Monday, July 14, 2014

Fish Ears

What is a blog named 'The Fish Ear" without a post about actual fish ears?

This past academic year, I had the opportunity to teach at a local high school - Mission Bay High.   I was paired up with a marine science teacher, Steve Walters, and we had a blast designing lesson plans based on my research expertise.  Steve was awesome to work with in the classroom.  Not to mention, he took me sailing a couple of times.

Steve and I.
Photo bombed of course.

Two of the lessons we taught stood out.

First, we raised white seabass in the classroom.  How cool is that?!

More than a billion people world-wide depend on fish as their primary source of protein and, unless you've been very out of tune with your 4th-grade-I-want-to-be-a-marine-biologist-self, you've at least hear of a few examples of poorly managed fisheries (orange roughy, bluefin tuna, "save the whales"... there are literally hundreds of species that could be on this list).  The sad truth about many of these over-fished populations is that they haven't bounced back, even after fishing pressure stopped.  What am I getting at here?  Well, humans are doing some good.  Raising white seabass is one of them. Hubbs-Seaworld Research Institute (HSWRI) releases thousands of white seabass every year as part of a 'stock-enhancement' program. Basically, they are helping rebuild the white seabass population by releasing extra baby seabass into the wild in the hope that more will survive to adulthood.  By raising white seabass in the classroom, the high school students become a part of the solution!

Cute juvenile white seabass!

A student measures the length of a juvenile white seabass.
In early June, the students got to release the seabass into Mission Bay - literally right outside the doorstep of the school. The students will now go on to save all the world's fisheries so that your children's children will know what fish tastes like (i hope).

In the News!

 The second lesson that stood out was a fish head dissection lab. The purpose of the lab was to look at how humans directly impact fish populations. More specifically, we were looking at how two different fishing methods (nets used to catch Alaskan chinook salmon vs. pole/line used to catch Lake Michigan chinook salmon) results in the removal of a group of fish that have a different size distribution.   While not a perfect case study, it is a cool example - especially since Alaskan salmon are considered a well managed sustainable fishery.  Students dissected otoliths (fish ear bones!) from wild caught Alaskan salmon fish heads that were donated by a local seafood company. Once they got over the fish smell, most of the students enjoyed the lab.

Otoliths can tell a scientist about the size and health of the fish it came from.  There is a direct relationship between otolith growth and fish growth, so the students were able to reconstruct the original fish length by measuring the length otolith.  They then compared the size distribution of fish caught in nets from Alaska and fish caught using pole and line from Lake Michigan. SPOILER: Nets target schooling fish, so all of the Alaskan salmon were very similar in sizes, whereas the Lake Michigan salmon displayed a wide range of sizes (or a "normal" or "gaussian" distribution).

In closing, I do not discourage you from eating fish. Quite the opposite actually.  Fish are delicious and can be very healthy! I would, however, encourage you to aim for wild-caught well managed species.  A great list of 'good' species to eat can be found here: (they also have a phone app).

Even though many lists like this exist, when it comes down to it (i.e., you're staring at a menu in a restaurant or looking at the fish on ice at the local market), it remains very difficult to know where the seafood is coming from exactly. Where the seafood come can make all the difference. Many species can be on both the 'avoid' or 'ok' list depending on where or how it was caught because different country/regions do not follow the same regulations.  Unfortunately, this make choosing sustainable seafood difficult.  Do the best you can (and always avoid farmed salmon)! 

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