How Can Climate Change Effect Our Trout?

With the help of our pals at the US Fish & Wildlife Office in Cortland, NY (Big thanks Justin and Gian!), we delivered BROOK TROUT eggs to nine aquariums at Dryden High School, Dryden Elementary School, Northeast & Caroline Elementary Schools (Ithaca, NY), Lehman Alternative School and Elizabeth Ann Clune Montessori school on Thursday, November 16.

The eggs in your aquariums are (or were) less than 1/4 inch in diameter, but even so, it was easy to make out two black dots in each- the eyes of the tiny fish inside!   These eggs were "eyed up", as the shells had already begun to thin and soften in preparation for hatching.  The big question on everyone's mind was, "how long will that take?" 

Suzanne Scheuring's students at Dryden High School wondered if there was a scientific way to predict when the eggs would hatch.  So, we put the question to Ryan Diehl, the hatchery manager at SUNY Morrisville's hatchery who provided our brook trout eggs.  He confirmed that, yes, you can predict the time between egg spawning (when the eggs are released and fertilized) and egg hatch.  

It is almost entirely dependent on the temperature of the water!

Ryan shared this table, from the US Fish & Wildlife Service's Fish Hatchery Management Handbook (1982), that provides information for both brook trout and brown trout.

We can see that for BROOK TROUT, the period from spawning (egg fertilization) to hatch is 144 days if the water averages 35 degrees F, but only 44 days if the water averages 50 degrees F.   Ryan shared that our eggs were spawned on October 12.  So, if we keep our aquarium temperatures close to 50 degrees, they should hatch about 44 days later - Nov. 25 or 26, just in time for Thanksgiving Break unfortunately!   Let's find out if they have hatched when classes return after the break!

Of course, in the "real world" outside, stream temperatures are much colder, as winter approaches, and are likely to be closer to 35 degrees than 50 degrees.  So brook trout eggs in a natural stream might not hatch for another 100 days under "typical" winter conditions.  That could be mid-February, which is actually perfect timing.

Our trout are born with a built-in energy supply, called a "yolk sack", that can nourish them for quite some time.  This is a perfect adaptation for being born in the middle of winter, when food is scarce.   If all goes according to nature's plan, by the time the yolk sack is used up, spring will have arrived and food will be plentiful for our hungry young trout.

Now that we know a bit about what effects the development of our trout eggs, what would happen if climate change caused our streams to become warmer throughout the year?   

Here's an example:  If average winter stream temperatures rise just a few degrees, to an average of  40F, for instance, our trout could be born in December, rather than February.  The yolk sack is not a bottomless buffet, however, and only will last so long.  What could happen to our trout? 

You can do a little of your sleuthing, to find out if climate change is already impacting our local trout habitat, or your favorite stream, by heading over to the Community Science Institute's amazing Water Quality Dataset that shows data collected by volunteers over the past ten or more years.  Just select your favorite stream and have a look!