Many fisheries I fish have size restrictions on fish (trout) you can keep from the waterway. Size limits are often put onto certain waterways for a number of reasons. Maximum size limits are to ensure that we leave large fish to spawn and create offspring that genetically have a greater chance of growing larger too. Minimum size limits are put on fisheries to ensure that anglers do not take fish which are potentially still growing (limiting their ability to become big fish).

It’s vital, for the longevity of our fisheries, that if these legal limits exist that we respect them. In the end it is likely to prolong our sport for us and our future generations.

When it comes to landing a fish on the river and determining if that fish is large enough or small enough to keep, depending on the minimum or maximum size limit, things can get tricky. However I have a tip for you to make it an extremely easy exercise.

An easy way to measure the size of a fish is to carry a piece of string/twine in your fly fishing vest that measures the legal length of a fish. Place a thick knot at the start of this piece of string and then measure out the maximum or minimum length of the legal length along the string. Now place another knot at the minimum legal length (and a third knot at the maximum legal length if one exists). You can now use that piece of string to pull out over any trout you catch to very quickly determine if it is of legal size.

It's cheap, easy to do and really quick to pull out when you have a fish in the net. Tie one up and give it a go.

Note: I'll be adding this tip to my website (http://www.startflyfishingnow.com), along with an image, so check it out if you want to see what I mean.