- lucid696Lv 41 decade agoFavorite Answer
Well, I might as well answer your question correctly. Regardless of whether the fertilization is internal or external, it is considered sex if two individuals collaborate for the process. Otherwise, it is asexual reproduction (division, cloning, budding, etc.)
There are some variations on all of these methods, as well as a few variations outside of these, but you should get most of what you need here.
To answer your question, fish typically breed externally. That is, a female fish will lay unfertilized eggs (some deposit them on a surface, others let them float through the water, etc.), and a male will fertilize them with "milt", or sperm.
This method is the most common throughout fresh and salt water fish, and is often referred to as egglayers or egg scatterers. There are various methods fish have for caring for the eggs -- some release them in the water column as mentioned before, while others attach them to a substrate. Others hold them in their mouth after fertilization until they hatch, and others build nests (of bubbles, like bettas) that hold the eggs.
Another common method is called livebearing -- which as the name suggests, results in the female holding the eggs internally until they hatch to give birth to live fish. For this, the fertilization occurs internally; males have a specially modified anal fin (called a gonopodium) that allows him to deposit his sperm in the female for fertilization. Mollies, platies, guppies, swordtails, etc. are all examples of this method.
Hope it helps!Source(s): Years of fishkeeping, years in the industry, and a degree in zoology.
- Anonymous1 decade ago
Most don't have sex. They mate and spawn, meaning that the female drops her eggs into the water and the male releases his sperm fertilizing the eggs.Source(s): This information and detailed profiles of over 2,500 aquarium fish along with over 11,000 photos of aquarium fish can be found at FishGeeks - http://www.aquaria.info Get your 2007 tropical fish calendars: Freshwater http://www.cafepress.com/fishgeeks.91944067 saltwater http://www.cafepress.com/fishgeeks.91939978