Clownfish Spawning

The spawning process begins with courtship. Three to five days prior to the actual mating ceremony, the male begins biting at the substrate, increasing the frequency of this action as the mating approaches. As the day nears, the female joins the male in biting the substrate. During the final pre-mating day the pair will become noticeably more aggressive, actively chasing away any fish that come near. After a brief courtship, which includes various forms of posturing, the female will lay her eggs upon a flat surface just to the side of their host anemone, in the area that they cleared of debris earlier. In host anemones that set their foot into soft sand substrates, the adult clownfish hunt for a flat substrate surface to work with. Such items as shells, sand dollars, coconut shells or most any human litter such as tin cans or plastic have been used. Just prior to sunup, the pair will nip at their host's tentacle, causing it to retract into the area where the female will lay her eggs. The female will make a few practice attempts at egg laying and then finally, as morning begins to appear, she rests her swollen abdomen against the intended nesting site and, using her pectoral fin, drags herself around the site while releasing the unfertilized, sticky, negatively buoyant eggs. The male swims closely behind her, fertilizing the eggs as he follows. The actual egg laying will take an average of two hours. For a pictorial featuring many of these spawning events, as well as a description, click here.

With the easy part out of the way, the pair must now defend their eggs from potential predators. The female moves away from the nest and usually goes directly into feeding mode, while the male jumps into action and now belligerently defends and diligently tends to the nest. The male quickly attacks any approaching predators, preferring to rely on an excellent offense as his best defense. That is, without hesitation, he will begin attacking and biting the intruder. When no threat is present, he fans the eggs with his tail both to aerate them as well as to remove any debris that may have settled onto them. Though the female occasionally assists the male, this is not considered to be common practice. In addition to fanning the eggs, the male removes any unfertilized or fungally-infected eggs by eating them. Depending on factors ranging from the female's size to the individual species, the eggs will number from 100 to 2,500. Their color will take on several different variations as they mature. Generally, eggs are pink to orange in color as they are laid and remain so for a couple days. As they age, their pink to orange will gradually fade to a drab gray or brown color. Finally, as the hatching nears, they become shiny silver with the fry's developed eyeballs clearly visible. Depending on which species are involved and the water temperatures at the nesting site, the eggs will hatch around day seven or shortly thereafter. They hatch as swimming larvae, and under the protection of night they join the tumultuous life of plankton. If the larvae win the equivalent of the clownfish lottery and survive, they will settle out in from 8 to 16 days.

Text by Henry C. Schultz III
Video courtesy of Erik Carrillo

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