Worldwide, the demand for wild fish is now greater than the ocean can supply. Southern bluefin tuna was once cheap and plentiful enough to go into canned tuna; it’s now an expensive rarity. There are two main ways of looking at sustainability: is the fish stock sustainable and does the fishing method cause environmental damage?
Australian fisheries are generally well managed, by international standards. But, of 97 stocks surveyed in the Australian Government Bureau of Rural Sciences’ most recent Fishery Status Report, 19 were classified as overfished and/or subject to overfishing. And more than 60% of our fish is now imported.
All fishing has an environmental impact, but some methods can be particularly destructive of fish stocks and other wildlife. Non-selective fishing gear may catch and kill immature fish and unwanted species thrown away as “bycatch”. Dolphins, turtles and seabirds — often vulnerable or endangered species — can become entangled in nets and killed. Lost or abandoned fishing gear continues to catch fish (and other marine life) until it falls apart — a process that can take years. Two methods are of particular concern.
Trawling In this widely used fishing method nets are towed behind a boat and dragged along the ocean floor. Trawling can damage the seabed, destroying marine life and habitats on which the fish depend for food. Trawling accounts for about 50% of the fish wasted as bycatch.
Drifting Long lines are used to catch tuna, marlin, swordfish and sharks. A main line, which can be a staggering 10km-80km long, floats on or near the ocean surface. Along this main line there are numerous branch lines with baited hooks. There’s concern about the impact on dolphins, whales and turtles, as well as endangered seabirds, such as albatross. Unfortunately “dolphin safe” or “dolphin friendly” claims on fish products mean very little. There’s no universal and independent verification of such claims. Undoubtedly, many companies try to do the right thing, but there’s no guarantee.
Aquaculture is a big industry in Australia. Snapper, barramundi, southern bluefin tuna, mulloway, Atlantic salmon and trout are grown in sea cages, while prawns are grown in saltwater ponds built in wetlands along Australia’s tropical coast. This might seem to be the answer to the problem of sustainability, but fish farming raises environmental issues of its own.
- Farmed fish are more crowded than in the wild and therefore more susceptible to disease. Antibiotics and other chemicals are used to control disease outbreaks, and diseases can spread to native fish stocks.
- Farmed fish can escape from sea cages. Atlantic salmon are voracious predators and can wreak havoc on native fish stocks — so there’s a moratorium on salmon farming expansion in British Columbia, Canada.
- Dissolved and solid fish waste from sea cages can pollute coastal waterways. Sea-cage fish are fed a diet that uses wild fish, such as sardines and mackerel, to produce fishmeal.
It takes 2-4kg of wild fish to produce 1kg of farmed Atlantic salmon. It would seem more responsible to eat the sardines and mackerel instead — and they're better sources of omega-3s.
Raising fish such as prawns, salmon and barramundi in fully enclosed tanks or ponds seems to be preferable, as the output of waste materials can be controlled. These operations can cause environmental degradation through clearing of mangrove forests and destruction of wetlands, but with appropriate care and expertise, fish farms can be ecologically designed and sustainably operated.
What CHOICE wants
In the UK, the Food Standards Agency is reviewing its advice on eating fish to take into account issues related to sustainability. CHOICE wants the next revision of the Australian Dietary Guidelines to consider the impact of fishing practices in its advice on eating fish.
Image courtesy of Tassel Group Limited