Introduction to Fish Farming

Introduction to Fish Farming

Fish farming is known as pisciculture in the academic world. It is a form of aquaculture involving the farming of aquatic organisms like fish, crustaceans, mollusks and aquatic plants. Fish farming involves raising fish commercially in ponds, tanks or enclosures.

Alternatively, Fish farming can also be refered to as the commercial production of fish in an enclosure or, when located in a body of freshwater or marine water, in an area that is penned off from the surrounding water by cages or open nets.

There are hundreds of species of fish among which are: sea trout, cyprinids, pangas catfish, freshwater fishes, silver sea bream, common carp, catla, greasy grouper, big head carp, nile tilapia, grass cap etc. but most of them are not suitable for fish farming in Nigeria for instance, either because of their nature or because of low demands in the fish market or profitability of their species.

That is why the most common fish species that fish farmers grow for commercial purpose are carp, salmon, tilapia, and catfish while catfish and tilapia are the most common species in Nigeria fish farming industry.

Meanwhile as a fish farmer, you must ensure that all fish ponds on the farm should be easily accessible for adding inputs and transporting harvested fishes from the pond with relative ease and safety.

Introduction to Fish Farming

Fish farming is the most common form of aquaculture, and commonly involves trout, salmon, tilapia, cod, carp, and catfish. For a species such as cod, whose numbers in the Grand Banks fishery off the east coast of the Canadian maritime provinces plummeted to near zero in the 1970s due to overfishing, and as of 2008 have yet to recover, the cod available from fish farming represents almost the sole source of the fish in North American markets.

Read Also: How to manage waste from a fish farm to avoid causing nuisance to the neighborhood

According to the United Nations Food and Agriculture Organization, roughly 32% of world fish stocks are overexploited, depleted or recovering and need of being urgently rebuilt. Fish farming is hailed by some as a solution to the overfishing problem.

However, these farms are far from benign and can severely damage ecosystems by introducing diseases, pollutants and invasive species. The damage caused by fish farms varies, depending on the type of fish, how it is raised and fed, the size of the production, and where the farm is located.

One significant issue is that—rather than easing the impact on wild populations—the farms often depend on wild fish species lower on the food chain, like anchovies, in order to feed the larger, carnivorous farmed species.

It can take up to five pounds of smaller fish to produce one pound of a fish like salmon or sea bass. Overfishing of these smaller “forage” fish has repercussions throughout the ocean ecosystem.

As is the case with industrial animal farms on land, the fish are often housed in unnaturally crowded and cramped conditions with little room to move. Fish may suffer from lesions, fin damage and other debilitating injuries.

The overcrowded and stressful conditions promote disease and parasite outbreaks—such as sea lice—that farmers treat with pesticides and antibiotics.

The use of antibiotics can create drug-resistant strains of diseases that can harm wildlife populations and even humans that eat the farmed fish.

Escaped fish introduce yet another threat into the environment. Each year, hundreds of thousands of fish escape farms and threaten the genetic diversity and survival of native species.

High stocking densities result in a significant amount of pollution from fish excrement and uneaten food, which in turn lead to poor water quality high in ammonia and low in oxygen.

Outdoor fish farms can also attract predatory marine animals, such as sea birds and sea lions, who are sometimes poisoned or shot by aquafarmers for eating the fish.

Despite evidence to the contrary, it is still a common misconception that fish do not feel pain. Slaughter methods in the aquaculture industry are appalling. Little to no attention is given to the suffering of the animals and most are fully conscious during slaughter, which can take many minutes.

Some species, such as salmon in the United States, are also starved for many days to empty the gut before they are sent to slaughter. Fish are most often not stunned and are killed by bleeding out, being hit on the head repeatedly, suffocating or freezing. In the US, as with many other countries, there are no regulations to ensure the humane treatment of fish.

Read Also: Factors to Consider Before Starting a Fish Farming Business

Years of unregulated and underreported catches of bluefin tuna in the Mediterranean Sea and Atlantic Ocean are threatening the existence of this severely overfished species.

To meet the high and growing demand for sushi in Japan and elsewhere, ranching of bluefin tuna is becoming a popular industry and is exacerbating the problem.

Fisherman use longlines and purse seines to catch the tuna before they reach breeding age and have time to reproduce. They are then kept in seafarms for 3–6 months and fattened with thousands of pounds of smaller wild-caught fish before being killed and exported.

The Different Forms of Fish Farming (Aquaculture)

(1) Extensive Fish Farms

Extensive fish farming utilizes natural photosynthetic production of food (algae, plankton, mollusks, crustaceans) to feed the fish. This type of farming isn’t the most productive, but it requires little labor, low overhead, and very little input from the farmer.

You just need water, some fish, and a way to pen them in. Things can obviously get more elaborate, but those are the bare minimum. Most tilapia and carp are farmed using extensive methods.

Extensive farming is obviously the most sustainable and does the least environmental damage, but it isn’t always economically viable and it doesn’t work for every species. Carnivorous fish (which is most of ’em) need to eat fish, or pellets made from fish. Salmon, for example, eat the fish that eat the plankton; they don’t eat the plankton directly.

On the other hand, tilapia, which feed directly on phytoplankton, and carp, which eat benthic animals (bottom feeder), are great for this type of farming because they don’t require food pellets or other, smaller fish for food.

(2) Intensive Fish Farms

Intensive fish farming uses an external food supply – pellets, fishmeal, corn, soy, even “feathermeal” – to feed the carnivorous fish. The population density is high, antibiotic usage is high, food waste is high, and sewage output is high in intensive fish farming.

Water quality is paramount and usually requires a robust water purification system, if the farm is a closed system, like a pond, ditch, or tank. If the farm uses cages in rivers or the open sea, water purification obviously isn’t as necessary.

Either way, intensive fish farming requires constant maintenance and vigilance. If management is poor or funding inadequate, things can get pretty bad: toxic runoff, antibiotic-resistant bacteria, introduction of farmed, perhaps diseased species into wild populations, excess food and waste influencing wild population densities, stressed out fish.

Heck, even if management is on top of their game, antibiotics are still a necessity, food is being wasted and eaten by wild sea life, which throws off local wild population densities, and the fish are living in cramped conditions which increases stress. It can be done well, and I’ll get into that next time, but it is difficult to do, and most aren’t doing it.

Read Also: Meaning of Recirculating Aquaculture System (RAS) in Fish Farming

(3) Shrimp Farms

Traditional shrimp farming took place in brackish water ponds or mangrove swamps, the shrimp’s natural habitats, and often involved other complementary species, like rice or fish. This was subsistence farming, suitable for a family or even an entire village, but not for an industry.

Today, shrimp farming displaces mangrove swamps and other coastal systems across China, Thailand, India, and Vietnam, among other countries. There are three primary types of coastal shrimp farms: extensive, semi-intensive, and intensive shrimp farms.

Extensive shrimp farming uses low densities, about two or three animals for every square meter of water, and generally do not need to supplement feed supplies. They’re on the coast, so the tide’s enough to keep the water fresh, and extensive farmers often use wild stock.

Semi-intensive shrimp farming ups the density to about 10-30 shrimp per square meter, increasing the requirement for food. In semi-intensive farms, shrimp get supplemental shrimp feed, and artificial algae blooms take care of the rest. In intensive shrimp farms, the shrimp populations reach even greater densities and rely almost entirely on supplemental shrimp feed.

Infectious disease is a frequent concern in shrimp farming. It kills profits, sure, but it also infects and kills wild shrimp living near or around the coastal farms.

Most shrimp diseases are viral, without any real treatment save for prevention, but preventing viral disease from spreading among shrimp in super-dense living conditions isn’t easy. And then there’s bacterial disease.

Most shrimp farms use antibiotics to cull bacterial diseases; one study found that 74% of Thai shrimp farmers surveyed used antibiotics in their operations. As the shrimp population increases in density, larger amounts of antibiotics are required. This leads to resistant bacteria, which is fairly common in both Vietnamese and Brazilian shrimp farms (and, I’d imagine, shrimp farms in general), and, again, spreads to affect wild populations.

(4) Shellfish Aquaculture

Shellfish farming is actually quite impressive. There’s very little active farming required, and, since bivalves tend to be sedentary creatures, farmers don’t worry about their clams escaping to deep water or their mussels fomenting for freedom.

Since bivalves are filter-feeders – water passes through their filters, leaving behind algae and other tasty microorganisms – they also require no direct food from the farmers. The filtering also serves as a water purification system.

Raised in the same farm as pooping, food-wasting fish, bivalves work especially well, eating the leftovers, cleaning the water of fish waste, and getting big and delicious in the process.

All in all, farmed shellfish – scallops, clams, oysters, mussels, and abalone are the big ones – are more sustainable than wild caught shellfish, and live quite similar lives, too.

(5) Integrated Agriculture-Aquaculture

The world is a massive system with millions of variables, each one interrelated to the next, working (or not) to make sure things flow smoothly. Obviously, we lowly hominids can’t recreate the near infinite complexity of the entirety of nature, but we can make decent attempts at small portions.

Asian rice farmers have been raising carp in their rice paddies for hundreds of years with great success. The carp eat the plankton, preventing the latter from outcompeting the rice for nutrients, comb the bottom soil, which releases more nutrients, and produce a steady source of fertilizer for the rice. 

There are plenty of other possible aquacultural-agricultural integration permutations used across the world, like rice/shrimp, fish/grass, fish/duck, fish/pig, fish/chicken, but the fish you come across in the big supermarket probably didn’t have a pig, duck, or rice plant for a friend.

While integrated aquaculture, in many cases, is more cost-effective than either monoculture by itself, the initial production costs and knowledge required is a large barrier for widespread adoption. 

That is, you can’t implement sustainable integrated agriculture-aquaculture systems on a large scale without knowhow, planning, and money. Recreating natural symbioses (even on a small scale) isn’t simple.

(6) Integrated Multi-Trophic Aquaculture (IMTA)

IMTA is very similar to integrated agriculture-aquaculture systems in that they create mini ecosystems, only IMTA is limited purely to aquatic species. So, instead of rice-fish farms, you’ve got fish-seaweed-bivalve ecosystems-within-a-farm. Very cool.

Perhaps the coolest example of IMTA on a large scale is Veta la Palma, a Spanish farm built on a former cattle feedlot that actually improves upon nature.

It produces tons of shrimp, bass, bream, and mullet each year. Each fish pond is lined with native plants that maintain nutrient balances in the water. Each fish forages for its own food in water that’s constantly replenished by the tides.

Over 250 species of birds (up from 50 before the farm was built) attend to feed on the farmed fish, a practice encouraged by the farmers because it means “the whole system is working.” And, most importantly, they produce fantastic seafood.

Read Also: Earthen Pond Management in Fish Farming

(7) Fish Ranching

They may not have big floppy ears that perk up, but fish can hear; they may not have big brains, but they can learn. Fish ranchers capitalize on both attributes by playing a specific sound every time the fish are fed.

Eventually, the fish associate the sound with food and, after plenty of conditioning, will come to the sound every time they hear it. So, rather than keeping the fish in crowded cages, nets, or ponds and feeding them weird pellets, ranchers let their fish range freely in open water, feeding on regular fish fare.

When it’s time to harvest, the sound will draw them back. Different species have different recall rates, though; in one ranching test using tilapia and carp in a large reservoir, only 13% of the original tilapia heeded the call, while over 2/3 of the carp came back.

But with the original crew came hangers-on – other carp, tilapia, and a few other fish species from the reservoir – and the ranchers’ final haul was over twice as big as the original group of fish. Another type of ranching uses fish with a homing instinct, like the Nepalese mahseer (a type of carp).

The mahseer hatches upriver and is fed for about a year, until it grows large enough to be released into the river. It spends a good two or three years in the wild eating (on mother nature’s dime!), growing, and working its way back to the original spawning grounds. The fully grown mahseer always returns to the place of birth, making harvesting a simple task.

Ranching definitely has its benefits. The fish get a more natural diet (although they start on pellets), which the ranchers don’t have to pay for and that doesn’t dose the surrounding environs with excessive nutrients; the fish aren’t crowded into unnatural habitats, lowering both the incidence of disease and parasites and the necessity of antibiotic administration; there are fewer packed crowds of pooping, scaly sewage production facilities to worry about.

As you can see, aquaculture has many faces, some homelier than others. It’s impossible to keep track of all the different types, because everybody does it differently and every species requires its own setup. They are simply too numerous and diverse.

Tomorrow, however, I’ll dig through the muck and explain which aquaculture products are worth eating based on nutrition and environmental concerns, because, let’s face it – that’s what it really comes down to, right?

 

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