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 www.aerospaceweb.org

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. 

References
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.




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