Been the topic of much discussion over the last week. My predecessor has old man wisdom about these things, and one of his core theories is that the severity of a “winter kill” largely depends on the starting water temperature and the rate of change during the cold period. Clearly the absolute minimum and duration are also huge… but he thinks that at this current starting temperature of 48-50F, fish may already be “conditioned” both metabolically and spatially, i.e. they’re used to being cold and they have moved to the most insulated bodies of water they are willing to travel to- often deep holes in creeks for winter trout.
FWIW the species that we classically see having the most visible and dramatic impacts are spotted seatrout and white shrimp. In 2010, I saw a seagull carrying off a lump of jumbo shrimp because when it gets to the mid-40’s for a couple days, they’re too cold to move and they start rolling over. same for trout. dolphins have a field day, pelicans and herons feet are freezing to the high marsh and the webbed skin between their toes begins to die, and adult shrimp roll around the bottom of the harbor with the tide until their antennae tie them together in knots, never to be free again.
maybe before 2010, but I can’t remember… it was before kids. A buddy and I took his 17’ scout out into the folly the day after a snow event. had to pile snow out of the boat at the landing, and otw to the spot we saw an osprey pluck a slow trout off a flat. got there, made a snowman on the boat’s cutting board with cut shrimp for arms, and caught red drum because metabolically those same temps don’t really bother them. Rap knows this.
so here’s the thing: it depends on a lot of stuff. surface area/depth/volume of water body, amount of current, amount of (frozen?) precipitation, intensity and duration of wind, intensity and duration of cold event are probably the biggest factors that we can put metrics on both ahead of time and afterward to document these things as Dave is so excellent at doing.
the retired old man knowledge has coined a new term in the last few days: “the slush effect”. Somehow, this seemed not to affect the seatrout in 2018 as much as I think most of us predicted. If we get howling winds across the water at the same time that we get significant frozen precipitation on those water bodies and the marsh, the resulting iterations of tidal flows from marsh surfaces and feeder creeks could supercool smaller bodies of water and maybe even mix with the larger ones to a degree that drives a historic cold event more than the air temperature alone could ever do in that same span of time.
so now i’ve said nothing for quite a few paragraphs because the last time we all thought we saw this coming, they turned out ok for the most part.
here’s a more fine-tuned metric for y’all to chew on than all of the above musings:
" When winter water temperature falls to 46 degrees or below for seven or more days, most of the overwintering brood stock is wiped out." [SCDNR - Shrimp]
46 is also considered the threshold temperature for spotted seatrout. bring on the reports of fish laying on the bottom, my boss is waiting for them.
