Fish reproduction occurs in coldwater, warmwater, and non-game fish. Each species differ in their courtship, nest building, habits, time they spawn, and the type of egg reproduction. The female fish reaches maturity sexually in order to spawn and with each species there are different calendars. The female maturity is dependent on their life span and whether or not they deposit eggs each year or only once in their life span. The female deposits the eggs where they will have the best chance to survive. The time to deposit eggs is dependent on temperature, light, water flow, food availability, and the salinity of the water. In streams the nest (redd) is usually located in the tail of a pool before the downstream riffle in the stream. The stream provides the eggs with clean water and oxygen. Fish develop faster when water temperature is near the maximum range for the species.
The calendar of species maturity brings about a need to migrate, which could be from a few feet to thousands of miles. Migration ensures that eggs are deposited in environments favorable for early life stage survival.
- There are three different ways fish reproduce:
- The female deposits eggs into a redd (nest) and the male fertilizes the eggs
- The female deposits eggs that are fertilized as they are expelled, and fall to the bottom to attach to each other or vegetation.
- The female retains eggs, which is known as a live birth.
Spawning occurs over a period of time within each species and different species spawn at various times of the year. The eggs are clear in color when deposited and fertilized in their redds. After a period of time an eye appears followed by the alevin. As the alevin or “fry” grows the egg sac that is attached at their stomach area is absorbed. After the sac is absorbed the alevin looks more like a fish and begins to feed on natural food in the area. The natural foods include insects, plankton, and other aquatic species. As the alevin grows bigger they tend to eat larger species. The young alevin need cool water with plenty of shaded hiding spots, such as brush, tangled roots, a variety of large woody material, all provided by a healthy riparian area.