Reproduction is a highly integrative and complex function that requires synchronised production of gametes by both sexes at an optimum time for survival of the offspring. Sexual reproduction is the most common form of reproduction in fish, but there are cases of asexual reproduction (parthenogenesis).

Fish show an enormous variety of reproductive strategies. Some change sex during their life-span, some are completely hermaphrodite and reproduce by self fertilisation or cross-breeding; others choose their sex according to their potential partner. Spawning strategies range from collective events, involving the release of millions of eggs in open water, to sophisticated nest building followed by parental care. Some species of fish even incubate eggs in their mouth or undertake internal fertilisation.

 

 

The process of reproduction is dependent on diverse environmental factors, such as temperature, day length and specific spawning substrates; it can also involve complex social interactions. Reproduction involves hormonal communication between the brain, the pituitary gland and the gonads. Neurosensorial regions of the brain detect environmental stimuli and send chemical messages to the pituitary, which in turn liberates gonadotrophins, acting on the reproductive organs, to stimulate the process of egg or sperm production. When both sexes are mature, pheromones are released to synchronise sexual behaviour in males and females.

 

 

Click here to access a list of Key Species and factsheets on the reproductive biology of farmed fish, laboratory models & those threatened in their natural environment.

A selection of short films are also available, illustrating the reproductive behaviour of certain fish species.