Fillet knife blades average between 4 and 9 inches in length, with the standard sizes being 4, 6, 7.5 and 9 inches. There is a lot variety, The main reason for these variances is in correlation to the size of fish they are used for. Larger fish require a longer blade, due to the wider girth and extra surface of the fish. Smaller fish, require a shorter blade for easier handling.
An “all-around knife” would consist of a 7.5-inch blade - this model will allow you to fillet small and large fish quite satisfactory, and with the least amount of struggle and effort.
Blade Material
Stainless steel is the standard of the fillet knife world. Unfortunately not all stainless steels are created equally. Most fillet knives do not say what type of stainless steel they are so your best bet is to go with one from a reputable company that will provide a metal blade that is extremely strong, durable, and corrosive resistant.
Flex Test
The amount of flex a blade has is an important consideration when choosing a knife. Flex can be critical to optimum cutting and slicing, and will make your task of filleting more easy.
Handles
Although the blade is the business end of a fillet knife, the handle certainly plays an important role. Comfort, grip, and execution can all be derived from a well-constructed handle, allowing an angler to fillet safely and effortlessly.
Rubber and plastic molded are both excellent choices. Rubber will provide a slightly greater grip, due to the fact it can be squeezed slightly. Both provide good traction. Both rubber and plastic can be cleaned easily. Of course, both materials are corrosive resistant, so your investment is bound to last a long time.
Make sure that the knife you purchase has a beveled area for your index finger. This is found at the spot where the blade meets the handle, and will provide extra insurance against slipping, while providing extra leverage.
Sharpening Stone
It goes without saying that your knife will lose its sharpness over time, rendering the cutting surface dull and ineffective. Some knives will come with a small hand-held sharpener, making the task of keeping a sharp edge quick and easy
Buying a knife that comes with a sharpener is advantageous, as it is manufactured for that specific blade, meaning that it will excel at the job it is designed for. It also means that you will never have an excuse for keeping a dull blade.
Sharpening stones come in a wide variety as well with course medium and smooth stone to hone your blade
Electric Knives
For those that like to clean a mess of fish regularly, an electric fillet knife might be the perfect option for you. These machines can effortlessly work through fish like a hot knife thru butter, saving time, effort and patience. They have a bit of a learning curve, and will take some time to get used to, the benefits are certainly viable. Electric filleting knives are excellent for larger fish such as Grouper and Amberjack or even Salmon. We use our electric filleting knives for this reason, it will cut down on the time you are battling a large fish to get the optimum fillet.
What ever your decision is make sure you take care of your investment. Keep it clean and sharp and always sheathed when not in use. There has been plenty of close calls on a pitching deck with a loose knife flopping around.