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== Predation strategies ==
== Predation strategies ==
In addition to the methods of consuming prey, there are a variety of other strategies that fish use to draw in or come into close proximity with prey on other creatures. Often fish take advantage of specific niches in their ecosystem or exhibit further physiological adaptations to achieve these goals.
In addition to the methods of consuming prey, there are a variety of strategies that fish use to draw in or come into close proximity with prey. Often fish take advantage of specific niches in their ecosystem or exhibit further physiological adaptations to achieve these goals.


===Cleaner Fish===  
===Cleaner Fish===  

Revision as of 20:39, 14 April 2015

Aquatic Predation

[1]

Predation Model

  • Energy vs. Cost
  • Factors Affecting Search:
    • For Predator: Hunger
    • For Prey: Camouflage
  • Factors Affecting Encounter
    • For Predator: Swimming speed, water clarity, illumination, schooling, detection mechanisms
    • For Prey: Morphology, activity level, pigmentation, distribution
  • Factors Affecting Strike:
    • For Predator: Alternative prey, location
    • For Prey: Body size, sensory ability
  • Factors Affecting Capture
    • For Predator: Mouth gape, strike speed, handling
    • For Prey: Escape capabilities, schooling, shelter seeking behavior [1]


Other Feeding Factors

The factors that affect juvenile feeding behavior. [2]
A clingfish in the Caribbean exhibits camouflage.
Some fish, such as the bridled burrfish, have defense mechanisms to avoid capture.
[3]
Fish often travel in schools to avoid predation.
Juvenile fish are the most susceptible to predation.
In the Caribbean, the lionfish is an invasive predator. Invasive species can alter the food web.
Nurse sharks are a common predator in the Caribbean. They are bottom-feeders.

Size is the most important factor in determining predation rates. For example, there is a decreasing rate of predation with jellyfish as fish larvae size increases. One fish that is commonly found in the Caribbean, the porcupine fish, inflates its body in order to increase its size, therefore decreasing the predators that would be capable of eating it. Predators would have to have a larger jaw in order to eat the porcupine fish. Predation occurs at all sizes of organisms. Microscopic organisms are predators, and so are large whales. The highest rates of predation occur on juvenile fish. This is because predation is most common during life transitions. After fish larvae hatch, the are more susceptible to predators. Fish are also susceptible to predators at another life transition - during mating. [4] Most fish are active either during the day or at night, not 24 hours. Their diurnal or nocturnal feeding is normally fixed genetically.[5]

Importance of Predation

Food Web

Predators help keep the food web in-check. Food webs are divided by trophic levels. Top predators have a “trophic cascade” effect on food webs - having a top-down effect on lower trophic levels. The elimination of predators can cause serious perturbations to an ecosystem. [1]

Important Evolutionary Force

Predation is a strong force of natural selection. The weaker species is eliminated. Fish predation is an important evolutionary force because when certain types of fish are targeted by predators they do not have as great of a survival rate. They are forced to acclimate, and as numbers dwindle and the more advantageous fish win out, and the fish population will evolve over time. [1]

Methods of Consuming Prey

Prey in an aquatic habitat are harder to capture than those on land due to the difference between the prey and the surrounding medium's density being lower in water; this causes the prey to be pushed away upon approach by a predator. For this reason, fish have developed a variety of methods to become successful predators in water. (need better source)

Suction

Fish opens its mouth and rapidly expands its oral cavity, thus creating a negative pressure. When the mouth is opened, water rushes in, drawing in the prey item from a distance. This is a common feeding technique of sharks (like the Nurse Shark), rays, and other fish (e.g. the Atlantic Guitarfish). [6] [7]

Ram

The fish swims over the prey while its is mouth open. Often used in adjunct with suction feeding technique. Ram feeders overtake the prey with body swift movements, and finish the attack with an explosive strike of suction feeding. At the very least, some compensatory suction is needed to eliminate the bow wave formed as the fish swim toward the prey. Tunas exhibit ram feeding in their predation methods. [8] The Great Barracuda is another fish that commonly employs this strategy. [9]

Pivot

Rather than translocate its whole body to reach prey, a predator may instead move only its head. Fish employing pivot feeding lift their entire head (including the mouth) to close the gap between it and the prey. It is much slower to accelerate a fish's whole body than just its head in order to close in on near by prey. Pipefishes, like the Harlequin Pipefish, often use this method of approaching prey. A lounger snout allows for faster approach of prey with just the turning of the head than a shorter snout; due possibly to this, it has been observed that longer-snouted pipefishes tend to feed on more agile prey than their shorter-snouted counterparts.[10]

Jaw Protrusion

Another way to get close to prey without moving the entire body is jaw protrusion. Here the fish extends its upper jaw in order to close the distance between its mouth and prey so suction feeding can be utilized. In addition to closing distance between predator and prey, the jaw protrusion allows for a larger mouth volume, resulting in a greater suction force being generated when the mouth is opened and the vacuum created. This adaptation can increase the total force exerted on prey up to 35%. The Spotted Grouper is a slow mover so it uses this jaw protrusion mixed with suction feeding to "inhale" live victims that swim close enough to its mouth. [11] Some Angelfish also have a protruding mouth as it gives them the ability to reach prey hiding in small crevices in the reef. [12]

Filter

Predators capture prey by pumping water through filtration structures. This method is seen in variety of species in zooplankton, bivalves, sponges, tunicates; common examples are Christmas Tree Worms, which passively use tentacles sticking to capture plankton, and the Giant Clam. [13]

Suspension Feeders

In this scheme, the predator actively captures nearby prey by using tentacles. This method is not entirely passive, some modify arm and pinnule postures to take best advantage of prevailing and changing flow patterns and velocities. This method is used by species throughout octocorals, crinoids, scleractinian corals. [14] The feather star is a common example of this feeding tactic. [15]

Physiological adaptations

Some coral reef predators develop physical traits evolved for a more advantageous and specialized predatory technique. An example is the parrot fish: it has beak like jaws for scraping algae off coral and teeth for grinding coral. [16]

Manipulation

Another means of capturing prey is by making physical contact with them and transporting them to the mouth. An example of this would be biting, which is used by sharks. [17] Another common example is the butterflyfish's technique of gripping a removing pieces from polychates, nemertean, corals, ascidians, echinoids, hydroids and other prey that attach themselves to hard substrate. [18] However, this form of predation is not limited to jawed fishes. Hagfishes and lampreys use teeth attached to dental plates that are extended and retracted during feeding, this pulls the prey into its mouth. Jawless fish can transmit the most force possible with this method but it does not allow for the faster feeding that allowed jawed fishes to become evolutionarily successful. [19]

Predation strategies

In addition to the methods of consuming prey, there are a variety of strategies that fish use to draw in or come into close proximity with prey. Often fish take advantage of specific niches in their ecosystem or exhibit further physiological adaptations to achieve these goals.

Cleaner Fish

These fish use a type of symbiosis, mutualism, to find and consume prey or food. The cleaner fish feast on the dead skin and ectoparasites found on the host fish. Cleaner fish attract clients by alerting fish to their presence with bright coloration, often a bright blue stripe. Cleaning gobies and wrasses are examples of fish that engage in this behavior.

Mimicry

One strategy to get close to prey is to pretend to be something else; the mimic could resemble harmless creatures or even creatures that are beneficial to the targeted prey. Mimics may copy the motion, coloration, or morphology of other fish. Sharing signals with harmless species to avoid identification by a host or prey is called aggressive mimicry. Some species of fish have the ability to switch between colors so they may not always be employing mimicry, this is called facultative mimicry. A well-researched example of mimicry in the coral reef environment is the mimicry of the Bluestreak Cleaner Wrasse by the Bluestriped Fangblenny, allowing it to engage in parasitism and feed on scales and tissues of its host. [20] The presence of mimics can actually diminish the ability of legitimate cleaner fish to forage for food, as hosts become cautious of cleaning stations that have large populations of mimics. [21]

Camouflage

Some fish may use coloration, appendages, or irregularities in the body to blend in with or even mimic inanimate objects in the reef environment. Common examples are the scorpionfish and the frogfish, which mimics, exceptionally well, pieces of coral. Camouflage goes hand-in-hand with the ambush predation strategy in which predators lay in wait for prey to, unknowingly, get close to them. [22]

Triggerfish

Some fish have ingenious methods of finding or subduing prey that are used in combination with physiological adaptations. Triggerfish are observed to dig out crabs or worms by flapping away debris with their fins or blasting the sand away with a jet stream of water shot from their mouth. They may also employ these methods or use their tough teeth and jaws to flip over sea urchins in order to avoid the urchin's spines. Triggerfish are so disruptive to small reef creatures they encourage other fish to adopt the predation strategy of following the triggerfish to get their leftovers. [23]

References

  1. 1.0 1.1 1.2 1.3 K.M. Bailey, JT. Duffy Anderson. 2001. Fish Predation and Mortality. Encyclopedia of Ocean Sciences (Second Edition). Pages 417-421.
  2. A. D. Nunn, L. H. Tewson, and I. G. Cowx. The foraging ecology of larval and juvenile fishes. Hull International Fisheries Institute, Department of Biological Sciences, University of Hull, Hull, HU6 7RX, UK. Published online: 26 October 2011
  3. Amsel, Sheri. “Food Webs.” Coral Reef Food Web. Exploring Nature Educational Resource. © 2005 - 2014. April 14, 2014. <http://exploringnature.org/db/detail.php?dbID=2&detID=1221
  4. Hixon, Mark A. 1991. Predation as a Process Structuring Coral Reef Communities.Oregon State University Publishing. http://hixon.science.oregonstate.edu/files/hixon/publications/026%20-%20Hixon%2091%20Sale%20book.pdf
  5. Houlihan, Dominic. 2001. Food Intake in Fish. Blackwell Science. Pages 189-209.
  6. http://www.mapoflife.org/topics/topic_401_Suction-feeding-in-fish-amphibians-reptiles-and-aquatic-mammals/
  7. http://www.ncbi.nlm.nih.gov/pubmed/9808831
  8. http://fishlab.ucdavis.edu/ReefFishFeeding.pdf
  9. http://www.academia.edu/599465/Feeding_biomechanics_in_the_Great_Barracuda_during_ontogeny
  10. http://rsif.royalsocietypublishing.org/content/4/14/561#sec-13
  11. No Title "Web. 2/25/2015 <http://www.miamisci.org/oceans/coralreef/predators/2grouper.html
  12. Filter and suspension feeders "Web. 2/25/2015 <http://www.coralscience.org/main/articles/aquaculture-a-husbandry-4/filter-feeders
  13. Coral Reefs and Climate Change - What lives on a coral reef - Teach Ocean Science "Web. 2/25/2015 http://www.teachoceanscience.net/teaching_resources/education_modules/coral_reefs_and_climate_change/what_lives_on_a_coral_reef
  14. http://www.coralscience.org/main/articles/aquaculture-a-husbandry-4/filter-feeders
  15. http://www.nova.edu/ocean/messing/crinoids/8%20Feeding%20mechanism.html
  16. No Title "Web. 2/25/2015 <http://www.miamisci.org/oceans/coralreef/predators/5parrotfish.htm
  17. http://www.biomechanics.ucr.edu/Higham%202011%20Fish%20Physiology.pdf
  18. http://fishlab.ucdavis.edu/F-G%20et%20al%20JEMBE%2001.pdf
  19. http://www.biomechanics.ucr.edu/Higham%202011%20Fish%20Physiology.pdf
  20. Visual Biology & Mimicry - Coral Reef Systems Multimedia." Visual Biology & Mimicry - Coral Reef Systems Multimedia. N.p., n.d. Web. 25 Feb. 2015.
  21. http://171.66.127.192/content/early/2011/08/16/rsbl.2011.0687.full.pdf+html)
  22. Camouflage among Pacific and Red Sea Coral Reef Creatures." Camouflage among Pacific and Red Sea Coral Reef Creatures. N.p., n.d. Web. 25 Feb. 2015
  23. Triggerfish, Triggerfish Pictures, Triggerfish Facts -- National Geographic." National Geographic. N.p., n.d. Web. 25 Feb. 2015.
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