Sharks play a vital role in our oceans' ecosystems
Source:
SBS Learn
6 Oct 2014 - 9:50 PM  UPDATED 16 Oct 2015 - 2:17 PM

Q1 Decreasing shark populations


Sharks live in every ocean of the world from the icy poles to the warm tropical waters.

Of the world’s approximate 350 species of shark, 180 live in Australian waters. Eight species are protected in the Australian Fishing Zone because, as apex predators of the marine food chain, sharks are vital to maintaining a balance in our oceans’ ecosystems.

Sharks are highly migratory and tend to always be on the move between habitats in search of food. This behaviour puts them at risk from fishing vessels because they are attracted by bait or other smaller fish and regularly become entangled in nets ending up as bycatch. Bycatch is the discarded waste left over after fishing vessels sort their catch. Twenty-five per cent of shark (and ray) species are listed as threatened with extinction by the IUCN, mainly as a result of fishing practices

The practice of shark finning is also a threat that is causing some species to decline significantly in populations. Live finning is banned in Australia, however, the AMCS reported that Australia exported at least 178 tonnes of shark body parts including fins to Hong Kong, the Philippines and Singapore in 2012.

A shark’s size is not an indication of its maturity; in fact, they vary in size from 25 centimetres to 18 metres. Unlike other species, they take a long time to reach sexual maturity and only start reproducing late in their life span. This slow reproduction rate coupled with risks associated with industrial fishing has impacted shark numbers. As a consequence, there are serious concerns that depletion of shark populations may upset the marine ecosystem at which they’re at the top.

 

Q2 What is shark finning?


Live shark finning is when sharks have their fins removed before they’re thrown back into the ocean, sometimes alive. Unable to swim or hunt, the finless sharks drop to the sea floor where they slowly die.

Ninety-five per cent of all shark-fin consumption is in Asia. They are regarded as a delicacy, particularly in Hong Kong where shark-fin soup can cost as much as $1,000 in a restaurant. Like flake in Australia, when buying or consuming shark fin, there is little way of knowing what the species is. The worldwide demand for shark fins is having a severe effect on shark populations.

Shark finning is illegal in Australian Commonwealth waters up to a distance of 322km offshore. It is, however, possible to buy shark fin in Australia from imported and Australian sources.

 

Q3 Why should I care about endangered sharks? 

As apex predators that have inhabited our oceans for more than 400 million years, sharks are crucial to the natural order of things in our oceans’ ecosystems. Since industrial fishing began in the 1950s the world’s shark populations have decreased by 90%. Each year 73 million sharks are killed around the globe.

There is increasing evidence to show that overfishing has economic consequences. In the American state of North Carolina, scallop farmers faced significant losses when it was found that cownose rays were eating their shellfish. When delving deeper into the issue, scientists discovered there was a proliferation of these rays as a result of a decline in their predators, sharks, due to overfishing in the area. 

Read more about the decline of sharks and its impact in North Carolina.

When one species is removed from the food web an ecological imbalance may occur. This can produce a decline in the numbers of some species and a proliferation of others. There are fears that the balance of marine ecological health is in global decline and that some species may eventually become extinct.

Flake is the common species cooked in fish n’ chips but threatened species such as school sharks are also sold in fish n’ chips servings. Without any regulatory obligation for these sellers to tell you what is under the batter you may be consuming a threatened species without knowing it. When commercial fishing trawlers fish for unthreatened shark species threatened species can also be caught as bycatch. A new standard in Australia has recently been introduced to limit flake to gummy shark. However it may take some time for these new regulations to come in to full effect so it is still good to ask what species you are eating.

 

Q4 ACTION What can I do?

 

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