Fish (other than catfish) is outstanding for weight loss/control as long as it is prepared in a healthy manner.
I eat a lot of salmon, tuna, shrimp, scallops, whitefish, tilapia. I probably eat fish every other day. Sometimes, twice or more in a day. The imitation crab legs (packaged "leg style" or lump imitation crab meat is basically very lean fat free whitefish. Almost pure protein. I eat it in salads, eggs, or just by itself.
You do need to be aware that TUNA and shellfish contain small amounts of mercury and if you eat too much too often you can start developing mercury toxicity. You should eat no more than 12 ozs of shellfish (that contain lower levels of mercury) and no more than 6 ozs of Tuna/lobster/halibut/orange ruffy per week. There's a lot of good information on this subject on the FDA and EPA websites.
Salmon, cod, whitefish aren't listed as being concerning regarding mercury levels.