Predation,+the+declining+numbers+of+predators+in+coral+reefs.

Predation, the declining numbers of predators in coral reefs.

Rachael Alfaro

Northeastern State University

I. Introduction

The Clown fish closes in on a crustacean creeping along the ocean floor of the Great Barrier Reef, as it strikes and begins to ingest the much needed meal it is then attacked from behind by a Moray Eel.(Wikipedia,2013) This is just an example of how many fish are considered predators. When thinking of predators in general the first thing to come to mind is probably large voracious species. Like the example above this is not always true.There is much more to predation than just the obvious large predators.

(photo courtesy of [|summitcountyvoice.com]  )

II. Predation

II a. What is it?

Predation is when two organisms have a symbiotic correlation and one species is acting as a predator and the other functions as the prey. Predation can serve as population control for instances if prey numbers are on the rise then predators in that area are probably scarce and vice versa (Biologyonlinedictionary). There is a hypothesis of Predation that discusses the interactions between species at different trophic levels or levels of nutritional value of the organism. Top-down is one form of an interaction. It means that when the trophic levels are low in a species then a species with a higher level is exerting a large influence on it. A low species example would be an herbivore, and a high species would be a predator in this case. Predators can uphold species richness while in low trophic levels by changing the prey to something that is more abundant than their usual choice.

This hypothesis theorizes that predators will drive to a point where extinction occurs to prevent prey species from competing with their ranks. When a prey species is rare the least likely they are to be taken out by a possible predator, this is because when there are more of a possible prey species that is what will go first.(Kricher,2011)

(photo courtesy of thewildclassroom.com)

II b. Where is it more common?

Predation is common everywhere there are living organisms. From the smallest bacteria to large predators like lions. The predation in the coral reef is very common and there is a vast variety of organisms living there at all times. Big predators are beginning to become limited in coral reef habitats. Fishing is thought to be the principal factor in the decline. People will pay top dollar for coral reef predators. Two large contributors are live reef fish food, and shark fin fishery trades. (2011)

Predation can also vary upon depth in the coral reef or ocean in general. A study was done in North Atlantic coral reefs on newly settled species. They found that the Grunts of this species, Haemulon settled in shallow habitats. And as they progressed there depth of the habitat would change with their maturing. (Jordan, Lindeman, and Spieler, 2012)

III. The decline of predators in coral reefs (photo courtesy of [|www.nceas.ucsb.edu]  )

III a.What is causing it?

As mentioned in the previous paragraph there has been a recent decline in predators in coral reefs in the recent years. (2011) Fishing has a huge impact on these predators even sustenance fishing has shown to lower the reef predator numbers. The evidence that they have found shows that the predator removal from the ecosystems may be triggering something called trophic cascades, (2011) where the chosen trophic levels of the predator lowers which in turn lowers the next lower trophic species and so on.(Wikipedia, 2013) The trophic cascades then result in phase shifts. They appear to be found in more alal-dominated reefs which have small echinoderms and plankitvorous fishes. Altogether these studies have indicated that conserving the top predators in coral reef habitats is very important to the conservation and understanding of their species. There has already been a significant amount of top predators removed which has altered the coral reef systems. An example of this is the extirpation of spawning accumulations of top predators in the coral reefs due to overfishing of predators as in snapper, and grouper. (Jordan, Lindeman, and Spieler, 2012)

III b. Why are coral reefs so vulnerable?

The coral-reef in general is vulnerable do to its high instability and diverse ecosystem with many required adaptations. Predation is a competition in these communities. Since there is a low survival rate, numerous attempts to reproduce are needed, using large size and longevity as an advantage. A small population turnover rate is the result. All of the decline in predators can lead to lower amounts of specific nutrients as oxygen, and salt contents that the fishes provide to keep a healthy balance with the coral. Without all of this harmonious balance the coral would collapse (2013)

III c. What can be done to stop?

A great example of conserving the reefs from depleted predators is in the Great Barrier Reef Park. To protect critical areas they have formed fishing specific zones which were created by the Australian Commonwealth. Examples of the zones are as follows: During the 2003 year, 4% of the total park area was “no-fishing zones, which included 24% of coral reef. There needs to also be an effective conservation program, that will determine the impact of the actions by management, and to understand the drivers of overfishing in general. (2013)

media type="custom" key="23510598"

IV. Conclusion

Predation is a very important part of the working ecosystem of the coral reefs. As in every trickle down prey and predator system there is a fine line between predator and prey. There must be enough of both to maintain a well working harmonious environment for fish and other organisms to live in. Without one or the other there would be mass chaos to the reef structure and life in general. The trophic levels of fish living in the coral reefs are also very important. There must be a balance of high and low levels to maintain species control. (Kricher, 2011) The overfishing of the large predators in coral reefs is a very big obstacle that we must overcome. While in fact us as humans use a lot of these fish as resources we must not let that interfere with the overall survival of species. To keep this under control we must take action as soon as possible. Whether it is creating fishing zones or banning of certain areas completely until the habitat can rebuild. (2013)

V. References 1. Amphiprioninae. (n.d.). In Wikipedia. Retrieved July, 2013, from http:..en.wikipedia.org/wiki/Clown_fish

2. Predation. (n.d). In Biology-Online Dictionary. Retrieved from http://www.Biology-online.org/dictionary/predation

3. Kricher, J.C. (2011). Tropical Ecology. Princeton, NJ: Princeton University Press.

4. Journal of Marine Biology Volume 2011 (2011), Article ID 725602, 14 pages doi: 10.1155/2011/725602

5. Jordan, L. B., Lindeman, K. C., & Spieler, R.E. (2012). Depth-Variable Settlement Patterns and Predation Influence on Newly Settled Reef Fishes. (Haemulon spp., Haemulidae). Plos ONE, 7(12), 1-11. doi: 10.1371/journal.pone.0050897

6. Human Impact on The Great Barrier Reef. The University of MIchigan. (July 19th, 2013). http://sitemaker.umich.edu/gc2sec7labgroup3/over-fishing