They are also strong leapers and fast swimmers, and at least one species, the black marlin, is sometimes cited as a contender for the fastest fish on Earth. The BBC has reported , for example, that a black marlin stripped line from a reel at feet per second, equating to about 80 mph kph , while the ReefQuest Centre reports marlins can leap at 50 mph 80 kph. Some experts consider those speeds unlikely, but nonetheless, marlins are famously fast and powerful swimmers, as immortalized by the blue marlin in Ernest Hemingway's " The Old Man and the Sea.
The third group of billfish is the swordfish, a single species and the sole member of its taxonomic family, Xiphiidae. Found in warm waters of the Atlantic, Pacific, and Indian oceans, swordfish are big, powerful swimmers and capable of incredible leaps. Swordfish are famous for their namesake "sword," but they also share the billfish family's penchant for speed. They can reportedly swim at more than 60 mph kph , although that faces doubts similar to those raised for sailfish and marlin.
Swordfish are undoubtedly fast swimmers, however, even if they have been overhyped. And while their speed is largely due to strength and body shape, scientists have also discovered another factor that makes swordfish so fast: oil.
According to a study published in the Journal of Experimental Biology, MRI scans revealed a complex organ in the upper jaws of swordfish that features an oil-producing gland connected to capillaries, which "communicate with oil-excreting pores in the skin of the head. There are 15 different species of tuna around the world, including some surprisingly large and powerful predators. Yellowfin and bigeye tuna can grow to roughly 8 feet 2.
Tuna are strong, fast swimmers, but similar to the billfish, their top speeds are commonly inflated based on anecdotes or unreliable accounts. While some sources claim tuna can swim up to 75 mph kph , research suggests that's unlikely.
A study concluded yellowfin tuna can swim at about 46 mph 74 kph , and a study found the giant Atlantic bluefin tuna probably has a maximum speed of about 33 mph 53 kph. The shortfin mako shark is commonly cited as the fastest shark alive today.
Its top speed is as difficult to pinpoint as that of many other fast fish, but it has been reliably clocked at 31 mph 50 kph , according to the ReefQuest Centre for Shark Research, which also cites a claim of burst speeds up to 46 mph 74 kph. That suggests it may have reached 68 mph kph during its sprint, although the ReefQuest Centre advises taking this lone finding with a grain of salt. Regardless of its exact top speed, the shortfin mako deserves its reputation as a toothy torpedo.
It makes a living by chasing down some of the other fastest fish in the ocean, including tunas, bonitos, mackerels, and swordfish. It's also famous for its acrobatic leaps while hunting, and in some cases has leapt into or even smashed through the boats of anglers trying to reel it in. Shortfin mako sharks are potentially dangerous to humans, although reports of attacks are relatively rare, and as with all sharks, we're far more dangerous to them overall.
Due mainly to threats from fishing, both as bycatch and a target species , the shortfin mako shark is listed as endangered by the International Union for Conservation of Nature. Haby, Jeff. In both A sailfish and B swordfish, the upper and lower figures correspond to the fish with the original and shorter bills, respectively.
Here, the body of each fish is wrapped by a thin tape and then coated in black paint for better visualization. Here, X 1 is the streamwise distance from the tip of lower jaw.
All these streamwise locations are ahead of the point of maximum body thickness. It is known that the critical Reynolds number for laminar-to-turbulent transition on a smooth flat plate is 3. Although the boundary layer flows are turbulent at this location for all the bills considered, there exist clear differences in the profiles of mean and rms velocities among different bill shapes Figure 9.
However, shortly after this location, the differences become smaller Figures 9B and C and the mean and rms velocities are nearly identical irrespective of the bill shape Figure 9C. This means that the flow development along the whole fish body is mainly determined by the shape of body including the head part, but not much by the bill itself.
Therefore, it is quite clear that the bill produces a turbulent boundary layer flow earlier as conjectured by Ovchinnikov [5] and Webb [29] , but these flow characteristics do not persist farther downstream owing to the favorable pressure gradient formed by the head shape of the fish.
The measurement locations are also plotted in each figure. At this location, the shape factors of boundary layer velocity profiles are about 1. From the present velocity measurement, it is concluded that the bill has a role in reducing the skin friction in the anterior part of fish, but the skin-friction reduction by the bill does not occur over the entire body. Therefore, the overall drag is nearly unchanged in the presence of the bill because the area in which the skin friction is reduced is small and the bill itself generates additional drag.
Motivated by their fast swimming speeds and peculiar shapes, we investigated the hydrodynamic characteristics of the sailfish and swordfish at their cruise speeds by installing taxidermy specimens in a wind tunnel, directly measuring the drags on the bodies, and probing the boundary layer velocities above the body surfaces. The drag coefficients of the sailfish and swordfish at the cruise conditions were about 0. These values of the drag coefficient were smaller than those of dogfish and small-size trout and comparable to those of tuna and pike.
The median and paired fins have been known as effective devices for enhancing the maneuverability or stability of the fish, but they inevitably increase the drag on the fish. Thus, the sailfish usually folds down the first dorsal, first anal, and pelvic fins in cruising or gliding.
However, it is still unknown why the swordfish have not developed to depress those fins unlike the sailfish. We also found that the boundary layer flow characteristics of both fishes are quite similar to each other: i.
The sailfish and swordfish have distinct morphological features from those of other fast fishes. For the sailfish, many V-shaped protrusions were found on the body skin and were tested for possible skin-friction reduction, resulting in nearly no drag reduction by the protrusions [31]. In the present study, we examined another possible role of the V-shaped protrusions in delaying flow separation if any by performing tuft visualizations and measuring the drag forces on the body with and without the protrusions, respectively.
Even in the absence of the protrusions, flow separation did not occur from the whole body surface, and the drag on the sailfish without the protrusions was even slightly smaller than that in their presence. This result indicates that the V-shaped protrusions on the sailfish skin do not make any role in reducing the drag at the cruise condition.
Another interesting morphological feature of the sailfish and swordfish is the bill. The roles of bill have been conjectured as a drag-reduction device by delaying the flow separation [5] , [29] or reducing the skin friction on the main body [7] , [30] , [38].
In the present study, we found that the drags with and without the bill are nearly the same. The bill generated a turbulent boundary layer flow at the initial part of head and reduced the skin friction only at the anterior part. However, this effect of skin-friction reduction did not persist farther downstream, because the strong favorable pressure gradient after mid-head part significantly changed the boundary layer characteristics and the boundary layer velocity profiles with and without the bill were nearly the same at the end of head part of each fish.
Furthermore, the bill itself generated additional drag which may be compensated with the reduction of skin friction at the anterior part, resulting in nearly no change in the overall drag at the cruise speed. Nevertheless, it was interesting to note that the drag coefficient based on the wetted area is lower with original bill of swordfish than that with shorter one, whereas the drag coefficients of the sailfish were nearly insensitive to the change in the bill shape.
Lastly, it should be mentioned that the present conclusions were obtained at the conditions of cruise speeds in gliding postures. The hydrodynamic characteristics of the sailfish and swordfish at the maximum speed or during undulatory swimming motion are important subjects to pursue in the near future, which we could not study owing to the technical difficulty of achieving high speed from our experimental setup or lack of information on their swimming kinematics, respectively. We appreciate the cooperation from the Korea Research Center of Maritime Animals for taxidermy specimens of the sailfish and swordfish.
We are also grateful to Dr. Sang-im Lee and Professor Piotr Jablonski for useful discussions. Performed the experiments: WS. Analyzed the data: WS HC.
Wrote the paper: WS HC. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field.
Introduction The sailfish Teleostei: Istiophoridae and swordfish Teleostei: Xiphiidae are large predators in the ocean, which have been known as the fastest fishes among sea animals.
Download: PPT. Table 1. Morphometric parameters of the sailfish and swordfish see also Figure 1. Tuft flow visualization To observe surface-flow patterns on the body of fish, a number of tufts are attached to one side of the body. Results and Discussion Morphometrics Table 1 shows the morphometric parameters of the sailfish and swordfish considered in the present study. Drag coefficients of the sailfish and swordfish The drags on the specimens of sailfish and swordfish in gliding postures, whose bodies are stretched straight, are directly measured in the wind tunnel.
Figure 5. Velocity profiles over the body surface of the sailfish. Figure 6. Velocity profiles over the body surface of the swordfish.
Role of skin protrusions The V-shaped protrusions on the sailfish skin did not reduce the skin friction in a turbulent boundary layer but each of them produced a pair of streamwise vortices that might be related to a delay of turbulent separation [31].
Role of bill As mentioned in the Introduction , possibilities of reducing drag by the bill have been suggested before [5] , [7] , [10] , [29] , [30] , [38]. Figure 7. Variations of the drag and drag coefficient from those with the original bill. Figure 9.
Velocity profiles over the body surface of the sailfish with different bills. Figure Velocity profiles over the body surface of the swordfish with different bills. Concluding remarks Motivated by their fast swimming speeds and peculiar shapes, we investigated the hydrodynamic characteristics of the sailfish and swordfish at their cruise speeds by installing taxidermy specimens in a wind tunnel, directly measuring the drags on the bodies, and probing the boundary layer velocities above the body surfaces.
Acknowledgments We appreciate the cooperation from the Korea Research Center of Maritime Animals for taxidermy specimens of the sailfish and swordfish. References 1. Berkely: University of California Press. Lane FW How fast do fish swim? Ctry Life: — J Fish Biol. View Article Google Scholar 4. Walters V Body form and swimming performance in the scombroid fishes. Am Zool 2: — View Article Google Scholar 5. Ovchinnikov VV Turbulence in the boundary layer as a method for reducing the resistance of certain fish on movement.
Biophysics — View Article Google Scholar 6. Ovchinnikov VV Swordfishes and billfishes in the Atlantic Ocean — ecology and functional morphology. Aleyev YG Nekton. The Hague: Junk, p. Nakamura I FAO species catalogue. Billfishes of the world. An annotated and illustrated catalogue of marlins, sailfishes, spearfishes, and swordfishes known to date. FAO Fish Synop 5: 1— View Article Google Scholar 9. J Exp Biol — View Article Google Scholar Videler JJ Body surface adaptations to boundary-layer dynamics.
Biological Fluid Dynamics. London: Soc Exp Biol Symp. Copeia 2 : — Hoolihan JP Horizontal and vertical movements of sailfish Istiophorus platypterus in the Arabian Gulf, determined by ultrasonic and pop-up satellite tagging. Mar Biol — Borazjani I, Sotiropoulos F Numerical investigation of the hydrodynamics of carangiform swimming in the transitional and inertial flow regimes.
Borazjani I, Sotiropoulos F Numerical investigation of the hydrodynamics of anguilliform swimming in the transitional and inertial flow regimes.
Proc R Soc B : — J Fluid Mech 5— J Fluid Mech R3. Drucker EG, Lauder GV Locomotor forces on a swimming fish: three-dimensional vortex wake dynamics quantified using digital particle image velocimetry. Drucker EG, Lauder GV Experimental hydrodynamics of fish locomotion: functional insights from wake visualization. Integ Comp Biol — Allan WH Underwater flow visualization techniques. J Exp Biol 81— Webb PW Hydrodynamics and energetics of fish propulsion. They feed primarily on small bony fish and cephalopods , which include squids, cuttlefish, and octopuses.
One calculation determined that they could swim at 60 mph, while another finding claimed speeds of over 80 mph. The swordfish has a long, sword-like bill, which it uses to spear or slash its prey. It has a tall dorsal fin and a brownish-black back with a light underside. The film "The Perfect Storm," based on the book by Sebastian Junger, is about a Gloucester, Massachusetts, swordfishing boat lost at sea during a storm.
Marlin species include the Atlantic blue marlin Makaira nigricans , black marlin Makaira indica , Indo-Pacific blue marlin Makaira mazara , striped marlin Tetrapturus audax , and white marlin Tetrapturus albidus.
They are easily recognized by their long, spear-like upper jaw and tall first dorsal fin. The BBC has claimed that the black marlin is the fastest fish on the planet, based on a marlin caught on a fishing line. It was said to have stripped line off a reel at feet per second, meaning the fish was swimming nearly 82 mph. Another source said marlins could leap at 50 mph. The wahoo Acanthocybium solandri lives in tropical and subtropical waters in the Atlantic, Pacific, and Indian Oceans, and the Caribbean and Mediterranean Seas.
These slender fish have bluish-green backs with light sides and bellies. They can grow to 8 feet long, but more commonly reach 5 feet.
Scientists studying the wahoo's speed reported that it reached 48 mph in bursts. Although yellowfin Thunnus albacares and bluefin tuna Thunnus thynnus appear to cruise slowly through the ocean, they can have bursts of speed over 40 mph. The wahoo study cited above also measured a yellowfin tuna's burst of speed at just over 46 mph.
Another site lists the maximum leaping speed of an Atlantic bluefin tuna at Bluefin tuna can reach lengths over 10 feet. Southern bluefin are seen throughout the southern hemisphere in latitudes between 30 and 50 degrees.
Yellowfin tuna, found in tropical and subtropical waters worldwide, can top 7 feet in length. Albacore tuna, capable of speeds up to 40 mph, are found in the Atlantic and Pacific Oceans and the Mediterranean Sea.
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