My Dad and I were just Striper fishing on Long Island Sound at the mouth of our harbor (didn't catch anything). The harbor is fed by a small river. It's probably tidal for a mile or two from where we were at the mouth of the harbor, so it's significantly salt/brackish water in the general location that we were fishing. Any tributaries in the area are the same way - big tidal influence, so I don't think there is any freshwater near where we were.
As I was fishing, I saw some mayfly spinners, probably a dozen of them doing their dance. They weren't linked up, but had very clear wings and were almost certainly spinners. They had yellow bodies with some brown markings on the top side of the body. I couldn't get one for a picture unfortunately. Moreover, there was no wind at all, and it's been pretty calm the past few days, so it's not like they blew down from far away, nor was there a significant light source that would have attracted them.
So any thoughts on what they were, or why they were so far from freshwater?
Hey Willy! we saw a few mayflies at the beginning of their season when the shad were running in the tidal Potomac, at Washington, D. C. in late April. i was sure some emerged right in front of us: nice yellowy tan ones with two tails, not very big, maybe 16s. and that water is not quite fresh. probably not as salty as your harbor, though.
According to W. Patrick McCafferty on page 95 of his wonderful book, Aquatic Entomology, in the paragraph describing aquatic habitats of mayflies, he says, "Although highly atypical of mayflies generally, at least one species has occasionally been found in tide pools, ..."
He doesn't go on to say which species this is, but perhaps someone reading this will. Et tu, Konchu!
Not sure if any actually "prefer" to live in brackish water, but certainly some wash down into it, and a few survive, at least for a little while. Spinners would dance over still saltwater just as likely as freshwater or a shiny car. I may try to investigate further, however...
Good info! I'm not sure the stripers would be too interested in the mayflies, when foot long bunker or 3 inch long sand eels are prevalent, but you never know. Thanks for giving a little insight into the mystery, I'll let you know if I can make any other observations about the bugs.
Summarizing/Paraphrasing from The Mayflies of Florida (1988 ed., pg. 127): Three species known from North America have been reported from saline/brackish waters: Callibaetis floridanus (Baetidae), Choroterpes mexicanus (Leptophlebiidae), Cloeon dipterum (Baetidae). Northern African species from the genera Cloeon and Caenis (Caenidae) have been found in these waters, so Caenis is a possibility here. A species from the genus Palingenia (Palingeniidae) may have been found in brackish waters.
I am aware of one ephemerellid species that has been collected from western brackish waters.
If anyone can grab some specimens from salt water, please let me know! For the time being, I'm going to stand by my assumption that mayflies' occurence in brackish waters is incidental.