Musings Of A Spiritual Atheist
Fish Farming

The environment, where we live, is our home, our garden, our farm, and our holiday camp. In fact, the base of everything we do. It is difficult to overestimate its importance, not just to us humans, but to all living things both animal and vegetable. As the number of people increases, so does the pressure on the environment and so does the necessity to ensure its continued viability. Ultimately, all of our food comes from the environment and the need to produce greater and greater quantities just makes it so much more important.

We have not always been successful in ensuring environmental viability. There are several examples where pressures on animals hunted as food sources has caused drastic declines in numbers, even to the point of extirpation or extinction. The cod fishery of eastern Canada is a typical example, where the cod were caught in unsustainable quantities until the stocks collapsed. Well over a decade later they have still not recovered. Historical examples are the dodo bird and the passenger pigeon, both of which were hunted to extinction.

This process is still going on, and as I write there is a dispute brewing on Canada’s Pacific coast between a first nation and a commercial fishery for herring. The commercial fishery takes herring for the roe, which is a delicacy in Japan. The first nation says that too many are being taken and that the herring stocks are declining. Since the herring are a traditional food source for the first nation, they are primarily concerned with ensuring that adequate stocks of fish are there for their food fishery, but in a wider context there is also concern over the survival of herring as a primary food source for many marine animals. Obviously, excessive commercial exploitation is self defeating, since overfishing will deplete fish stocks and reduce catches in the future which, in turn, will reduce profits.

Fish and other kinds of sea food can be a major source of protein in our diets. Due to this there have been attempts made to raise captive fish in a manner similar to how captive sheep are raised, that is, to farm them. Contrary to what many people assume, this is not a modern innovation. Goldfish, the ones kept as ornamental fish in ponds and aquaria, were originally bred from the carp being raised as food fish in ponds in China. Much the same story applies to koi, hybrid carp developed in Japan. Many ponds in Britain are artificial and were originally dug to raise carp and other native species as food for the monks in monasteries. Fish farming is an old practice and, as originally done, it was an effective way to raise food fish. A large pond could be prepared either by diverting water from a stream into a natural or artificial depression, then retaining the water with a weir, or by building two weirs across a suitable stretch of a stream to widen and deepen it. The fish would feed naturally on whatever grew in the retained water before being periodically netted. With minimal ongoing effort and cost a reliable protein source was obtained.

Unfortunately, fish farming in Canada has a poor reputation, particularly in coastal British Columbia. There are several reasons for this, mostly involving the environment, particularly the marine environment. Fish farms in BC raise salmon species predominantly, usually in coastal inlets, and use nets or open mesh pens to confine the fish. The waste products from the fish, faeces and uneaten food, sink to the sea floor and are flushed by the tide, at least partially.

One common farmed salmon species in BC is Atlantic salmon, and there have been instances where dozens of penned fish of this species have escaped into coastal waters. The fear is that they may eventually spawn and introduce a feral population to compete with the native species. This has not been shown to occur as yet, but they have been observed by river mouths and the question remains open. Experience with other animal species has shown that non native feral animals can often out compete and replace native species in suitable ecosystems, so the fear is that feral Atlantic salmon may cause one or more of our native species to be diminished or locally extirpated in some parts of the BC coast or, in the worst case scenario, be driven into extinction altogether.

A second major concern is that large numbers of salmon being kept in close proximity, as they are in a pen, may facilitate the spread of disease. When one fish is infected, it may not be long before other fish are involved. This has been the case with viral diseases, and the only resolution is to kill all the fish and bury them. Another disease of concern is fish lice. These attach to the fish’ gills and weaken the fish, particularly if it is a juvenile. Particular concern has been expressed that juvenile wild fish leaving the rivers may pass close enough to the farmed fish to be infested, thus increasing the incidence of lice and inhibiting the full growth potential of the fish.

Farmed fish have to be fed. There is insufficient natural food to sustain a population in the thousands, so food pellets have to be provided. These are made from fish. Most of the fish used comes from natural source fisheries and are a major burden on wild fish populations. The species turned into pellets are usually not those suitable for human consumption but are species that are major sources of food for wild fish of many species. Reducing the populations of these fish can have an impact on growth and survival rates of many fish species, including wild salmon. There is no indication that this is a problem as yet but the subject has been raised as a likely problem in the future if the rate of expansion of fish farming increases.

Large numbers of fish will produce large amounts of faecal matter. Along with uneaten feed this sinks to the sea floor. The expectation is that tides will sweep this material from the sea floor out into deeper water where it will disperse into the greater marine environment. Since fish farms are usually put into remote bays, the ocean is capable of absorbing this locally dense but globally insignificant material. In practice, the sweeping by tidal forces is not always as efficient as proclaimed and significant amounts of the material remains under the fish pens. This has the effect of inhibiting other sea life, including shellfish. To a degree this is self limiting in that should the pens be removed the sea floor will be cleaned over time and return to its original condition.

While not usually viewed as such, fish faeces are a valuable resource. Gardeners love materials like that for pampering ornamental plants. Fish fertiliser sells very well, even though it is made from ground and composted fish bodies. Faeces are traditionally seen as a superior source of nutrients for plants, as is fish compost, so fish faeces would be like gold. That is, if it were available. In my opinion, fish farmers are missing a major opportunity for sales by allowing the wastes associated with fish farming to simply fall to the sea floor instead of collecting them and composting, then marketing as an upscale home garden fertiliser.

The difficulty with doing this is the collection of the faeces and food wastes. Building suitable collectors underneath the pens would undoubtedly be expensive in an open environment, such as the bays where these pens are located. This is just one difficulty among many negatives associated with open pen fish farming. The resolution to most of these would be closed pen farming, that is, growing the fish in large concrete or heavy plastic lined tanks on land. These would need to be fitted with filters and water recirculators, which would enable all detritus to be removed and to oxygenate the water. This is not dissimilar to raising fish in an aquarium, but would be on a massively greater scale.

Where would the sea water come from for this? Essentially the same place as now, that is, the sea. It would be easy enough to pump sea water from a bay into these tanks periodically. The displaced, used water would be returned to the sea by releasing it into a column of sand and gravel to mimic natural filtration through soil and trap any solid particles. In the infrastructure needed to do that, coarse filters or settling ponds could capture faeces and uneaten feed for further processing into fertiliser and providing a small secondary income. This would, to a large extent, answer the criticisms of open net fish farming as a source of contamination of the marine environment and enable fish farming to expand.

Closed containment is not a new nor innovative practice, although its application to farming salmon may be novel, as it has been used for centuries. Since carp ponds were often artificial, the original way fish farming was done was in a closed containment system of constructed fish ponds. For many years, trout have also been farmed in a similar way. They are commonly grown in relatively small ponds from which any natural fish have been removed and which have then been stocked with trout fingerlings. This has been used very successfully for many years, both in BC and in other parts of Canada and could well be expanded, preferably with artificial ponds rather than sterilising natural ponds.

There is one opportunity in trout farming that has been ignored as far as I can tell. Trout eggs are available by the millions if a farmer were to require them for a project, so it has mystified me as to why there has been no production of small trout of a size similar to those fish found in canned sardines and herring, both of which are very popular food items. It would appear to me that canned trout fingerlings, or slightly larger, would be suitable as an upscale item in many situations and events. Even though these fish would have to be juveniles, that would not bar them from being a valuable food source. After all, the original Brisling sardines are juvenile herring and quite popular, especially in northern Europe. It would mean, though, that they could be raised to marketable size within a few months. The facilities for doing so may already exist as trout fingerlings are raised frequently for stocking sport fishing lakes.

Although not grown in Canada, the ultimate farmed food fish are Tilapia species or, more accurately, Tilapia hybrids. Tilapia are species of Cichlids, a group of fishes that are predominantly carnivorous and found in various warm weather countries. The species that are farmed are often hybrids of those native to the Middle East and North Africa and are vegetarian rather than carnivorous with a high food to protein conversion rate, enabling them to be raised to marketable size in a short time. One of the advantages to farming Tilapia in areas of the world that have cold winters is that they are not able to naturalise. In cold regions they die during the winters, thus limiting the likelihood of a feral population being introduced by accident. In Canada they would be most suited for closed containment pens in warmed buildings if year round production is necessary, or in unheated buildings during the warmer months if not. They have also been suggested as a suitable fish for the final stage of a biological treatment system for human wastes, feeding on the water hyacinth and similar plants grown abundantly in the system and being a protein source at the same time. At present, farmed Tilapia is imported into Canada from warmer climes.

If there were large numbers of fish farms they could reduce some of their feed costs by ensuring that the waste and offal from the fish processing plants is used to make fish feed to be reused in the farming operation. For every two fillets from a fish there is a central carcass. If this were diverted into making feed the pressures on the natural environment would be diminished considerably. Keeping in mind that farmed Tilapia are vegetarian and do not require fish protein as food, the carcasses left after their fillets have been removed could go to replace the natural fish used for making feed for trout and salmon.

It is clear that systems could be established which would facilitate fish farming on a relatively large scale and produce considerable amounts of high quality protein. However, there needs to be investment in integrated farming operations with species that can support each others requirements without degradation of the marine and fresh water environments. What is lacking is the will and the investment.


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