The prospect alone of learning to fillet fish can be a daunting one for an absolute beginner. Experts can make it look easy but the reality is that different species of fish are not only of hugely varied shapes and sizes, they very often have extremely diverse skeletal structures. A prior knowledge of relevant bone arrangements and how the flesh actually sits attached to the bones is imperative for each species you intend trying to fillet. This can be obtained either online, from a book on the subject, or simply by asking a friend or acquaintance for tips and advice. All this knowledge aside, if there is one absolutely essential factor relating to filleting fish properly, it is that you obtain a dedicated filleting knife possessing a number of necessary features.

Fish Filleting Knife
Credit: Gordon Hamilton

Basic but extremely functional fish filleting knife

Sharpness of the Blade

Whatever kitchen task you happen to be undertaking in relation to cutting or chopping, the sharpness of the knife blade is almost always of paramount importance. In relation to filleting fish, one thing that is likely to happen where the knife blade is not sharp enough is that you are likely to tear rather than cut cleanly through the flesh of the fish. This is almost certain to spoil final presentation and possibly the preparation of the dish completely. There is also the possibility that an insufficiently sharp knife can become caught in the flesh of the fish, leading to a potentially serious accident. If a quality knife sharpener is not something you already have at home, you may wish to look to buy a product which comes with a dedicated sharpening stone as part of the deal. This does not usually add much if any extra cost to your purchase.

Filleting a Mackerel
Credit: Gordon Hamilton

Mackerel are in relative terms fairly easy to fillet but if your knife is not sharp enough, you will tear the flesh rather than cut neatly through it

Shape of the Blade

There are some fish filleting knives which have an absolutely straight blade while some blades know a slight curvature. If you are intending filleting only round fish such as cod, haddock or whiting, you will find that a straight bladed knife is ideal for your purpose. If on the other hand you are looking to fillet fish with more complex bone structures such as flat fish, it may be that you will find a curved bladed knife easier to guide around the more complex bone structure. 

Filleting a Codling
Credit: Gordon Hamilton

A long thin blade is required for getting right in to the bone structure of a codling and slicing off the fillet in one piece

Blade Flexibility

The flexibility of the blade in a fish filleting knife is absolutely critical, regardless of which type of fish you intend cleaning. Rigid bladed knives are simply of no use when it comes to guiding the blade around the often complex bone structures of a fish. Although no knife without a flexible blade should ever be sold labelled a fish filleting knife, it remains important to know this requirement where you are perhaps choosing a loose knife from a general display in a store.

Filleting a Pollack
Credit: Gordon Hamilton

Pollack and similar fish have complicated spinal structures so blade flexibility is absolutely imperative

Finger Guards

No matter how careful you may be, there always exists some possibility of an accident occurring when you are using an extremely sharp knife. The key is in minimizing that risk in any way you can and a finger guard of some type is a huge benefit in this sense. Look therefore for a knife which has a bulbous protrusion at the base of the handle where it meets the sharp edge of the blade. This is a feature to help prevent your fingers slipping all the way on to the blade where they for some reason slip on the handle. It is fair to say that that the overwhelming majority of filleting knives in the modern era will have this guard as standard.  

Filleting a Rainbow Trout
Credit: Gordon Hamilton

It's all too easy for your fingers to slip on to the blade where an appropriate guard is not present, particularly when butterfly filleting the likes of a rainbow trout

Rapala 7 1/2 Inch Soft Grip Fillet Knife / Single Stage Sharpener / Sheath
Amazon Price: $17.99 $15.15 Buy Now
(price as of Jan 31, 2016)
Available in four different sizes to suit your individual requirements, this excellent filleting knife also comes with a transport sheath and a sharpener. It has a soft grip handle and a no-slip knuckle for extra safety and its stainless steel blade is easy to clean and keep razor sharp.

Transport Sheaths

Sea fishermen in particular will often take a filleting knife on their trips in their tackle box or bag. It can be used either in the preparation of fresh bait or to clean and fillet fish immediately after they are caught. If you intend taking your knife out of the home with you, be sure to purchase one which comes with a sheath designed for transporting to limit the possibility of an accident occurring. I myself actually have two good quality filleting knives, one of which stays in a drawer in my kitchen and the other in my tackle bag. I really find it to be of great use when out on or at the sea. Just do remember to clean a transported knife after each and every trip to keep it in prime condition.

Filleting Ling
Credit: Gordon Hamilton

Ling cod have four fillets which require to be removed due to their bone structures and all the required knife features are brought in to play

Price Range and Cost

Like so many other items, these knives come in a very significant range of prices. Where you can afford to do so, it is advisable to buy one at the higher end of the price range to help ensure you get one of the highest quality. This will not only make it more likely that you have a better performing blade, it is also likely to last longer where you continue to look after and care for it properly.

Filleting a Flounder
Credit: Gordon Hamilton

Flat fish like flounder are among the trickiest of all to fillet and without the right tool for the job, your chances of success are minimal