Steelhead: Early Mortality Syndrome

Eco systems are complex and dependent on a wide variety of factors.  For example, Lake Ontario & it’s tributary system have 159 invasive species, Lamprey Ell, Alewife, Zebra Mussel, Goby, etc…..  Any of which can impact of a single species or the entire fishery. The current disorder with some Steelhead has been determined by the DEC, in conjunction with Cornell University, as B-1 deficiency.  The direct cause is the Alewife (Sawbelly / Mooneye)!  This 4-8” invasive baitfish is an invasive and its skin contains Thiaminase, a substance that prevents the fish from absorbing Thymine (B-1). The alewives and Thiaminase have always been a significant problem for Lake Ontario’s native fish; Landlocks and Lake Trout. So it is somewhat surprising to see the steelhead impacted this way. “This is the first time B-1 deficiency has affected adult Steelhead in the Salmon River”, per Fran Verdoliva, DEC Salmon River Program Coordinator. The alewives invasion (1873) displaced the primary forage base in the lake; Ciscoes, the native forage fish to Lake Ontario. We have yet to see an estimate on how many Steelhead are affected. Anecdotally, we think it is a small percentage. Initially, among many guides, it was thought that the 2010 flood resulted in diminished Chinook Salmon natural reproduction resulting in less predation on Lake Ontario Alewives.  This would have made more Alewives available for Steelhead.  However, Fran Verdoliva says that the spring of 2011 seining resulted in normal numbers of Chinook fingerlings. Certainly the 2024 salmon run was different.  Many make the case that there were significantly fewer fish but according to Fran, they had no problem collecting salmon for the hatchery.  Perhaps we were all spoiled by the record runs of 2012 & 2013! The run was certainly dispersed and this can be explained by examining weather conditions. The winter of 2013-14 saw 27′ of snow on the Tug Hill Plateau. The spring and summer were wet and cold, up to 10 degrees below normal. The Lake Captains had such a hard time catching Kings that many eventually went back to targeting Lake Trout. They credit the weather pattern and, specifically, it’s effect on the thermocline. The thermocline moved all summer making it difficult to locate and pattern fish. Very few King Salmon were caught on the lake last summer! The salmon starts its transition from apex predator to spawning factory by June its 4th year. There are many factors that impact on this transition and its length. The “churning” thermocline dispersed the big pods of fish into smaller pods and the biological clock of these small pods went off at different times resulting in dispersed and very sporadic spawning runs. Add to this the result of the lake being locked up with ice and cold water for so long. With no exposed surface, the water stratified under the ice and so did the zoo-plankton, the alewives and the steelhead.  Steelhead are omnivorous by nature and usually feed on a wide variety of forage. BUT if you have an unlimited supply of cheeseburgers, that’s what you eat.  Some numbers of steelies focused on Alewives. We have seen, or heard, of NO Browns affected. Makes sense as Browns seemed to be focused on exploiting the Gobies. Flash forward to later in the fall of 2014. This was our “best Steelhead season” in both size and numbers!!!  Late September or early October we started seeing dying steelhead at Douglaston Salmon Run (DSR). We continue to see them each day, usually one or two.  We haven’t seen any floating down river since 21 Dec.  The affected fish we did see were “FAT” and healthy in appearance and initially we thought they may have been caught and not released properly. Again we are NOT seeing large numbers of dead fish.  A fish dies, floats downstream and drops in a soft seam or back water.  These seams and back waters tend to concentrate dead fish over time, giving the impression of large numbers.  When this phenomenon is picked up on the internet, it takes on a life of its own!  This winters Steelhead catch has been consistent and we look forward to spring drop-backs. Remember:  The DEC has been able to not only treat adult Trout affected by B-1 Deficiency, but also their eggs with great success. A couple or few hundred dead chromers’ is sad, but 10 years ago, with the old 3 trout limit, those fish went home in coolers.