The problem with overfishing

Diagram credit: University of Waikato

Diagram credit: University of Waikato

Ocean overfishing can be described as simply depleting fish stocks at rates that are too high for the fished species to replace by reproducing. Overfishing is a non-sustainable use of the oceans because catching more fish than the system can support leads to the overall deterioration of the system.

The demand for fish is increasing at an annual rate of 3.2 percent, outperforming world population growth at only 1.6 percent. The combination of population growth, urbanisation, rising incomes and the expansion in fish production has meant that fish consumption per capita has increased from an average of 9.9 kg in the 1960s to 19.2 kg in 2012.

The increase in fishing efforts over the last 50 years to meet the demand for fish in addition to unsustainable fishing practices have pushed many fish stocks to the brink of collapse. According to Food and Agricultural Organisation (FAO) estimates, over 70 percent of the world’s fisheries are either overexploited, fully exploited (and in imminent danger of overexploitation) or significantly depleted.

Due to the collapse of coastal and pelagic fisheries around the world, the fishing industry are now having to go deeper in the ocean and further down the food chain in order to obtain catches. In fact up to 40% of the world’s fishing grounds are estimated to be in waters deeper than 200 metres. It is only a matter of time before these fisheries too are returning lower and lower yields.

A study published in the journal Science in 2006 has predicted if fishing continues at the current rate then all of the world’s fisheries will have collapsed by the year 2048.

Targeting top predators such as tuna, sharks and billfish eventually disrupts marine communities, resulting in an increased abundance of smaller organisms (such as plankton, krill, anchovies etc) at the bottom of the food chain, which ultimately affects the rest of the marine ecosystem. Each species has a role to play to keep the oceans productive and so if the food chain breaks then it will have a consequence on all organisms in the food chain. For example overfishing may cause increased algal growth and threats to coral reef health.

Overfishing not only affects the balance of life within marine food chains, but also the social and economic wellbeing of coastal communities relying on fish for their livelihoods. Approximately 1 billion people depend on fish as their primary source of protein particularly in developing countries. In addition fishing is the principal livelihood for millions of people. Overfishing therefore threatens their long-term food security. Many fisheries have closed as a result of excessive fishing including the Atlantic Canadian Cod fishery in the 1990s. Overfishing does not guarantee that people’s livelihoods are protected because eventually people will be out of work as the fishing business won’t be sustained.

On top of these impacts, many modern fishing methods are unsustainable in their own way by being severely destructive. Bottom trawling, for example, is capable of destroying entire habitats on the bottom of the ocean floor. Other destructive fishing methods include beam trawling, gill netting and bycatch. These unselective fishing practices and gear cause huge destruction on non-target species. Bycatch for example causes the unnecessary death of billions of fish as well as marine mammals and turtles.

In order to meet the growing demand for fish and in an environmentally sustainable way, the fishing industry needs to ultimately stop taking fish faster than the oceans can replenish and improve fishing practices so it is not wasteful and damaging. This can be achieved by increasing fisheries management oversight, government regulations and the traceability of fishing activities so that the rules and regulations that exist are better implemented and enforced. One key part of the overfishing crisis is the illegal, unregulated and unreported fishing and so attempting to prevent this from happening would be hugely beneficial.

The establishment of Marine Protected Areas will play a huge role in conserving and boosting fish stocks. Only 1.6% of the oceans are currently designated as MPAs and approximately 90% of existing MPAs are subjected to fishing. No-take zones are essential for healthy oceans since they allow depleted fish populations to recover and also provide a source of refuge for other species. These protected areas also allow the oceans to recover from other anthropogenic threats such as bleaching, which will not only sustain the vast biodiversity, but also improve food security for those who rely on the ocean for their daily sustenance.

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Lucy Grable

Lucy Grable

MSc Species Identification and Survey Skills student at Reading Uni | BSc Marine Zoology | Website Editor MARINElife | Zanzibar humpback whale researcher|Marine wildlife enthusiast

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