An easy way to remove pesky little pin bones from fish fillets is with your vegetable peeler. Run the blade of the peeler against the grain of the fish and the bones will stick out. If you can't remove them with your fingers, try using a pair of tweezers. Or if you are a gadget lover, you can buy a special tweezerlike fish-boning tool.
Fish and the slow cooker are not natural buddies, and care must be taken to ensure that fish does not become woefully overcooked. That's why there are so few fish recipes, and most of those recipes have a long cooking time for the other ingredients; then the fish is added last so it doesn't overcook.
When choosing a fish for your slow cooker, select sturdy fish like swordfish, salmon, halibut, cod, and tuna. The fish should be cut into 1-inch pieces or larger, and they are added during the last hour of cooking, at the most. To test whether or not the fish is cooked, flake it with a fork. If it's fully cooked, it should flake easily.
Shellfish toughens if it's overcooked, so the same timing principle holds true for shellfish such as shrimp and scallops. Stir them in for the last 15 to 60 minutes of cooking time, depending on the quantity and cooking temperature.
Delicate fish like sole and flounder should not be used in slow cooked recipes. They are too thin for slow cookers and will fall apart.
Ellen on Edibles
Sauté is a common cooking term taken from French. It literally means "to jump." The idea is to keep food moving in the pan by stirring it frequently, if not constantly. Sautéed food is cooked in a little hot fat in a shallow pan, over medium-high or high heat. This causes the food to release its natural sugars and intensify in flavor. Sautéed food should sit lightly in the fat and should not be submerged in it.
Sturdy vegetables like carrots, potatoes, and celery are staples for the stew pot and, by extension, the slow cooker. And believe it or not, it takes longer for these vegetables to cook in the slow cooker than it takes most meats or chicken. When prepping hard vegetables, peel and trim them as usual, then cut them into bite-size pieces so they'll cook faster.
More delicate vegetables, like green beans, peas, and snow peas, should be added for the last hour of the cooking time. If you're anxious to serve food as soon as you walk in the door, it's better to cook these tender vegetables in the microwave and then stir them into the slow cooker. If they cook for the whole time, they will be an unappealing gray color and very mushy.
You'll see that in most recipes one of the first steps is to sauté the onions and garlic before being adding them to the slow cooker. This preliminary cooking process makes the onions and garlic sweeter and less sharp. (I've skipped the step in recipes where this doesn't matter.)