Saturday, March 1, 2014

Where Have All The Fishes Gone?

Atlantic Dawn
Ever since mankind discovered fish were good eating we've been harvesting them from the sea. Going from primitive spears and nets in dugout canoes to massive factory fishing trawlers capable of on board fish processing, we've also become increasingly sophisticated and efficient in our fishing techniques.  In fact we've become so efficient we're now in danger of completely wiping out most of the commercially valuable species that exist.

Take, for example, The Atlantic Dawn, the largest and most technologically advanced fishing trawler in the world. This Irish ship is more than 470 feet long with a crew of 63 and two 10,000 horsepower engines that can propel it up to 18 knots and pull nets hundreds of metres wide through the ocean. Also referred to as a midwater trawler, where the nets are pulled through free water, as opposed to a bottom or demersal trawler, where the nets are towed along the sea floor. When operating at full capacity it can catch, process, and freeze 400 tons of fish a day, store 7,000 tons of frozen fish in its hold, and stay out at sea for 5 weeks at a time.  

Midwater trawling catches pelagic fish such as anchoviestuna, and mackerel, whereas bottom trawling targets both bottom living groundfish such as flounder, halibut, and sole, and semi-pelagic species such as cod, squid, shrimp, and rockfish. However, while trawling has been around since the 15th century the main problem with this method hasn't changed; namely lack of selectivity.  Marketable fish of both legal and illegal size get caught, along with non-target fish, and animals such as dolphins, sea turtles, and sharks. And, with bottom trawling, there is unbelievable damage to the environment as a result of gear being dragged over the seabed.

Yet another type of net is the gill net that traps fish as they try to swim through a seemingly invisible mesh that has been set up either on the ground or allowed to float freely in the water. These set nets or drift nets can be up to 50 kilometers in length and, while they have little or no impact on the ocean floor, they still catch plenty of non-target fish and, if they get lost or abandoned, they drift through the water as ghost nets catching anything in their path. Whales, seals, and dolphins are the most susceptible, and the piteous images of them caught up in the netting is truly heartbreaking.

Sea lion caught in net

An even more alarming development however is the Russian factory ship Lafayette. A fishing vessel with no ability to actually do any fishing, it serves as the mother ship fish factory for a fleet of massive trawlers. It takes their catches, processes them, and then sends them off to market on other transport vessels. Measuring the size of an aircraft carrier at over 1,000 feet in length, this is the world's largest fishing vessel and, it's capable of processing and freezing 1,500 tons of fish a day and can store up to 14,000 tons on board, which is the equivalent of 33 million standard 425 gram tins.

The Lafayette and other similar style factory ships cruise the world's major fisheries harvesting, amongst other things, pollack in Alaska, sardines off the Namibia & South African coastline, and mackerel in the waters of Chile & Peru. At one time these fisheries were thought to be limitless but, like the collapsed cod fishery of Atlantic Canada, they are slowly but surely getting wiped out.  Overfishing and poor regulation are the main culprits and now 3/4 of all the world's fisheries are near to or have already exceeded their maximum sustainable yield.

As the world population increases and the benefits of eating fish became more widely appreciated, the demand for fish also increases.  However, since the 1980's the amount of fish caught in the wild has peaked and has since stabilized at around 80 million tons a year.  To make up the difference between demand and supply, the fish farming/aquaculture industry has been rapidly expanding at an annual growth rate of more than 8%, and has now exceeded the production of fish caught in the wild. 

Worldwide, the most important fish species used in fish farming are carp, salmon, tilapia, and catfish, also known as basa. While fish farming has the potential to take some of the pressure off wild fish stocks it can also aggravate it in other ways.  On the one hand there are fast growing fish like tilapia which can feed on algae or any plant-based food making them less costly to raise and thus become the preferred fish of the industry. The drawback, however, is that tilapia, carp & catfish don't have the high levels of omega-3 fatty acids that are the reason dieticians recommend eating fish. Salmon, on the other hand, have very high levels of omega-3 but, because they are carnivorous, they also require large amounts of protein and, it takes several pounds of fish food/meal to produce one pound of farmed salmon. 

400 tons of Chilean mackerel
One of the main ingredients used in fish meal is mackerel and in the 1990's there were nearly 10 million tons caught worldwide with 5 million tons caught by Chile alone. While some of it is used for human consumption, the majority of it is used to produce fish meal & oil, the main ingredients of food for farmed salmon. Worldwide mackerel production is now down to 5 million tons and the Chile fishery is rapidly collapsing with less than 1/2 million tons being caught in recent years. Peruvian & Chilean anchovies now make up the majority of fish meal & oil being fed to farmed salmon in Canada. But most disturbing of all is the fact that one-third of the combined global wild fish harvest is used for making fish meal & oil, in other words fish food.

Atlantic salmon
Strangely enough, while the wild Atlantic salmon fishery is commercially dead due to overfishing and habitat destruction, it is by far the most popular species used for salmon farming, and makes up more than 1/2 of all wild and farmed salmon produced worldwide.  Raising Atlantic salmon in pens on the Pacific coast has generated a lot of ecological controversy, but little scientific proof, with the real issue being a fight for market share between the Alaskan commercial fishermen and the salmon farming industry. Owing to a very successful fish hatchery program also referred to as "ocean ranching" Alaska salmon are allowed to market their catch as wild, but the fact remains that wild salmon need to eat 10 kg of fish to produce 1 kg of salmon, and farmed salmon only need to eat 2 kg of fish to produce 1 kg of salmon.  This is because, unlike wild salmon, farmed salmon don't have to spend as much energy looking for their food.  So if you want to talk about reducing the pressure on other fish stocks, farmed salmon are obviously the better choice.

West coast salmon farm
Even still, it's easy to see these fish feed to salmon ratios are not sustainable, especially with the demand for salmon increasing every year. Work continues on substituting vegetable proteins such as soybean for fish meal though salmon don't tolerate or properly metabolize plant based carbohydrates. Other substitutions that have been identified are ragworms, algae oils, and by-products from seafood processing along with different diets at different stages of the salmon's life such as using vegetable oil in the growing diet and only using fish oil towards just before harvesting. Another option might be genetically modified salmon such as the new AquAdvantage salmon, an Atlantic salmon with Chinook salmon genes that allow it to grow twice as fast.

Bait ball and dolphins
Of course we aren't the only ones who like to eat fish, even if we think they're only there for us. The great sardine run of southern Africa occurs every year from May - July when billions of sardines/pilchards spawn and move along the coast in shoals of 7 km or more in length and 1.5 km wide. Dolphins round them up into bait balls and, along with sharks, birds, and other game fish, quickly take advantage of the feast. It's a reminder of the abundance the ocean is capable of producing, and that we need to think carefully about how we harvest it and what we use it for, before we wonder where it's all gone.

1 comment:

  1. Nelson, excellent, excellent article. Very educating.