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Commercial Fishing

The Australian fishing industry

In 1996-7, there were 12,834 tonnes of tuna, 113,991 tonnes of other fish, and 27,856 tonnes of prawns caught in Australian waters ( 1 ). This catch represents the death of millions of animals, not only the intended prey, but also the huge numbers of unwanted animals that are caught. Southern bluefin tuna, eastern gemfish, school shark (flake) and tiger prawns are being overfished, and their populations have been seriously reduced. For tuna, for example, catches declined steadily from 1961 to 1991, "excessive fishing having reduced the spawning stock to a level well below that regarded as biologically safe" ( 2 ).

Overfishing has caused problems around the world, for example, the collapse of the cod population in New Foundland (Canada) and in the North Sea ( 3 ). Not only has the population of cod been severely reduced by many years of over-fishing, but it is now having trouble recovering due to the effects of global warming in the North Sea ( 4 ).

Recreational fishing also plays a part in reducing fish populations. Around Adelaide recreational fishermen catch as many King George whiting as commercial fishermen, and in Sydney harbour they catch 25 times more bream than commercial boats ( 5 ). Recreational fishing is estimated to account for 50% of all fish caught in NSW and Victoria, more in Queensland, but less in the remaining states ( 6 ).

Fishing methods

Trawling

Trawling is where large nets are pulled behind boats. They are used to catch prawns and some species of fish, but they scoop up everything in their path. For some species the nets are dragged along the ocean floor.

Trawling doesn't kill only the intended animals - there is a very large by-catch. An estimated 50,000-90,000 tonnes of non-target animals are discarded altogether over 8 Commonwealth fisheries, about 85% of this bycatch coming from the Northern Prawn Fishery (NPF) and the South Eastern Fishery (SEF)( 7 ). As a government report stated ( 8 ):
" Much of the non-target catch is discarded, particularly in trawl fisheries. From the quantitative information available, the proportion of discards is largest in the NPF, where 95% of the total catch is discarded. The proportion is also large (50-86%) in the SEF... ".

Most of the by-catch is dead or dying, and is thrown overboard. It includes many fish species, endangered sea turtles, and sea snakes. In the past, prawn trawlers caught an estimated 5000 turtles a year, of which up to 40% died. An estimated 120,000 sea snakes were also caught, and again about 40% died ( 9 ). As of the year 2000, prawn nets must have turtle exclusion devices fitted to help turtles escape, since these nets have been recognised as a key threatening process to these endangered animals.

Deep trawling or dredging for scallops also damages the seabed. It rips up plants, sponges and coral, including the internationally protected black coral ( 5 ). It has been likened to clear felling a forest, leaving behind a marine wasteland ( 10 ):
" A trawl net scrapes the seabed, funnelling a precious catch into its trap. cod, haddock, and flounder are the intended prey, but this device is indiscriminate. The hard wire of the net's leading edge cuts a swath through the jungle of bottom-dwelling creatures. Sponges, bryozoans, and many others are smashed to bits ".

Trawling levels the seafloor and stirs up silt, with the muddy water reducing photosynthesis in plants. It can take 10 years for the seabed to fully recover. Ironically this damage reduces the populations of the very fish species the trawlers are trying to catch ( 10 ).

Longlining

Longlining is where ships lay out long lines with baited hooks hanging from them to catch fish such as tuna. Japanese boats in Tasmanian waters alone lay around 3.3 million hooks in a season ( 11 ).

About 30 different species are caught on the hooks, many of them considered to be "trash". An estimated 34,000 blue sharks are accidentally caught by the Japanese fleet in Tasmania in a season. In the past, the fins were cut off for shark fin soup and the body was thrown overboard ( 11 ). Since 1995 the whole shark is supposed to be used ( 9 ).

Longlines also kill sea birds who follow boats and dive for the baits on hooks. Birds such as petrels, shearwaters and albatrosses drown when they are caught on the hooks or become entangled in the lines. An estimated 2700 albatrosses were killed by Japanese longliners in Australia in 1993. Longlining is considered a key threatening process to the population of the wandering albatross ( 9 ). To reduce the bycatch of birds, it is recommended that lines be set at night and that bird scaring streamers be flown above the lines.

Other concerns about longlining include the discarded bands from bait boxes which collar marine mammals such as seals, and pieces of lost line that entangle and drown various animals ( 12 ).

Purse seining

Purse seining is where a net hanging vertically in the water is drawn into a circle by a boat. The bottom of the net is then drawn together and everything inside the net is hauled into the boat.

The aim is to catch schools of fish such as tuna or pilchards. However, unintended species swimming with the schools of fish are also caught. There is concern that coastal seining will reduce the food supply for animals such as fairy penguins.

Gill netting

Gill netting is where a line of net is left hanging vertically in the water to catch edible sharks. They are caught by the gills and drown when they swim into the mesh of the net. In tropical waters gill nets are also used to catch barramundi. Here dugongs are the unintended victims. In some areas their numbers have fallen by as much as 80%, due in part to being caught in fishing nets, but also due to Aboriginal hunting, destruction of their sea grass habitat, and boat accidents ( 13 ).

Until 1986 the Taiwanese used nets up to 30 km long in Australian waters. An estimated 14,000 dolphins were caught in such nets between 1981 and 1985. In 1986 the length of nets was limited to 2.5km. Australian shark fishers use gill nets of about 1 km, but of course many unintended fish species and other marine animals can still be caught in these nets ( 9 ). For all the victims, including the intended species, it is a very miserable death. When nets are damaged and pieces lost, they can continue to entangle animals for many years to come in so-called "ghost fishing".

Pollution

The fishing industry produces pollution in the form of oil, sewage, lost lines and nets, and plastic packaging. A study in Tasmania in 1989-1993 found that 1.5%-2.0% of Australian fur seals were entangled in plastic bands, rope or net ( 9 ).

An eye witness on a prawn trawler in the Gulf of Carpentaria painted a grim picture of widespread pollution ( 14

Fish farming

Fish farming is claimed to be the answer to the decline and, in some cases, even the collapse of wild fish stocks due to overfishing and environmental degradation. However, as a CSIRO journal commented:
"... aquaculture brings its own problems- the same issues that face other intensive agricultural enterprises, such as cattle feedlots and poultry farms-the result of keeping large numbers of animals in a confined space " ( 15 ).

Fish farming is not an environmental saviour. The main fish farming industries still depend on wild fish stocks. Tuna are caught from the wild to stock cages, and tuna and salmon are fed fish caught from the wild. The high concentration of animals in fish farms also produces pollution.

The largest concentration of fish farming is in Tasmania (Atlantic salmon and ocean trout) and South Australia (southern bluefin tuna) ( 16 ).

Tuna farming at Port Lincoln (SA)

Tuna farming began at Port Lincoln in 1990, when the tuna fishing industry was on the point of collapse ( 17 ). By 1996 there were 64 sea cages in the sheltered waters of Boston Bay ( 18 ).

The cages hang from floating pontoons, 40-50 metres in diameter, which are anchored to the sea floor. The inner net which holds the fish drops 7-10 metres and has a bottom. The outside predator net extends to the sea floor. A standard cage can hold 1700 tuna ( 17 ).

Tuna to stock the cages are caught from the wild as they migrate through the Great Australian Bight ( 19 ). Previously the tuna were caught by poling, where fish are heaved into a boat on a pole once they snap at bait. More recently the fish have been caught in purse seine nets, transferred underwater to towing cages, and pulled slowly to Boston Bay ( 17 ). However, because netting catches many animals other than the intended ones, fishermen are being encouraged by the government to go back to poling tuna directly into the towing net ( 17 ).

With the poling technique, 20-35% of the tuna died within the first 2-3 weeks after capture. Even the survivors lost weight and took a week to begin feeding well. Deaths are said to be lower now that tuna are captured with nets, but no figures are given ( 20 ). Divers check the inner net for dead fish and the predator net for entanglements of other animals every 1-3 days ( 21 ).

Tuna can be kept in cages at density of 4kg/m3. They are fattened for 4-9 months to a weight of around 30kg, depending on the demands of the customers. The tuna are destined for the high priced sashimi market in Japan ( 17 ).

In some European fish farms antibiotics area added to the feed. For example, in Norway in 1987 about 1.5 tonnes of antibiotics were used to produce 1 tonne of salmon. Following the introduction of vaccines, 100kg of antibiotics are now used to produce 1 tonne of fish. No antibiotics have been used in Tasmania for the last 5 years ( 22 ). According to the Department of Primary Industries (SA), no antibiotics are used in Port Lincoln ( 23 ).

Killing methods

There are regulations requiring mammals and birds to be killed with the least amount of pain and stress. These animals are stunned so that they are unconscious during the slaughter process. No such regulations exist for fish.

Tuna in Port Lincoln are gaffed onto a platform and killed by the "iki jima" method. A corer is pushed into the brain region of the fish, and a wire rod is pushed though the hole and down the spinal column ( 23 ).

Salmon in Tasmania are anaesthetised in carbon dioxide saturated ice water before their gills are cut and they bleed to death ( 24 ). However, a researcher from Bristol University has raised doubts about carbon dioxide stunning( 25 ). When fish are placed in the stunning tank, "they try to escape violently".

" The fish are usually unable to move within 1 minute but do not lose sensibility for 4-5 minutes. Fish could have their gills cut whilst still conscious if lack of movement was taken for unconsciousness. If gill-slitting was carried out unsatisfactorily, it is possible that fish could recover consciousness whilst bleeding " ( 25 ).

On some fish farms overseas, trout are packed into bins while still alive, leaving them to die of suffocation. In some cases, ice is also packed into bins. The researchers from Bristol University have shown that in trout taken from warm water, brain activity continues for an average of 2.6 minutes. During this time the fish struggle violently. It takes 11 minutes for all movement to stop. When trout are removed from icy water, it takes 9.6 minutes for brain activity to stop. In other words, the ice water is prolonging their stress as they slowly suffocate ( 26 ).

Fish can be killed instantly by a blow to the back of the head, although if not done properly this method causes injury and pain. Fish can be electrocuted by passing a current through a tank for a few seconds ( 25 ). The researchers at Bristol University concluded:
" ... taking fish out of water ... falls short of the welfare requirement for instantaneously rendering the fish insensible. Other methods of fish slaughter, such as concussion or electrocution, are more likely to achieve this end " ( 26 ).

Environmental problems

Solid waste accumulates beneath tuna cages, including mainly uneaten food and tuna faeces. It is estimated that 20-30% of food is wasted and sinks to the bottom ( 27 ). Soluble nitrogen waste products are excreted from the gills ( 28 ). Around 65% of all nitrogen consumed by the fish is eliminated in this way, with a further 10% eliminated in the faeces ( 28 ). Every day 10-20g of solid waste per square metre accumulates, in other words, 20-40kg under a 50 metre cage every day ( 20 ).

Another report concluded that for every 100 tonnes of feed there is 10 tonnes of solid waste and 5 tonnes of soluble nitrogen waste ( 25 ). It has been estimated that 100 tonnes of fish produce as much waste as 7000 humans ( 19 ). Since over 2000 tonnes of tuna were slaughtered in 1995/6 ( 16 ), waste equivalent to that of over 140,000 people was discharged into Boston Bay untreated. Sites where cages are anchored are supposed to be left fallow every 18-24 months to minimise build up of waste in the same place ( 17 ).

The build up of nutrients can lead to increased concentrations of phytoplankton. In 1990, 600 tonnes of chinook salmon in sea cages in New Zealand died due to an algal bloom. There were high levels of nitrogen and phosphate nutrients in the water, and researchers commented:
" Excretory products and nutrients leached from excess fish feed from the salmon farms might have contributed to this pool, but the relative significance of this source is not known " ( 29 ).

The predator nets outside the fish cages entangle marine mammals. Between 1993 and 1996, 32 dolphins and 4 sea lions were reported dead in these nets at Port Lincoln ( 21 ).

In the UK, Dichlorvos has been used to rid salmon of sea lice. Dichlorvos is very toxic to marine shellfish, and has been linked to cataracts and blindness in wild salmon ( 25 ). While there are some sea lice at Port Lincoln, they are not a major concern and no chemicals are used ( 23 ).

High levels of copper and zinc have been found under salmon cages in Scottish lochs, levels up to 24 times higher than safety limits. Copper is in antifouling paint on the cages (to remove unwanted plant and animal growth), while zinc is used to galvanise the cages and in fish food ( 30 ). The levels of these metals are high enough to damage the marine environment.

Fish farming is wasteful

Fish farming doesn't increase the overall amount of protein available as food. On the contrary, it actually decreases protein.

Tuna are fed mainly pilchards. In South Australia there is a quota of 1500 tonnes of pilchards a year which can be caught by the tuna industry ( 20 ). However, pilchard stocks are declining, and pilchards have also been imported for tuna feed. Huge numbers of pilchards died along the southern coast of Australia in 1995 and again in 1998 of a herpes-like virus. Pilchards imported to Port Lincoln as tuna feed came under suspicion as the source of the virus, but the connection has not been proved ( 15 ). Nevertheless the Bureau of Resource Sciences notes ( 13 ):
" The introduction of fish and fish products (for example, feed) for the fish farming and aquarium industries has the potential to introduce pests and disease organisms ".

During feeding, pilchards are shovelled from feeding boats into the tuna cages until the tuna stop feeding. The tuna are fed 4-7% of their body weight daily. It takes up to 17kg of pilchards to produce 1 kg of high priced tuna ( 17 ). In the case of Atlantic salmon in Tasmania, it takes about 7kg of mackerel, made into fish meal pellets, to produce 1kg of salmon ( 19 ).

Fish farms actually decrease the total amount of protein available as food, not only for humans, but for other animals in the marine food chain.

Massive die-off in 1996

In April-May 1996, 1700 tonnes of tuna died, around 75% of all the fish farmed at Port Lincoln. A government investigation concluded that the deaths were a freak occurrence. High winds produced by the remnants of cyclone Olivia churned up particles from the sea floor, which clogged the gills of the fish ( 18 ).

Several other possible connections were ruled out. Death rates in individual cages were not related to stocking density. Oxygen levels in the water were satisfactory, and micro-organisms were not present in sufficient concentrations to cause disease. Death rates did not seem to be related to how long a cage had been established and, therefore, how much waste had accumulated underneath it. However, there was a high level of suspended sediment in the water, and death rates were related to the depth of water in which a cage was anchored. Cages were anchored in 15-22 metres of water, and more fish died in the shallower water ( 18 ).

The report concluded: " Tuna are pelagic ocean water fish with uniquely large gill surface areas to body weight ratios ( the largest of any finfish) and so probably poorly adapted to sediment laden waters ."

" The effects of the suspended sediments, whether physical, toxic or stress related, are considered to have caused the copious quantities of mucous on the gills of the tuna which in turn led to respiratory difficulties resulting in asphyxiation ."

Fish farming is not the answer to declining fish stocks and the damage caused by commercial fishing. The real answer is to change to a more humane and more resource-efficient vegetarian diet. Go to our section Vegetarianism - the cruelty-free diet for some suggestions.

I would like to see References for this document on commercial fishing.

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