Distribution, diversity, and abundance of garden eel larvae off west Sumatra, Indonesia

Garden eels of the subfamily Heterocongrinae (family Congridae) are long, slender, planktivorous eels that live in colonies in shallow sandy tropical marine habitats, but little is known about their early life history because their leptocephali are rarely collected. This study examined the species composition, distribution, and size of a large collection of garden eel leptocephali in Indonesian waters off west Sumatra on both sides of the Mentawai Is. in June 2003 to learn about the diversity and larval ecology of garden eels in this region of the Indian Ocean. 371 Gorgasia and 104 Heteroconger leptocephali were collected, which may have included about 9 species of the 2 genera. Based on vertebral counts of adult garden eel species from the eastern Indian Ocean region, the leptocephali of G. maculata, G. preclara, G. taiwanensis, H. hassi, H. obscurus, and H. tomberua may have been collected, but adults of the last species have not been reported from the region. At least 2 other species of Heteroconger and another species of Gorgasia leptocephali were also collected. Leptocephali of G. preclara, G. taiwanensis, and H. tomberua appeared to be the most abundant in the collections. Wide size ranges of Gorgasia (9-68 mm) and Heteroconger (14-104 mm) leptocephali were collected, but no metamorphic specimens were caught. The smallest sizes and the greatest abundances were collected in the northern region of the study area near the most extensive areas of continental shelf along west Sumatra, suggesting that many garden eel leptocephali had been transported offshore by strong currents. A similar widespread distribution of garden eel leptocephali was present off west Sumatra in Sept.-Nov. 1929, which suggests garden eels and their larvae may typically be abundant there.