As Brian sails the Atlantic Ocean, we reflect on the problems caused by extensive fishing of the world’s oceans.

Over 200 million people are dependant upon fishing for their livelihoods, and 1 billion rely on fish as their primary source of protein ⁽¹⁾.  This high demand is a major threat to marine biodiversity. Unsustainable fishing practices are causing fish stocks to decline to the point where many are no longer economically or biologically viable.  As the prey species of top predators vanish, food chains collapse and marine ecosystems suffer.  Overfishing can lead to the loss of entire groups of species and the functions that these species provide in the ecosystem.

Other overexploited marine species include shellfish (e.g. clams, lobsters, prawns) and large animals such as whales and sharks.  Sea cucumbers are collected in huge numbers in the tropics to be sold as a food delicacy in countries like China and Korea.  This is an extremely valuable source of income to communities in developing countries, particularly South Pacific islands, but if it remains unchecked, the resource will be eliminated and the income will vanish.  The shark finning industry is the cause of much controversy and campaigning by organisations such as the Shark Trust, who are trying to stamp out this wasteful and inhumane activity that is decimating many shark populations.

By-catch is another major impact of fishing, whereby animals such as turtles, seabirds, sharks and dolphins become accidentally caught on fishing hooks or in nets.   Huge numbers of these species are caught every day and discarded, dead or dying.  Long-lining for tuna and swordfish has a particularly high by-catch rate.  Methods are being developed to attempt to reduce this, but the struggle to persuade commercial fishing operations to adopt them is difficult.  A less widely known issue is the discarding of hundreds of tonnes of unwanted fish that occurs on nearly every commercial fishing trip.  In fact, a quarter of all fish caught in the North Sea and North Atlantic are discarded.  Reasons for this include low market value, fish being below minimum catch size, quotas being reached, lack of storage onboard, and so on. In some cases, commercially valuable or threatened species are discarded because the vessel is not permitted to catch that particular species.

Declining fish stocks have a huge effect on predators such as dolphins and sharks. Scientists on Earthwatch projects past and present, such as Spanish Dolphins and Dolphins of Greece have been working to address this problem.  Earthwatch scientists from our Dolphins of Greece project have been studying the decline of common dolphin (Delphinus delphis) around the Greek island of Kalamos and found the cause to be overfishing of their prey.  Those blamed are the modern commercial seine net fishing boats which now compete with the local artisanal fishermen.  Research by Earthwatch scientists is being used to inform recommendations for management policies to help prevent this dolphin population, and others, from disappearing completely.

However, it is not all doom and gloom! For the fish lovers amongst us we can make the right choice and eat sustainably sourced fish, as not all fishing practices are unsustainable. Consult the Marine Conservations Society’s Good Fish Guide, and see Earthwatch’s recent article on how we can “Have our fish(cake) and eat it” for more information.

Find out how you can contribute to the Earthwatch oceans appeal by visiting www.earthwatch.org/europe/oceansappeal.

Until next time, keep up the good work Brian and best of luck with the next leg of the journey.

Nat Spring, Senior Research Director (Earthwatch)

⁽¹⁾ FAO (2000) The State of World Fisheries and Aquaculture 2000. FAO, Rome, Italy