Never before in human history have our oceans been under so much threat from human activity. Many scientists believe we are entering the sixth major extinction event in the history of life on earth. In the oceans, nearly 20% of the 1,045 sharks and ray species, 12% of groupers and 86% of marine turtle species are threatened with extinction. Biodiversity extinction rates are currently around 1,000 -10,000 times higher than historical background rates and this has been caused directly or indirectly by man.
These high extinction rates and the reason so many species are threatened in our oceans (particularly over the last 50 years) has been a direct result of overfishing. Commercial fisheries have advanced in fishing methods, using bigger nets and faster boats and, due to increasing demand, they have deployed harmful and destructive fishing practices such as FADs (fish aggregrating devices), purse seine nets, longlines and bottom trawling. These harmful fishing practices capture anything and everything in their nets, not just the target species and in doing so, species such as turtles and sharks are caught. This is known as bycatch.
Adding to the concern is overfishing at the single species level (targeted fishing). Many of the fisheries that capture marine products focus on top predators such as sharks, marlins, swordfish and tuna. Removing vast quantities of large predatory fish can alter marine ecosystems out of proportion to their abundance. The problem is not only assigned to poor fisheries management; many indirect human activities such as coastal development, alien species, habitat loss, fertiliser run-off, pollution from shipping traffic and sewage disposal are all compounding the problem.
Shark and ray species are currently threatened from targeted fishing and as bycatch. Sharks are particularly vulnerable due to the lucrative market for shark fins that has rapidly grown over the last 20 years. The demand is coming from Asia, where shark fin soup is considered a delicacy. Hong Kong is one of the largest traders in the shark fin market, representing at least 50% of the global trade. It is estimated that around 70–100 million sharks are killed each year for their valuable fins (dorsal, pectoral and tail). Find out more
Sea turtles are one of the most vulnerable animal groups in the marine environment. Used for food, medicine and kept as pets, including aquaria, the eggs, juveniles and adults are all targeted. They are particularly vulnerable due to the variety and number of threats they face. The seven species of sea turtle rely on ocean systems for migration, where many of them get caught in longlines and end up as bycatch, but they also rely on terrestrial systems for nesting. Poaching of eggs has been a huge problem over the last 20 years along with loss of nesting sites due to coastal development.
Whales and dolphins have been hunted for hundreds of years for a wide range of reasons. The whaling industry reached a peak in the 1950s and 60s when around 70,000 were killed every year. An international moratorium (ban) was eventually imposed in 1986. However, Japan, Norway and Iceland together still kill over 2000 whales each year. Dolphins face a wide range of threats including noise pollution, hunting and capture for entertainment. The biggest threat, however, is the wide range of fishing methods that capture dolphins as bycatch. Find out more
Tuna stocks around the world, in particular those of the five main commercially sought-after species – skipjack, bigeye, yellowfin, bluefin and albacore – are a very serious conservation concern due to ever-increasing fishing pressures. Unfortunately, tuna is one of the world’s favourite fish and, as a result, fetches a very high price at market. In addition, tuna is at the heart of the luxury Asian sushi and sashimi markets. In Japan, a single bluefin tuna (Thunnus thynnus) can sell for up to $400,000. Quotas are set for tuna fisheries but it is widely believed that they are too high and that they are violated by as much as 50%.