Differentiating between male or female fish is not always easy, especially so, as both salmon and sea trout change their appearance as the season progresses. Hopefully the following information will help you in determining the gender of your catch.
The male salmon is the fish that is prone to the greatest degree of change in appearance. At the end of April when the fish begins to move upstream it is silver in colour and extremely well built. At this stage of the season it is probably the most difficult to differentiate between male and female. The male has a slightly more pronounced “beak” than the female, basically a minor elongation of the lower and upper jaw. During autumn the fishes head will increase in size and the lower jaw will develop into more of a “hook”. The coloration is black through brown with smaller reddish patches. Spots are for the larger part situated above the midline of the fish. At this point of the season the female can be perceived as being extremely long and of great size, she does not display the oversized head or the pronounced “hook” jaw. Quite often the female will display a slight protrusion, similar to a wart upon the lower jaw. This is not to be confused with the males “hook”. The autumn coloration will be black through brown with the belly sometimes showing shades of blue through purple. The female will not display the reddish patches common in the male. Again spots will mostly be situated above the midline of the fish.