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A photographic guide to the larvae of coral reef fishes

By Shane Graber - Posted Oct 22, 2012 11:00 AM
This photographic guide is being compiled and updated by Benjamin Victor, a researcher that, according to his CV, is interested in studying the "larval ecology of coral reef fishes and its role in determining biogeography and population dynamics." For those interested in the larval stage of reef fish (breeders immediately come to mind), this is a website you should check out.
A photographic guide to the larvae of coral reef fishes

An example of the number of larval photos available on the website.

Benjamin is performing a gargantuan feat: attempting to photo-document and identify as many larval fish as possible using plankton tows, a microscope, and sometimes DNA analysis to positively identify these fish. The current focus of his work centers around Caribbean gobies and blennies as these families comprise about a third of all reef fishes in the area.

In his own words:

Virtually all of the thousands of species of tropical reef fishes have a larval stage that spends weeks to months in the open ocean before returning to the reef to settle. This transition from pelagic larvae to settled juveniles is a profoundly important time for reef fishes. ...

Despite its undoubted importance, this transition has not been comprehensively studied and one of the reasons this may be true is the lack of information on late-stage larvae. I have been collecting these larvae, mostly by netting at a nightlight directly over the reef, but also with crest-nets and other techniques for many years. In addition, I have focused my daytime collecting on what some of us call "new recruits", the recently-transformed juvenile fishes that suddenly appear in the morning on the reef.

For some reason, almost all of the reef-fish larvae I collect at a nightlight are late-stage larvae ready to settle onto the reef. This is not an artifact of their attraction to the light: I have towed plankton nets in the area and I get a similar size complement of larvae. In addition, other techniques to collect incoming larval fish, such as crest nets, yield the same size categories of larvae.

The simplest explanation for this phenomenon is that larval fish that are ready to settle somehow maneuver themselves into on-reef currents, perhaps just by rising to the surface water layer. There has been recent research indicating that reef-fish larvae are good swimmers and can actively orient towards reefs. Whichever way they manage it, almost all of the larvae I capture are around the particular settlement size range for their species. This can be very helpful in identifying larvae.

If you are looking for information on larval fish and their various morphologies, definitely take a look at Benjamin's website.

Author: Shane Graber
Location: Indiana

Shane has kept saltwater tanks for the last 12 years, is a research scientist, lives in northern Indiana, and is a proud Advanced Aquarist staffer.


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