Customers catch happy hour at Olympia Oyster Bar, 4214 N. Mississippi Ave. (Mark Graves/Staff)

Oyster happy hours have transformed the way we think about consuming oysters. They challenge the perceptions that oysters are unaffordable or must be baked in butter and bread crumbs to be edible. Instead, happy hours celebrate raw oysters as a fun, affordable treat.

Although many Portland establishments have oyster happy hours, for this article I focused on four oyster bars. They all offer oysters on the half shell at discounted prices for at least two hours on weekdays. Three offer drink specials. Two offer other happy-hour food items, a nice bonus. All had at least two varieties of oysters at happy-hour price, and each featured Pacific Northwest oysters.

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Netarts Bay is home to some of Oregon's most prized oysters. (Motoya Nakamura/2013)

A note: Not all oysters are created equal. Oysters are filter feeders and therefore take on flavor qualities that match the waters where they grow. This phenomenon, known as "merroir" within the oyster community, is especially apparent in raw oysters. It's why oysters are generally named after the body of water they're harvested from - Hammers from Hammersley Inlet, Netarts from Netarts Bay, etc. Merroir is a buzzword to keep an eye out for - or to throw around to prove your sophistication at oyster happy hours.

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John Williams shucks oysters at Dan and Louis Oyster Bar. Williams says on busy days he'll shuck about 800 oysters. (Mark Graves/Staff)

It's also worth noting that you are consuming raw seafood sitting in an oftentimes gritty shell, so here are a few things to watch for:

Shell pieces and dirt: Shuckers usually work quickly, and oyster shells are flaky and sometimes dirty, so it's not uncommon to get a few pieces of shell or dirt in the meat. Just pick it out; it doesn't mean there's anything wrong with the oyster.

Whether the meat is detached from the shell: Most shucked oysters will be completely detached from their shells, but sometimes the shucker (intentionally or not) will leave a little piece of the oyster connected. This doesn't affect taste or quality, but you'll look pretty silly trying to slurp an oyster if it's still stuck to its shell. If it is, just disconnect it with that little fork they give you.

The aroma: In case you've got a negligent shucker, sniff each oyster before you pop it in your mouth. It should smell fresh and like the sea. If it smells like rotten fish, stay away.

Here's a look at Portland's best oyster happy hours, ranked by category.

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Customers catch happy hour at EaT: An Oyster Bar, 3808 N. Williams Ave. (Mark Graves/Staff)

EaT: An Oyster Bar--Best Happy Hour Deal

EaT is the only Portland oyster bar offering dollar oysters during happy hour. EaT now offers about 15 varieties of West Coast oysters but will soon add East Coast oysters. Happy hour typically features two varieties. When we went, these were Chelsea Gems and Hammersleys - both from the Puget Sound and both delicious.

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Customers catch happy hour at EaT: An Oyster Bar, 3808 N. Williams Ave. (Mark Graves/Staff)

In addition to raw oysters, the standard menu features po'boys, fried/baked/Rockefeller oysters, and lots of Cajun staples.

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Customers catch happy hour at EaT: An Oyster Bar, 3808 N. Williams Ave. (Mark Graves/Staff)

The restaurant, among the largest and most versatile of the oyster bars, is decked out in true Cajun style. There are TVs for sports and special events including an "Oyster Bus" tour on the last Saturday in May: all-you-can-eat oysters and lots of beer and wine on a tour to the Coast and back.

3808 N. Williams Ave., 503-281-1222, eatoysterbar.com, happy hour all day Tuesday, 3-5 p.m. Monday and Wednesday-Friday.

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Dan and Louis Oyster Bar, 208 S.W. Ankeny St. (Mark Graves/Staff)

Dan and Louis Oyster Bar--Best Happy Hour Menu

Dan and Louis is - by far - Portland's longest-running oyster happy hour. This historic downtown restaurant has been around since the early 1900s. It's a huge, beautiful place that provides a glimpse into old Portland. Go for the experience, but if you're looking for an engaged, super-knowledgeable shucker, there may be better options.

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A happy hour order at Dan and Louis Oyster Bar, 208 S.W. Ankeny St. (Mark Graves/Staff)

When we went, Dan and Louis offered six oyster varieties (all West Coast), three for the happy hour price of $2 an oyster: Hammersleys, Stretch Islands and Totten Inlets, all from Washington. Dan and Louis doesn't offer happy hour drink deals but does have an extensive and reasonably priced happy hour menu - another reason to visit.

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Customers catch happy hour at Dan and Louis Oyster Bar, 208 S.W. Ankeny St. (Mark Graves/Staff)

208 S.W. Ankeny St., 503-227-5906, danandlouis.com, happy hour all day Monday-Tuesday, 4-6 p.m. Wednesday-Friday

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Customers catch happy hour at Flying Fish Oyster Bar, 2340 N.E. Sandy Blvd. (Mark Graves/Staff)

Flying Fish Oyster Bar--Best Oyster Selection

Flying Fish is the tiniest oyster bar we visited, with the biggest selection. It's a little tricky to find, tucked into a small corner inside Providore Fine Foods. With only eight seats, oyster happy hour at Flying Fish is a fairly intimate experience, which - if you're into chumming it up about oysters - can be a bonus.

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A happy hour order at Flying Fish Oyster Bar. (Mark Graves/Staff)

The menu includes 15 West Coast, British Columbia and occasionally East Coast oysters - all offered at happy hour price. Flying Fish does have the priciest happy hour of the four we visited - the happy hour deal is 50 cents off all oysters - but the opportunity to try any oyster on the menu is pretty special. Plus, the owner/shucker, Lyf Gildersleeve, is as enthusiastic as he is knowledgeable. We tried Kumamotos, Netarts, Fat Bastards, Kusshis and Olympias. Flying Fish was the only bar offering Oregon oysters when I visited. Geographically speaking, though, Washington oysters are often closer to Portland than bivalves from Oregon.

2340 N.E. Sandy Blvd., 971-806-6747, flyingfishoysterbar.com, happy hour 3-5 p.m. Monday-Friday

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Customers catch happy hour at Olympia Oyster Bar, 4214 N. Mississippi Ave. (Mark Graves/Staff)

Olympia Oyster Bar--Most innovative

Fairly small with an inviting, nautical atmosphere, Olympia has the most interesting menu of the four oyster bars visited. Inspired by owner Maylin Chavez's Mexican heritage, creative and delicious ingredients like cucumber pico de gallo, agua chile rojo and chimichurri abound.

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A happy hour order at Olympia Oyster Bar, 4214 N. Mississippi Ave. (Mark Graves/Staff)

Olympia offers six Northwest (and occasionally East Coast) oysters, with two varieties available during happy hour for $10 a half-dozen and $20 a dozen ($18 on Tuesdays). We tried Baywaters and Night Tides, both great. I'm an oyster purist, so I love them raw, but I do recommend Olympia's cooked oysters. The kataifi, fried in shredded phyllo with smoked avocado and serrano jam, was one of the best, most inventive fried oysters I've tasted.

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A happy hour order at Olympia Oyster Bar, 4214 N. Mississippi Ave. (Mark Graves/Staff)

Olympia also has a strong focus on oyster-wine pairings; they've got a great wine list and knowledgeable wine guy.

4214 N. Mississippi Ave., 503-841-6316, oobpdx.com, happy hour 4-6 p.m. Tuesday-Thursday, 2-6 p.m. Friday