Just how much do we know about larval (baby) fishes?

Larval Ocean Sunfish
2.7 mm larval Ocean Sunfish Image: G. David Johnson

Fish larvae (babies) are strikingly different in appearance to the adult (parent) fish. With this conundrum in mind, our very own larval fish guru, Dr Jeff Leis, recently reviewed how much we know about Indo-Pacific fish larvae. Turns out, while great progress has been made, we still have so much more to learn.

Why do we care about fish larvae? Well, other than being seriously fabulous (as you can see by the above image of a larval Ocean Sunfish), we need to understand the entire life cycle of a fish in order to manage them for fisheries and biodiversity purposes. Currently, the biggest obstacle to our understanding is identifying the larvae. Not only do larvae most often occupy a different habitat to their adult form, but they also have specialisations which make them look entirely different.

Jeff found that we know more about the larvae of commercial species of fishes ( e.g. Tropical Snapper [Lutjanidae]) and those that easily reproduce in aquaria (e.g. Damselfishes [Pomacentridae]), than the most common fish of the Indo-Pacific region. In fact, less than 50% of fish families in the region have larvae that have been described (identified). So for the 3000+ species of fish living in the Indo-Pacific region, we only know what 10-34 % of the larvae actually look like. In some of the families with the most species –such as Gobies, Morays, and Wrasses – we know how to identify larvae for only a handful of species.

Genetics and aquaculture have been two recent scientific endeavors which have greatly expanded our knowledge in the area of larval fish identification. However, it is the labour intensive taxonomic and morphological work of the “Godfathers” of larval fishes - Alhstrom, Moser, Richards, Okiyama and Leis, which has contributed most profoundly to our understanding of larval fishes.

The Australian Museum plays a vital role in larval fish taxonomy, particularly those from the Indo-Pacific region. By cataloguing larval fish specimens identified and described by Jeff (and others) we have one of the world’s best reference collections for larval fishes. Unfortunately many of the established larval-fish experts like Jeff have retired and there seem to be few, if any, jobs for the next generation of “larvos”.

So who’s up for helping identify and describing fish larvae?

Amanda Hay
Technical Officer, Ichthyology

More information:
Leis, Jeff M., 2014. Taxonomy and systematics of larval Indo-Pacific fishes: a review of progress since 1981. Ichthyological Research DOI 10.1007/s10228-014-0426-7.