Telling the difference between male (known as Cock fish) and female (known as Hen fish) trout can be tricky in immature fish but in sexually mature fish there are three things to look for that are dead give aways. Firstly, the lower jaw or kype – male fish have a distinct hook shape to their lower jaw. Secondly, the anal fin – male fish tend to have a concave shape on the trailing edge. Thirdly, the colour – when spawning male fish colours become darker and more contrast, especially the red in the Rainbow. In immature fish all these differences exist but they are less obvious. The photos below show each of these criteria nicely in mature and similar sized fish. Remember these three characteristics can also be used to estimate the age of a trout – a male fish with a nice kype and bright colours is already 1-2 years old. Also, when gutting fish a mature female (2 years or older) will contain Roe (brightly coloured orange eggs).
If you would like assistance in identifying your catch please do not hesitate to contact us. Remember catch and release; survivability decreases with time out the water so it is better to get a picture and debate it later than dawdle and risk the fish.
If you enjoyed this article we also have a variety of other Trout related stories, tutorials and articles you might like to read:
Follow Us On Social Media... Fish The Fly knows how everyone loves updates, photo's and videos, so keep updated with all the latest fly fishing news from South Africa below!