Spiny water fleas

[rolmops]

Is there a logical reason why the east end of Lake Ontario seems to be loaded with these fleas while out of Sandy/Hamlin I still have not seen any?

[whaler1]

They are here. Really not that much of an issue. Even when they are bad they are manageable. 

[Gill-T]

The Niagara and Genny flow does not have any real flea contributions. Prevailing winds and currents push them East. 

[schreckstoff]

Lower density of flea predators in the east, relative to the west might contribute.

[rolmops]

16 minutes ago, schreckstoff said:

Lower density of flea predators in the east, relative to the west might contribute.

What you just mentioned implies that this invasive flea has become part of the food pyramid within the lake and their presence may cause the food supply to increase, unless of course they have replaced a native species. So what eats them?

[Gill-T]

Alewives, juvenile predators 

[schreckstoff]

Spot on rolmops! Fleas, both Bythotrphes (spiny water flea ) and Cercopagis (fishhook water flea) are major parts of the diets of Alewife, Smelt, Cisco, & age-0 Chinook (and probably many other fish species). Data suggest Alewife often feed heavily on fleas late into the fall, essentially adding extra time to the Alewife growing season in years when the fleas are abundant.  That “extra” Alewife growth seemed to  start around 2004 which coincided with substantial water clarity increases  & flea density increases.
 

As you noted Fleas definitely eat native zooplankton that Alewife previously ate. The earliest predictions were that fleas would decimate the food source of Alewife. Our observations support the idea that fleas essentially “package”  smaller plankton into a larger, more efficient to consume, Alewife food source. The heavy presence of them in 2025 Age0 Chinook diets  was a new and interesting wrinkle. If interested the Biomonitoring sections of the annual DEC reports have all of this in a lot more information. 

[LongLine]

I believe the '23 annual report said one specie is more numerous in spring and the other in fall.  Does this mean alewife have a preference?  Also, is there a North shore vs South shore prevalence? 

[schreckstoff]

If my memory serves,the fishhook flea (Cercopagis, one that grabs and wads up on line)  is more abundant earlier in the season before the spiny water flea Byth, which becomes abundant late summer /fall. Bythotrephes is a lot bigger so Alewife definitely prefer  that when available.  I have never looked to see if there’s a difference between the north and South Shore.