Seafood stars north of the bridge at Petermen in St Leonards

Josh Niland wants the world to eat more fish. He's so serious about it, there isn't a skerrick of meat on the new Petermen menu. Instead, the fish IS the meat.

Niland's devious strategy of treating fish as if it were steak, chops, sausages and salumi was honed at his flagship Saint Peter, at Rose Bay's Charcoal Fish and at his Fish Butchery stores in Paddington and Waterloo.

For Petermen, he has created a range of large-format fish dishes that act as ensembles designed to make the protein a star.

The Mooloolaba chateaubriand ($120 for two, $240 for four) is the most obvious example, with South Coast yellowfin tuna treated like filet mignon. The rosy-pink rounds come with a tumble of shoestring fries, surrounded by satellite dishes – mushrooms, garlic warrigal greens, sauce bearnaise.

Think of it as a benign dictatorship. This is how the chef wants you to eat his fish, with the correct accompaniments, so that's how he serves them.

There's also a focus on vegetables – harissa eggplant, pickled vegetables from Duck Foot Farm, and lovely craggy empanadas ($13 each). Stuffed with wilted saltbush, they're served, probably gratuitously, with a fruity, oily, finely chopped Turkish ezme salad of roasted red peppers and herbs.

Co-owner Julie Niland has given the long window-lined space a contemporary Scandinavian feel, brightened by paintings from the irrepressible Ken Done, an artist obsessed with ocean life. Bare solid tables of sustainable rubberwood have a mid-century air, and the bar has handsome art deco elements – as well as Never Never's stunning Oyster Shell gin for appropriately saline martinis.

The oysters themselves are listed, unusually, by age. Pristine Merimbula three-year-olds ($7 each) are so briny and celebratory they force me to go all classic and order muscadet – a crisp, minerally, good-value 2019 Domaine St Martin ($70). Muscadet is also the go with stunning Goolwa pipis ($38) swimming in a surfy froth of their own juices.

Niland's temperature-controlled dry-ageing makes the most of oily varieties such as leaping bonito ($16), whose clean, raw flesh is precision-sliced and seasoned with bone soy. Glistening tiles of velvety yellowfin tuna ($20) come sauced with a sharp but sweet Ananda caper and black garlic vinaigrette, finished with caper leaves.

Head chef Joshua Osborne keeps flavours either crisp and clean or roguishly fruity and oily; with a rough-and-tumble of shelled Jervis Bay mussels bathed in a dirty-red achiote (annatto seed) vinaigrette ($16) that I love.

Most reports on the Saint Peter oeuvre concentrate on the exotica – fish-eye crisps, cod fat salted caramels. I'm more taken with how Niland has captured the essence of coral trout, dry-ageing then grilling it so the skin is as crunchy as crackling yet the flesh is relaxed and almost sweet.

It comes as an ensemble ($145 for two), on a bed of fruity chimichurri that is as finely chopped as mirepoix, with a line-up of Richard Mohan's O Couto peppers (one of which is – surprise! – hellishly hot) and a very cute crumbed croquette of collar meat.

Western Australia's marron weighs in at 350 grams ($80), its shell darkly crimson, its juicy, pull-apart lobster-like flesh oozing with curry butter.

After all that, Julie Niland's desserts offer a refined finish, with a classic take on apple tart ($18) that sees apple "scales" glazed with verjuice and topped with grilled vanilla bean ice-cream.

The systems aren't quite bedded down yet, with some waits for both tables and dishes. Small wonder. Petermen is a vastly ambitious operation, with as many arms as an octopus. There is also a kid's menu (the couple have four children; they know their market) with barbecue fish, salad and chippies. The cult Saint Peter Sunday brunch has also crossed the bridge, with double tuna cheeseburgers and sea urchin crumpets.

It's as brave as anything else the Nilands have done, but also more approachable and enjoyable. At this rate, the world will definitely be eating more fish.

The low-down

Drinks Small cocktail list including a few low and no-alcohol, and a list of fruity whites and light reds, many with an oceanic theme

Vibe Smart Scandi-minimalist fish bistro with hidden depths

Go-to dish 350g Manjimup marron, curry butter and fried bread, $80