Monday, January 5, 2009

Profile - Oyster Farming

An Ancient Industry
Oyster farming was first practiced by the ancient Romans in Great Britain, likely developed in tandem with pearl farming. It is an important component of the seafood industry in many countries, including France, Canada, Japan, and the United States. Commonly farmed varieties include the Eastern, Pacific, Belon, Sydney rock, and Southern mud oyster.

Oysters grow in intertidal and subtidal areas. Though they will sometimes attach to a soft bottom, they prefer hard and rocky shores. They have two highly asymmetrical yellow or off-white valves (shells), which are usually quite rough and sharp. All oysters are "born" male, and miraculously become female after a year.

Three main methods are used for cultivating oysters.
  1. Natural Beds - Seed oysters are scattered over an existing bed and left to mature.
  2. Racks, Bags or Cages - Oysters are seeded in one of the aforementioned receptacles, suspended above the bottom, which can then be raised to allow for harvesting.
  3. A Tank - Oysters are grown in an artificial maturation tank. The temperature and salinity can be altered for optimal growth, and calcite and aragonite can be added to help the shells develop faster. This method is the most expensive, but most effectively protects the oysters from predators and poachers.

Thursday, November 27, 2008

Sea Lettuce

Sea lettuce is a type of edible green algae found on coastlines worldwide. It is a popular food source in many countries, such as Japan, China, Ireland, and Great Britain. Commonly added to salads or soups, it is high in protein, fibre, and vitamins and minerals.

Thursday, November 20, 2008

Integrated Multi-Trophic Aquaculture

Integrated Multi-Trophic Aquaculture
Neither monoculture nor polyculture, IMTA is a technique that involves utilizing the waste from a fed species to feed other species kept in the same environment. This creates a balanced ecosystem with enhanced profitability and stability as well as better environmental sustainability. While monoculture is the farming of a single species, and polyculture is the farming of multiple similar species, IMTA incorporates multiple species from different nutritional or "trophic" levels in the same system. For example, a farm could incorporate shrimp, which are fed by the farmers, with seaweed and shellfish, which would make use of any waste nutrients from the shrimp.

Some issues have been raised concerning the potential for contaminants being passed from one species to another. However, there has so far been no noticeable levels of heavy metals, pesticides, or other toxins. Worries that mussels grown near salmon farms could have a fishy taste have also been allayed. In fact, their meat yield is significantly higher as a direct result of the increased nutrients from the salmon pens.

There are two major IMTA projects in Canada.The Bay of Fundy project is a collaborative effort involving industry, academics, and government. It incorporates Atlantic salmon, blue mussels, and kelp working together in a self-contained ecosystem. The Pacific SEA-lab research initiative propogates sablefish, scallops, oysters, blue mussels, urchins, and kelp in a more complex system.

More Info:

Species Profile - Koi

Not all aquacultured fish are bred for food. Some, such as the Koi, or "brocaded carp", are bred for their ornamental qualities. Not technically a species, the koi is a domesticated variation of the common carp.

Koi breeding started in Japan in the 18th century. Rice farmers noticed that some carp were more colourful, and started to capture and raise them. The rest of the world was not aware until the early 20th century, by which time several colour patterns had been established. Koi quickly became extremely popular in Japan, and soon spread worldwide when advances in shipping made it possible to transport them safely.

Koi are hardy, cold-water fish, benefiting from water between 15 and 25 degrees Celsius. Since their bright colours attract predators it is important that they are kept in ponds with deep areas, overhangs, and trees. Koi are omnivorous and can be fed anything from peas and lettuce to watermelons. When fed, they will recognize the person feeding them, and can be trained to eat from one's hand.

More Info:

Thursday, November 13, 2008


Tilapia are one of the most popular food fishes in the world. The tilapia tribe consists of almost a hundred species of cichlid. Due to large size and fast growth, they are growing in popularity as a farmed fish.

Tilapia are omnivorous, commonly eating aquatic vegetation and scavenging for dead plant and animal matter. They tend to live in fresh and sometimes brackish environments such as streams, lakes, estuaries, and rivers. Like other fish in the cichlid family, tilapia exhibit complex breeding behavior, looking after and guarding their eggs and fry, and some tilapia actually raise their young in their mouths.

As an Invasive Species
A significant population of African tilapia has been introduced to North America and other continents through aquaculture and private aquariums. Because they are large, breed prolifically, and tolerate widely varying water conditions, they have no problem quickly spreading throughout an entire lake or river system. They dig in the substrate causing turbidity, consume indigenous plants, and compete with local fish for food, often completely dominating the ecosystem.

Tilapia in Aquaculture
Tilapia are the third most popular farmed fish in the world, after carps (goldfish, koi, etc) and salmon. They are an excellent source of protein, offered in both higher end restaurants and rural fish markets. They are so easy and profitable to farm that a recent estimate for the FAO put the total annual production at roughly 1.5 million tonnes. Being omnivorous, they can be fed on a diet of grain and vegetable matter, which avoids the problem of global protein loss that threatens the sustainability of fish like salmon and tuna.

Thursday, November 6, 2008

Catfish Farming - Overview of Methods

There are three main systems for farming channel catfish: levee, watershed, and cages.

Levee Ponds
Levee ponds are built on a flat area with earthen levees on all four sides, between 4 to 6 feet high. Water is often supplied from a well. If sufficient aeration equipment is used, as many as 4,500 fish per acre can be supported.

Watershed Ponds
Watershed ponds are built on slopes, often in a series of stepped ponds. They are formed by build
ing dams to catch runoff water. Like levee ponds, they are generally 4 to 6 feet deep, since making them shallower allows weeds to grow, and making them deeper can cause low oxygen problems.

Cages can be used to let a catfish farmer grow fish in a lake or pond where harvesting and monitoring fish would normally be extremely difficult. Care must be taken to ensure that the cages do not become clogged with algae, and that there are no more than 1,000 fish per acre of surface area.

Wednesday, October 29, 2008

Fish Farming - Misc

For every kilogram of farmed salmon, it takes between 1.8 to 4.7 kilos of protein pellets. These pellets are made from other fish. In Canada it is illegal to feed fish with food that humans could eat, so the farms ship fish protein in from developing countries with lower food standards. This means that the poorer people there have a harder time getting fish, a vital source of protein for them. This is referred to as "Global Protein Loss."

The majority of salmon farmed here in BC are Atlantic salmon. Atlantic salmon are more susceptible to sea lice than Pacific salmon. Normally, they aren't a major problem, as Pacific salmon are able to resist them. However, sea lice thrive in the pens of the less resistant Atlantic salmon, and reproduce in great numbers. These populations then spill into the ocean and cause significant detriment to the wild stocks.