Wally and Tony

The Shark's Helpful Role in the Ocean

Sharks play an important role in the ocean food chain. If sharks decline to seriously low numbers, commercial fisheries could be threatened. In Australia, one lobster fishery is threatened, because the declining number of sharks cannot control the lobster eating octopuses.

Photo by J. E. Maragos

Puppet Lobsters Lobster

Photo by J. E. Maragos

Puppet Octopuses Octopus

Sharks reproduce similar to mammals in that they have a low rate of reproduction and do not spawn like fish which have a thousands or millions of larvae, hoping for a certain percentage to sustain the species. Sharks play an important role at all tropic levels of the ocean ecosystem from scavengers to super-predators. Scavengers prey upon dead or dying animals, super predators help to control populations and maintain prey species diversity by concentrating on the most available species. Is important to the ecology of the seas by removing the weakest, sick and dead so that the fittest survive.

Photo provided by U.S. Fish & Wildlife Service

Shark eating prey

The balance of the ecosystem is extremely important because all organisms belonging to the ecosystem depend upon each other to maintain this balance. All living organisms within an ecosystem are called a community. The organisms within a community are co-dependent upon each other. The relationship between these organisms form a food web. A food web is a series of interconnecting food chains. The intricate links between organisms supporting each other form a food chain. This food chain is only one strand in a complex tangle of relationships. The marine food chain in Coral Bay consisted of:

Lobsters who were eaten by octopuses, who were eaten by sharks.

Octopuses eating Lobsters
Shark eating Octopuses

Plants form the base of almost every food chain on Earth. Plants use energy from the sun to make their own food through photosynthesis. In turn, some animals eat plants, and other animals eat the plant eating animals. Like on land, most animals that live in the ocean depend on plants for food. And at the bottom of the food chain is probably the most important - phytoplankton. Millions of these tiny marine plants drift near the ocean's surface. Tiny animals called zooplankton eat the phytoplankton as well as clams, corals and small fish. Animals such as fish, jellyfish and even some whales eat zooplankton. Larger fish and animals eat some of the animals that eat zooplankton and so forth. If one link within this food chain were missing it would create adjustments or an imbalance within the community. If the large shark was missing in this food chain, the large predator fish population would grow. This may cause depletion of the smaller prey fish, causing an imbalance. Therefore, the population of a species is also an important aspect of the ecosystem hierarchy. Every ecosystem, no matter how fragile, supports an individual. Sharks eat the weak, sick and dead fish which maintains a healthy ocean ecosystem, enabling the fittest to survive.

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