Males vs. Females

QUESTION: How do you tell the difference between a male and female fish, and do they differ in their behaviour and diet? TOM ADCOCK, VIA FACEBOOK

This is a great question to kick things off, and one that I’m frequently asked. Telling the difference between a male and female carp can, at some times of the year be relatively easy, but at others it’s often far more tricky - I’d say that the spring is the easiest time to do so.

Let’s start with a female carp. During the spring, she’s likely to have a large, rounded and soft belly. This large belly is an indication of the two ovaries that the fish is carrying in readiness for spawning. More generally, female carp, when viewed from above as they swim, tend to have more rounded heads and pectoral fins. In the spring they can sometimes look a little lopsided, as it’s not uncommon for there to be a difference in the size of an individual’s ovaries.   

Next up, the male fish. Throughout the year, males are generally more torpedo-shaped, have a more pointed snout and longer fins. During the spring, they frequently develop spawning tubercles over their gill plates, along their flanks and on their fins. Spawning tubercles have the appearance of grains of sand on the fishes’ bodies and can give them a slightly rough feel if rubbed gently.

Close to spawning time, the male fish will frequently produce sperm from their vents. This is often observed when male fish are placed on an unhooking mat (look for a bright, white discharge).

In terms of their diets, I don’t believe there’s a great deal of difference between the two sexes, but their behaviour certainly can differ. From what I’ve observed, male fish commonly fight the hardest when hooked, and when we’re handling carp at the fish farm, they are the ones that always give me the toughest time. If I want to look good for a fish shot at the farm, I always try to pick up a round-looking female, and avoid the testosterone-fuelled, rocket-shaped males!