California WaterBlog

By Miranda Bell-Tilcock

. . .

That’s no moon. 

That is the lens of a fish eye. While it looms large in the photo, this lens is tiny, approximately 3-5mm in diameter, similar to a small bead on a friendship bracelet. How did we even capture such a zoomed in photo of a small lens? We use a very nice built-in camera microscope to capture images like the one in today’s blog. Not only do these microscopes help us capture beautiful images, they also make training a lot easier, since they have a screen that lets other people see what you are doing under the microscope in real time!

While they’re small, they can provide so much information for researchers. Fish lenses are made up of layers and have the ability to reconstruct the diet of the fish, which can also help inform researchers of what habitat that fish used throughout its life. One study was able to use fish eyes to differentiate habitats that juvenile salmon can use while in freshwater such as the hatchery, floodplain, or staying within the river. Lenses are also being used to better understand thiamine deficiency in Chinook Salmon by identifying what the salmon were consuming while living in the ocean. Another study looked at how different shark eye lenses were compared to bony fish like salmon! But peeling technique is also important. And that’s just the tip of the iceberg… or the outer peel of the lens! There’s still lots to learn about fish eyes and how we can use them to better understand fish in our ecosystems. 

About the Author

Miranda Bell-Tilcock is the Deputy Director of the Center for Watershed Sciences (CWS). Prior to this position change, her research at CWS focused mainly on fish eye lenses and isotopes, such as Chinook Salmon eyes, to reconstruct their life history. Her work on fish eyes and isotopes was featured on National Public Radio’s Science Friday. Miranda enjoys hanging out with her three children when she’s not working, as well as baking bread and other tasty treats.

Further Reading

Bell-Tilcock, M. 2021. Fish eyes: the hidden diet journal. California WaterBlog.

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