The answer is yes and no because it depends on the knife and the grind of the blade. Most fishing knives are easy to sharpen, especially if they come from a good quality manufacturer and are made of stainless steel. But, the flexibility of the knife can determine how easy it is to sharpen its blade. The more flexible a knife is, the harder it can be to use a whetstone to re-sharpen it. Flexible blades can give too much bend, which in turn makes for an uneven grind. The correct way to ensure the best sharpen of a blade when using a whetstone is to apply minimum pressure with the blade against the grinding stone. It is important to not over sharpen your blades. The absolute best way to sharpen the blades of most fishing knives is to apply even, but firm pressure. Most fisherman’s knives are thin and with just a little work, your blade will be back to razor-sharp in no time.
However, the grind of the knife will also affect the ease with which it is sharpened. Some grinds are easier to sharpen, while others take more skill. It is important to know which grind your knife is before you attempt to sharpen the blade. You can easily damage the blade trying to sharpen it to a hollow grind design if, in fact, it is an asymmetrical grind blade. If you are unfamiliar with sharpening blades, it is best to find a professional or someone who can teach you. Over time, as you get to know your knife, you can to learn how to sharpen it back to perfection.