The first factor to consider is if the fish is farmed or wild caught. If it is farmed you need to then look at how, is it Maori culture, which is where it is farmed in the ocean, or is it on land aqua culture. If it is wild caught, you need to look at how it is caught, is it using damaging methods such as bottom trawling or long lining. What species and where they are caught, will also be a factor to consider as some species can be abundant in certain areas, however depleted in another.
We do need to reduce our overall seafood intake however, to help benefit the planet. As our population has grown species have rapidly depleted, and the planet's ecosystems are struggling to maintain our species current diet. If we all reduce our intake, and when we do eat seafood ensure it is from inland farmed fish and pole and line caught wild fish, we can help make a big difference in restoring the planet's ecosystems.
The following information has been gathered from MCS's good fish guide, for further information and to review other types of fish please click here.
Species to avoid
Rays, Sharks and Skates
In general, skates and rays are vulnerable to overfishing because they grow really slowly, mature late in life and produce few young.
Sharks are top predators and are extremely important in marine eco-systems.
A lot of shark species are currently threatened with extinction.
Sharks, rays and skates are highly vulnerable to depletion.
It is estimated that 100 million sharks are killed each year.
Cod are usually farmed in the ocean and not inland.
Cod are a bottom dwelling fish, and therefore are caught by using bottom trawling - destroying the sea bed, coral reefs and habitats.
Many Atlantic Cod populations are in a depleted state.
Icelandic and Alaskan Cod are currently being well managed, therefore are the most sustainable option.
Majority of tuna is caught using long lines, which is a method that often kills sharks, turtles, dolphins and seabirds.
During the 60's, 70's and 80's tuna stocks were vastly depleted.
Tuna are very energy expensive, therefore, farming is highly inefficient.
Pole and line caught tuna is the most sustainable option, and Skipjack and Albacore tuna are currently in a better state of abundance.
Prawns and Shrimp
Farming is often very destructive to the coastal ecosystem, this is because it results in destroying mangroves and seagrass.
Farming in developing countries is increasing and unregulated.
The prawns and shrimp are fed fish meal, which is ground up wild fish.
To catch wild prawns and shrimp, the method of trawling is used - destroying the sea bed, coral reefs and habitats.
In the UK we have closed land based prawn farms, which are the most sustainable option.
Conger Eels have very low resilience to fishing and spawn only once, after which the females die. Therefore, many captured eels will be juveniles and not have had a chance to spawn.
European Eel populations are at an all time low: they are Critically Endangered on the IUCN Red List and urgent action is needed to recover the stock.
European eels are fished in all life stages, from juveniles (aka glass eels) to adults (silver eels), and those that are fished do not have the chance to breed.
Farming relies on catching juveniles from the wild and growing them in captivity, as they can't be bred in captivity, and therefore contributes to the depletion of wild stocks.
Groupers are largely overfished, with hugely depleting numbers.They are assessed as vulnerable to highly vulnerable to overfishing.
Groupers are not managed, and are often caught with fishing methods detrimental to their vulnerable reef habitat.
Swordfish has been heavily exploited throughout its range and previously overfished, remaining heavily so in the Mediterranean.
The primary method of capture though, long-lining, continues to impact on vulnerable species such as seabirds, turtles and sharks. Whilst there are measures in use to reduce these impacts, more needs to be done to ensure they are effective and that impacts to these species are minimised.
A number of swordfish fisheries in the Atlantic and Southwest Pacific have been certified as well managed and sustainable by the Marine Stewardship Council (MSC), so make sure to look for any products that carry their blue eco-label. Improvements to management in other fisheries has recovered populations; with the North Atlantic, Western North Pacific, and Indian Oceans all having fairly healthy fisheries.
It is a highly vulnerable species, and has been heavily overfished throughout its range.
There is little management in place to protect the species, except in Norway.
IUCN categorises Atlantic halibut as Vulnerable in Europe and Endangered globally.
Greenland halibut is a long-lived, slow-growing species, making it vulnerable to exploitation by commercial fisheries. In west Greenland, populations are declining and subject to overfishing.
Capture methods include trawling, gillnets and longlines.
Atlantic halibut is widely farmed although in small quantities compared to other species. Unlike salmon and cod, halibut can be farmed in closed tanks as well as in open pens. Choose halibut farmed in closed, shore based production systems such as those used in Scotland, as environmental impacts of production are mitigated.
Hand-line caught mackerel from the southwest of England remains the best choice thanks to its ring-fenced quota and low impact methods.
The mackerel stock in the North-East Atlantic is in a good state and in general is caught by pelagic trawling and purse-seining - relatively low-impact and well-targeted fishing methods.
Farmed Oysters and Mussels
Shellfish farming is a low-impact method of aquaculture and high quality water standards are required for cultivation of shellfish for human consumption.
Mussel farming requires no feed inputs therefore farming of mussels is a good way of producing seafood.
There are no chemicals used in mussel farming.
Rope grown or hand-gathered mussels, if taken from the wild, have a lower environmental impact than those harvested by mechanical methods such as dredging.
Abalone can be farmed on land in aquaculture systems that are enclosed, referred to as "recirculating systems", which means that all water and waste are contained.
Abalone graze on seaweeds for food. As there are no environmental interactions and no depletion of resources for food this makes abalone a really sustainable seafood choice.
Char can be farmed on land, and as a result the use of land based production systems address many issues of environmental concern that can be associated with farmed fish production.
Artic charr has a lower requirement for fish in its diet compared to other salmonid species and in UK and Icelandic production responsibly sourced feed is used.