Spawning behavior of garden eels, Gorgasia preclara and Heteroconger hassi (Heterocongrinae), observed in captivity

The behavior and reproductive ecology of typically nocturnal marine eels is poorly known but garden eels (Congridae, Heterocongrinae) are familiar tropical marine eels. They live in colonies and protrude their bodies from burrows during the daytime to feed on zooplankton. Apparent daytime courtship/spawning-like behavior has been observed within the colonies but actual spawning and fertilized egg production has not been confirmed. This study describes observations of splendid garden eels (Gorgasia preclara) and spotted garden eels (Heteroconger hassi) spawning in low light at night and producing fertilized eggs in a large multispecies public-display tank in the Sumida Aquarium. Video recordings of 5 of 17 detected spawning or egg or sperm release events documented the spawning behavior of G. preclara, and positively buoyant fertilized eggs of both species were collected. Their spawning behavior while protruding from widely spaced burrows confirms that garden eels likely spawn within their colonies with their pelagic eggs drifting away with currents.