External fertilization
Eggs and sperm are released into the environment. Common among many bony fishes.
Internal fertilization
Sperm is transferred into the female reproductive tract; common in several fish groups.
Egg laying
Eggs may attach to vegetation, rock, gravel, nests or drift in water.
Live-bearing
Some fish retain developing embryos internally and give birth to live young.
Mouthbrooding
Parents protect eggs or young in the mouth.
Parental care
Nest guarding, fanning and brood protection can improve survival.
Breeding seasons
Typical timing, not fixed dates
Temperature, rainfall, photoperiod, food supply, river flow and latitude can shift spawning.
| Fish | Typical period | Variation | Egg/young | Method |
|---|---|---|---|---|
| Goldfish | Spring/warming | Latitude and temperature | Adhesive eggs | External spawning |
| Koi | Spring–early summer | Pond temperature | Adhesive eggs | External spawning |
| Common carp | Spring–early summer | Region and water temperature | Adhesive eggs | External spawning |
| Nile tilapia | Repeated in warm water | Seasonal in cooler regions | Mouthbrooded | External fertilization + care |
| Salmon | Often autumn | Population/latitude | Gravel eggs | External fertilization |
| Trout | Often late winter–spring | Population/temperature | Gravel eggs | External fertilization |
| Guppy | Repeated when favorable | Warmth/food | Live young | Internal fertilization |
| Betta | Environmental/captive | Rainfall/warm water | Bubble nest | External fertilization |
| Clownfish | Repeated when favorable | Reef/lunar/environmental cues | Adhesive eggs | External fertilization |
| Seahorse | Seasonal in many populations | Geography/temperature | Male-brooded | Internal egg transfer |
Life cycle
Egg → Adult
EggFertilized egg
EmbryoOrgan development
LarvaEarly stage
FryYoung fish
JuvenileGrowth
AdultMaturity