13:12 the bluefin tuna is the pinnacle of bony fish evolution. so when we look at all the fish in the sea as well as in aquatic environments anywhere we've got lots of species -over 25,000 species -and while some people think i was a little tuna-centric -it's proper to think of a bluefin tuna at
the pinnacle of bony fish evolution bc they are very recent fish their evolutionary history doesn't go back very far and in particular the bluefin tuna w/in the tuna lineage is a fish that currently probably coalesces about a million to 1.2 million yrs ago.13:52
CJ -so that is more recent than homo sapiens ....
BB -i won't answer that sorry.... 14:28 i think what a lot of people don't understand is that tunas are warm and we don't understand why we are warm so one of the things that we do is that we are interested in understanding what's the advantage of being a warm animal. and we think that tunas offer sort of a window in that world bc to be warm in water and to breathe with a gill makes it a challenge bc a gill acts like a convective cooling system as a radiator. so to be warm in water is hard number one to be warm if you are fish is very difficult. so what we are trying to understand is what is the advantage of this warmth that tunas have that you have and that birds have and what i think it is all about is expansion and being able to perform in a wide variety of temperatures. and what we hope to do is do a lot of accurate measurements on tunas and compare them to living extense species such as their sister taxa which might be an animal such as the benito and make these side by side comparisons. we can't really do that with mammals or relatives called dinosaurs. and certainly they are not here today so we can only speculate what were the steps to becoming warm. and with the tuna clade we can actually get some hearty answers on whether hot muscles make you a faster fish 15:37
Cj-can't do this lna lab or aquarium
15:44 BB-right. one of the nice parts of situation right now is we have got a lab in monterey in pacific grove, at stanford that gives us the opportunity to study fish in captivity and if we didn't have that lab work with the remote technologies and develop them first in the lab before spending the effort and the physical time at sea trying to put these instruments in so one of the key steps in getting to hatteras this year was having the capacity of working with live tunas right in our backyard prior to getting out in the real ocean were everything gets more difficult as soon as the waves start rocking us around 16:20
CJ -so how did it go today?
26:32 Rich -our boat didn't do much. we couldn't even bring one up, but we had a great cruise
H: yeah, it was sort of a nature cruise today we just observed a lot of nature.
CJ -no bites, no nothing?
H -I didn't hear of any bites a tall. i think there was one bite on the fish finder but other than that absolutely nothing. we saw a bit of bait jumping. turtle, some spotted dolphins
27:00 R -the only tuna i heard of were yellow fin i didn't hear of bluefin. i hit 2 marinas tonight and i didn't hear of anything other than yellowfin.
27:08 CJ -how can you have such a good day one day, and such a bad day the next day?
27:12 R -well, that i don't know -that's what i am hoping someone is going to tell us. but the tracking boat headed out to see, and maybe the tuna followed them?
H -wasn't the water mass really different today then it was yesterday?
27:30 R -yeah, rip was running strait out -so i don't know.
CJ -i know captain bob gets very frustrated when ah -
R -that's putting it mildly. no, we had a good time and he did a nice nature cruise
27:56 CJ -so what happened yesterday to the tuna you were following?
Dave -(works on the tracking boat) well, as soon as we tagged it -like the other longer track we had, it headed right up to diamond shoals, then headed up that way for quite a while. got into about 100 feet of water or so, and then we headed east and eventually we ended up in the gulf stream. we ended up covering a lot of ground. heading east basically. in the middle of the night btwn 2 and 3 they just gave us the slip -we couldn't keep up with it any more and that was it. we looked for it for about and hour and a half and then gave it up.
CJ -how does a tuna with a tag on it give you the slip?
Dave -well, when if think about it -you know the fish -this is about a 300 lb fish ...and the fastest we can go with our gear in the water is we can go 8 knots for a while, but we don't like to sustain 8 knots and if they decide to take off they can move faster than 8 knots. so, what can happen sometimes is you'd be coming up on it and you get kinda close and sometimes if it is really deep it is hard to get a really good directional and then suddenly if that thing takes off in a opposite direction then what you are facing by the time you get turned around and that thing is moving it is tough to catch. it's a big ocean out there too. as soon as you loose the signal you have a small window of time to pick it up again and once you miss it it is gone. so basically it is bc it is a big fast fish
29:38 CJ -you are following theses particular fish with an acoustic signal just for a day or two, right after they are tagged, right?
29:46 Dave-the ideal track for us right now would be the full 48 hours ........ .