Evolution: Survival: Coral Reef Connections
For predators caught at depth and consuming reef prey, the Western and Central Pacific Ocean through Predator-Prey Relationship Studies. The sea is full of all kinds of beasts that could easily make a meal out of a man, but fortunately, these top ocean predators have other prey in mind! mainly eat different types of fish, but have been known to bite other large marine animals, as well as humans. 5 Symbiotic Relationships in the Ocean. Theoretically, the interaction between marine mammals and their prey insight into the effects of predator-prey relationships on ecosystem dynamics and.
Unfortunately, they are poorly equipped to defend themselves against predators, such as barracuda, but some find protection by schooling with better-armored fish. Algae occur in a kaleidoscope of forms and colors on the reef, but they have one main function: Thus they are called "primary producers.
One important algal group, benthic bottom-dwelling algae, rapidly grows over dead coral and other inert objects, providing a grazing yard for herbivores, such as parrotfish. Their gentle disposition disappears, however, in the presence of another favorite food: When feeding, the butterflyfish turn into vicious predators, darting in to rip off the anemones' fleshy tentacles.
Having evolved resistance to the anemones' toxins, they need only get past clownfish guards to pick off a delicious meal. Packed with miniature toxin-loaded harpoons nematocyststhe tentacles of sea anemones provide an excellent deterrent against almost all would-be predators. Saddled butterflyfish, though, have evolved resistance to the toxins and apparently relish the tentacles.
Still, to grab a meal, the butterflyfish must get past the anemones' second line of defense: One such predator, the smallscale scorpionfish Scorpaenopsis oxycephalaclosely resembles the reef's rocky, algae- and coral-encrusted bottom, where it lies in wait for crustaceans and small fish, such as gobies.
Safely tucked in coral crevices or half-buried in sand and rubble, gobies Gobiidae family maintain a low profile on the reef to avoid predation. In addition, they have evolved independently swiveling eyes that constantly search the water for potential attackers. But their efforts can be foiled by ambush predators, like the smallscale scorpionfish, whose camouflage prevents gobies and other prey from seeing them until it's too late. The two fish benefit by the association; a third fish, however, has evolved to take advantage of them both.
Using a devious disguise and copycat behaviors to attract larger fish, the fanged ambush predator, called a fangblenny, rips living tissue from surprised prey. In the world of predators and prey, the normal rule is that big creatures eat smaller creatures.
But sometimes the tables are turned, as in the case of the bluestriped fangblenny Plagiotremus rhinorhyncosa small but sinister predatory fish. Evolved to perfectly mimic the bluestreak cleaner wrasse, the fangblenny falsely advertises cleaning services to larger fish, such as the reef lizardfish.
Once the bigger fish moves in close, the fangblenny attacks and darts away with a mouthful of sushi. With beautiful, ornately designed shells, coneshells are highly sought-after by shell collectors. These gastropods have evolved as deadly predators, however; a single puncture from their venomous radula modified tooth can rapidly paralyze and even kill a human.
Of course, coneshells evolved not to defend themselves against collectors, but to efficiently kill prey, such as the blueband goby. Gobies are the most diverse fish family on the reef, with more than species described. The trophic level refers to the position an organism occupies in a food web. We also care about other upper-trophic predators such as seabirds, seals, whales, dolphins, and sharks.
These complicated relationships are why we have developed laws and mandates to protect the whole ecosystem, not just one part. Predators can be either specialists or generalists. Specialists like brown pelicans need one or two prey types to survive and reproduce, so a lack of either of those causes problems. Generalists may be able to switch between two or more prey types, eating whatever comes their way, but they may still have restrictions—such as prey that is the right size, particularly for a small seabird chick; in the right place, like near a breeding colony where parents must return to feed young or along a migration route; or available at the right time, including during breeding when more food is needed or in winter when other food is scarce.
The prey must also contain enough energy because lack of a particular fatty, energy-rich species such as anchovy can slow predator growth and cause problems with nutrition, eventually leading to unhealthy populations. How do these results apply to other marine ecosystems? Since other predators in the California Current also seem to follow this one-third rule, then other predators in systems around the world may follow it as well.
This rule also seemed to hold for different prey types, including small pelagic fishes, including sardine and anchovy; juvenile predatory fishes, such as rockfish; and invertebrates, like squid.
In the Gulf of Alaska and Bering Sea, killer whales have been implicated as a contributing factor, but not the main one, in the decline of Steller sea lions and harbor seals through the s. Field observations along the Aleutian Islands indicate that these population declines were followed by a decline of sea otters in the s and that this decline was caused by killer whale predation. Killer whales may have begun supplementing their diet with sea otters because they could not sustain themselves on the low numbers of remaining seals and sea lions.
It is not yet clear what ultimately caused the decline of Steller sea lions and began this spiraling change of events. However, it is apparent from mathematical calculations of population sizes and energetic requirements that there are sufficient numbers of killer whales in Alaska to prevent the recovery of pinniped populations. Thus, it is conceivable that populations of pinnipeds and otters may not recover to former levels of abundance until the predation by killer whales is reduced by a reduction in killer whale numbers or by a shift in killer whale diet to other species of mammals such as dolphins and porpoises.
In addition to directly affecting the abundance of their prey, marine mammals can indirectly affect the abundance of other species by outcompeting them or by consuming species that prey upon them. Contrary to popular opinion, the harbor seals were likely benefiting salmon because they affected the abundance of hake, a species of fish that is one of the largest predators of salmon smolts.
However, the immediate result of the cull was not an increased number of salmon caught, but a decrease and failure of the razor clam fishery. It turned out that the seals were primarily eating stariy flounder, which fed on the razor clams. Without the seals, the predatory flounder population grew unchecked. Species such as crabeater seals Lobodon carcinophagaAntarctic fur seals Arctocephalus gazellaleopard seals Hy-drurga leptonyx and penguins chinstrap, Adelie, and macaroni increased and moved the Antarctic marine ecosystem to new equilibrium levels.
Increases were also observed in minke whales Balaenoptera bonaerensis and squid-eating king penguins due perhaps to reductions in the respective abundance of blue whales B. All of these species appear to have directly benefited from an increase in prey, which was caused by the removal of whales. Penguins and seals may now be hindering the recovery of baleen whale stocks in the Antarctic.
Marine mammals are generally considered to be opportunistic foragers who select from a number of alternative prey according to availability. This is based on the relatively large number of different species that have been reported in the stomachs and feces of marine mammals. Steller sea lions, for example, are known to eat over 50 different species of fish, and even the occasional seabird. However, their diets are typically dominated by 5 or fewer species, suggesting that they may not be truly opportunistic feeders.
Little is yet known about the choices that marine mammals make when foraging.Food Chains Compilation: Crash Course Kids
Presumably what marine mammals eat is a function of nutritional value, ease of capture, and digestibility, all of which are invariably linked to the abundance of both predators and prey. These are complex biological interactions about which little is known. Functional response curves represent rates of predation in relation to the density of prey. In most species, the rate of capture rises with the density of prey to some maximum level.
These relationships between prey density and predation rates tend to be nonlinear and asymptotic, indicating that there are maximum limits to the rate that predators can capture and process prey, which are independent of prey population size.
Marine Predator-Prey Relationships: Study Says Prey Density More Important Than Total Biomass
Establishing these functional relationships for different species of prey is fundamental to fully understanding the foraging ecology of marine mammals. This has not yet been done for marine mammals and will require experimentation in captivity or observational studies in the wild using electronic data collection techniques.
Ecosystem models are another technique for gaining insight into the effects of predator-prey relationships on ecosystem dynamics and structure.
- Ocean Predators Need a Quarter to a Third of the Prey Population to Maintain Productivity
- Marine Predator-Prey Relationships
Using a series of mathematical equations to account for the flow of energy from one group of species to another, the models can estimate the extent of competition between species and the effect that changes in abundance of one species will have on other species in the ecosystem. One such model was constructed for the Bering Sea to understand whether the declines of Steller sea lions and forage fishes such as herring and the increases in pollock and flatfish between the s and the s were related to the commercial removal of whales.
Removing historic numbers of whales from the simulated ecosystem resulted in an increase in numbers of pollock.