Tuesday, November 24, 2009

Prawn Fisheries: A Net Loss

“Give a man a fish and he will eat for a day. Teach a man to fish and he will eat for a lifetime.” – Chinese proverb.

For millennia humans have taken from the seas. As hunter gatherer tribes we learnt to rely upon the ocean’s bounty to feed ourselves and our villages. Historically, humans have occupied coastal settlements and lived in harmony with the surrounding ecosystems, taking to the seas with spears, lines and nets to gather edible marine life. In the last fifty years, the population of our planet has exploded to the extent that we now have more than twice as many mouths to feed. This population explosion is still happening at an exponential rate, and with every passing day we increase our demands on the planet’s precious natural resources. Long gone are the days of the Chinese proverb when fishing meant feeding your family; we are now a global population of seafood lovers, with an appetite far greater than ever before. How long will it be before we are left fighting over the scraps of a plundered ocean?

Bluefin tuna for sale at Tsukiji Fish Market, Japan

To meet ever-increasing demands, we have devised more efficient, more intensive fishing methods which increase catches to a level that can fuel the global fish market. One of the most destructive and intensive of these practices is trawling. This involves sinking a weighted net to the bottom of the ocean and dragging it along seabed. The nets can be kilometres wide, and will trap anything in their path, often removing things like corals from the seabed, thus destroying entire habitats and anything that inhabits them. Bycatch from these nets can often include turtles, sea birds, and even marine mammals such as dolphins and whales!

Trawlers will typically target one individual species, and so edible fish such as tuna and sharks are often discarded as bycatch and thrown over the side, dead or alive. According to the WWF, up to 30 million metric tonnes of bycatch is dumped back into the ocean every year.

A deep sea bottom trawler hauling in the catch

The most wasteful of trawl fisheries is prawn fishing, and it is estimated that for every 1kg of prawns taken from the ocean around 15kg of bycatch is discarded. In the Gulf of Mexico alone shrimp trawlers drag up 35 million juvenile red snappers as bycatch every year (WWF); enough to have a devastating effect on the population. A number of countries have banned deep sea trawling in their waters and imposed the use of Bycatch Reduction Devices (BRDs) in an attempt to reduce the impact of intensive fishing on their marine environment. However, trawling is still the only method to fish for prawns on a commercial scale and continues uncontested in international waters.

Endangered species such as turtles and sharks are often caught as bycatch. For every 1kg of prawns, we waste 15kg of marine life.

An alternative to trawling for prawns is prawn farming. Rearing prawns in ponds is a common practise in tropical regions especially and can produce huge yields. This aquaculture method is however no less destructive to the environment. Areas suitable for prawn ponds are typically located along the coast as they need salt water. In order to make way for the ponds, aquaculture companies will have to clear mangrove forests which are important habitats for both marine and terrestrial life. Mangroves are essential to the health of our oceans as they are the nursery grounds for our fish and act as a natural coastal defence, protecting the land from tsunamis and protecting the coral reef from sediment runoff. According to the UN Food Agency we have destroyed 20% of our mangroves in the last 30 years alone, making it the fastest disappearing ecosystem on the planet.

Furthermore, prawn farms require a large amount of fish to feed the captive prawns; for every 1kg of prawns harvested,2kg of fish is needed as feed. These fish are usually small species with little market value, however they are species which many poor people typically rely on to form the main source of protein in their otherwise restricted diet.

Prawns are a favourite of seafood lovers the world over, but how much longer can we sustain the demand?

Currently there is no guaranteed way to ensure that the prawns you buy in supermarkets or restaurants are ethically sourced. Due to the nature of their harvesting, prawns are one of the most environmentally damaging food options available to us. Unlike issues such as climate change which some may explain away as a ‘natural phenomenon’, this problem is undeniably manmade and the solution is clear; reduce the demand and we reduce the destruction.

Please feel free to add your comments below; we would like to hear your opinions on this matter.

1 comment:

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