Although many fish in the wild and in captivity are egg-laying varieties, some fish do give birth to live young. Known as live-bearers, these fish raise their young to term as any mother would, giving birth after a period of time. Understanding the symptoms of pregnant fish will make it possible to better plan for the upcoming birth. Newborn fish are called fry and are extremely vulnerable due to their size upon being born.
Not many fish species are live bearing. Live-bearing fish give birth to live young rather than laying eggs in the aquarium. Examples of live-bearing fish varieties include fancy guppies, mollies, moonfish, platys, four-eyed fish and swordtails. All of these varieties exhibit signs of their pregnancy before the fry are born.
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In the back of the abdomen of the fish is a spot known as the gravid spot. This spot in the fish will grow both larger and darker when eggs have been fertilized, indicating that fry are beginning to develop inside. The gravid spot is already a naturally darker spot in the fish, but it grows nearly black over time during pregnancy.
Although not always the case, some female fish have greater difficulty swimming when they are close to delivery. This is because the fry developing inside her are beginning to weigh her down. This does not occur in all female fish, though it should still be watched out for because it is a telltale indicator of pregnancy.
Refusal to Eat
Another telltale indicator that a female fish is pregnant is that she begins refusing food just before delivery. Many species of fish are naturally voracious, so when a fish suddenly refuses food, especially at a scheduled feeding time, this is a solid indicator that she is coming close to delivery.
It is completely normal for a pregnant fish to spend more time hiding or seeming to explore plants and decorations in the aquarium. This is an indicator that she is coming close to giving birth, and that she is looking for a place to go through the process. This is an indicator that she is only one or two days away from the labor process.