Fish Winter Survival: Under Ice, Metabolism, Climate
This audio overview provides insight into fish winter survival strategies, explaining how cold-blooded species adapt to cold freshwater environments. Fish slow their metabolisms and reduce activity, gathering in schools and moving to deeper waters that are denser, warmer, and more oxygenated. Ice cover and snowpack provide crucial insulation against frigid temperatures.
For cold-water fish like lake trout, walleye, and pike, winter is a time they thrive, utilizing biochemical adaptations and different enzyme configurations to maintain body processes. Some fish, like koi, may even burrow into soft sediments to become dormant. The overview also addresses the significant impact of climate change, detailing how warming waters and reduced ice volume threaten cold-water fish habitats, affecting their breeding and feeding behaviors, and increasing vulnerability to predators like the sea lamprey. It highlights the cultural significance of ice fishing and the challenges faced by culturally important species like the whitefish.
0.000000 5.880000 Welcome to everyday explained your daily 20-minute dive into the fascinating house and wise of the world around you
5.880000 10.900000 I'm your host Chris and I'm excited to help you discover something new. Let's get started
10.900000 18.280000 Okay, so picture this you step out Chris winter morning and you're looking across this huge still lake
18.280000 20.280000 Mm-hmm, and the surface is just
20.280000 27.720000 Solid ice, right silent foos and solid. Yeah, that classic winter scene. Exactly. Yeah, and up here
27.720000 33.760000 You know, we're all bundled up maybe got some hot chocolate going, but what about down there under all that ice
33.760000 39.000000 What are the fish actually doing? It's not like they can just you know throw on a tiny puffer vest
39.000000 42.880000 No, they definitely can't and that hidden world that's a
42.880000 46.480000 Exactly what we're diving into today, right? You might think everything just sort of
46.480000 54.960000 Grimes to a halt down there frozen still. Yeah, like suspended animation or something, but the reality is actually way more interesting and honestly
55.440000 59.960000 Pretty clever and that's our mission for this deep dive, isn't it? We want to unpack the
59.960000 64.480000 frankly ingenious ways fish survive the winter cold for sure
64.480000 69.540000 We're talking everything from like cozying up in the muck for a long snooze the ultimate
69.540000 74.500000 Stakation to becoming these surprisingly fast predators in water that's nearly freezing
74.500000 78.520000 We really want to get into their amazing adaptations and we also need to touch on how
78.520000 84.200000 Climate change is starting to mess with things. That's a big part of the story now definitely so for this
85.200000 91.080000 Exploration we pulled together insights from quite a mix of sources. Yeah, we've got scientific papers
91.080000 100.000000 Observations from aquatic institutes ecological reports NOAA data even some historical context think of it like we've cracked open
100.000000 103.360000 I don't know fins declassified winter survival guide
103.360000 107.120000 Huh, I like that giving us the insights scoop on life under the ice
107.120000 113.900000 That's the plan a really comprehensive look. Okay, so let's start with the absolute basics. Hmm fish are cold-blooded
113.900000 119.220000 Right Ectothermic which isn't just a saying it means their body temperature basically just mirrors
119.220000 122.780000 Whatever the water around them is doing exactly unlike us, you know
122.780000 128.020000 We shiver we generate heat fish don't have that internal thermostat so when the water gets cold
128.020000 133.580000 They get cold their whole system starts to slow down. It's a direct response. Okay, but here's where it gets kind of weird
133.580000 138.380000 Wonder for right water itself. Yes water has this really peculiar property that's
139.540000 145.660000 Absolutely key for fish survival in winter. You mean the fact that it doesn't just get colder and colder the deeper you go
145.660000 151.800000 Precisely while the surface might freeze solid at zero Celsius or 32 Fahrenheit
151.800000 157.220000 Water is actually densest heaviest at four degrees Celsius
157.220000 162.500000 That's about 39 Fahrenheit densest at four degrees C. Okay, so what does that mean for the lake?
162.500000 165.820000 It means that four degree water sinks it goes down to the bottom
166.020000 171.740000 So counterintuitively the deepest part of the lake is usually the warmest part in winter. Wow
171.740000 177.980000 Okay, so it's like the lake stratifies it forms layers based on temperature exactly thermal stratification
177.980000 183.980000 You get this relatively warmer stable zone right at the bottom or refuge. It's not exactly a hot tub down there
183.980000 185.460000 I imagine it's definitely not a hot tub
185.460000 190.980000 But it's significantly warmer and more stable than the freezing surface water or the air above the ice
190.980000 194.180000 It's a fish sanctuary basically nature's a little heating system
194.180000 199.460000 Yeah, and this whole setup this layering. It gets established before winter really hits right in the fall
199.460000 205.780000 Yes, absolutely. There's a critical event called the fall turnover as the surface water cools down in autumn
205.780000 212.340000 It gets denser and sinks right and it pushes the warmer often less oxygenated bottom water up
212.340000 214.460000 This mixes the whole lake
214.460000 216.460000 So it stirs everything up
216.460000 220.300000 Distributing oxygen from the surface layers down to the depths you got it
220.300000 227.620000 It's like the lake taking a deep breath before winter seals the lid super important for getting oxygen down deep before the ice forms
227.620000 233.260000 And then the ice plus any snow on top acts like insulation like a giant blanket
233.260000 237.900000 Yeah, it shields the water below from the windshield and the really frigid air temperatures
237.900000 244.140000 Helping maintain that stable slightly warmer deep zone the lake is basically prepped for winter
244.140000 245.980000 Okay, so the fish head down deep to this
246.780000 252.540000 relatively warmer spot, but what are they actually doing down there because it sounds like there are a couple of different strategies
252.540000 259.100000 That's right, broadly speaking you can think of two main approaches two schools of thought you might say for winter survival
259.100000 263.100000 Okay, play on me first you've got what we could call the winter rest crew
263.100000 268.540000 These are mostly your temperate fish species think base, bluegill, perch
268.540000 272.780000 ones we think of being active in summer exactly and their strategy is basically
273.820000 282.140000 Slow and steady or maybe slow and sleepy so what does that look like do they just hang out pretty much when the temperature drops enough
282.140000 287.340000 They often gather in big groups or school safety in numbers or warmth
287.340000 294.060000 Probably more about conserving energy, but maybe a bit of both and they sink down to those deeper warmer areas
294.060000 298.860000 We talked about okay down to the four degree zone and once they're there their whole metabolism just
299.900000 305.740000 tanks it slows way way down. How slow are we talking? I mean their heart rate might drop to just a few
305.740000 311.180000 beats a minute they barely move their need for oxygen and food decreases dramatically
311.180000 314.620000 So it's like a fish version of hibernation, torpor. Very much like torpor
314.620000 319.260000 Yeah, they're just existing in slow motion trying to burn as few calories as possible
319.260000 322.860000 And some they get even further right like actually burrowing. Oh, yeah
322.860000 325.420000 some species like
325.420000 331.580000 certain types of carp, koi, even some gobies, they'll actually wriggle down into the soft mud or sediment at the bottom
331.580000 333.980000 Seriously, they use the mud as a blanket
333.980000 340.540000 Effectively yes, it provides extra insulation against slightly colder water currents that might still exist down there
340.540000 344.460000 It's a proper little winter hideout a muddy cocoon
344.460000 349.020000 Wow, so next time someone says a fish is stuck in the mud maybe they're just having a nice winter nap
349.020000 352.060000 Could be just enjoying their five star muck resort
352.060000 354.700000 Okay, so that's the rest crew. What's the other strategy?
354.700000 360.380000 Ha, now we get to the winter warriors these are the fish that seem to well love the cold
360.380000 362.300000 Love it while the others are napping
362.300000 367.100000 Pretty much in places like the Great Lakes region Michigan for example when winter hits hard
367.100000 370.780000 These fish don't slow down they often become more active
370.780000 373.740000 They emerge from the depths and are kind of in their element
373.740000 377.420000 Okay, who are these guys and how on earth do they pull that off?
377.420000 387.180000 Quake species like lake trout, burbot, some types of salmonids, and the how is all about amazing biochemical adaptation
387.180000 389.900000 Biochemistry, like their internal chemistry changes
389.900000 395.740000 Sort of, it's more that they have evolved enzymes those proteins that drive all biological reactions
395.740000 396.940000 Why a catalyst?
396.940000 403.740000 Exactly, they have enzyme versions that are specifically configured to work efficiently at very low temperatures
403.740000 409.820000 near freezing even, whereas our enzymes or those of the winter rest fish would just seize up
409.820000 411.180000 They become really sluggish, yeah
411.180000 416.700000 But these winter warriors their internal chemistry is optimized for the cold
416.700000 419.980000 It's like they have a high performance winter mode built in
419.980000 423.660000 That is fascinating so they're not just tolerating the cold they're thriving in it
423.660000 427.260000 Thriving is the right word they turn the cold into an advantage
427.260000 432.940000 Is there a downside though like does this specialization make them less good in summer?
432.940000 436.620000 That's a great point yes there are trade-offs take lake trout
436.620000 440.540000 They're super efficient predators when the water's down around 40 Fahrenheit
440.540000 444.140000 Maybe even a colder okay, they actually move around more actively and hunt better then
444.140000 447.580000 But if the water gets much above say 60 Fahrenheit
447.580000 451.020000 They start getting stressed their cold optimized system doesn't work as well
451.020000 456.540000 So they really are specialists definitely and in winter they become these really effective predators
456.540000 461.820000 They can even use the underside of the ice or the lake bottom to corner prey that's slowed down by the cold
461.820000 467.260000 Like using the environment as a tool clever very so while the usual summer top dogs like pike
467.260000 470.060000 Walleye or panfish are down deep
470.060000 476.780000 Conserving energy the winter warriors take over their usual haunts exactly the whole ecosystem dynamic shifts
476.780000 479.500000 It's a seasonal changing of the guard you could say wow
479.500000 485.900000 Okay, so whether they're resting or worrying they still need oxygen right even the slow ones absolutely
485.900000 488.380000 Breathing is non-negotiable
488.380000 495.100000 Gills are the primary tool obviously pulling dissolved oxygen from the water still works even when they're barely moving yep
495.100000 500.940000 Gills are efficient but interestingly some fish can also absorb a bit of oxygen directly through their skin
500.940000 509.340000 Or other highly vascularized tissues especially if oxygen levels get low really like breathing through their skin in a very limited way yes
509.340000 514.940000 And some fish in shallow spots have even been seen gulping tiny air bubbles trapped under the ice
514.940000 520.220000 Just grabbing a quick extra bit of O2 resourceful but you mentioned low oxygen
520.220000 523.660000 That can be a problem can't in the noxic conditions
523.660000 527.900000 It can be a huge problem especially later in winter or in certain types of lakes
527.900000 528.860000 How does that happen?
528.860000 532.540000 Well, if you get really thick ice and especially a heavy snow pack on top
532.540000 533.740000 I blocks the sunlight
533.740000 534.540000 Exactly
534.540000 539.180000 No sunlight getting through means no photosynthesis by the underwater plants and algae
539.180000 541.420000 And photosynthesis produces oxygen
541.420000 548.540000 Right so the main oxygen source gets shut off meanwhile you still have decomposition happening at the bottom which uses oxygen
548.540000 550.060000 So the oxygen levels can just
550.060000 551.420000 Deplete
551.420000 558.220000 They can drop dangerously low creating hypoxic low oxygen or even a noxic no oxygen zones
558.220000 562.220000 And that's incredibly stressful potentially fatal for fish
562.220000 563.740000 Even with their slowed metabolism
563.740000 566.860000 Even then basic functions still require some oxygen
567.580000 573.180000 Fish stuck in those zones get weak susceptible to disease and can die off in large numbers
573.180000 575.340000 It's a major winter bottleneck
575.340000 577.980000 So they need to be able to sense that and move if possible
577.980000 579.420000 Ideally yes
579.420000 583.580000 But moving also costs energy which is exactly what they're trying to conserve it's a tough balance
583.580000 585.260000 Okay what about food?
585.260000 589.020000 If everyone slowed down is there anything to eat?
589.020000 592.460000 The whole food web slows down for sure it's not like the summer buffet
592.460000 594.700000 But it doesn't stop completely
594.700000 596.140000 So what are they eating?
596.140000 599.500000 They might find some dormant insect larva in the sediment
599.500000 601.420000 Maybe a very slow moving minnow
601.420000 603.740000 Perhaps even some decaying organic stuff
603.740000 607.660000 They'll often be more active during slightly warmer parts of the day
607.660000 610.620000 Or just lie and wait for something easy to drift by
610.620000 612.460000 Minimal effort is key
612.460000 614.700000 Which totally explains ice fishing
614.700000 615.660000 Absolutely
615.660000 619.580000 Ice anglers know this that's why they use those bright flashy lures
619.580000 621.580000 To get noticed in the dim light down there
621.580000 622.220000 Yep
622.220000 625.180000 And they often have to put the lure right in the fish's face
625.180000 626.220000 Basically
626.220000 628.700000 Because the fish isn't likely to chase far
628.700000 629.980000 It needs an easy meal
629.980000 632.060000 Something worth the tiny energy expense
632.060000 633.260000 And patience
633.260000 634.220000 Lots of patience
634.220000 635.740000 A lot of patience is required
635.740000 638.780000 You're waiting for a sluggish, not particularly hungry fish
638.780000 640.940000 To decide your lure is worth a nibble
640.940000 645.260000 In this whole situation the cold, the low food, potential low oxygen
645.260000 647.420000 It has to be harder on some fish than others
647.420000 648.060000 Definitely
648.060000 652.700000 There's generally a higher mortality rate for smaller, younger fish during winter
652.700000 653.900000 Just having build up the reserves
653.900000 654.620000 Exactly
654.620000 658.140000 They haven't had as much time during the warmer months to pack on fat
658.140000 661.340000 They have less of a buffer to get through the lean times
661.340000 663.340000 It really is survival of the fittest
663.340000 665.820000 Or perhaps the fattest in winter
665.820000 671.340000 Okay, so we've got this incredible picture of adaptation to a tough season
671.340000 675.260000 But what happens when winter itself starts acting weird?
675.260000 677.580000 Yeah, that's the transition we need to make
677.580000 680.620000 Because the winter's fish have adapted to R-changing
680.620000 683.260000 And that brings us to the impact of our warming world
683.260000 684.140000 Climate change
684.140000 684.860000 Right
684.860000 687.740000 We're seeing particularly in places like the Great Lakes region
687.740000 690.780000 That fresh waters just aren't freezing over as early
690.780000 693.820000 Or sometimes the ice cover is much less extensive
693.820000 695.180000 Or doesn't last as long
695.180000 697.340000 Which misses with ice fishing, sure
697.340000 699.420000 But the impacts on the fish must be way bigger
699.420000 700.140000 Much bigger
700.140000 702.940000 Think about those winter warriors, the cold loving fish
702.940000 704.540000 The ones optimized for the cold
704.540000 708.300000 Yeah, warmer average water temperatures put them under stress
708.300000 711.980000 And it makes them more vulnerable to things they might normally handle better
711.980000 712.540000 Like what?
712.540000 713.660000 Like predators
713.660000 716.540000 A key example in the Great Lakes is the sea lamprey
716.540000 719.180000 Oh, those invasive parasitic fish
719.180000 719.980000 Exactly
719.980000 723.180000 They're not native and they actually prefer warmer water
723.180000 726.540000 So as the lakes warm, lamprey can thrive
726.540000 728.140000 Feed for longer periods
728.140000 731.260000 And put more pressure on native cold water species
731.260000 734.380000 Like trout and salmon who are already struggling
734.380000 736.780000 So the native fish are stressed by the warmth
736.780000 739.100000 And their main parasite gets a boost
739.100000 739.740000 That's rough
739.740000 741.100000 It's a double whammy
741.100000 744.460000 And species like salmon, walleye, cisco, trout
744.460000 747.660000 They're finding it harder to locate those really cold water refuges
747.660000 749.900000 Below 60 Fahrenheit that they need
749.900000 752.060000 Affecting where they feed, where they breed
752.060000 753.500000 Their whole life cycle
753.500000 756.460000 Spawning might be disrupted if traditional grounds are too warm
756.460000 759.420000 Feeding efficiency drops, growth slows
759.420000 762.060000 It's even forcing changes in fish stocking programs
762.060000 764.060000 Sometimes the water just isn't suitable anymore
764.060000 765.660000 For the fish they used to stock there
765.660000 766.940000 And you mentioned cisco
766.940000 769.420000 Isn't white fish really important in that region too?
769.420000 769.740000 Yeah
769.740000 770.940000 Culturally
770.940000 772.220000 Hugely important
772.220000 776.060000 White fish, or adic mig, in Ojibwe, Moan
776.060000 780.140000 Has been a vital food source for indigenous communities for centuries
780.140000 783.660000 Winter fishing for white fish is a deep cultural tradition
783.660000 786.700000 Early European explorers relied on them heavily too
786.700000 789.500000 But their populations have had issues before climate change
789.500000 790.620000 Oh absolutely
790.620000 792.460000 Historically, massive damage was done
792.460000 794.060000 Especially during the logging boom
794.060000 796.460000 In the late 1800s, early 1900s
796.460000 798.380000 How did logging hurt fish?
798.380000 800.860000 Deforestation led to massive erosion
800.860000 804.540000 Rivers filled with sediments, smuttering the clean and gravel beds
804.540000 807.260000 White fish need for spawning in early winter
807.260000 810.940000 Plus overfishing with more efficient gear took a huge toll
810.940000 811.980000 Have they recovered at all?
811.980000 813.500000 There's been progress
813.500000 817.180000 Habitat restoration, removing old dams, replanting riverbanks
817.180000 821.420000 Plus better fishing management has helped white fish populations rebound in some areas
821.420000 822.300000 But now
822.300000 824.220000 Now warming waters are the new threat
824.220000 828.940000 Exactly, it's this new pervasive pressure that affects their ability to find cold water
828.940000 832.780000 Impacts their food sources and potentially disrupts spawning cues again
832.780000 836.300000 And losing a key species like white fish doesn't just affect fishing
836.300000 838.380000 It ripples through the whole food web
838.380000 839.420000 Precisely
839.420000 842.140000 They eat smaller things, bigger fish eat them
842.140000 843.420000 They're a linchpin
843.420000 845.740000 They're decline impacts biodiversity
845.740000 849.020000 The stability of the entire Great Lakes ecosystem
849.020000 851.420000 And we see the changes like superior, for instance
851.420000 853.900000 Clearly, it shows less ice cover over time
853.900000 854.860000 It's not subtle
854.860000 859.180000 So, okay, the picture seems a bit grim with climate change factored in
859.180000 861.980000 Is there anything we can actually do?
861.980000 863.740000 Do these fish have a fighting chance?
863.740000 865.020000 They definitely have a fighting chance
865.020000 866.460000 And yes, there are things we can do
866.460000 868.860000 We have tools, mitigation strategies
868.860000 871.420000 It requires effort, working with nature
871.420000 872.620000 Like what kind of things?
872.620000 876.380000 Well, restoring natural vegetation along streams and rivers is huge
876.380000 879.500000 Planting trees and shrubs, how does that help fish?
879.500000 881.500000 Shade, it keeps the water cooler
881.500000 886.860000 Plus, the roots stabilize the banks, reducing that harmful sediment runoff that smothers spawning areas
886.860000 888.620000 Okay, make sense, what else?
888.620000 891.020000 Sustainable fishing practices are crucial
891.020000 895.180000 Things like catch limits, size restrictions, maybe seasonal closures
895.180000 900.060000 Ensure we don't put extra stress on populations already dealing with environmental changes
900.060000 901.900000 Managing the human impact
901.900000 902.860000 Exactly
902.860000 905.500000 And broader land use changes matter too
905.500000 908.780000 Anything that reduces pollution and runoff entering the waterways
908.780000 911.340000 helps keep the water cleaner and healthier
911.340000 913.900000 Native plantings in general help water quality
913.900000 915.820000 What about understanding what's happening?
915.820000 916.620000 Research
916.620000 917.980000 Absolutely vital
917.980000 922.380000 ongoing scientific studies help us track changes, understand impacts
922.380000 925.980000 But also, citizen science is incredibly valuable
925.980000 928.700000 You mean like volunteers monitoring water quality?
928.700000 932.380000 Yeah, or anglers reporting unusual catches or conditions
932.380000 937.500000 The more eyes we have on the water, gathering data, sharing observations based on experience
937.500000 943.180000 culture, science, the better our understanding and the quicker we can respond effectively
943.180000 947.420000 So combining scientific rigor with local knowledge and observation
947.420000 952.380000 That combination is powerful, it gives us the best chance to develop effective conservation strategies
952.380000 955.260000 and support these fish as they face a warming world
955.260000 958.140000 It sounds like their future really depends on our actions then
958.140000 961.740000 They have the incredible resilience, but we need to give them that fighting chance
961.740000 963.340000 That sums it up perfectly
963.340000 968.060000 Their ability to rebound, to adapt hinges significantly on the choices we make now
968.060000 969.500000 Well this has been fascinating
969.500000 973.420000 Thinking about that seemingly barren frozen lake surface
973.420000 976.860000 And knowing that underneath there's this whole complex world
976.860000 979.500000 Fish either in deep slow motion naps,
979.500000 980.540000 Broad in the mud
980.540000 981.820000 Cozying up for the winter
981.820000 985.340000 Or these biochemical marvels, the winter warriors
985.340000 988.140000 Actually using the coal to their advantage
988.140000 990.060000 Hunting actively into the ice
990.060000 993.420000 It's way more dynamic than I ever imagined
993.420000 998.460000 It really is, life finds a way and often in truly surprising and intricate ways
998.460000 1000.540000 The resilience is just incredible
1000.540000 1002.380000 It really makes you think though, you know
1002.380000 1005.740000 Fish have evolved these amazing strategies over vast amounts of time
1005.740000 1007.820000 Adapting to predictable seasonal cycles
1007.820000 1009.740000 Right, honed over millennia
1009.740000 1011.900000 But now the climate is changing
1011.900000 1012.380000 Yeah
1012.380000 1013.740000 Relatively quickly
1013.740000 1015.980000 What kind of new adaptations might we see?
1015.980000 1020.860000 If this pace continues, could they evolve entirely different, maybe even stranger
1020.860000 1022.940000 Ways to cope in the coming centuries
1022.940000 1024.540000 That's the big question, isn't it?
1024.540000 1028.460000 Evolution is usually slow, but strong pressure can accelerate things
1028.460000 1031.820000 Maybe behavioral shifts first, then physiological
1031.820000 1036.380000 What does life really look like when your whole environment keeps throwing curve balls at you?
1036.380000 1038.860000 It's definitely something to ponder
1038.860000 1041.100000 Well beyond just sending in a frozen lake
1041.100000 1044.220000 And that wraps up today's episode of Everyday Explained
1044.220000 1047.660000 We love making sense of the world around you, five days a week
1047.660000 1052.620000 If you enjoyed today's deep dive, consider subscribing so you don't miss out on our next discovery
1052.620000 1055.100000 I'm Chris and I'll catch you in the next one