Pennsylvania Angler & Boater - November/December 2017 - 56

THE CHECKERED SCULPIN
-The Colder the Better

by Rob Criswell
photo by the author

It's a hot, muggy August day. You're tired and overheated from a
long, strenuous hike when you come to a deep, crystal clear pool
in a small stream. You are so hot that you decide to jump in to
refresh, clothes and all. However, as you hit the water, you realize
it isn't a cool brook, it's a 54-degree F spring, and you exit as
quickly as you entered. Welcome to the world of the Checkered
Sculpin, Cottus sp. cf. cognatus, where "the colder the better" is
the rule for survival.
The Checkered Sculpin inhabits only the coldest waters, and
in Pennsylvania, is confined to a few springs and spring runs in
the Potomac River Watershed in Franklin County. This specific
habitat and small range accounts for its rarity in Pennsylvania.
In fact, the Checkered Sculpin's global distribution is quite small.
It ranges from Franklin County south through the Maryland
panhandle into a small section of Virginia and West Virginia.
Many sculpin species are similar, confusing and difficult to
identify and classify. The Checkered Sculpin is no exception. For
years, the Checkered Sculpin was lumped with the Slimy Sculpin,
Cottus cognatus, a more northern species that also requires
very cold waters. However, recent research has identified clear
distinctions between the two species in appearance and genetics.
Although recognized by experts as a valid species, it has yet to be
formally described as one.
The Checkered Sculpin assumes the typical sculpin form,
which is compressed from above with the eyes in the upper
area of the flattened head. This appearance has resulted in
an appropriate nickname for this group-Miller's Thumb, a
reference to a human thumb caught between two mill stones.
Other names include blob, stargazer, gudgeon, muffle-jaw
and muddler. The sculpins serve as the pattern for the famous
Muddler Minnow streamer fly, a favorite of many trout anglers.
The Checkered Sculpin is a small fish, with adults ranging
from 2- to 3-inches. The largest recorded specimen is a 3.6-inch
sculpin from Virginia. Its scales are reduced to small prickles,
and the pectoral fins are large, fanlike and well-suited to a fish
that dwells on the bottom. Its coloration is variable, as with other
sculpins, but the checkered pattern on its lower sides, from where
it gets its common name, is somewhat distinctive.
With the exception of its requirement for very cold streams,
it could be termed a habitat generalist. Checkered Sculpins have
been found over gravel, rubble, mud and even silt and aquatic
vegetation is often present in its domain. Although streams

56

inhabited by this fish are generally clear, one run in which it
occurs is consistently cloudy.
It appears that most spawning occurs in April. During that
time, the males may become nearly black in color. Although
Checkered Sculpin spawning has not been studied, it is
probably similar to that of other closely-related sculpins. Males
excavate a cavity beneath a rock or other object and defend
this nest against other males by an action that resembles the
barking of a dog. The defeated male then temporarily loses his
darkened coloration. The male also "barks" and bites a female's
head or fins to initiate egg-laying. The eggs are deposited on
the ceiling of the cavity, averaging 300 or so, and hatch in about
2 weeks. Life expectancy is generally 4 to 5 years.
Sculpins often hide under rocks or in dense vegetation
during the daytime and become active as dusk approaches.
They hop across the bottom in quick, darting movements.
The diet of the Checkered Sculpin is probably similar to other
stream sculpins and would include mostly aquatic insects and
small crustaceans, such as shrimp-like amphipods. Fish eggs,
usually those of minnows and other sculpins, are occasionally
eaten as well. And, sculpins are a delicacy for larger trout.
The future of the Checkered Sculpin in Pennsylvania
is uncertain. It only occupies a fraction of a mile to a few
miles in each of the five streams where it occurs, so a
single pollution event could conceivably wipe out an entire
population. During a status survey of the Checkered Sculpin,
many springs where it probably originally occurred have been
destroyed or modified.
Warmer water temperatures resulting from climate
change are another threat. Four of the known populations
of Checkered Sculpins live in water temperatures not
exceeding 61-degrees F, but one stream, with what is probably
Pennsylvania's largest population of Checkered Sculpins,
had an August temperature of 66-degrees F, which may be
approaching the thermal limit for this sculpin.
Given its small overall range and the importance of
Pennsylvania's populations, the Checkered Sculpin is listed
in the 2015-2025 Pennsylvania Wildlife Action Plan. There is
little doubt that, given its rarity and the threats that face it, it
will become listed as a threatened or endangered species once
its formal description is published. Until then and afterward-
the colder the better.

Pennsylvania Angler & Boater * November/December 2017	

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