Sun . 19 Apr 2019

Bait ball

bait ball lure, bait ball
A bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre It is a last-ditch defensive measure adopted by small schooling fish when they are threatened by predators Small schooling fish are eaten by many types of predators, and for this reason they are called bait fish or forage fish

For example, sardines group together when they are threatened This instinctual behaviour is a defense mechanism, as lone individuals are more likely to be eaten than large groups Sardine bait balls can be 10–20 metres in diameter and extend to a depth of 10 metres The bait balls are short-lived and seldom last longer than 10 minutes

However, bait balls are also conspicuous, and when schooling fish form a bait ball they can draw the attention of many other predators As a response to the defensive capabilities of schooling fish, some predators have developed sophisticated countermeasures These countermeasures can be spectacularly successful, and can seriously undermine the defensive value of forming bait balls

Contents

  • 1 Background
  • 2 Formation and dissolution
  • 3 Predator strategies
  • 4 Predator cooperation
  • 5 Mixed species feeding
  • 6 See also
  • 7 Notes
  • 8 References
  • 9 External links

Background

Sardine bait ball Bar jacks working a small bait ball Edge of a large baitball See also: Shoaling and schooling

Small pelagic fish live in the open water, so unlike demersal or reef fish, they cannot hide among kelp, or in crevices in coral, or under rocks on the bottom This leaves them vulnerable to attack by large predatory fish, as well as other predators, such as marine mammals and seabirds As a result, small pelagic fish usually aggregate together in schools for protection Schooling fish have evolved sophisticated evasion techniques When they school they have many eyes, which makes ambush difficult, and their silvery bodies dazzle, which makes it difficult for predators to pick out individual fish They react to movements from a predator with lightning reflexes, rhythmically streaming up and down with rapid direction changes When a predator approaches, they can split and reform behind the predator During the final stages of an attack, they can explosively disband in all directions and then just as rapidly reform Defensive manoeuvres like these appear to be choreographed, though they are not Within the school itself, there is no centralized intelligence aware of how the school has configured itself Rather, the schooling behaviour is the emergent consequence of relatively simple rules followed by each individual fish in the school, such as remaining close together, moving in the same direction, and avoiding collisions with each other

Some species of forage fish, driven by nutrient availability and their life-cycle stage, form vast schools at predictable locations and times of the year Normally, schooling works well as protection from occasional predators But when fish school in vast numbers they can attract correspondingly huge numbers of predators, including seabirds, sharks, tuna, billfish, pods of dolphins, and killer and humpback whales Aggregations of predators on such a scale means the schools can be attacked on all sides, and panicked into forming bait balls

A bait ball is a last-ditch defensive measure adopted by fish schools when they are overwhelmed and more effective defensive strategies have broken down Schooling fish are easier to attack once they abandon their free streaming behaviour and form into a tight bait ball Many predator species have learned that by interacting cooperatively they can panic schooling fish into forming a bait ball This cooperative behaviour can occur both intraspecifically among the individuals within a predator species and interspecifically across individuals belonging to more than one predator species

Formation and dissolution

The process that leads to the formation of a bait ball typically starts when predators locate a fish school deep below the surface The predators make rushes and use various scare tactics to force the fish school to the surface, herding it at the same time into a compact volume The alarmed fish, trapped against the surface above and surrounded all about, abandon their coordinated schooling movements and become chaotic Their graceful and disciplined schooling strategies of uniform spacing and polarity degrade into frenetic attempts by each fish to save itself In this way, a dense bait ball forms as each fish scrambles to get away from the surface of the ball and hide in the interior The symmetry of this centripetal action forms a sphere, the shape with the minimum surface area for a given volume This exposes the fewest number of fish on the surface to the predators The movement, sound and smell can attract more predators, including different predator species, until there is a carousel of them, each species using their own characteristic predatory strategies Fish that break loose are singled out and eaten A frenzy can develop as predators compete, the water reddening with blood as shredded flesh and scales drift to the depths As the bait ball reduces in size and number, it becomes progressively easier for the predators to target the remaining survivors

Predator strategies

Pair of whales lunge feeding

Predators have devised various countermeasures to disrupt the defensive shoaling and schooling manoeuvres of forage fish Often this involves charging the school or bait ball at high speed

Some whales lunge feed on bait balls Lunge feeding is an extreme feeding method, in which the whale accelerates from below a bait ball to a high velocity and then opens its mouth to a large gape angle This generates the water pressure required to expand its mouth and engulf and filter a huge amount of water and fish Lunge feeding by rorquals, a family of huge baleen whales that includes the blue whale, is said to be the largest biomechanical event on Earth

Swordfish charge at high speeds through forage fish schools, slashing with their swords to kill or stun prey They then turn and return to consume their catch Thresher sharks use their long tails to stun shoaling fishes Spinner sharks charge vertically through schools, spinning on their axis with their mouths open and snapping all around The shark's momentum at the end of these spiralling runs often carries it into the air

Gannets plummet from heights of 30 metres 100 feet, plunging through the water leaving vapour-like trails behind like fighter planes They enter the water at speeds up to 86 kilometres per hour 53 mph and descend to depths of 34 metres 111 feet Gannets have air sacs under their skin in their faces and chests which act like bubble-wrap, cushioning the impact with water

Predator cooperation

Sailfish work together, raising their sails to make them appear much larger so they can "herd" a school of fish or squid Aerial view of a bubble net Group of humpback whales lunging through the centre of their bubble net

The most effective strategy predators use against schooling fish is to first scare them into forming a bait ball Strategies such as those outlined in the previous section, can work to a degree against freely streaming fish schools, but work much better if the fish school is first compacted into a bait ball It is difficult for predators working individually to scare a fish school into a bait ball, and they usually work together in a cooperative effort

  • Thresher sharks compact their prey by swimming in circles around them, splashing the water with their long tails, often in pairs or small groups They then strike sharply at the bait ball to stun the fish with the upper lobe of their tails
  • Schools of forage fish can draw silky sharks in large numbers Silky sharks have been documented "herding" such schools into a bait ball trapped against the surface, and then consuming the entire school When attacking tightly packed fish, silky sharks charge through the ball and slash open-mouthed, catching the prey fish at the corners of their jaws Although multiple individuals may feed at once, each launches its attack independently
  • Pods of many dolphin species commonly herd a school of fish into a bait ball while individual members take turns ploughing through and feeding on the more compacted shoal Corralling is a method where fish are chased to shallow water where they are more easily captured Some dolphins takes this further with strand feeding, driving prey until they are stranded on mud banks, where they can be easily accessed Dolphins have also been observed blowing bubbles to startle and separate individual fish from a bait ball
  • The humpback whale uses a feeding technique called bubble net feeding A group of whales swim in a shrinking circle blowing bubbles below a school of prey fish Forage fish show a strong fear of bubbles and can be easily contained within a bubble curtain The shrinking ring of bubbles encircles the school and confines it in an ever smaller cylinder The whales then lunge feed, often as a synchronised group, suddenly swimming upward through the "net", mouths agape, swallowing thousands of fish in one gulp The ring can begin at up to 30 metres 98 ft in diameter with perhaps a dozen whales cooperating Using a crittercam attached to whale's back it was discovered that some whales blow the bubbles while others dive deeper to drive fish toward the surface, and yet others herd the prey into the net by vocalizing Some humpback whales also scare schooling fish by slapping their tails lobtail Although many whale species lunge feed, only humpbacks use bubble nets
  • Killer whales usually hunt larger fish, such as salmon, individually or in small group of individuals However, forage fish, such as herrings, are often caught using carousel feeding The killer whales force the herring into a tight ball by releasing bursts of bubbles or flashing their white undersides They then slap the ball with their tail flukes, either stunning or killing up to 10–15 herring with a successful slap The herring are then eaten one at a time Carousel feeding has only been documented in the Norwegian killer whale population and with some oceanic dolphin species
  • Sperm whales may also herd prey

Mixed species feeding

External images
Bait ball symphony
Cooperative hunting by sailfish
Bronze whalers charge a baitball

Fish that school in large numbers can draw the attentions of many different predator species The attraction of huge numbers of prey fish means that these predator species, which might otherwise be mutually antagonistic, usually cooperate with each other in pursuit of their common goal

Bryde's whales often track dolphin groups as they herd prey species As soon as the dolphins corral the prey, the whales lunge feed through the centre

In 2001, Clua and Grosvalet proposed a four stage model to describe mixed species feeding behaviour involving common dolphins, tuna and shearwater sea birds

  • In the preparation phase, the dolphins rapidly circle the fish school to compact it
  • In the intensification phase, the bait ball is further structured by dolphins circling and foraging the periphery of the ball, while shearwaters forage from the ocean surface
  • At the mature phase, the dolphins temporarily scatter as giant tuna lunge vertically through the centre of the ball At this point the concentration of the bait ball is optimal
  • Finally in the dispersion phase, the tuna and sea birds disperse, and some dolphins return to forage on the remnants of the ball
External video
Fish bait ball in open water Blue Planet, BBC
Bait Ball Feast The Great Feast, BBC
Bluefin tuna eat bait ball National Geographic
Shearwater attack! - Blue Planet BBC Wildlife
Amazing bait balls & predatory fishermen BBC
Marlin feeding on sardine ball YouTube
Marlin & Tuna Feeding Blue Planet: Open Seas

Most years, off southern Africa between May and July, billions of sardines specifically the Southern African pilchard Sardinops sagax spawn in the cool waters of the Agulhas Bank and move northward along the east coast of South Africa This great fish migration is called the sardine run Their sheer numbers create a feeding frenzy along the coastline The run, containing millions of individual sardines, occurs when a current of cold water heads north from the Agulhas Bank up to Mozambique where it then leaves the coastline and goes further east into the Indian Ocean During the sardine run, as many as 18,000 dolphins, behaving like sheepdogs, herd the sardines into bait balls, or corral them in shallow water Once rounded up, the dolphins and other predators take turns ploughing through the bait balls, gorging on the fish as they sweep through Seabirds also attack them from above, flocks of gannets, cormorants, terns and gulls The sardine run is featured in the first episode of the 2001 BBC nature documentary The Blue Planet and in the 2008 3D IMAX documentary film Wild Ocean

A similar great migration of herrings occurs each year during the summer plankton bloom along the coast of British Columbia and Alaska The migration is featured in the final episode of the 2009 BBC wildlife documentary Nature's Great Events In winter, the coastal fjords and inlets are relatively lifeless, and the resident Steller sea lions must dive deeper and further from the coast to catch the widely-dispersed herring Humpback whales overwinter in the warm Pacific waters off Hawaii, where new mothers suckle their calves They begin their 3,000 mile journey north in early spring, when the sea lions also give birth to their young Spring storms disturb nutrients in the water which, together with the strengthening power of the sun, act as the catalysts for the plankton bloom Huge shoals of herring arrive to spawn, turning the shallows milky white The herring sift plankton from the water In their wake come larger predators, including Pacific white-sided dolphins and killer whales Common murres dive under the herring shoals and pick off the fish from below, pinning them to the surface Their defence is to form a bait ball, but gulls gathering on the surface attack them from above The finale to the programme features unique underwater footage of humpbacks engulfing whole bait balls, and reveals their co-operative hunting behaviour called bubble-netting

See also

  • Feeding frenzy

Notes

  1. ^ Megurran, AE 1990 "The adaptive significance of schooling as an anti-predator defense in fish" Annales Zooligici Fennici, 27: 51-66
  2. ^ Partridge BL 1982 "The structure and function of fish schools" Scientific American, 2466 114–123
  3. ^ Magurran AE and Pitcher TJ 1987 "Provenance, shoal size and the sociobiology of predator-evasion behaviour in minnow shoals" Proc R Soc Lond B, 2291257: 439-465 doi:101098/rspb1987000
  4. ^ Reynolds, CW 1987 "Flocks, herds and schools: A distributed behavioral model" Computer Graphics 21 4: 25–34 CiteSeerX 10111037187 doi:101145/3740137406 
  5. ^ Parrish JK, Viscido SV and Grunbaumb D 2002 "Self-organized fish schools: An examination of emergent properties" Biol Bull 202: 296 –305
  6. ^ a b Seifert DD 2010 Water Column: Finishing School November 2010, Dive Magazine UK
  7. ^ Hamilton WD 1971 "Geometry for the selfish herd" Journal of Theoretical Biology 31: 295-311
  8. ^ Reeves RR, Stewart BS, Clapham PJ and Powell J A 2002 National Audubon Society Guide to Marine Mammals of the World Chanticleer Press ISBN 9780375411410
  9. ^ Potvin J and Goldbogen JA 2009 "Passive versus active engulfment: verdict from trajectory simulations of lunge-feeding fin whales Balaenoptera physalus J R Soc Interface, 640: 1005–1025 doi:101098/rsif20080492
  10. ^ Helfman GS, Collette BB and Facey DE 1997 The diversity of fishes Page 326, Wiley-Blackwell ISBN 978-0-86542-256-8
  11. ^ a b Seitz, JC Pelagic Thresher Florida Museum of Natural History Retrieved on December 22, 2008
  12. ^ Oliver SP, Turner JR, Gann K, Silvosa M and D'Urban Jackson T 2013 "Thresher sharks use tail-slaps as a hunting strategy" PLoS ONE, 8 7: e67380 doi:101371/journalpone0067380
  13. ^ Compagno, LJV 1984 Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date Rome: Food and Agricultural Organization pp 466–468 ISBN 92-5-101384-5 
  14. ^ "Carcharhinus brevipinna, Spinner Shark" MarineBioorg Retrieved May 9, 2009 
  15. ^ Ropert-Coudert Y, Gremillet D, Ryan P, Kato A, Naito Y and Le Maho Y 2004 "Between air and water: the plunge dive of the Cape Gannet Morus capensis" Ibis , 146: 281–290
  16. ^ Brierley AS and Fernandes PJ 2001 "Diving depths of Northern Gannets: acoustic observations of Sula bassana from an autonomous underwater vehicle" Auk, 118: 529–534
  17. ^ Bonfil, R 2008 "The Biology and Ecology of the Silky Shark, Carcharhinus falciformis" In Camhi, M; Pikitch, EK; Babcock, EA Sharks of the Open Ocean: Biology, Fisheries and Conservation Blackwell Science pp 114–127 ISBN 0-632-05995-8 
  18. ^ Martin, RA Open Ocean: Silky Shark ReefQuest Centre for Shark Research Retrieved on September 12, 2009
  19. ^ US Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service "Coastal Stocks of Atlantic Bottlenose Dolphin: Status Review and Management Proceedings and Recommendations from a Workshop held in Beaufort, North Carolina, 13 September 1993 – 14 September 1993" PDF pp 56–57 
  20. ^ Neumann D R and Orams MB 2003 "Feeding behaviours of short-beaked common dolphins, Delphinus delphis, in New Zealand" Aquatic Mammals, 29: 137–149
  21. ^ Hain JHW, Carter GR, Krau, SD, Mayo CA and Winn HE 1982 "Feeding behaviour of the humpback whale, Megaptera novaeangliae, in the Western North Atlantic" Fishery Bulletin, 80: 259–268
  22. ^ Sharpe FA and Dill LM 1997 "The behavior of Pacific herring schools in response to artificial humpback whale bubbles" Canadian Journal of Zoology, Can J Zool, 75:725–730
  23. ^ Acklin, Deb 2005-08-05 "Crittercam Reveals Secrets of the Marine World" National Geographic News Archived from the original on 12 October 2007 Retrieved 2007-11-01 
  24. ^ Prepared by the Humpback Whale Recovery Team for the National Marine Fisheries Service, Silver Spring, Maryland 1991 Recovery Plan for the Humpback Whale Megaptera novaeangliae National Marine Fisheries Service p 105 
  25. ^ Weinrich MT, Schilling MR and Belt CR 1992 "Evidence for acquisition of a novel feeding behaviour: lobtail feeding in humpback whales, Megaptera novaeangliae" Animal Behaviour, 44: 1059–1072 doi:101016/S0003-34720580318-5
  26. ^ Bubble net feeding Alaska Whale Foundation Retrieved 31 March 2011
  27. ^ Similä, T & Ugarte, F 1993 "Surface and underwater observations of cooperatively feeding killer whales" Can JZool 71: 1494–1499 doi:101139/z93-210 Retrieved 2010-02-26 
  28. ^ Nature's finest caught on camera BBC News, 21 October 2004
  29. ^ Arnold PW, Birtles RA, Sobtzick S, Matthews M and Dunstan A 2005 "Gulping behaviour in rorqual whales: underwater observations and functional interpretation" Memoirs of the Queensland Museum, 51, 309–332
  30. ^ Goldbogen JA, Calambokidis J, Shadwick RE, Oleson EM, McDonald MA and Hildebrand J A 2006 "Kinematics of foraging dives and lunge-feeding in fin whales" Journal of Experimental Biology, 209, 1231–1244
  31. ^ Clua and Grosvalet F 2001 "Mixed-species feeding aggregation of dolphins, large tunas and seabirds in the Azores" Aquatic Living Resources, 141: 11 - 18 doi:101016/S0990-74400001097-4
  32. ^ Produced by Hugh Pearson and Joe Stevens 2009-03-18 "The Great Feast" Nature's Great Events BBC BBC One 

References

  • Burgess EA 2006 "Foraging ecology of common dolphins Delphinus sp in the Hauraki Gulf, New Zealand" MSc thesis, Institute of Natural Resources, Massey University
  • Dement J Species Spotlight: Atlantic Sailfish Istiophorus albicans littoralsocietyorg Retrieved 28 March 2011
  • Leighton TG, PR White and Finfer DC 2009 "Hypotheses on the acoustics of whales, dolphins and porpoises in bubbly water" Proceedings of the Third International Conference on Underwater Acoustic Measurements, Technologies and Results
  • Fetecau R 2010 "Collective behavior of biological aggregations in two dimensions: a nonlocal kinetic model" Mathematical Models and Methods in Applied Sciences, August 2010
  • Marshall Cavendish Corporation 2004 Encyclopedia Of The Aquatic World Page 164, Marshall Cavendish ISBN 978-0-7614-7418-0
  • Mate BR 2010 "Sperm whales instrumented with ARGOS-GPS-TDR tags demonstrate coordinated dive behavior suggesting cooperative 'bait-ball' feeding on Humbolt squids" Proceedings from the 2010 AGU Ocean Sciences Meeting 
  • Robinson KP, Stevick PT and MacLeod CD 2007 An integrated approach to non-lethal research on minke whales in European waters European Cetacean Society, Special publication series, No 47
  • Robinson KP and Tetley MJ 2007 "Behavioural observations of foraging minke whales Balaenoptera acutorostrata in the outer Moray Firth, north-east Scotland" J Mar Biol Ass UK, 87: 85–86 doi:101017/S0025315407054161
  • Sfakiotakisa M and Tsakiris DP 2007 "Neuromuscular control of reactive behaviors for undulatory robots" Neurocomputing, 7010-12: 1907-1913
  • Steiner L 1995 "Rough-toothed dolphin, Steno bredanensis: a new species record for the Azores, with some notes on behaviour" Life and Marine Sciences, 13A: 125–127
  • Waters, Hannah 2010 Now in 3-D: The shape of krill and fish schools Scientific American Invited commentary, 10 November 2010

External links

  • Queuing up for dinner: Dolphins enjoy sardine feeding frenzy Daily Mail, 15 July 2009 – this article has some spectacular images
  • Computer simulations of bait balls
  • How Humpback Whales Catch Prey With Bubble Nets ScienceDaily 24 June 2011

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Bait ball


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    29.10.2014


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