The Cardinal Rule is don't overcook it - overcooking spoils the flavour and texture of fish. Fish is cooked as soon as it loses its translucent appearance and turns opaque (generally white) all the way through (although increasingly people are choosing to eat certain fish, such as Tuna and Salmon, rare).

To test, insert a fork into the thickest part of the flesh and gently divide it, it's cooked if it flakes easily. With a whole fish or cutlet, the flesh should come cleanly away from the backbone.

Most fish lend themselves to a number of cooking methods, such as those detailed below.

Cook only a few pieces at a time, so as not to overcrowd the pan. Remove when cooked and keep warm while you cook the remainder. Cook in a large heavy-based frying pan in a small amount of hot butter and oil combined (or in ghee, clarified butter). 

Cook for 3-5 minutes (depending upon thickness) on each side, turning once only, until fish is golden and flesh flakes when tested. Small whole fish, fillets or cutlets can be coated in flour or a mixture of flour and cornmeal or breadcrumbs to give a crisp finish. 

Types of fish to pan-fry - Sole, Flounder, Bream, Dory, Whiting, Perch, Tuna, Snapper, Ling, Gemfish, Jewfish, Redfish, whole small fish.

Pat the skin with paper towel to make sure it’s as dry as possible. Sprinkle with salt and pepper (some chefs say a thin dusting of plain flour helps too). Get your pan really hot, add a small amount of oil then put the fish in skin-side down and gently press down with an egg lifter to prevent the skin curling. Cook the fish three-quarters of the way through on the skin-side, you should start to see the flesh turning opaque around the edges of the fillet, indicating that it’s cooked through, then turn the fish over to just finish cooking (1-2 minutes). Don’t be afraid of a hot pan and resist the urge to turn fish too soon, and you’ll have crisp skin like the professionals.

Fillets, cutlets, and whole fish should only be turned once during grilling. Score a thick whole fish, or thick fillets, with 2-3 diagonal cuts across the body on both sides for even cooking.

Brush the skin or flesh with oil, melted butter and/or lemon juice or white wine to prevent it drying out. Place fish under a preheated grill and cook under moderate heat, allowing 2-3 minutes for thin fillets and 4-5 minutes for thicker pieces, or until flesh flakes when tested with a fork.

Types of fish to grill - oily or moist fish, such as Mullet, Blackfish, Tailor, Ling, Gemfish, Perch, Sardine, Flounder, Sole, Bream.

This entails placing the fish in just enough liquid to cover it and gently heating, just below boiling point, until the fish is tender. 

Whole fish, fillets or cutlets can be poached in water and/or wine, court bouillon, milk or beer. If the fish is to be served cold, it may be left to cool in the poaching liquid to retain moisture and flavour.

Types of fish to poach - firm-fleshed fish, such as Ling, Snapper, Gemfish, Perch, whole Whiting, Dory, Parrotfish, Coral Trout.

Most whole fish, fillets or cutlets can be baked in a preheated 180-200ºC oven, unless the recipe specifies a different temperature. Whole fish can be stuffed before baking. 

Put fish in an ovenproof dish or casserole, with seasoning (salt, pepper, herbs, spices) and liquid (water, stock, court bouillon, wine, milk, tomato juice), covered or uncovered, and bake until tender. 

Alternatively, wrap fish (especially fillets, cutlets and steaks) and seasonings in lightly greased aluminium foil or baking paper.

Types of fish to bake – firm-fleshed fish, such as Salmon, Trout, Barramundi, Bream, Snapper.

Half fill a large, heavy pan or deep-fryer with clean oil and heat to about 185°C. Coat the fish with flour, batter or egg and breadcrumbs and lower it carefully into the hot oil with tongs or in a basket.

Cook only a few pieces at a time for 3-7 minutes (depending upon thickness) until golden and flaky. Lift out and drain on paper towels. Keep warm while cooking the remaining fish.

Types of fish to deep fry - most thin fillets, such as Whiting, Flathead, Mackerel, Trevally.

Half fill a wok or saucepan and bring to the boil, reduce heat a little, but keep the water at a gentle rolling boil. Season fish with salt and pepper, place in a steamer basket and place steamer over boiling water.

Cover securely so no steam escapes and cook until flesh flakes when tested. Steam whole fish for 10-20 minutes per 500g depending on thickness of fish.

If steaming more than one fish at a time, ensure they are similar in size and calculate the cooking time according to the size of the individual fish (rather than total weight).

Types of fish to steam - moist firm-fleshed fish, such as Gemfish, Ling, Warehou, Snapper.

If cooking on an open BBQ plate or char-grill, follow directions for pan-frying (including suggested fish). 

If cooking in a covered (kettle) barbecue, follow directions for baking (including suggested fish). Brush the seafood (rather than the BBQ plate or grill) with oil before cooking, as this will minimise smoke. 

Do not place seafood over a flaming fire, wait until the fire has burnt down to a bed of glowing embers, although this is not necessary if the fire is under a metal plate.

Place whole fish, fillets, cutlets or steaks in a container (with thick edges pointing outwards) with a little liquid (water, wine, stock), cover loosely with microwave-suitable plastic wrap and cook at medium range, until the flesh flakes (see timing notes below). 

To ensure even cooking, arrange thicker portions of the fish near the edge of the dish with thinner parts towards the centre and arrange fish in a single layer, don't overlap. There is no need to defrost frozen fish before cooking but allow extra cooking time. Some dishes, such as casseroles, need to be stirred a couple of times during the cooking period to allow even distribution of heat through the food. 

Microwave Cooking Times
Fish fillets - 5 minutes per 500g on medium-high, +50 seconds more for thicker fillets, or until flesh flakes
Whole fish - Large - 6 minutes/750g on medium
Whole fish - Small - 3-4 minutes on medium

Types of fish to microwave - fish with high moisture content, such as Barramundi, Flathead, Salmon, Morwong.

The biggest mistake people make when cooking seafood is overcooking. Fish flesh has a more delicate structure than red meat or poultry, so heat penetrates it, and cooks it, very quickly. The trick is to take it off the heat just before you think it’s fully cooked, as the residual heat in it will continue to cook it on its way to the table. Flesh that has just turned opaque is the key. Cook fish skin-side down as the skin protects the flesh from overcooking. Watch the edges or sides of the fillet: turn thin fillets (such as Garfish) when the edges turn opaque; with thick fillets wait until the flesh has turned opaque about ¾ of the way up the side of the fillet, then turn. The second side will only need a minute or 2 further cooking, depending on thickness, it’s cooked when it flakes easily when tested with a fork. And remember, some fish, especially oily fish like Salmon, Tuna and Yellowtail Kingfish, are great served rare – but always buy sashimi-grade if you plan to serve them this way.

Rocklobsters and crabs are suitable for steaming, poaching, stir-frying, baking, grilling and barbecuing. Above all, avoid overcooking, once the shell turns bright orange and the flesh turns opaque (white), they are cooked. 

To boil them see below. Do not recook cooked crustaceans, use them for salads, sandwiches or cold seafood platters; if a recipe requires you to cook crustaceans, buy them green (uncooked).

The trick with seafood is not to overcook it – the flesh is delicate and cooks quickly so the less time it spends in contact with heat the better. This method of cooking crustaceans will give you a succulent result every time. 

Bring a large saucepan of water to a rapid boil and add ½ cup (150g) of salt for each 2.5 litres of water. Place crustaceans into the boiling water, cover and start timing. Cook 

• mud crabs and rocklobsters for 1 minute per 100g;
• blue swimmer crabs, marron and bugs for 1 minute per 50g;
• prawns, yabbies, redclaw and scampi for 1 minute per 25g average body weight (e.g. if 15 prawns weighs 1kg, that’s 67g average body weight, so cook for 2½ minutes).

Remove from the water and set aside; do not refresh in iced water. Cook larger crustaceans, such as crabs and rocklobsters, individually so the water returns to the boil as quickly as possible. If cooking more than one marron or bug at a time, base cooking time on average body weight (as for prawns), not total weight.

Before boiling any live crustacean, it’s essential to chill it in the freezer for 30–60 minutes (depending on size) until it becomes completely insensible. It’s neither humane nor good cooking practice to put an animal that hasn’t first been well chilled into boiling water, as the stress renders the meat tough. Some sources suggest that adding a little vinegar to the cooking liquid makes it easier to remove the meat from the shell.

Fish stock is quick, easy and inexpensive to make. It’s a great standby to have in the freezer as a base for soups and sauces and fish bones are cheap, or sometimes free if you have a regular fishmonger. Bones from white-fleshed, non-oily fish are ideal, as dark-fleshed or oily fish will give the stock a stronger flavour. Wash heads and bones well to remove any trace of blood, which would give the stock a bitter flavour, then place them in a large saucepan or stockpot, cover with water, add a few bay leaves, peppercorns, onion and lemon and simmer for 20 minutes.

Our Sydney Seafood School recipe for Fish Stock is avaialble on the Recipes pages.

In plate-sized whole fish, test by gently pulling on the dorsal (top) fin, it’s cooked when the fin comes out without any resistance and the eye is completely opaque. In larger whole fish look inside the belly cavity towards the backbone to check that the flesh there has turned opaque.

The shells of crustaceans, including Prawns, Crabs, Rocklobsters and Bugs, turn bright red when they’re cooked. Their flesh is quite delicate, so once the heat has penetrated the tough shell the meat cooks quickly. If crustacean meat has been removed from the shell, it’s ready as soon as it turns from translucent to opaque.

Bivalves (shellfish with a double hinged shell, such as Vongole, Mussels and Pipis) are among the quickest and easiest seafood to cook, as they tell you when they’re ready … by opening. Before cooking them, ensure each shell is firmly closed, or closes when gently tapped (discard any that don’t), then add them to a hot pan over a high heat, with or without a little oil, wine or other flavourings, and cover them for a minute or two, giving the pan a good shake occasionally. As soon as you hear them start to pop open, remove the lid and, one by one as they open, transfer them to a bowl. If a few stubborn ones remain, cover again for a minute or two. Any that still remain closed can be prised open over the sink and checked – if they smell good, they will be; if in doubt, discard them.

Cephalopods, as this group are known, require either very quick cooking over a high heat or very long cooking over a low heat – anything in between renders them tough. If cooking quickly, toss over a high heat just until their translucent flesh turns opaque. Otherwise, cook over a very low heat with some liquid (braising) until the flesh is tender and can be easily pierced with a wooden skewer.

The key is removing the transparent membrane that lines both side of the tube. Once you’ve cleaned and skinned squid (or cuttlefish), lay the tube out flat on a work surface and firmly wipe both sides with paper towel to remove the membrane; wiping across the tube, not from top to bottom, works best. It’s also important to cook squid, cuttlefish and octopus either quickly over high heat or slowly over low heat – anything in-between and it tends to be tough.

Try this fool proof method for poaching whole fish, typically salmon, to serve cold: place the fish in cold salted water over a low heat and cover. As soon as the water starts to simmer with tiny bubbles appearing, remove from the heat, uncover and leave to cool in the poaching liquid; by the time it’s cooled, it’s perfectly cooked and very moist. As a larger volume of poaching liquid takes longer to heat and cool, this works equally well for smaller fish such as trout. It’s worth investing in a metal fish kettle to poach large whole fish. If serving hot, poach fish under 1kg for 1 minute/100g (min. 5 minutes), adding 5 minutes for each additional kilogram.

The ‘milky’ problem sometimes observed in cooked Yellowtail Kingfish and other species is due to a microscopic parasite (from the class Myxosporea), which forms spores in the flesh of the fish while it is still alive. The parasite occurs in fish caught in warmer waters.

Symptoms aren’t evident until the fish is cooked – in its raw state it is perfectly fine to eat. Once cooked however, the flesh collapses into a mushy mass, which looks and tastes unappetizing – although it is not harmful in its raw or cooked state. 

The collapse in the flesh is due to the action of an autolytic enzyme called protease. It becomes active at certain pH levels and certain temperatures, and then breaks down the protein and elastin in the flesh, causing it to ‘melt’ into a mushy mass. It is most active at low pH (around 3) and at cooking temperatures. Ironically the fish’s taste and texture is unaffected if eaten raw. 

Similar microscopic spore-forming parasites are seen in other species of fish including Swordfish, Barracouta, Lemon Sole, Hake and Flounder. In raw Yabbies and Prawns the presence of this parasite is indicated by a white milky-coloured flesh instead of the usual translucent flesh; it is not evident in cooked crustaceans, as the flesh turns white anyway when cooked.

If you encounter this problem, inform your fishmonger immediately and return the fish for an exchange or refund. Your fishmonger should, in turn, receive a refund from his supplier.

When cooking Mussels, there are often a few stubborn shells that don’t open regardless of how long they’re cooked. Traditional wisdom was to discarded these (as they may have already been dead prior to cooking), you can, however, pry them open away from the plate of food, and if they smell good, they’re good to eat. If they are bad, your nose will tell you! It’s still important however to discard any Mussels prior to cooking that aren’t closed and don’t close when gently tapped, as they’re not alive and it’s impossible to tell how long they’ve been dead for. And remember to remove Mussels from the pan as soon as they open so as not to overcook them.