Aquaculture has emerged a popular and efficient way to grow and rear marine and aquatic life for consumption. Various species of fish, shellfish and even plants are grown in tanks, ponds, man-made inland systems or open water cages in the ocean until they reach market size. On a large scale, aquaculture could lessen the need for finding and catching wild fish for food or ornamental purposes i.
Aquaculture has grown exponentially in recent years. Aquaculture shows tremendous promise in being a long-term source of food to sustain a growing population. However, it has its fair share of problems. There are many reasons why aquaculture is good for the environment.
In , the total seafood consumed in the world was more than million tons. Of this, 90 million tons were taken out of freshwater and marine habitats. This practice can lead to overfishing, which happens when more fish are caught than can be replenished naturally. This can cause certain fish species, like Atlantic bluefish tuna, to become extinct.
Overfishing can impact marine ecosystems as well. For example, cod feed on herring. If herring are overfished, the cod population is adversely affected. Upsetting links on the food chain has consequences up and down the line. Aquaculture could help decrease the effects of human consumption of fish on freshwater and marine water habitats by producing food without taking away from overfished environments.
Fish, plants and shellfish produced in aquaculture farms are also used to rebuild species populations in freshwater and saltwater habitats. A lesser-known benefit is that plants grown in aquaculture provide material used in pharmaceutical, nutritional, and biotechnology products. Aquaculture can also potentially be used for treating sewage and wastewater. For example, in India, treated sewage is first passed through ponds of duckweed and next through ponds of prawns and carp.
The reality is that all of these things can be true. In terms of broad environmental impact, aquaculture has the potential to grow food more efficiently than most forms of animal agriculture as it can be done with substantially less reliance on natural resources.
In the past we have made a lot of environmental mistakes on land and as we increase our focus on fish farming, we are presented with an opportunity to not make those mistakes again in our relatively untouched oceans. This means being incredibly careful in the decisions we make around the species we choose and where we place our farms, the choices we make in feed, and the scale of the farms we are looking to build.
Farmed shellfish like oysters , mussels and scallops are some of our most sustainable food options. Compared to other forms of aquaculture, they require no additional feeding as they tend to draw their nutrients directly from the ocean currents in which they are grown. In this way, they create an incredibly direct link from sunshine to highly nutritious animal protein via plants in the form of plankton.
In some cases farming shellfish actually reduces pollution and improves water quality. For example, fertiliser runoff from land based farming is a common water pollutant, but shellfish have the ability to filter this from the water and convert it into food. This also has the added benefit of reducing the likelihood of toxic algal blooms in the area where shellfish farming occurs. Back on land, redclaw crayfish , marron and yabbies farmed in ponds also often use no additional feed other than the occasional bale of hay to fertilise pond water making these farmed species good sustainable options.
There are very different ecological standards across the major species farmed in Australia with Atlantic salmon , barramundi , rainbow trout and yellowtail kingfish all grown in very different ways.
The challenge being that these forage fish, usually species like anchovies, sardines and mackerel are caught by factory trawlers and traded all over the world. As for the issue of escaped fish from farms, which does still happen occasionally, underwater cameras now closely monitor cages, and divers regularly inspect cages with this in mind. Farmed seafood is incredibly resource efficient, especially when compared with other animal proteins beef, pork, chicken.
The feed conversion ratio, which is the measurement of how much feed it takes to produce the protein, is 1. This means that essentially one pound of feed produces one pound of the protein. As farmed fish are closely monitored in comparison to wild fish, farmers have more control over variables. This can positively impact the environment and the fish. Farmed fish are generally free of environmental contaminants like mercury and heavy metals, as they exclusively eat human-processed feed.
The farming of filter-feeders, like shellfish, can improve water quality. These creatures eat excessive nutrients in the water, which, in turn, prevent the buildup of effluent. This system is called polyculture, or integrated multi-trophic aquaculture IMTA. Sustainable fish feeds are on the rise. Fishmeal and fish oil used in feeds may come from trimmings from processing plants.
Additionally, substituting plant proteins for fishmeal in feeds is also becoming more prevalent. Farmed fish should no longer be dismissed as unsustainable.
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