Out on the West Coast the most popular bait is herring. The herring is caught and then starved for several weeks, and then electrocuted in net pens, resulting in a firmer belly baitfish. Otherwise, the bellies will blow out when trolling, and salmon are not attracted to a gut pile being pulled through the water.
Herring, like alewives are plankton feeders. So when thinking about buying herring, one should look for a whole baitfish, with scales on it. Do not use the cut bait that is sold in tubs. It does not have scales on it. They are a byproduct of the Japanese roe market. These filets have been run through pumps, resulting in a loss of scales. This product is called, or referred to as cut bait. A whole bait is a far superior product to use.
Cut bait has to be brined in a salt brine to keep it from falling apart. It stinks and smells. Good quality bait should smell fresh, and be whole, and should not stink. If you want to use cut bait, take a filet knife, and cut your own from whole bait. Also, with whole bait you will generally get 12 or more whole fish per tray of bait, as compared to 6 filets with the pre-cut bait for the same price. So with a filet knife a package of whole bait you will land up with 24 filets if it is filets you are looking for. But, I can not overemphasize the importance of using whole bait.
On the West Coast you can not give away the tubs of pre-cut bait. Because everyone out here knows to buy whole bait. This whole thing of buying pre-cut bait is a gimmick that is being pushed off on the East Coast consumers, and is starting to roll over into the Great Lakes.
Caveat emptor...<buyer beware>
...Jerry Bechhold