It's a Thursday night at Jax Fish House, and the joint is hopping.

Three women perched at the bar are celebrating their singlehood, smiling at the bartenders and knocking back oyster shooters ($4), miniature martinis floating fat oysters in a spicy, vodka-splashed bloody mary mix. One, it seems, is never enough.

The misted patio, a downtown summer pastime, is rollicking with cosmopolitan city slickers, lapping up the late-day sun and consuming ingenious liquids, like the sweet basil martini ($9), a mix of muddled basil leaves, gin, fresh-squeezed lemon and Lillet Blanc.

The dining room, minute as a minnow and enclosed by red brick walls graffitied with multicolored crayons, is moody and dim. The eye-catching lights cast an effervescent glow on the aquarium teeming with rainbow-striped fish darting through reefs of coral.

But despite the ambient lighting and lulling fish tank, Jax is not romantic. It is rambunctious and loud and packed to the gills on a nightly basis with glamorous crowds.

It's easy to fall under the spell of its charms, so long as you realize that it's not the place for quiet conversation.

Instead, Jax is a full-tilt party.

It's been this way since 1997, two years after owner Dave Query opened the first Jax Fish House, still going strong in Boulder. And like the original incarnation, the LoDo Jax has stayed the course, steadfastly becoming more seasoned and polished with time. The maturation is evident on the floor and in the kitchen.

While the space is barely bigger than a clamshell with droves of diners desperate for your table, the waitstaff never makes you feel rushed. They give you ample time to peruse the menu and encourage questions to which they have all the answers. There is no pressure to order your main dishes at the same time as your starters, and the bill arrives only after you've asked for it. The servers are, without a doubt, some of the most professional, friendly and accommodating in Denver.

And the kitchen, overseen by executive chef Sheila Lucero, is equally adept at making you feel terrifically happy.

For proof, just take one bite of the crab cakes ($13), two fat, misshapen, griddled-until-golden gifts from the Gulf, generously lumped with blue crab (and little else), judiciously spiced and held together with a whisper. They're accompanied by a creamy horseradish sauce and a marmalade rejoicing with citrus flavors, both of which are delicious.

So, too, is a starter of oysters and squid ($14), a generous plate of hot oysters and rings lightly fried to a crisp mahogany, sharing space with gingered gelee and ponzu aioli.

Jax is an oyster bed of bivalves, with a chalkboard highlighting both East and West Coast varieties. The oyster sampler plate ($17.95), an ever-changing roster shucked in the bar, yields eight specimens on the half shell on a plate of rock salt. The choices range from plump and creamy Hurricane oysters to the more oceanic and briny Goose Points.

Bobbing in luxurious red curry cream, a heap of black mussels ($9 per pound), their meat plump and pink, catapulted me into a stupor. The black cod ($16), silken, flaky and nearly creamy in texture, was bolstered by dots of sturgeon caviar, a river of lemon syrup and French toast, the sum of its parts simultaneously sweet, salty and savory.

As dusk turns to darkness and the ceiling becomes a near luminescent ripple of waves gliding across the room, Jax becomes even more inviting. It's easier than ever to appreciate Lucero's Sunday-night-only cioppino ($30), a triumphant fisherman's wharf, rich with crab, mussels, scallops, shrimp, salmon and linguine. The Alaskan king crab dinner ($29), served with skin-on red potatoes, corn on the cob and an impossibly sweet merus-cut crab leg with drawn butter and lemon wedges, is also excellent.

A slab of grilled steelhead trout ($24), supple and strong-flavored much like salmon, is ringed by a piquant red pepper romesco and herbed chickpea frites that are annoyingly addictive. A trio of trembling scallops ($26), pan-seared until they're the hue of honey, are livened with a risotto spiked with fresh peas and pea shoots.

By the time you leave Jax, the din will still be deafening, but part of the fun here is arriving on the early side. That way, you're in harmony with the buzz.

lmidson@gmail.com

Jax Fish House

* Grade: A-

* Address: 1539 17th St.

* Hours: 4-10 p.m. Sun.- Thurs; 4-11 p.m. Fri.-Sat.

* Food: Seafood

* How much: $9-$16 starters; $4-$12 soups and salads; $11-$45 main dishes; $3-$8 sides; oysters on the half shell (market price)

* Reservations: Highly recommended

* Noise: Lively

* Information: 303-292-5767 or jaxfishhouse.com

* Parking: Meters and valet Thursday-Saturday