The Fascinating Mating Strategies of Reef Fish

Reef fish exhibit a wide array of mating strategies, from harems to life-long couples to gender switching to pregnant males. Let’s look some of the more unusual strategies.

The parrotfish is often seen in large schools of rather bland coloured fish accompanied by one or two brightly coloured fish. The brightly coloured fish are the males, but they were not always males.

Most parrotfish are born females but depending on environmental and social pressures may transition to male. This is known as protogyny. This transition is often accompanied by a dramatic change in coloration.

This is not random. Protogyny is common in the fish world and provides some significant advantages when it comes to survival. The more females, the more eggs. The eggs are broadcast over the bottom substrate and are then fertilized by the single male. Very efficient.

If the male dies, one of the many females will transition to male and life goes on.

The very popular clownfish is a different story. Clownfish start life as a male (the Movie Finding Nemo was not entirely accurate). For those that have seen clownfish on the Reef, living within their anemone, you probably noticed one large and very dominant clownfish and a few smaller clownfish.

The large clownfish is the female and the smaller clownfish are males. All clownfish are born male. However, at some point, a male clownfish will transition to female. This is known as protandry. The transition is accompanied by an increase in size and dominance.

The strategy here is, in small groups of fish, it is beneficial for the female to be the largest to lay more eggs, resulting in greater reproductive success. Regarding the smaller males, one of the males will be slightly larger than the others. This is the dominant male and will breed.

At some point, the female will die and the largest male will transition to female and take over the group.

Probably one of the most unique mating strategy is that of the seahorse (yes, a seahorse is a fish). The males get pregnant! A female seahorse deposits her eggs inside the male’s egg pouch. The male delivers live young, and they’re basically miniature versions of adults.

Most seahorse species are monogamous, often forming lasting bonds with their mates. Every day, male and female seahorses perform elaborate courtship displays that involve circling each other, changing colour, and even holding tails. That’s decidedly civilized for a fish.

Contributed with thanks to Whitsunday Conservation Council.

‍