There is a lot of very exciting research involving otoliths being carried out around the world. Some of the research is focused on the otolith itself, but most of it uses some feature of the otolith as a tool to another end. What follows is our view of the most promising of the up and coming fields in otolith research - the fields that we see as making substantial strides in the near future. There may be others, but these are the fields that we currently have our eyes on:

Summer 2010 Program in Iceland focusing on Fish Ecology and Modeling (with ageing component):  The University of Iceland has announced the continuation of a series of intensive, graduate-level summer courses to students pursuing a degree in fisheries science, marine ecology, or biological oceanography.   Their announcement says:  "It is a great opportunity to experience the magic of the long summer “nights” of midnight sun and the natural wonders of Iceland while taking courses that will prove useful in your graduate studies and beyond. Please take a moment to check out our 2010 Graduate Summer Program. We will be offering our popular course Fisheries Ecology: Management and Conservation of Marine Resources in a Changing Ocean (http://www.marine.is/fisheco.html) taught by University of Iceland faculty as well as visiting professors, such as Dr. Steven Campana and Dr. David Conover. This course includes 3 days of hands-on instruction in otolith-based fish ageing (annual).  We also have added two new courses entitled: Introduction to Hydrodynamic Modeling and Ecological Modeling (http://www.marine.is/grad.html). No tuition, only a moderate registration fee and all courses are offered in English. For further information, visit our web site http://www.marine.is and see all of the exciting things that Iceland has to offer.

2009 Otolith Symposium Completed:  The Fourth International Otolith Symposium in Monterey, California in Aug 2009 turned out to be a very successful and interesting meeting.  With more than 260 attendees representing 35 countries, the opportunities for networking and learning new skills were endless.  Plus, of course, the venue was gorgeous!  Keep your eyes tuned for news of the next Otolith Symposium in 2014 (perhaps in Majorca, Spain???).

Statistical Program for Age Validation based on Edge Analysis:  Okamura and Semba (2009) published a paper detailing a statistical program for validating annual growth band formation based on edge analysis (whether or not the growing edge of the otolith or vertebra shows an opaque or translucent zone across the year).  To our knowledge, this is the first such statistical analysis that has been developed for analyzing edge-type data, which has usually been analyzed in an ad hoc and non-rigorous manner.  The authors have made the R code for this program available at their website.

Symposium Completed:  Advances in Fish Tagging and Marking Technology:  An international symposium on fish tagging and marking, including biological markers such as otolith elemental fingerprints and genetics, was held 24-28 February 2008 in Auckland, New Zealand.  Other sessions included those dealing with acoustic telemetry, archival and satellite tags.  The symposium web site presents more information, including plans for a peer-reviewed book.  It was a good meeting!

New Paleothermometer:  Everyone is on the look-out for the ideal paleothermometer; something that can be used to reconstruct temperature history without the confounding effects of salinity or water composition.  For use with otoliths, stable oxygen isotopes are usually the best bet, but only if the isotopic composition of the water is known.  The 2007 paper by Ghosh et al. presents an alternative based on combinations of stable carbon and oxygen isotopes.  It's not a panacea, but it avoids complications due to water composition.

Web-based Otolith Identification Software:  Although there now a number of otolith atlases around the world which can be used to identify species based on otolith shape and appearance, the AFORO web site presents the first web-based automated species identification software based on otolith shape.  The program uses several mathematical methods of shape analysis (including wavelet analysis), and requires nothing more than uploading a suitably-oriented otolith image on a black background.  Species identifications are currently limited mainly to the Mediterranean, but the image database is being expanded to other areas.  

Maximum Likelihood Software:  With the realization that elemental fingerprints can be used very effectively to separate mixtures of fish coming from different sources, there is increasing demand for the maximum-likelihood based software to separate the group mixtures.  Discriminant analysis is not a good option here, since the 'priors' parameter is unknown.  In the Statistical Analysis section of this web site, we've released a working copy of the Integrated Stock Mixture Analysis (ISMA) program (written for the S-Plus environment) for use in separating stock mixtures based on elemental fingerprints or other continuous or categorical variables.

Otolith Symposium Completed:  The Third International Symposium on Fish Otolith Research and Application in Australia was a tremendous success!  A combination of technical workshops, state of the art papers, and a superb venue combined to make this an excellent learning experience for all 300 of the participants (representing 35 countries).  A dedicated issue of Marine and Freshwater Research 56 (Issue 5) has now been published containing the symposium proceedings.  The volume can be viewed on-line at http://www.publish.csiro.au/nid/126/issue/974.htm .  

New Otolith Equipment:  Several companies around the world have developed new equipment for preparing or interpreting otoliths.  No endorsement of any of the following is implied, since we have not used any of them, but some look interesting.  For example, Pilses has developed a sectioning machine specifically designed to section otoliths.  Benetec also offers an otolith sectioning saw as part of its all-inclusive Otolith Processing Line.  For polishing several otoliths at once, South Bay Technology offers a MultiLap Polishing Tool with precise controls over individual otoliths.  Finally, Ratoc System Engineering has developed a semi-automated daily increment measurement system.

Photographic Atlas of Fish Otoliths:  The otolith collections for this book took nearly 20 years to complete, but the Photographic Atlas of Fish Otoliths of the Northwest Atlantic Ocean has now been published.  The book includes light microscopic and SEM images of 580 sagittal otolith pairs representing 288 species and 97 families of fish from the northwest Atlantic.  Also included are images of lapilli and asteriscii from most families, and an overview essay of factors affecting otolith shape.  The book is available from NRC Research Press.

Otolith Methods:  New sections have been added to the Methods page of this web site, expanding the coverage to subjects other than that of otolith microstructure.  Currently included are pages on preparation for elemental analysis, decontamination, embedding in epoxy for examination of annuli, and the preparation of thin sections using an Isomet saw.  The sections on otolith preparation for microstructure examination have also been completed.

Quality control in production ageing:  In an informal survey of fisheries labs around the world, we determined that a minimum of 800,000 otoliths are aged annually, most of which is done in mass production fashion by stock assessment laboratories.  Some labs use quality control (QC) protocols and have validated reference collections, while some prefer a riskier life.  Two recent reviews thoroughly summarize the do's and don'ts of age validation and quality control.  The review paper in J. Fish Biol. (Campana, 2001) focuses on age validation and QC protocols, and perhaps surprisingly, soundly criticizes the oft-used marginal increment method of age validation.  Taking a more technical approach, a multi-authored book entitled Manual of Fish Sclerochronology, edited by Panfili et al., includes chapters dealing with a range of applications and methods.  A particularly novel aspect of the book is the inclusion of a multimedia DVD and videos concentrated on techniques.  The book was published in the fall of 2002, and is available from IRD Editions of IFREMER in France.

Age validation of long-lived fishes using fallout and radiocarbon from nuclear testing: Kalish introduced this field, and now our lab is into it in a big way. To our mind, this is THE best way to validate the ages of long-lived fishes, with none of the assumptions that plague other approaches. And the technology and implementation is only going to get better. Stay tuned!

Elemental fingerprints as natural tags: The original dream that the elemental and isotopic composition of the otolith might serve as the ideal non-genetic stock marker has faded. But what has emerged instead - somewhat unexpectedly - is that the elemental fingerprint works just like a natural tag of a group of fishes, with complete stability over short periods of time. This gives the ability to reliably track the movements of those fish no matter where they go and who they mix with. It's just like a large-scale tagging experiment, but without the time and expense of having to tag them in the first place. In many stock mixing situations, we predict that this will give better discrimination than anything else, including microsatellite DNA!

Stock mixture analyses based on maximum likelihood estimation:  The topic may make your eyes glaze over, but if you're using elemental fingerprints to classify fish into groups, you'll want to read up on this approach.  Almost everyone in the otolith field has become fixated on discriminant function analysis to classify unknown fish into two or more reference groups, but they don't realize that discriminant analysis can give grossly misleading results when you don't know the answer ahead of time (the priors).  Here's one area where the geneticists are way ahead of us - they've been using MLE-based stock mixture analyses for years. For an example, read CJFAS 56:1873-1881 (1999).  And stay tuned for an integrated stock mixture analysis capable of handling both elemental fingerprint and DNA data at the same time.

High resolution magnetic sector ICPMS: The best tool for analyzing the elemental composition of an otolith just got better. The magnetic sector ICPMS is able to distinguish between many isobaric interferences and the target element, thus allowing more accurate assays for certain key elements. Is there really as much Fe in otoliths as some have reported, or is the 'Fe' really interference from CaOH? This is the instrument that will tell us the answer!

Probe-based reconstruction of temperature history using oxygen isotopes: Lots of people have used oxygen isotopes in whole otoliths to determine the mean water temperature in which the fish lived, and some have used micromilling techniques to zero in on seasonal or annual temperature histories. The new generation of computer-controlled microsamplers allow even more detailed sampling.  Laser or ion probe-based techniques are the next logical step, allowing (in principle) monthly, weekly or even daily temperature histories. It's not quite there yet, but it will be.

Mass-marking using calcium-binding compounds or temperature: It's already here, and it's working great! A number of labs and hatcheries are now routinely mass-marking millions of young fish before release into the wild. Some have already used recapture results to test ecological theory, but the possibilities are virtually untapped.  For the first application as a tag of newly-hatched marine fish in the wild, read Nature 402:802-804.

Computer-assisted ageing: the big dream is to have an image analysis system age the otolith for you while you kick back and do nothing. Dream on! Even with the ongoing advances in imaging and artificial intelligence, we are unlikely to see a general purpose, fully automated ageing machine in the near future. On the other hand, the resolution and dynamic range of image analysis systems is improving rapidly, implying that image enhancement will become easier than ever. We should also see reductions in the numbers of otoliths required for routine ageing, due to improvements in quality control and the introduction of maximum likelihood statistical techniques for predicting age based on otolith morphometry.