Vulnerability of the Spotted Sea Trout to cold, Trout Stun Events and Trout Kills Along the Crystal Coast. By Dr. Bogus (Updated 2/23/18)
Trout kills (cold stun events) are normal and not as infrequent as you might imagine and have an important impact on natural mortality of spotted sea trout. In the fall and winter trout move south and then reenter the backwater deep creeks for food and shelter against the winter temperatures. If the water temperature falls, as a cold front moves in, sometimes after a snow event, the trout can seek deeper waters for protection. If the temperature drops too quickly they may or may not have time to seek deeper warmer waters. Remember, trout, as are most fish (there are exceptions), are cold blooded and their body temperature is the same as the water around them. As they get colder their body metabolism slows and their speed of movement and feeding and digestion slow considerably. Remember when you trout fish in the winter, the idea is to move your bait, slow, slower and slowest to get a hit, or “bump” from a lethargic trout.
There is always a debate on what the “cold stun” temperature for a trout is, that is the temperature where they lose swimming control and float to the surface upside-down (they have swim bladders) where they may freeze and die. That temperature is somewhere around 39 to 41 degrees or so, but the stunning of the fish it is not instantaneous, it takes some sustained time at or around a critical stun temperature to incapacitate the fish and it may also somewhat depend on the fish’s age as well. So, just a rapid drop in water temperature of a short duration will not be cause a major trout kill, but would mainly impact fish in very shallow waters like the North River. Also many fish may feel the drop in temperature and have enough time to escape into deeper water in time to protect themselves. Where major trout kills occur, the temperature drops rapidly, often preceded by snowfall, which (the snow and sinking cold-water runoff) also will contribute to rapid water cooling, and then followed by an extended cold air and water temperatures, with water temperatures holding in the 30s for a several days.
We have seen a number of these events over the years. The first major one I witnessed was the devastating trout stun event of January 2003. I was not in North Carolina during the snow storm and frigid cold of 1989, so I don’t remember that event, but by all accounts it was also epic. More recently we have had a rapid succession of stun events in January 2010, December 2010 and January 2011 which led to the total closure of trout harvest both recreationally and commercially, by NCDMF. It also lead to dropping the bag limit, eventually to 4-fish/day and raised the minimum length to 14-inches to ensure the fish have at least one year to spawn before they are subject to harvest. I’m sure there were other trout kills during my 20-plus years in North Carolina and Emerald Isle that I haven’t documented.
As you may know, I routinely keep ocean surf and Bogue Sound water temperatures on a nearly daily basis. I have some data going back to 1995 and daily data date since 1999, when I moved to my Emerald Isle home permanently. For the stun events that I mentioned above I have the following Bogue Sound and ocean surf water temperature data.
January 22-28, 2003: In the aftermath of a snow storm, Bogue Sound temperatures dropped and remained in the 30s and as low at 30-degrees in a salty slush for the entire week. Many of the creeks were frozen over. Ocean surf at Bogue Pier went as low as 36-degrees, which is about the lowest I’ve ever measured in the surf.
January 3-13, 2010: Bogue Sound remained in the 30s or very low 40s during that entire week and a half, with a low of 35-degrees. Ocean temperature bottomed out during that time at 43-degrees during that week.
December 19-30, 2010: In 2010 we actually had two stun events in the same year. Again after another snow storm (It doesn’t snow in Emerald Isle, does it?), Bogue Sound temperatures rapidly plunged into the 30s with a low of 33-degrees. It should also be noted that almost the entire month was unusually cold with an average of only 41-degrees for the month! The surf reached a minimum of 42-degrees during that period.
January 9-15, 2011: Right after the frigid December 2010 and trout kill, temperatures, already primed for disaster, dropped again into the 30s (low of 33-degrees) for another trout kill event for basically the third event in a little more than a year. This was the final event that precipitated the dramatic closure of the trout harvest and restructuring bag (4-fish/day) and size limits (14-inch minimum) when the harvest restriction was lifted in mid-June, 2011.
January 29-30, 2014: We have saw a rapid drop in temperatures caused by the so-called Arctic Polar Vortex, setting record low temperatures here in eastern North Carolina and around much of the nation. Surf temperatures dropped to 47-degrees around Bogue Pier and I’ve measured Bogue Sound temperatures at a very cold 35 and 34-degrees. We did not had a snow storm prior to this drop in temperatures and the Polar Vortex has weakened and rapidly receded, from whence it belongs (the Arctic!) after just a couple of days. The water was cold but has rebounded to near normal for mid-January and although we have seen skim ice on the creeks, even that has receded as well. It appeared that the short duration of the freeze minimized the deleterious effects on our beloved trout. Unfortunately, by the end of January 2014 we had another attack of the Vortex, this time preceded by a snow and ice storm, resulting in some trout kills. The result again was a harvest closure for both recreational and commercial fishermen.
February 16, 2015: We have had some sustained cold again, this time thanks to a Siberian Express and also preceded by a wintery mix of ice and snow resulting in reported trout kills this winter as well. This past week I have measured ocean surf temperatures as low as 40-degrees and as low as 34-degrees in Bogue Sound. There are reports of trout kill events from Dare County south to the in Belhaven and the Pungo River, and areas around the Neuse River, including Broad Creek and around Havelock, such as Slocum (I’ve seen the photos thanks to Fin Chaser Charters) and Cahoogue Creeks. I have personally looked and talked to people around Deer Creek and Broad Creek along Highway-24 in Carteret County, and haven’t had any reports of stunned or dead trout in those areas. As I write this there hasn’t been any information from Dr. Louis Daniel and NC Marine Fisheries of possible closings of speckled trout harvest…yet. On the other hand we have another bout of cold thanks to another Siberian Express and the possibility of wintry precipitation. All we can do is wait and hope. Time to bundle up!
UPDATE for 1/2017: Big chill January, 7, 8, 9,10, 2017 after winter storm.We had winter last week, and some spotted sea trout were killed. It happens often here in the old North State every couple of years. I have been trying to keep up with reports on trout kills to get an idea of the scope of the problem this year. Here is what I gathered. Reports of kills seem fairly localized where the most significant kills was reported in the North River and Ward’s Creek where many fish, juvenile to 20-plus inches fish littered the banks of the river. Other less significant reports include the areas around Harker’s Island, the White Oak River in Stella, Hadnot Creek along the White Oak, Queens Creek and some scattered fish appeared in the New River Creeks. Importantly a report from the Pungo River and associated creeks (Pantego, Slade, etc.) were negative where significant kills had taken place in recent years. To my surprise I did not see or hear of any stunned or dead fish in the Highway-24 Creeks, which had been ice covered during part of the freeze. In fact the big chill seemed to run out the spike trout and drive in the 3-pounders.
Also, NCDMF has come out with new guidelines: “Internal Guidelines for Adaptive Management for Cold Stun Management”, dated 12/14/16 to address a move to a more quantitative metric to trigger action (i.e. harvest closures).
UPDATE for 2/23/18: As most of you know, I, the consummate scientist, have religiously taken water temperatures for well over 20 years. Why? It tells us who and when as far as the comings and goings of fish on our local waters. In the winter it also can raise flags as to the safety of some of our favorite commercial and recreational species, specifically the speckled trout who are known to be susceptible to cold water temperatures. Speckled trout are a warm water fish are the cold spells as we have experienced recently can lead to so called “cold stun” events or as I call them…troutsicles!
In fact over the years as I have amassed reams of water temperature date, we have also documented such trout kill/stun events every two to three years. This past week I measured surf temperatures at Bogue Pier as low as 38-degrees (Fahrenheit) and as low as 29 and 30-degrees in the ice and slush of Bogue Sound. The last time I saw water temperatures reaching these lows were in late January 2003, after a snow event and freeze which led to a very significant trout kill.
In late December 2010 into early January of 2011 we had a series of cold events that were extreme enough for our NC Department of Marine Fisheries close all harvest of speckled trout and adjust both bag and size limits for when the season reopened. More recently new cold stun guidelines have been put in place to, on a regional basis address the issues of cold stun events with speckled trout. These guidelines based on experimentally validated water temperature criteria and visual cold stun parameters of affected fish, were instituted for the first time this past week in response to the extreme weather conditions. This proclamation closes the commercial and recreational spotted seatrout fishery due to cold stun events, in accordance with the management strategy outlined in the N.C. Spotted Seatrout Fishery Management Plan. The spotted seatrout fishery will open June 15, 2018 by proclamation.
So how wide was the scope of this year’s cold stun event? Locally we have heard of stunned and dead trout numbering in the hundreds in fish in the North River and at least 1000 estimated in the White Oak River near the train trestle around Stella, Gayle’s Creek, Pungo River and there were also stunned fish reported as far north as Kitty Hawk Bay and as far south as Surf City. There were also reports of trout kills in Virginia. Indeed a wide ranging situation. Also remember the number of floating fish, that initially lost equilibrium doesn’t account for the many that remain on the bottom unseen. The NCDMF may do some bottom trawl surveys to get a better handle on the total numbers. Other fish killed? Visual confirmed reports were of red and black drum, flounder mullet and probably more.
And please remember, during this closure NO possession of spotted sea trout is allowed from fishing or scooping up of dying or dead fish. I repeat NO possession of speckled trout is allowed until the closure is ended by proclamation, presumably on June 15, 2018 by our new Director of Marine Fisheries, Steve Murphey. Steve was recently appointed to take place of the interim director Braxton Davis who will return to his full-time role as director of Coastal Management.