Fishy Bottoms

Have you ever, on a nice, cold wintery day, sat outside and stared at an ice-covered pond and wondered if there is anything alive under the ice sheet? No? Well, I was curious enough to recently send off an email about this to a good friend of the Gardens, City of Elkhart’s Aquatic Biologist, Daragh Deegan. This man is sharper than a pike’s tooth and passionate about the aquatic life in the region’s lakes and streams. My previous conception of fish in winter was one of swimmers in a state of hibernation doing nothing, but then I watched a great documentary on fish in alpine lakes. In it, I saw eel spawning in the middle of February…under the ice. Who knew? I did not, so I emailed Mr. Deegan asking if and what the fish in our ponds might be actively doing this time of year. Here is his response to my query. 

JOSH: What are the fish likely doing under the ice in Wellfield’s ponds? Are they just hanging out drifting around twiddling their thumbs?

DARAGH: Unfortunately, while fish may not be twiddling their thumbs during the winter, they are down there twiddling their fin rays. Fish are coldblooded animals whose metabolism and activity is controlled by water temperature. So, when the water in the ponds at the wellfield is 33 degrees, so is the body temperature of the fish. They don’t hibernate in the winter but enter a “torpid state”, where they are very inactive and feeding sparsely. While fish can be caught by ice anglers, their energy requirements are small, so very small baits will only entice them to bite. There are some fish that are a little more active in winter than others. Examples are the northern pike, walleye and yellow perch, which are all considered coldwater species that are found in colder climates. Yellow perch, for example, feed more actively during the winter to nourish their eggs, and spawn very soon after ice melt. 

An interesting phenomenon fish biologists can observe in colder climates like ours is changes in growth rings on a fish scale. As their metabolism slows down in the winter, the growth rings on their scales get closer together, making a banded pattern on the scale, and when viewed under a microscope, we can actually age the fish with these winter growth brands.  

JOSH: Are any other active life forms underwater this time of year doing stuff?

DARAGH: Most aquatic animals become far less active in the winter. But that doesn’t mean that there aren’t some kickin it. Larval insects, like some of the midges and stoneflies, are actively feeding and getting ready to transform into flying adults as soon as the ice melts. Like humans, small fur bearing mammals like beavers, muskrats, river otters, and mink are less active in the winter and like to bundle up in their homes, but they need to emerge every few days to grab a bite to eat.  

JOSH: Are there some really cool species or behaviors you think are fun to highlight about freshwater species this time of year?

DARAGH: I think the winter behavior of turtles is really interesting. Like fish, turtles are cold blooded animals that become much less active in the wintertime and will usually sit on the bottom of a pond or stream until the ice melts. The big difference with turtles, however, is they have lungs – not gills, but can survive for days on end under the water in the winter. Their metabolism shifts so they can survive in this semi-dormant state and live off body reserves. They can also pick up some oxygen in the water by swishing around and letting the dissolved oxygen bubbles hit highly vascularized tissue on their body. There’s some sources that suggest that turtles can breathe through their butts.

Okay, on that uplifting factoid, I am going to sign off. Until next time, stay warm, and as my Grandma used to say, “Always listen to the municipal aquatic biologist in your life”.
Josh Steffen, Horticulture and Facilities Manager

Missed seeing Josh’s latest posts? Click on any of these links to learn more:

  • Home-Grown Ornamentals 
    As we transition into fall, our horticulture staff is exploring some common native plants you can look for during your next visit to Wellfield and consider adding to your own landscape. Continue reading
  • Transitioning Gardens – Plants for Fall 
    New horticulture staffer Mary tells us some of her favorite fall plants and why you may want to include some of them in your garden – and where you can check them out on your next visit to Wellfield! Continue reading
  • Indoor Oasis
    Cody tells us about how his love of house plants lead him to a career choice, and how too much love can sometimes be a bad thing when it comes to plants! Continue reading
  • Plant Diagnostics
    The plants are in the ground, they are growing and blooming, but now comes the challenge: diagnosing issues some of our plants are having. Here’s what our horticulture team does when they can’t solve the problem themselves. Continue reading
  • Plants Tammy Has Not Seen Before
    Our horticulturalist, Tammy, took a cool field trip to a local nursery and picked up some interesting plants to display in our Sensory Garden. Continue reading

Want to be notified whenever we post? Enter your email here. We promise not to bug you too much, and we’ll never sell your info.