Speed, that is what is important. — Glenn Gould
Determining the fastest fish in the ocean is not easy. There is a large body of research conducted by placing various fish species in swim tunnels where flow and water velocity are monitored and controlled. With that, you can only measure sustained swimming speed, which is biologically important in terms of energy use and growth, but does not help us in determining who’s the fastest fish in the ocean. Despite our human obsession with the “fast and furious”, the truth is, research on maximum speed is scarce, and it’s difficult to track down the sources that determined how the existing list of fast swimmers was compiled.
Sailfish at pole position
As it stands right now, sailfish win the top crown for the fastest swimmers — and are supposed to be in the Guinness World Records (but a search of the official database at the time of writing returned “page does-not-exist”). The record was obtained in a series of speed trials carried out at the Long Key Fishing Camp in Florida, where one sailfish took out 300 feet of line in three seconds. We adore sailfish- we love them so much that we conducted a multi-year tagging project sponsored by Sir Richard Branson. Isn’t it cool when Sir Richard blogs about your work?!
Well, having a line in your mouth and fighting for your life does not make it a fair determination of how fast you can swim. So our colleagues from the Central American Billfish Association of RSMAS, University of Miami came up with their own estimates using accelerometer-equipped electronic tags (these are popup satellite archival tags, or PSATs — it’s a bit like your iPhone in an Otterbox). They programmed the tags to stay on a sailfish for a month and recorded acceleration, among other things, while a sailfish was swimming around and conducting its own business in the ocean (see title picture). At the end of the track, they obtained a maximum acceleration, measured in standard acceleration a.k.a. “G-force” (1 G ~ 9.8 meter per second square or ms^-2), of 1.79 G. If you convert G-force to speed, 1.79 G is approximately 17.5 ms^-2. The U Miami team reckoned, if the sailfish sustained such an acceleration for a mere 2 seconds, it would break the current record by 10 miles an hour — revising the sailfish’s top speed to 78 mph. To put this in perspective, they compared sailfish’s 1.79 G to the sports car Bugatti Veyron’s 1.55 G, which reaches 0–60 mph in 2.4 seconds.
There is a new twist to sailfish’s claim as the top fish. A new study published by Stefano Marras and Takuji Noda et al. (2015) concluded sailfish’s swimming speed is vastly over-estimated, and does not exceed 10 ms^-1 or 23 mph, which is one-third of U Miami’s estimate. The team documented sailfish hunting down prey using high-speed videography and accelerometry for periods up to 34 minutes.
Sorry sailfish, Bluefin tuna just motored past you…
It turned out that here at the Large Pelagics Research Center, with funding from the Guy Harvey Ocean Foundation, we were able to test out the same PSAT tag models on free-swimming, giant bluefin tuna off Port Mouton, Nova Scotia, Canada. Giant bluefin aggregate annually in this area to feed and fatten, and the region supports both commercial and world class sport fisheries. Bluefin have always been a favorite species of ours, and we have been studying them since 1993. We figured it’s time to pitch bluefin tuna into the “fastest fish” contest! The collected acceleration data are just a small part of our long term, major dataset documenting bluefin tuna migration, behavior and ecology in the western north Atlantic.
When our fishermen partner tracked down a reporting PSAT tag shed off a 800-lb giant bluefin, recovered and sent it back to us, we could not believe the tag’s data download in front of our eyes. Bluefin literally destroyed this tag model simply by swimming fast, very fast- and it sheared apart! Our “traumatic” experience led the manufacturer to reinforce their later version tags (well-engineered tags are not supposed to break into two, but no refund for us for the sheared tag, of course!).
Astonishment aside, we could get right down to the data to see what actually happened to the tag, very much like in CSI Miami. The luxury of recovering a tag means we have access to the entire data log. We summarized the data for you in the table below:
Our giant bluefin blew past the sailfish’s maximum acceleration record easily, reaching a maximum of 3.27 G, or approximately 32 ms^-2. You can do the same calculation i.e., 144 mph if the tuna did it for 2 seconds, just like the folks at U Miami did, and compare it to whatever performance car of your choice.
The point is clear — bluefin tuna simply “out accelerated” sailfish by 1.8 times.
Events of over 2 Gs did not correlate with diving activities as there was no big change in recorded depth (milling around at 20 meters) nor did the tuna leap into the air. So we know the fish was moving quickly, horizontally, within a short vertical range, possibly chasing after prey. (What was the prey? Probably mackerel or herring). If the tag had not be broken into two pieces, we would certainly see over 2 Gs acceleration occurring routinely in bluefin tuna.
Where did the bluefin eventually go?
We know you must be curious about where the tagged bluefin went. Unfortunately the tags did not stay attached for that long (and remember the shearing?), but the tuna did cover quite some ground in the Northwest Atlantic. This is not something new, as we know bluefin have diverse movement patterns over the entire Atlantic Ocean. You can learn more about bluefin movement in our previous studies like this one.
Normally we could show you very interesting tracks with daily positions, but we did not have much luck with this batch of tags, 3 out of 8 returned any positioning data, yielding only 36 positions in total. Plotting those few positions up made a very, very sad map, so you have to live with a pretty map showing trajectories from our field site in Canada instead.
Within our community, we have been vocal about hardware performance and true costs of equipment. It is something very practical and not as sexy as seeing your tagged shark trekking to the Mariana Trench, but it does pose a serious concern to us in conducting any good research.
Estimating speed from free swimming fish, through body acceleration, is an avenue worthy of further investigation. We’ve shown in our study that giant bluefin are capable of achieving high (~3) G-force, much higher than that recorded for sailfish. Moreover, our study is the first to document the magnitude of acceleration in bluefin. We know that the US Navy and ocean engineers love the bluefin tuna’s sleek, torpedo shaped body, and use it as a model (e.g., MIT’s RoboTuna) for optimal hydrodynamic design. With longer sampling, new information regarding the biophysical and sensory capabilities of bluefin can be uncovered. So let the next race begin!