THIS FRIDAY is the last day of the rockfish ban in the lower Potomac, meaning that as of Saturday you can keep up to five of the endangered striped bass you catch there, as long as they're between 14 and 34 inches.

That creel limit applies to the stretch of the Potomac from the D.C. line near the Woodrow Wilson Bridge to the Chesapeake Bay. Right now, however, fishing in the lower Potomac isn't great, according to Captain John's Crab House and Marina at Cobb Island.

In the Washington stretch of the Potomac, where there are no limits on rockfish, the number of stripers has dropped off, but the size has picked up, according to Dan Ward of Fletcher's Boat House.

The rockfish now being caught off Fletcher's are generally between 10 and 12 pounds, but last weekend "several" rockfish of more than 12 pounds were taken, Ward says. A 4-pound hybrid striper also was brought in to Fletcher's, as well as two 3-pound largemouth bass, he adds.

Those largemouth are not big compared to what's upriver, but they are pretty good catches for the Washington Potomac. There are also big catfish -- a 101/2 pounder was brought in by a child not much bigger than that, Ward reports.

The herring in the Potomac have dropped off -- which makes them a valuable bait right now. The rockfish and catfish are hungry for herring, and when they run into herring -- including the strips of herring on the end of your hook -- "it's like a starving man seeing a filet mignon," says Ward.

In the Chesapeake, the small bluefish have moved in, and the big blues are still around, reports Pat Raley of Sister's Store in Point Lookout, Md. In addition, she says, the alewives have returned after a dropoff of the baitfish a few weeks ago. DINING ON CRABS

Last week we told you how and where to catch blueclaw crabs. Now comes the best part -- eating them.

Despite its fierce appearance, the blueclaw crab is a taste delight. Its meat is sweet and succulent, and well worth the time spent getting to it.

To cook the crabs, you need a steamer pot. That's a pot that has two sections. The top section is taller and has holes in the bottom to let the steam through. You also can boil the crabs if you want, but around here most folks prefer to steam them covered with their favorite crab spice. Here's how:

First, bring the water to a boil. Some people say adding a beer to the water gives the crabs extra flavor. Now pretend you are Michael Jackson and put on your protective glove. The faint-hearted can use tongs to place the live crabs in the top part of the steamer.

Each layer of crabs should be sprinkled fairly heavily with the spice. Note, however, that the spice is very salty and you may prefer to cook the crabs without it. Instead, you can put spice on the table for those who want to spinkle it on the crab meat as they are eating.

When the pot is full, cover it and place it over the boiling water. Let it steam for 30 minutes. The crabs should now be a bright reddish-orange color.

Cover a table with several layers of newspapers and dump the crabs in the middle. Supply everyone with a short paring knife. Wooden mallets are useful for breaking open the legs and claws.

There are about as many ways to eat crabs as there are people who eat them, and none of the ways we've tried is easy or entirely satisfactory. Every person will evolve his own style, but here is a starting point:

First, pull off the top shell by grasping it by one of the long points on either side and holding down the bottom by the legs. Some hard-core crab lovers eat the yellow-green and orange stuff inside, but most people won't even consider it. The next step is to strip off and discard the lungs, which are the gray, feathery, finger-like organs on each side. They taste terrible.

Now, pull off the tab on the bottom and use the knife to cut the crab in half, from front to back. Pull off the legs or cut them off by slicing through the softer top shell. Separate the paper-thin top shell from the bottom and use the knife to dig the meat out of the channels in the body. Once you get the hang of it, you'll get the large chunks of meat out first and then settle down to digging for the smaller chunks. Repeat the process for the other side.

To get at the claw meat, place the knife across the claw near the pinchers and tap the back side of the knife lightly with the mallet or the handle of another knife. The idea is to crack the claw shell but not cut through it. Now carefully break the claw at the cut and pull gently. The claw meat should emerge whole. The leg segment just before the claw segment also contains good meat. Use the same technique on it. THE TANGLED ANGLER SAYS:

Bloodworm is not the name of yet-another horrible disease. Rather, it is the name of a fat, juicy saltwater worm that is a favorite food of many fish, such as spot, croakers and tautog.

Most bloodworms available here are shipped in from Maine, where they are harvested commercially be digging them out of the mud flats when the tide goes out, according to bait wholesaler Mike Baldea of Mike's Baits in Annapolis.

They are more expensive than nightcrawlers or other earthworms but are a more effective bait for saltwater species because they are the fish's natural food and don't lose their color as rapidly. You can buy them in most bait shops near the Chesapeake Bay or the ocean for from $2.40 to $3 a dozen. Around here, you can get them at Fletcher's Boat House on Canal Road, at Columbia Island Marina, Holiday Sports Shop in Silver Hill, Md., and at Shepherd's Live Bait and Tackle in Alexandria.

Bloodworms resemble their earthworm cousins but have hundreds of tiny legs on each side and four small pincers inside their mouth that can administer a stinging bite, Baldea says. So be careful when handling them. SAFETY TIP OF THE WEEK

When near the water, attach a sportsman's band to your eyeglasses. This will keep the glasses on your face when you lean over and will save you some money, not to mention trouble on the way home if you have poor vision.