As a consumer, understanding the impact of fishing practices on the environment can be a little daunting. Considerations range from personal ethics — is eating fish the same as eating animals? — to practical questions: is locally fished tuna worse than imported sardines? Being a discerning consumer, however, is no longer a question of abstaining from eating fish. Many of us would like to continue eating seafood — we just don’t know how to do it sustainably.

Although the latest report from the Department of Agriculture, Fisheries and Forestries has noted that the number of overfished local species has dropped from 24 in 2005 to 15 in 2009, destructive fishing practices are still in use. The Australian Marine Conservation Society claims that although Australia enjoys sound environmental credentials, its seafood production is ranked 31st out of the top 52 seafood-producing nations.

The fishing industry uses a quota system, which caps the amount of fish and seafood any one fishery can bring in, but this can mask the wider, accompanying environmental damage. In particular, dredging and trawling techniques cause significant damage to their environment: both involve raking the ocean floor for their catch, and by-catch of turtles, sharks and sea mammals is common. Long-line fishing involves expansive lines of baited hooks, which often take turtles and albatross along with them.

Much of the available literature, however, can be confusing and contradictory, and is often directed towards the environmentalist rather than the consumer.

As a rule of thumb, small fish such as anchovies, sardines and herring are more sustainable than larger, more predatory fish.  For every metric tonne of these fish, about 50 litres of oil is used, compared to 2000 litres for flounder, swordfish, tuna and sole.

However, such statistics obscure the fact that small fish such as anchovies, sardines and herring are often imported and carry their own hefty carbon footprint. And eating the Australian sardine, seemingly the best option, is also risky — the trawling methods used to catch them destroy the habitat and seals are often caught as by-catch. The most sustainable small fish would therefore be whitebait, but it’s not always readily available.

Aquaculture, the farming of fish and seafood, can be similarly misleading. In many countries, it is seen as a successful solution to overfishing, but mainly in the farming of herbivorous fish. In Australia, many farms breed carnivorous fish, a practice that carries hidden consequences. One kilogram of tuna, for example, may require up to 10 kilograms of sardine feed. And as those fish are indiscriminately trawled from the ocean floor, the potential for by-catch is just as significant as for wild fish.

So, what to do? Determining which species of Australian fish (and other seafood) to avoid will greatly reduce wanton consumption. Generally, we can expect any fish that are long-lived or slow-growing; from the deep sea; and from the shark or ray family to be bad. Local fish trump imported fish.

The Australian Marine Conservation Society has, with the help of an independent academic and fisheries expert, developed a rough guide for Australian seafood. Among the species receiving the “red prawn” of disapproval are barramundi, Atlantic salmon, scallops and farmed trout.  Those receiving the “green flounder” go-ahead are Australian salmon, bream, whiting, trevally and squid. Hard copies of the guide can be ordered, and a digital copy is available as an app.

Finding a fishmonger with a reputation for sustainable produce would be the next step. Otherwise, ask a supplier to list more sustainable alternatives to fish listed in recipes.  The website Good Fish Bad Fish has a food converter that allows you to plug in the fish you’d usually use, and comes up with a better alternative. According to the converter, snapper has a generally low sustainability rating, and suggests replacing it with bream, mulloway or blue-eye trevalla.

The Australian Conservation Foundation, however, has approved one snapper from the Port Phillip Bay fishery. Their guide culls the selection further, singling out fisheries whose product has the least impact on the environment — the premise being that a species generally classed as “sustainable” can still be fished unsustainably. On their list are the yelloweye mullet from Coorong in South Australia, the silver trevally from Corner Inlet in Victoria, squid from Hawkesbury River, NSW, and barramundi from Cone Bay in WA.

Overwhelmingly, the biggest problem for a nation of foodies is eating out. Good Fish Bad Fish is trying to tackle this problem by initiating a fledgling guide for restaurant goers. The entries rate each eatery (only five at this point) and indicate what proportion of the fish available are sustainable. Choosing the right fish and chips may still be still be up to the consumer, though, but the Good Fish Bad Fish and the AMCS guides are useful here.

Finally, if canned tuna is a non-negotiable item on your shopping list, Greenpeace has a guide for selecting the most sustainable products available in supermarkets. And for those leaving for international waters, Friend of the Sea and the Marine Stewardship Council have resources for several countries.