Anglers report reduced hatches
By Stephanie Lynn EBS CONTRIBUTOR
The buzz on the river this summer is that local
anglers have noticed changes in the abundance of aquatic insects and the timing
of their hatches.
“I think the biggest thing everyone is talking
about is that the hatches have been really sporadic,” said Solomon Ohman, shop
staff at Grizzly on the River. Ohman observed multiple insect orders emerging
simultaneously, instead of thick clouds of a single taxon.
Ennion Williams, outfitter and guide for Big Sky
Trout with 24 years of experience on the Gallatin, detected a diminished
salmonfly hatch, in particular.
“The bugs were there, but there weren’t any
heavy hatches all at once,” Williams said, adding that high water and cooler
temperatures coupled with last summer’s algae bloom could have impacted salmonfly
emergence this year.
Although a few studies have linked environmental
changes with shifts in the life cycle of aquatic insects, this is still an area
of active research, according to Sean Sullivan, an aquatic ecologist with
Rhithron Associates, Inc. With those limitations in mind, Sullivan suggested a
few factors unique to this summer that may be linked to the observations of local
anglers.
Summer started slowly this year with a cold, wet
early July when compared to the past couple of years. Air temperature in the
beginning of the month was, on average, a few degrees below normal. The number
of days above a certain temperature drives the hatches of many insect species,
thus cool weather could limit their emergence.
Due to many days with precipitation, streamflow
at the Gallatin Gateway gauge has been slightly above average since last October
with water levels climbing into the 75th percentile—25 percent above average—early
last month. High spring flows sustained into the summer could suppress emergence
because insects have remained in their springtime refuge later into the season.
Finally, nuisance algae growth from recent years
that lingers in the channel could impact both habitat and dissolved oxygen
levels to the detriment of insect populations.
Local conditions are superimposed over a
statewide trend. Research by the Montana Natural Heritage Program reported
broad declines in salmonfly distribution across Montana. These sensitive
species were first threatened by dams and mining. Within the past 30 years,
siltation and increasing water temperatures have started to impact their
abundance.
In addition to these factors, the response of
insects to environmental changes depends on the species in question. Due to the
fact that three species in the salmonfly (Pteronarcyidae) family are
native to Montana, scientists need more data to accurately explain fluctuations
in the life cycle of these aquatic insects.
“There is a growing recognition that the fly-fishing
community has a unique opportunity to provide data to help validate any
observed trends in phenological shifts,” Sullivan said. He encouraged river
lovers to contribute their knowledge to an iNaturalist project called “The
River’s Calendar,” which is designed to document emergence periods for the aquatic
insects of North America.
Despite the salmonfly shortage, Jay Markevich,
shop manager for Gallatin River Guides, reported that the fishing is still
good, speculating that both the size and quality of fish caught on the Gallatin
increased this summer.
Stephanie Lynn is the education and communications coordinator for the Gallatin River Task Force.
