Marine Fisheries: To Fish or Not To Fish

Since the dawn of time, we have reaped the bounty of the oceans. But with the scale and intensity of modern day fishing the marine fisheries we rely on are under threat. With warnings of an impending global good crisis, Sophie Maycock gets the facts on this worrying problem, and investigates possible solutions.

Marine fisheries are responsible for supplying 100 million tonnes of food, a staggering 19% of total human animal protein for consumption. But these fisheries are now in peril across the world especially throughout the Atlantic, Pacific and Mediterranean. The marine fish catch has reached its upper limit and plateaued since the 1990s, with the Food and Agriculture Organisation (FAO) recording a significant shift in fish landings over the past 50 or so years.

The global fish market is huge business employing approximately 200 million people worldwide with revenue of approximately US$ 70 billion per year globally. Of this sum, US$ 13 billion is predicted to be exports from developing countries and therefore this market has huge social, economic and political ties.

Although marine resources do fluctuate naturally on their own, the FAO now predicts that we are removing approximately 8% of the oceans’ total primary productivity per year, meaning that 22% of fish species are over-exploited in an unsustainable manner. Furthermore, landing has shifted over the past 50 years to smaller fish, invertebrates and planktivorous fish, meaning that marine ecosystems are changing globally. Directly, fishing clearly decreases global fish stocks, leading to the collapse of some species such as in the anchovy fisheries of Peru and Chile, Japanese and Californian sardines, the Canadian cod and New England groundfish. Fishing can have far more complex effects, both directly and indirectly, degrading the ocean ecosystem as a whole. For instance, size-selective fishing means that average size, age, and genetic diversity of a species can be affected, causing reduced resiliency of the species as a whole. Similarly, increasing capture of juveniles or undesirable species by accident has also affected non-target species across the globe.

Indirectly fishing can also radically alter near-shore ecosystems by either changing or destroying the benthic habitat. Dredging, trawling and long-hauling or the use of explosives can remove the bottom dwelling organisms vital to the structure of the seafloor. For instance coral reefs and seagrasses have been seriously damaged, causing dramatically decreased recruitment and increased predation for many species which use these areas as nurseries or for shelter respectively. Furthermore, the effects of marine fishing are also impacting inland waters, with marked declines also reported in many freshwater habitats across the globe.

This global crisis is thought to be caused by many factors, including poor management, over-capitalisation and poor understanding of the environment.

Firstly, the huge market for fishing and vital economy that it provides for hundreds of countries across the globe means that many governments are supporting increased harvest rates due to social pressures. Thus we find the need for management strategies that make fishing viable and sustainable for everyone, particularly those in developing countries which rely on the industry so greatly to support their economy. However, management strategies have failed to achieve sustainability and this is thought to be in part due to a lack of ecosystem specific approaches. Difficulties in sampling complex marine environments make it very difficult to map population fluctuations and makes predicting when a population is near collapse almost impossible. Furthermore, there are huge gaps in the data, particularly in less-economically developed countries, meaning that the true extent of the ever declining fish-stocks becomes even harder to estimate. Similarly, the true decline of global populations can be masked by the opening of new fisheries.

To avoid a global food crisis due to the collapse of the marine fisheries we would ideally decrease the mass we remove from the ocean in a year to a more sustainable level, but growing global populations appears to make this impossible. Therefore, we need far more accurate and regular data collection to monitor wild fish stocks across the globe, coupled with ecosystem-specific approaches and adaptive management of each area under pressure. Areas should be seasonally fished and given periods to recover under protection, with consideration given to other ecosystems such as nursery habitats which are vital to support the ocean ecosystem as a whole. Similarly, protecting juveniles and breeding stock would allow some recovery from these population declines. The Ecological Society of America has now advocated a holistic approach to the interactions between species in an ecosystem, to achieve sustainability through active management and the rest of the world would follow suit. But with mounting pressures of impending climate change, global economic crisis and drastic population growth, has the world left it too late to protect our oceans?

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