Fish are known for large amounts of eggs, the main reason for this is survival for fish eggs is extremely low, in many cases only 20 percent of the eggs laid will make it to adulthood.
How Many Eggs do Fish Lay?
Fish usually lay hundreds to tens of thousands of eggs. The term describing the ability to produce plenty of offspring is called fecundity.
Fecundity varies for different fish species and within the species between individual fish, depending on its age, habitat, and whether the fish protects the eggs or not.
Some fish in fast-flowing rivers like rainbow trout spawn once a year, and a 13-inch female can produce up to 3 000 eggs over the course of one spawning (which usually lasts a few days).
On the other hand, a female brook trout can produce only around 100 eggs in the first year of life, but a 3yo female can lay between 500 – 1 000 eggs. Female sea trout can lay about 800 eggs per 1 lb of bodyweight, and female brown trout can release close to 900 eggs / 1 lb.
Some predatory fish dwelling mainly in the lakes, like 18″ female largemouth bass, can lay up to 64 000 eggs. The number of eggs depends on the size of the fish, with smaller females (11″ – 12″) laying only up to 3 500 eggs.
One nest of smallmouth bass may contain between 2 000-16 000 eggs, but the biggest females can deposit up to 27 000 eggs during spawning. Smallmouth bass females would release 20 – 50 eggs at a time, every 4-10 seconds, to give the male fish time to fertilize them properly.
The smaller fish often targeted by predators, like bluegill, can lay up to 100 000 eggs per spawn. Small females in their first year of spawning can produce only around 1 000 eggs, but the numbers grow with the growth of the fish.
A 2 meter long female sturgeon can lay around 400 000 eggs, but bigger ones can release over 4 million eggs.
How Often do Fish Lay Eggs?
River-dwelling rainbow trout spawn once a year, usually around September – October. They make nests out of gravel, called redds. The female digs a hole lays eggs, and when the male fertilizes them, the female covers the eggs with more gravel to conceal them.
Largemouth bass spawn two or three times a year, in spring, when the water reaches 65 – 75F. In the northern parts of the US and in Canada, the spawning starts in late April and lasts till early July. In southern states, it starts in March and ends in June. The male bass makes a nest where the female deposits the eggs.
Bluegills usually spawn three times during one summer but can spawn as many as five times, depending on water temperature and food availability. Their spawning season lasts from May till late August, with the peak in June, when water temperatures are the highest, 67 – 80F. The whole colony would spawn simultaneously, and the spawning would last 6 – 12 hours.
Some fish, like sturgeon, may not spawn every year. For sturgeon, spawning needs perfect conditions. The requirements include the proper reaction to the length of light in spring, clear water with shallow rock or gravel bottom, where the eggs can adhere, water temperature, and flow to oxygenate the eggs. When they decide to spawn, it usually occurs between April and May, when waters reach 53 – 58F.
Which Fish Lays the Most Eggs?
The ocean-dwelling grey grouper is the winner in “the most offspring” competition. The biggest female can lay close to 340 million eggs in one year.
Right after is mola fish. This strange-looking fish can lay up to 300 million eggs in one spawning season.
Next, behind mola and grey grouper is bluefin tuna, laying 10 million eggs during one spawning.
Why do Fish Lay so Many Eggs?
Many different factors weigh on the fecundity of fish. The species, size, habitat, food availability, and a number of predators are just a few.
Some fish, like trout, would lay eggs that lodge themselves between gravel, and after that, the parenting ends. Even though the eggs are deposited in a sort of a nest, they lay in fast-flowing water, partially exposed to the strong current and predators. Even during a good year, only up to 80% of eggs hatch.
The male largemouth bass would protect the eggs in the nest, but once they hatch and the fry reaches around 1 inch and starts to swim around in search of food, the protection ends, and the little fish are on their own. Out of the big number of eggs that hatch, only 5 – 10 fish would reach over 10 inches.
There are like bluegill that would spawn multiple times a year, laying thousands of eggs each time. The reason behind it could be the high numbers of predators (including other sunfish) who find bluegill eggs, fry, and fingerlings to be an effortless and readily available meal.
Sturgeon parents don’t build nests or protect their offspring. In fact, the female and male release eggs and milt in the strong current. In those conditions, the chances of eggs being fertilized are slim. Additionally, most sturgeons don’t breed until they are about 20 years old and don’t spawn every year, hence the need to lay so many eggs.
The amount of eggs laid by fish varies greatly, however, most fish, especially game fish lay hundreds to thousands of eggs. This allows for the survival of the species, as majority of the eggs are at risk from many things including predators and weather conditions,