Today we had the opportunity to
watch the collection of Brooke Trout’s sperm and eggs. Even though it sounds a
bit gross, it was actually a really interesting process.
Brooke Trout were Native in some
streams in our general area, but in the 1930s, loggers came in and ruined their
habitat. Rainbow Trout were used to stock up the streams instead of Brooke
Trout. Now, TNACI is experimenting to see whether or not Brooke Trout can
survive in some of these same streams.
Kathlina Alford at the TNACI
propagation facility captures Brooke Trout and raises them for breeding in
order to increase their population in our area. To breed these fish, she
collects sperm and eggs from the Brooke Trout that are kept in her tanks (which
are freeeeezing by the way). These Brooke Trout were pretty young- from 2013
and 2014.
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| Collecting trout from the tanks |
First, we collected the fish from the cold tanks with nets and sorted them out by gender. Kathalina explained that females
have a rounder, fatter belly, and are dull in color while males are more
colorful and have a locked jaw that juts out.
Next, water temperature, pH level,
and the dissolved oxyegen in the water of the tanks were recorded.
Third, each fish (we did males
first) was put into a solution of Tricane, a substance that is used to drug the
fish so the fish are easier to work with.
After this, the fish’s PIT tag (a small identity tag) was
scanned so the fish could be recognized, and the sperm could be recorded.
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Next, each was dried off with a towel, measured to the millimeter, and weighed
to the .1 gram.
Finally, Katalina took the fish and
squeezed its abdomen. If it was successful, a small white drop would come out
of the fish: a sperm! But if it wasn’t successful, poop was the result. A
designated person recorded whether or not the fish donated sperm.
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| Figure 1 you can tell this fish was successful because of the white drops inside of the bowl! |
Sperm is only good enough for about
two hours so this process had to move quickly! After all the sperm of Brooke
Trout from the 2013 was collected, it was put in the fridge and the 2014 fish
were squeezed. The younger ones had less sperm to give, but sperm nonetheless.
After the males were squeezed, it
was time for the females! The process was almost exactly the same. One
difference was that the females were weighed once before they were squeezed and
again after they had no more eggs left. This is because some females can give
up to 40% of their body weight when losing eggs! Needless to say, after they
are rid of their eggs, their bellies become puny and floppy.
When the first female was squeezed,
I was shocked at how many eggs the tiny fish contained. They were yellow and
round and a lot bigger than the sperm. However, some female fish that were
squeezed and didn’t give any eggs. These fish are called “green”. This means
that the fish has eggs, but they aren’t ready to be fertilized.
Although we were a little bit
squeamish at first, this process of collecting sperm and eggs was a really cool
to watch and we learned a lot! We are sad that this was our last time at the
propagation facility! Thank you so much to Kathlina for letting up help out a
little bit and for teaching us a lot of stuff about Sturgeon and Brooke Trout!
