Natural spawning has been replaced by artificial spawning of eggs and subsequent incubation of them in mechanical incubators.
For mating, male and female zebrafish were maintained in one tank at 28.5 °C on a 12 h light/12 h dark cycle and then the spawning of eggs was triggered by giving light stimulation in the morning.
The greater hydration associated with the spawning of pelagic eggs (>90% water) in vast numbers would have severely loaded the maternal ovary with water, and probably led to batch spawning, which is the prevalent means of reproduction in the extant Acanthomorpha.
The spawning of pelagic eggs by many marine teleosts (termed pelagophils), where water content may reach up to 95% in weight, has been proposed as a mechanism to provide a water reservoir in the embryo to compensate for the passive water efflux due to the hyper-osmotic effect of the seawater until osmoregulatory organs develop [ 7, 8].
Some of the worms do this at dawn on the day before the moon reaches its last quarter, others on the following day; on the second day of the spawning, the quantity of eggs liberated is so great that the sea is discolored.
The cane toad is a prolific breeder; females lay single-clump spawns with thousands of eggs.
Spawning and retention of eggs and larvae within fjord basins sheltered from coastal currents is a likely mechanism for maintaining genetic differentiation among the local populations (Knutsen et al. 2007), in combination with high site fidelity and natal homing of older cod (Espeland et al. 2007; Svedäng et al. 2007).
It is worth mentioning that few egg numbers may be attributed to either egg loss, releasing larvae at the late stages, or beginning of spawning of new egg lay.
It is worth to mention that few eggs' number may be attributed to either egg loss, releasing larvae at the late stages or to beginning of spawning of new egg lay.
They are protected under planning law, so someone should sneak out at night with a bucketful of eggs (spawn?) and pour them into every pond, ditch and puddle where new housing developments are proposed on farmland.
The farmers need to have plenty of young fish on hand just before the flood arrives.This is not a problem for fish such as riverine carp that can easily be induced to spawn and produce millions of eggs at a time.
