Marine Fish Day Five Reproduction

Reproduction Sexes are usually separate with paired gonads in the body cavity.

Reproduction Spawning and larval development must take place during the most favorable conditions.

Reproduction Timing is controlled by sex hormones which are triggered by environmental factors Day length Temperature Food availability

Reproduction Some fish are hermaphrodites: produce both male and female gametes. They usually breed with different individuals to ensure cross fertilization.

Hermaphroditism Sequential hermaphroditism (sex reversal): all individuals begin life as one gender but change into the other gender when necessary for reproduction. Very prevalent in sea bass and groupers.

Hermaphroditism In clownfish all individuals begin as males. The dominant fish changes gender to female and the largest remaining male becomes the mate.

Hermaphroditism If the female dies or is removed from the environment, the largest male will change gender and the next male will take its place.

Reproduction Most fish will change their color when they are ready to breed.

Reproduction They will display courtship behaviors (dancing or postures) to indicate to the other fish in the area that they are ready to breed.

Internal fertilization Some fish go through copulation (especially the cartilaginous fish – males have penis-like structures called claspers).

External Fertilization Broadcast spawning – release of gametes into the water is more common. When fish release their eggs into the water they typically release many more than will survive as they are a good food source for other organisms.

Reproduction The fewer eggs fish produce the more care they provide for them. Some fish will defend their breeding sites or nests. Some fish physically carry the eggs after they have been fertilized (pipefish and seahorses).

Oviparous Fish that spawn eggs. Often the egg drops to the bottom of the ocean to develop. Have a large yolk sac for nourishment. Most bony fish.

Ovoviviparous Eggs develop inside the female and she gives birth to the live young. In some sharks the embryos are not ready to be independent when their yolk sac is consumed. They must find other means of nutrition and consume unfertilized embryos in their mothers reproductive tract.

Ovoviviparous

Viviparous Sharks that have embryos that absorb nutrients from the walls of the mothers reproductive tract. Similar to mammals but without a placenta.