Thursday, May 2, 2013

Otolith Shape and Fish Movement

Hey there fishheads!

So as we learned in Joy’s post on the FACT array, tracking fish movements is an important part of fisheries science. In particular, it is important to know whether fish from different places are mixing or remaining geographically isolated (why? see below); however, this can often be a tricky thing to figure out. With this in mind, today I want to introduce a method I think is pretty darn cool…(cue drum roll)…otolith shape analysis! Now, for anyone who may be thinking oto-what now?, fear not! First, watch this handy 1:30 video, and then we can all share in the excitement-

Awesome, right? As a technique, otolith shape has been used to look at stock structure in a whole variety of different species, from goatfish to cod to king mackerel down here in Florida. I used otolith shape in my master's degree to look at stock structure of greater amberjack in the Gulf of Mexico (results coming soon). Now, otolith shape analysis doesn't always work or lend conclusive results (as can happen with any scientific method), but it is a nice technique that can be used to supplement tagging or genetic analysis methods, and as it is relatively simple and inexpensive (once the otoliths are collected, the analysis is essentially free), it can be a quick first step into examining stock structure. 

Ok, so you may be asking why geographic connectivity matters in the first place...Well, imagine that a species is fished much more heavily in one location than another; if these two regions are not mixing, then you could end up with localized overfishing (which is never a good thing). Furthermore, different stocks will often have different patterns of growth and recruitment, and so may need to be managed differently. Therefore, determining stock structure patterns is crucial to the sustainable management of our fisheries resources.

If you are interested in learning more about this and other neat uses of otoliths, check out this website by Campana's otolith research lab:, or the Aforo database at: Or just google scholar otolith shape analysis and check out the numerous studies utilizing this technique!