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Big Fish a Long Way from Home: Using ear bones and teeth to unravel migration in Amazonian fish Hegg, Jens.. University of Idaho, 21 Mar 2016. Experiment. doi: 10.18258/6836
Scroll through the Protocols on the Right for the full story of how to decode the chemical signals in fish otoliths and sawfish teeth.
Reconstructing movement based on the chemical records of fish hard parts is well established science, with a large base of literature to support the methods. But, the core of the methods we will use are clearly explained from a couple of sources you can check out if you want:
The Online Otolith Lab
Our Previous Paper on Amazonian Catfish
One of the Papers that Started it All
This section is a bit more in depth, but I'll try not to get too technical. Still, I'll make sure you can dig in as deeply as you'd like through the links. This method is extremely diverse, it pulls from as far away as nuclear chemistry and dating the age of the earth to fisheries, and physiology...all with a healthy dose of statistics greasing the wheels. The otolith preparation protocol even has some small connection to the Rubber Boom era in the Amazon, when wealth was so profligate that legend has it people sent their laundry from Manaus to Paris to be washed!
Here is a great video that introduces many of the concepts of our otolith work from a researcher working on arctic grayling.
The biggest challenge in planning the catfish study is going to be finding a sampling scheme that can break this humongous migration into parts that can be studied easily. Collecting a sample large enough to understand movements in the entire population with any statistical power would make for a HUGE sample set.
Rather than study the entire population we might need to focus on a particular population from one tributary so that can collect a sample that is small enough to reasonably analyze but comprehensive enough to provide answers. This strategy will also give us the ability to answer more detailed questions about the natural variation that exists within their migration.
The sawfish study will be more challenging. This type of analysis is not well developed in sawfish but shows some promise. Our experience in hard-part chemistry in other species gives us a leg up in trying to push these techniques further and glean more information about sawfish movement and ecology.
Until we have settled on a sampling plan it is hard to be too definitive about our analysis, or even our specific hypotheses beyond the methods we have specified. Broadly though, we hypothesize that in a species as diverse and geographically distributed as goliath catfish there is likely to be variation in the timing and patterns of migration that we don't currently understand simply because we haven't been able to study these migrations in detail. Also, there is evidence that these fish, like salmon, may return to the rivers where they were born to spawn. These observations lead us to the hypothesis that we would expect to find variation in migration behavior between major tributaries of the Amazon and perhaps even within individual tributaries.
Our sawfish study is perhaps the biggest unknown in the project. Very little work has been done on the species in general, and even less on microchemistry. For this first round of work we will be testing the hypothesis; Can life history records be reconstructed from sawfish teeth?., It's a pretty basic hypothesis, but it's one that hasn't ever been tested. If we are able to reconstruct some life history data from these sawfish teeth than we will proceed to try to figure out what it is. We would hypothesize that the most evident chemical change would be between salt and fresh water, so we'll be hoping to uncover some evidence of this salt to fresh water movement first before looking for other details of their lives.
As we continue reporting on our work here we will update you with our analysis plans.
Browse the protocols that are part of the experimental methods.