Class
- Insecta. Order - Hemiptera. Family - Corixidae (over
100 species)
Common
Names:
Waterboatman,
Boatman, Water Bug, Water Beetle, Paddle Bugs
General:
This is
the only non-biting or non-stinging member of the water bugs. It should
not be confused with the larger Backswimmer (family - Notonectidae).
Since it doesn't bite like the Backswimmer, the boatman is a preferred
food source of trout in our interior lakes. If you have ever been stung
by a Backswimmer you will understand why the trout tend to avoid them.
Also note that the boatman is a water 'bug' and not a beetle (Order
Coleoptera).
Life Cycle:
Waterboatmen
spend most of their life in the water but do not have gills. When a
tiny boatman nymph hatches from the egg it will swim to the water surface
to get its first breath of air. It will also grab an air bubble with
its modified legs and then swim back down to the lake bottom. Throughout
its life, the boatman nymph will make many trips to the surface to replenish
this air bubble for that is how it breathes. However, this bubble does
act somewhat like a gill in that it absorbs oxygen from the water allowing
the boatman nymph to stay submerged for long periods of time. Over the
course of the summer the nymph will feed on aquatic vegetation, algae
and a few aquatic larva of other species and gradually mature into an
adult. When the timing is right, the adult will swim to the surface,
hesitate while the wings dry and then take flight. It will join a few,
or many thousands of other Waterboatmen in a mating flight. The adults
will mate in flight and then re-enter their aquatic home where the fertilized
female lays her eggs on the submerged stems of aquatic vegetation.
Appearance:
The boatman
is characterized by two 'paddle' like appendages that are used for swimming
(or paddling) through the water. These paddles are one set, of three
pair of legs and are the farthest from the head. The widened paddle
like appearance is from the 'swimming hair' on the ends of this set
of legs. The other legs of the boatman also have hair, which is used
to hold the air bubble for breathing. While clasping this air, the 'paddles'
are the only easily apparent legs since the others are held close to
the body with the bubble. These bugs have large compound eyes and the
head almost appears to be a part of the elliptical shaped body.
Size:
In the
fall boatmen get up to about 1/3 inch in length (large females can reach
½ inch) and are generally smaller (about 1/5 inch) in the spring. When
extended the paddles are about as long as the bug.
Colour:
The upper
winged surface of the adult is actually a rich, dark brown with black
mottling that will appear as almost black at a casual glance. The underdeveloped
wings of the immature are black. The underside of a boatman is generally
a white to yellowish color but may also be a pale green. The air bubble
that the boatman carries underwater next to its underside will often
give a silvery appearance to the abdomen.
Movement:
The boatman
is only semi-aquatic. Adults will leave the water and fly. When returning
to the water the boatmen will often splash down, grab an air bubble
at the surface and then use their paddle-like hind legs to swim to the
lake bottom. Even while staying in the water the boatman will swim to
the waters surface to grab a fresh air bubble and then back down to
the lake bottom. Most of this water travel is therefore almost straight
up and down in short jerky movements. The buoyancy of the air bubble
makes the trip to the surface much faster than the return trip to the
lake bottom, which requires constant paddling.
Habitat:
Boatmen
prefer the weedy shallows but can be found throughout the lake when
flights are occurring. The shallower waters provide more food for the
boatmen and a shorter trip to the surface for their air supply. The
trapped air bubble allows the boatman to stay submerged for prolonged
periods of time. They can tolerate a variety of water conditions from
polluted to running waters as well as our lakes.
Importance
to Fly Fishing:
When
I started compiling my fishing records on the computer I was somewhat
surprised to find that Waterboatmen were the fifth most important food
source for trout in our Interior lakes. Although the boatmen are primarily
a food source in the spring and fall, these bugs comprise about 6% of
the trout's diet throughout the year. In the spring, the boatmen will
get up to 10% of the trout's total feed and in the fall this can go
up to about 20% of total feed.
The boatmen
are available to the trout throughout the year. I have recorded boatmen
as a part of the feeding samples in every month but July and I suspect
I will eventually get some then. The trout seem to feed on the boatmen
more readily during the daylight hours than the evening or after dark.
Hatches:
Waterboatmen
don't actually have a 'hatch' like Chironomid and many other aquatics,
but take flight from the water in the spring and in the fall for mating.
This is when the trout primarily feed on them. With their air bubble
acting somewhat like a gill, the boatmen will stay submerged and hidden
throughout most of the mid-summer months. However, the observant fisherman
will see at least a few boatmen in the lake throughout the remainder
of the year.
Most of
our interior boatmen have a single generation per year. The mating flight
for those occurs in the fall. However, at least one species has two
generations per year with a spring mating flight in addition to the
late fall mating flight. This two generation species is generally smaller
in size than the single generation species.
In the
spring the boatmen are actively going into mating flights and being
readily consumed by the trout from ice-off until about the first week
in May. Naturally this will vary with elevation. In the fall, mating
flights at higher elevations can begin by August 23rd and continue through
October or heavy frosts at the lower elevations. The average peak for
the mating flights often occurs about mid September.
Flies:
I would
suggest that you never tie an imitation of a boatman larger than one
half inch in length and never with lighter colors on the upper (or winged)
portion. With either of those combinations, the trout may mistake the
fly for a Backswimmer and actually shy away from the fly. Most of my
boatman imitations are about one quarter inch in length and the wings
are often just black. If you can, try to tie the fly with a flattened
appearance with it wider from side to side than from top to bottom.
A dubbed body can be trimmed into this shape and will hold air much
like the boatman's air bubble. The paddles should extend out perpendicular
to the body and it is best if you can get the ends wide like a paddle.
Partly stripped peacock herle seems to work as well as anything. The
underside or body can be yellowish, pale green, whitish, or even silver
to represent the air bubble. I have even tried Syran Wrap to get the
bubble appearance but find the dubbing does just as good a job as anything
(until it gets waterlogged) and provides the fly with some buoyancy
much like the real bug.
Fishing
Tips:
Fish fairly
small flies (1/4 inch?) tied to imitate the boatman in the spring. The
size of fly can be increased in the fall to about one half inch. Try
to fish the fly up or down in the water column rather than parallel
to the bottom. The retrieve shouldn't be too fast. Try a slow and steady
retrieve or try very short jerky pulls to imitate the paddling motion
of the bug. You can even fish the boatman as a dry fly and let it sit
on the surface for a cruising fish to find.
Fishing
the fly up or down in the water column is a bit tricky. With a weighted
fly and dry line the fly is only retrieved upward in the water. As a
suggestion, try tying your boatman as a dry fly or at least very buoyant
and fish it with a sinking line. When you cast out, let the line sink
while the fly floats. After a bit the fly will sink as it is pulled
down with the line. At that point begin your retrieve with very short
jerky pulls. It will imitate the boatman as it dives towards the bottom.
Continue until all the line is retrieved because the second part of
the cast is pulling the fly towards the surface like the boatman rising.
This method tends to work better with shorter casts and moderate water
depths.
Particularly
in the fall, and secondly in the spring, the Waterboatmen is a very
important food source for the trout. Try some experimentation with your
flies and method of fishing. When you find the right combination it
can be a very effective way to catch those trout.
WATERBOATMAN
General:
When
I started compiling my fishing records on the computer I was somewhat
surprised to find that Waterboatmen were the fifth most important food
source for trout in our Interior lakes. Although the boatmen are primarily
a food source in the spring and fall, these bugs comprise about 6% of
the trout's diet throughout the year. In the spring, the boatmen will
get up to 10% of the trout's total feed and in the fall this can go
up to about 20% of total feed. 