Thursday, October 29, 2015

Flying Fish: Flight, Flotsam, and Fishing Rights, by Don Orth

Flying Fish Connect

Flight, Flotsam, Fishing Rights, and

Sushi Caviar  

Flying Fish are just way too cool for words.  Imagine that you are in a boat far from the sight of land and numerous fish with wings appear out of nowhere and glide barely a meter above the ocean waves.  The flying fishes are classified with other needle-shaped fishes in the order Beloniformes (Greek belon means needle); this order also includes the medakas, needlefishes, halfbeaks, and sauries.  All flying fishes are in the family Exocoetidae and they have greatly enlarged pectoral and pelvic fins for gliding, and a greatly enlarged pectoral girdle and pectoral muscles.   The Greek term meaning "sleeping outside" was used to name the family because early naturalists believed that the flying fish actually left the water to sleep on shore!   I’m not making this up; it’s from Pliny the Elder in Naturalis Historiae.  Their connection to flotsam is another story that illustrates how the fallacy of false causation confused Ichthyologists for many decades.  Finally, flying fish were the target in a two-decade-long dispute over fishing rights between the nations of Barbados and Trinity & Tobago.
Atlantic Four-winged Flying Fish Hirundichthys affinis.   Source 
Flying fish do not truly “fly,” but they do glide directly over the surface of the ocean water without flapping their "wings."  Flying fish leave the ocean in order to escape from predators, notably the mackerel, tuna, swordfish, marlin, and dolphin fish. In order to escape the ocean, the flying fish swim toward the surface at amazing speed (close to 30 body lengths per second) with lateral fins furled.  They leap through the water surface at a take-off speed of around 40 miles per hour (18 m/sec), expand their lateral fins and continue tail beating at up to 50 beats per second.  Yes, 50 beats per second!  Forward thrust and steering are aided by an enlarged bottom lobe of their caudal fin (i.e., hypocaudal).   Flying fish can then glide from 50 to 400 meters.  Watch a video of flying fish by clicking here or here.   Some species, referred to as “four-wingers,” have enlarged pectoral and pelvic fins and are able to glide longer.  During flight (15-20 m/sec) the tail is held high and still for stability.   At the end of their flight, the air speed falls and the fish re-enters the water tail first.   

Flying fish are small (15  - 50 cm maximum length) fishes and begin to exhibit flight at about 5 cm.   There are 67 species of flying fish in 8 genera and their distributions are limited to waters warmer than 20–23°C, presumably because muscles do not function at cooler temperatures.      
The flying fish beginning its flight (left) and about to dip its tail at the end of free flight (right).  Drawings from Davenport (1994).
The natural design of flying fish has similar elements to a modern fixed-wing aircraft.   The large pectoral fins have an upward (dihedral) angle from the horizontal.   The vertical median fins and horizontal pelvic fins control pitch during flight.   The most anterior pectoral fin rays are bound together to form a stiff leading edge.  

Top Drawing of flying fish from Davenport (1994)  Bottom  Aircraft from

The mouth of the flying fish is blunt and small for feeding on crustacean zooplankton and larval fish in the epipelagic zone.    Some flying fish also eat salps, which are planktonic tunicates.   Flying fish feed at night and are attracted to light, a behavioral trait that has been used by harvesters to attract and easily capture them.

The spawning sites were long a mystery.     Eggs were scarce in surface neuston net samples in areas with abundant mature adults.  Observations of larvae indicated a tendency to swim up in the water column. Fish Attracting Devices (FAD), such as coconut palm branches, banana leaves, sea weed, and other debris, set by commercial fisherman become so laden with flying fish eggs that they would sink when later freed from the boat.    The mystery was solved in one experiment that offered spawning substrata at different depths; here the scientists discovered a strong preference by flying fish for laying eggs on substrata at 20 meters depth.    

Matthew Jones, in a note in Nature (1872), described an egg nest in Sargassum weed.  The egg nest was "woven together by a maze of fine elastic threads . . . from which depends the clustering mass of eggs. These threads are amazingly strong, especially at their terminal bases, … are apparently twisted together like the fibres of a rope . . . thereby rendering the fabric solid and secure."   In 1872, the prodigious scholar Louis Agassiz attributed these egg masses to the Sargassum Fish Pterophryne histrio; thus egg nests on Sargasso weed were long believed to be due exclusively to Sargassum Fish.    

Only when investigators examined the eggs microscopically was it clear these eggs had polar filaments, a characteristic of flying fish eggs.  The "nests" in the Sargassum weed that are composed of the threads and attached eggs were made by flying fish, while the Sargassum Fish produced a different egg-raft.  It took decades, before Eugene Gudger, Curator of Ichthyology at the American Museum of Natural History, hatched, reared, and photographed the eggs, larvae, and juveniles to resolve the confusion.    Recently Philip Stevens, Florida Marine Research Institute, and associates observed a massive spawning aggregation of flying fish in the absence of flotsam, substantiating the hypothesis that the Sailfin Flying Fish (Parexocoetus brachypterus) do not require flotsam for development.   Clearly there is more to learn about the flotsam and flying fish connection.

This connection between flying fish and flotsam has permitted a new roe fishery for flying fish eggs to emerge in Japan.  Here the fishery targets the egg stage for marketing as flying fish caviar.   The Japanese word, tobiko, means flying fish roe.     Tobiko is used in many sushi dishes.  No fishing regulations have yet to be devised for this roe fishery.   

Fishing captains know how to use the presence of flying fish to locate large piscivorous fish that are feeding nearby.   On a fishing trip off Cozumel in 2008, the captain sighted flying fish in the distance.  As we trolled closer to the rough water where the fish were feeding, each member of the party would get sea sick.  We took turns catching Blackfin Tuna and getting seasick.   Everyone had caught a fish but me, until the last strike of the morning came from a cow dolphinfish that was actively feeding amidst the school of flying fish.  Adult Mahi Mahi (Dolphinfish) feed mostly on bony fishes and the flying fish can comprise a substantial part of the diet.
Author with Mahi Mahi Coryphaena hippurus caught off Cozumel by watching flying fish.  Photo by Valerie F. Orth.
Most species of flying fish support small scale fisheries and the annual landings are locally significant.  The flesh is good quality, although the flying fish are often used as bait to capture larger predatory fish species.   Perhaps the most important pelagic fish in eastern Caribbean is the Atlantic Fourwing Flyingfish (Hirundichthys affinis), which are targeted along with dolphinfish on the same fishing trip, though with different gears.   Dip netting and surface gill netting are used to capture flying fish.    In this fishery, the flying fish reach a maximum length of 29 cm and are vulnerable to the commercial gears at first sexual maturity which occurs within the first year.  Growth rates were determined only after investigators confirmed that rings on the otoliths (ear bones) were daily marks.  Juveniles grow fast and maximum size is reached within one year, which is likely their maximum age as well.   
This eastern Caribbean fishery is of particular economic and cultural importance to Barbados where it supports several processing companies and represents over half of the annual landings ($2.65 million US ex-vessel value).   Between 3,000 to 4,000 tons are captured annually from eastern Caribbean stock from Barbados, Dominica, Grenada, Martinique, St. Lucia, St. Vincent, and Tobago by 3500 fishers (Headley 2010).  Barbadian fisherfolk had long fished for flying fish aggregations in the Caribbean.  When Trinidad & Tobago established its exclusive economic zone to expand economic control of ocean fishing to 370 km, a dispute arose over the rights to catch flying fish off the coast of Tobago.  This dispute lead to the first investigations into harvest strategies, migration, and population stock structure in the eastern Caribbean.  The dispute persisted between the larger and more sophisticated Barbados fishing industry and the much smaller Tobago fishing industry.   This dispute was resolved only after 20 years of conflicts, and involved the use of individual transferable quota and rent agreements to permit access of fisherfolk from Barbados.  
National Dish of Barbados includes Cou-cou and flying fish.  Source.
Flying fish are a very significant cultural asset to the people of Barbados.  Barbados is marketed as the “land of the flying fish.”  The Barbados Hotel and Tourism Association website says “Spend a day on a white sandy beach. Try some flying fish. Enjoy a rum punch. Learn to trade the rush, rush for the slow and easy.”   Flying fish are the most widely eaten fish in the country largely because it is cheap and plentiful.   Fishing employs 15% of the workforce in Barbados and is second leading source of income after tourism.  A national dish in Barbados features the flying fish (Hirundichthys affinis) and ‘cou-cou,’ made from cornmeal, okra, bananas and breadfruit.    Flying fish even appear on coins and stamps of Barbados.    
Stamp and coin from Barbados with flying fish.
The flying fish reminds us of the long and difficult scientific process of uncovering aspects of the life history of fish.   The epipelagic zone of the ocean is relatively easy for humans to access for the study of fishes.  Yet, it took a territorial fishing rights conflict to stimulate study of population characteristics of just one species.   All human communities have cultural and economic dependencies on fishes; the eastern Caribbean is a microcosm of the importance of flying fish in other tropical and subtropical ocean locales.  Finally, remember that even the famous Louis Agassiz committed the logical fallacy of false causation and because of his prominence, the error persisted for 60 years.   The study of fishes proceeds in fits and starts, with only occasional fast glides to a new discovery. 

Blake, A., and B.A. Campbell. 2007.  Conflict over flying fish: the disputebetween Trinidad & Tobago and Barbados.   Marine Policy 31:327-335.
Dasilao, J., and K. Yamaoka.  1998. Development of the vertebralcolumn and caudal complex in a flyingfish, Parexocoetus mento mento (Teleostei: Exocoetidae). Ichthyological Research 45(3):303-308. 
Davenport, J.  1994. How and why do flying fish fly? Reviews in Fish Biology and Fisheries 4(2):184-214.
Gudger, E.W., 1905.  A note on the eggs and egg-laying of Pterophryne histrio, the Gulfweed Fish.  Science 22(573):841-843.   
Headley, M. 2010. Harvesting of Flyingfish in the eastern Caribbean: A Bioeconomic Perspective. United Nations University Fisheries Training Programme, Iceland [final project].
Hunte, W., H.A. Oxenford, and R. Mahon. 1995.  Distribution and relative abundance of flying fish (Exocoetidae) in the eastern Caribbean. II. Spawning substrata, eggs and larvae.  Marine Ecology Progress Series 117:25-37.
Lewis, J.B., J.K. Brundritt, and A.G. Fish. 1962.  The biology of the Flyingfish Hirundichthys affinis (Gűnther).  Bulletin of Marine Science 12(1):73-94.
Mahon, R.  1989. Developing a management strategy for theflyingfish fishery of the eastern Caribbean. Proceedings of the Gulf and Caribbean Fisheries Institute 39: 389-402.
Oliveira, M.R., M.M. Carvalho, N.B. Silva, M.E. Yamamoto, and S. Chellappa. 2015.  Reproductive aspects ofthe flyingfish, Hirundichthys affinis from the Northeastern coastal waters of Brazil.  Brazilian Journal of Biology 75(1):198-207.
Park, H., and H. Choi.  2010.  Aerodynamic characteristics of flying fish in gliding flight.  Journal of Experimental Biology 213:3269-3279.     
Stevens, P.W., C.K. Bennett, and J.J. Berg.  2003.  Flyingfish spawning (Parexocoetus brachypterus) in the Northeastern Gulf of Mexico.  Environmental Biology of Fishes 67(1):71-76.

Friday, October 16, 2015

Red-bellied Piranha (Pygocentrus nattereri): The World's Most Misunderstood Fish, by Don Orth

Sharp teeth, bright red belly, and grey and silver flecked scales on a laterally compressed body -- these characterize the Red-bellied Piranha.   That's one way to describe it.  Teddy Roosevelt in Through the Brazilian Wilderness referred to them as “most ferocious fish in the world.”    Since his book was widely read, many people were aware that the piranha  …will snap a finger off a hand incautiously trailed in the water; they mutilate swimmers—in every river town in Paraguay there are men who have been thus mutilated; they will rend and devour alive any wounded man or beast; for blood in the water excites them to madness. They will tear wounded wild fowl to pieces; and bite off the tails of big fish as they grow exhausted when fighting after being hooked.”  Ever since the cult film, Piranha, appeared in 1978,  frenzied feeding attacks cause otherwise sedate mid-westerners to scream “Piranha!”  In one segment of the film, the resort owner impatiently asks “What about the #$%* piranha?”   in reply, the manager deadpans  “They’re eating the guests sir.”    Hilarious!   No fewer than six movies on Piranha have been released for modern audiences.   Check one out at the nearest Redbox this weekend! Just don't expect more than 2 stars.

After witnessing Red-bellied Piranha feeding on helpless goldfish in a fish tank, every 12-year old boy wants one.   Feeding behavior in captivity was meticulously described by Fox (1972).  Each day he observed the attacks of the Red-bellied Piranha on a much large goldfish.   In 88% of feeding trials, the piranha attacked the tail.  Other attacks were on the eyes of the goldfish.  Both strategies quickly reduce mobility of the prey.   By the way, it is unlikely that that experiment would be approved by your Institution's Animal Care and Use Committee today.  The aggressive frenzied feeding is the primary mystique of the Red-bellied piranha, popularized by stories of a man’s face being eaten off, piranhas eating a duck, and many more frightening stories.  But, there is much more to this fish than what you view on Jeremy Wade’s River Monsters.  
Red-bellied Piranha.  Photo by Greg Moine.
The Red-bellied Piranha is certainly a devout carnivore and preys on much larger prey.  The Red-bellied Piranha is the best known of the piranha species.  The Red-bellied Piranha is a member of the large and diversified family  of fishes that includes the tetras, silver dollars, South American trout (Characiformes, Characidae).   The pacus, silver dollars and prianhas form a subfamily named Sarrasalminae with 80 species.        Although not all piranhas are carnivores, the name piranha actually means “tooth fish” in the Brazilian language Tupí.  The Wimple Piranha Cataoprion mento actually feeds on the scales of other fishes.  Yes, it’s a real mode of feeding called lepidophagy.
The Red-bellied Piranha is widely distributed in the freshwater tropical rivers of South America.   Of the 30 or more Piranha species, it is the one most commonly sold in the tropical fish industry.    However, this is not a beginner's fish.   It is a shoaling fish and will do better in a tank with many other Red-bellied Piranhas and, therefore, you must have a very large aquarium to keep the species.   Many Red-bellied Piranhas quickly outgrow their keeper’s fish tanks.  That cute little 1-inch piranha will easily grow to 6 inches in a year with proper care.  Consequently, many are released in waters of North America.  The released Red-bellied Piranha eventually will be caught by some bait-dunking fisherman.  Each year Piranha fears are arise as the Red-bellied Piranha , or it’s relative the Pacu,  Colossoma sp., is captured in some location river or lake. 

Earlier this year, a Red-bellied Piranha was caught by an angler in Lake Bentonville, ArkansasMany times the reports of a 3-6 pound piranha in a local lake go viral in the media.   Every time (Yes! Every damn time!) this turns out to be the vegetarian Pacu, a characid that grows to over 50 pounds.   Just look at the teeth!  Small pacu resemble the Red-bellied Piranha.   Just last month a 4-pound pacu was caught in a central Indiana lake.   
Close up photo displaying teeth of the Pacu (left) and the Red-bellied Piranha (right). Source.
Of all the tropical fish raised in the industry, the Red-bellied Piranha generates the greatest reaction in the way of state and local laws and ordinances prohibiting their sale and possession.    At least 24 states prohibit the possession and sale.  Many other cities also have ordinances prohibiting Red-bellied-Piranha.    The concern expressed by Teddy Roosevelt is evident today, as cattle ranchers and farmers are worried that a released Red-bellied Piranha will eat a cow (which locals did demonstrate for Roosevelt), or eat the face or feet off of swimmers.    Many of the fishes that co-evolved with Red-bellied Piranha have behavioral or morphological defenses to minimize or prevent attacks.  Our native fishes (and humans, of course) have no such defenses against attacks by the Red-bellied Piranha. 
States that prohibit possession of Piranha.  Sourc:
Most reports of the Red-bellied Piranha are based on a single fish captured and these are often only 3-6 inches.   For example, in Virginia, the only Red-bellied Piranha was a single 6-inch specimen taken from Indian Lake, a borrow pit in the Virginia Beach area (Stone 1987).  In most states, it is unlikely that the Red-bellied Piranha can survive over winter.   Cold-winters are the climatological tool in preventing establishment of invading populations of Red-bellied Piranha.    They do spawn readily in captivity and at temperatures common in many North American waters.  The risk that released Red-bellied Piranhas will establish populations is much greater in southern states.  The minimum temperature that kills a Red-bellied Piranha can be determined in lab studies.  One such study by Bennett et al. (1997) suggests that it is very likely Red-bellied Piranha can be established in waters of southern California, Texas, and Florida, although there is considerable year-to-year variability in winter severity. Two cases are known.   In 1993, officials in Hawaii located and destroyed an outdoor breeding operation for Red-bellied Piranha.   In 1977, officials in Florida eradicated a population of a different species of Piranha near Miami; this population persisted 13 years before its eradication. 
Map of likelihood of the Red-bellied Piranha overwintering. Bennett et al. (1997).

The Red-bellied Piranha is an important and fascinating part of the aquatic community in its native range.  Some of the observations on captive Red-bellied Piranha's informs our understanding of its role and life history.   Spawning behavior is described mostly based on captive specimens.  There are not  too many biologists snorkelling to observe Red-bellied Piranha in their native habitats that are murky with limited visibility. But see the video of Jeremy Wade with PiranhaSounds made by the Red-bellied Piranha are a critical means for their communication. Red-bellied Piranha use
fast sound producing muscles to contract tendons along the swim bladder (Millot and Parmentier 2014).  Red-bellied Piranha use sound for communication though the specific nature of this communication is still largely unstudied.   Because of the murky nature of their native habitats, communication helps individuals in shoals to find mates and share food locations.   Red-bellied Piranha seem to shoal in similar size groups, with smaller ones in floating meadows and largest specimens moving to marginal vegetation. 

Habitats used by different sizes of Red-bellied Piranha. Duponchelle et al. (2007)
The present diversity of piranha derived from a common ancestor that swam in the proto Amazon-Orinoco river drainages 9 million years ago.  Sea level changes and river basin and geological differences created many opportunities for unique types of piranha to speciate.   It is unlikely we can even begin to speculate how the Red-bellied Piranha might adapt if established in the Southern United States because so few populations have been studied to describe basic life-history.   In one of the few studies, Duponchelle et al. (2007) were surprised to find that females spawned at least twice during each breeding season in the Bolivian Amazon.   In the white waters of the Brazilian Amazon, the Red-bellied Piranha had two reproductive seasons per year (Queiroz et al. 2010).  The Red-bellied Piranha likely adjust their reproductive strategy to the availability of food in their environment.  
Number of larvae (vertical gray bars) and frequency of mature gonads (solid line) by month.  Horizontal lines represent high water (solid black) and low water (open bars).  Queiroz et al. (2010).
In closing, the Red-bellied Piranha is not a fish to be taken lightly and its commerce and risk of release will continue to keep us on high alert for newly established populations.  Most guides to tropical fish keeping list the Red-bellied Piranha among the fishes to avoid.   A solitary Red-bellied Piranha will be a boring fish to keep and they are not suited to a community aquarium.  Since its danger to humans has already been greatly exaggerated, I refrained from describing attacks that resulted in loss of digits, or other body parts including male genitalia because the movies are scary enough.  
Where possession is legal, Red-bellied Piranha can be maintained and even bred in captivity and will live for many years.    Before you commit to raising the Piranha, read the Complete Pet Owner's Guide.   In addition to responsible husbandry the Red-bellied Piranha should never be released. Euthanize unwanted specimens and deposit them in a natural history museum.       

Fascinated with the most misunderstood fish?  If you want to learn more, visit the only educational website dedicated to the Piranha and its close relatives


Bennett, W.A., R.A. Currie, P.F. Wagner, and T.L. Beitinger.  1997. Cold tolerance and potential overwintering of the Red-Bellied Piranha Pygocentrus nattereri in the United States.  Transactions of the American Fisheries Society 126(5):841-849.

Duponchelle, F., F. Lino, N. Hubert, J. Panfili, J.-F. Renno, E. Baras, J.P. Torrico, R. Dugue, and J. Nuñez. 2007. Environment-related life-history trait variations of the red-bellied piranha Pygocentrus nattereri in two river basins of the Bolivian Amazon. Journal of Fish Biology 71:1113-1134.
Fox, R.M. 1972. Attack preferences of the red-bellied piranha (Serrasalmus nattereri).  Animal Behaviour 20(2):280-283. 

Janovetz,  J.  2005.  Functional morphology of feeding in the scale-eating specialist Catoprion mento.  The Journal of Experimental Biology 208:4757-4768.

Millot, S., and E. Parmentier.  2014.  Development of the ultrastructure of sonic muscles: a kind of neoteny?  BMC Evolutionary Biology 14:24 

Queros, H., and A.E. Magurran. 2005.  Safety in numbers?  Shoaling behaviour of the Amazonian red-bellied piranha.  Biology Letters 1:155-157.  

Schleser, D. 2008. Piranhas: Complete pet owner's manual.  Barron's Educational Series.  96 pp.

Stone, S. 1987. 6-inch piranha found in pit at Indian Lakes. Virginia Pilot and Ledger Star, 23 August 1987.