influencing fish size in BC still waters.
who love to paddle still water ponds and lakes in search of fly rod adventure,
British Columbia is the nirvana. The choices range from tiny azure jewels
at high altitude, to sea level expanses of dark fresh water, that are
only steps off salty, clam-infested beaches.
has such a variety of still water (lake) opportunities that it truly causes
the mind to reel. Some offer tiny, colorful trout in endless, easy profusion
while others grudgingly give up salmon-sized trophies every other day
fishers are intrigued, and perhaps even besotted, by the lure and search
for really large trout. It isn’t always clear why some still waters have
large trout and others have only small ones. The influencing factors are
complex, but we humans have a penchant for converting the complex into
simple black and white.
is probably just such a simplification which hopefully, will provide you
with a few more tools to unravel the secrets of still water fishing.
lake is located, the surrounding geology, and the climate are most important
determiners of productivity and the ability to grow large trout.
local factors, such as shape of the lake bottom, amount of available spawning,
presence of other fish, lake elevation, water quality and man’s activities
also contribute to the potential for large trout. Consider these factors
the next time you are planning a safari to new still waters.
located in different parts of British Columbia may not be the same in
their basic capability to produce large trout.
a scientific paper was published by Drs. T. Northcote and P. Larkin which
looked into the productivity of BC lakes. They were able to divide the
province into 10 regions, according to the different ability of each region’s
waters to support and grow aquatic life (productivity).These regions reflect
the differences in geology and climate that occur in the province.
and Larkin were looking for several specific lake parameters that could
be measured, and that would provide a ready indicator of productivity.
They found one factor, the total dissolved solids (TDS) content of the
water, to be a very useful indicator of the general level of productivity
of lakes province wide.
TDS is the
amount of minerals and nutrients (phosphorus, calcium and others) that
is dissolved in lake water. It is measured in parts per million (ppm).
Very low TDS levels are considerably less that 100 ppm, and moderate to
high levels are much greater than 100 ppm.
We can get
a rough guideline on a lake’s potential to grow fish flesh by understanding
the productivity regions of the province which are defined primarily by
TDS and a few other factors .
1 explains the different
productivity regions of BC, including their location, TDS, and other characteristics.
2 provides TDS readings
for some well known lakes in various parts of the province.
the TDS level help to explain why it takes almost a miracle for lakes
near Vancouver to grow trout larger than a foot, and why a fingerling
rainbow stocked into a Merritt pothole will be 4 pounds in only two years!
productivity will be influenced by surrounding geological conditions:-
notably, the chemical composition of the rocks and soils, and how easily
this material will be available to lake waters.
nitrogen and calcium are particularly important nutrients for all aquatic
life. Where areas are rich in these nutrients, and where they are easily
available through erosion, lakes have higher productivity. These conditions
occur in the central interior of the province.
On the coast,
conditions do not favor productivity because so much of the area lacks
the appropriate nutrients, or these nutrients are tied up in very difficult
to erode granite formations. Exceptions to this, are the lakes that reside
in the southern part of Vancouver Island and the Gulf Islands. Here, the
rainfall is lower, and nutrients are more available in surrounding soils.
and temperature are climatic factors that also have a major influence.
areas where precipitation is very high (particularly the coastal mainland
and parts of Vancouver Island), lakes will not be able to retain eroded
nutrients, as they will quickly be flushed away. A high lake flushing
rate, combined with surrounding substrates that are very difficult to
erode, guarantees low productivity. These waters often have well-defined
and numerous tributary streams.
precipitation, and easily eroded surroundings endowed with nutrients (like
the Interior), is a formula for abundant aquatic life and a potentially
rapid rate of growth for fish. Small lakes with this lucky set of conditions
are extremely rich, because the available nutrients have lots of time
to go into solution, and they stick around for a long time. These waters
often have no well-defined tributary streams, except possibly for a short
period in the early spring, during snow melt and runoff.
average annual summer and winter temperature can also influence lake productivity.
Lakes that have long, very cold winters and short cool summers (like those
in the far north of the province) have shorter periods when water temperatures
are optimal. This reduced “growing season” means that fish will take much
longer to achieve an interesting size.
has an incredible variety of lake types, ranging from very large bodies
of water with steep sides and great depths, to tiny, shallow, saucer-like
shape of the lake bottom is another factor to consider when searching
for waters that might hold larger fish.
that are shallow (have very low average depth) are generally able to produce
more life than lakes that are steep and deep (have very high average depth).
Productive lakes have plenty of shallows where sunlight is able to penetrate.
This stimulates plant life and aquatic fish foods, such as plankton, scuds
Rain. TDS = 4 ppm. The formula for tiny trout
of good spawning for trout is seldom desirable when the objective is
large fish. Abundant spawning and early rearing means lots of young
fish will enter the lake and compete for a fixed food supply. The more
fish competing, the smaller in size they will be.
coastal lakes, with greater rainfall, usually have more streams and
spawning areas than very productive interior waters, where rainfall
is low and spawning streams are in short supply. Many interior trout
waters have no natural spawning, and fish presence is entirely dependent
on annual stocking.
waters may have limited natural spawning, and it may not be available
every year :- these can be trophy waters!
of Other Fish
presence of other fish may be beneficial, or detrimental, in helping
to determine the possible presence of bragging-size trout.
that are accessible to migratory fish (trout or salmon) may provide
some very interesting fishing for larger trout. These trout may be present
to take advantage of abundances of salmon juveniles or eggs. The trout
may only be around for a short period of time, and successfully finding
them will require detailed local knowledge.
other circumstances, resident trout in a lake may be able to take advantage
of a local population of forage species like shiners, chub or kokanee.
fish eaters may allow the trout in some generally unproductive waters
to achieve trophy status. Some species of trout are more adapted to
being fish eaters (ie cutthroat trout and certain stocks of rainbow
many lake situations, other fish (especially non-salmonids like redside
shiners and pike minnows aka. squawfish) can mean serious competition
for the trout population. These other fish may out-compete trout for
food, or they may be trout predators. The result can be a lake containing
a few small trout, with the possibility of some old monsters that have
been able to survive the competition/predation by eating their enemies.
as the climate can influence a lake’s “growing season”, so can elevation.
The higher the elevation of a lake, the shorter is the period of optimal
temperature for organisms to grow. Therefore, as elevation increases,
the expectation of finding really big fish should also diminish. However,
rules do not exist without exceptions. High elevation waters that have
high basic productivity (as indicated by their TDS) with limited spawning
and low angling harvest, can provide a supply of portrait-sized fish.
Water Quality Aspects
contains a variety of materials and gases, either dissolved or in suspension.
Water is also subject to various conditions (ie. be hot or cold). Water
quality is the sum of these contents and conditions. These may or may
not be beneficial, depending on our perspective - in this case it’s
things that influence the potential for large trout being present.
have already looked at some basic water quality aspects such as the
presence of dissolved minerals (nutrients). Other water quality aspects
such as dissolved oxygen and extremes of temperature are important.
some lakes, very low levels of dissolved oxygen or extremely high water
temperatures may mean that trout cannot survive. Many of the ultra-shallow
but highly rich interior lakes are in this category.
conditions may produce extremely low, or no, oxygen levels and fish
may die (winter kill). Occasionally, summer temperatures may create
lethal conditions (summer kill). It is only man’s intervention, in the
form of winter aeration or the stocking of trout species that are more
tolerant to high temperatures or low oxygen, that allow fish to be there.
ponds/lakes, whether they be in the unproductive coast or the rich interior,
have water that is very acidic and low in productivity. Every region
of the province will have some lakes in this category, so the big fish-
scouting angler may decide to give these a pass.
that are glacially influenced may be cloudy (turbid) with glacial “flour”
that is suspended in the water, and may be very cold. The suspended
particles will affect sunlight penetration of the water, and thus the
amount of photosynthesis and plant growth that can occur. The average
temperature during the growing season will be lower, reducing productivity.
little rain, TDS 300 ppm. The proof is in the net!
BCs population increases, and the demand for more still water angling
grows, there are a number of factors related to human activity that
may influence the presence of large trout.
shore and upland development can affect fish populations by changing
the quality of lake waters. Mostly, this is negative. It increases turbidity
(suspended sediment) levels and adds pollutants to the water that may
be toxic to fish and fish food.
some rare cases, organic pollution (septic tank runoff) may add nutrients
and increase the lake’s productivity and ability to grow larger trout.
growth (with more anglers) creates a greater demand for stocking lakes,
and increased stocking potentially results in more waters with bigger
fish. Some of these waters will have ideal conditions for large trout.Many
interior waters can only have trout populations if they are stocked
hatchery stocking adds too many fish, resulting in a decrease in average
culture and small lake management is becoming more sophisticated, especially
in the science of selecting special brood stocks to suit certain lake
conditions. These “designer” trout can do well and grow large, where
other traditional rainbow brood stocks will not.
growth in the angler population invariably comes the illegal transfer
and introduction of unwanted (and often highly detrimental) species
like redside shiners into high quality trout fisheries. Shiners, and
their sort, eventually out-compete rainbow trout for a lakes’s available
or uncaring anglers illegally using live bait (fish or insects) can
transport undesirables and leave them to explode in a new environment.
of trout by anglers has an influence on the availability of the larger
specimens. In very rich lakes, where trout grow rapidly and the number
of large fish is substantial, harvest may not have a serious impact
on all but the very largest members of the population.
less rich waters, large fish are rare and can easily be cropped -off
as angler use and take increases. In the past, some of these unproductive
waters had a reputation for monster fish. Weaver Lake and a few other
waters near Vancouver and elsewhere on the coast, produced rainbow trout
of 10 pounds or more. These undoubtedly were very old fish, and only
existed because very few anglers were able to harvest them. One of these
lakes had absolutely whopper rainbow, but in addition to very low angler
harvest, the fish had another secret :-they dined richly on salamanders!
large trout in BC still waters can be an interesting and rewarding science.
This adventure is certainly more effective when you consider those factors
that make fish large.
a potentially productive area (surrounding geology and climate), and
a lake with the right qualifications in terms of high nutrient level,
moderate elevation, more shallows than deep water, and remote from the
hordes. In doing this, you greatly increase your chance to capture that
fish of a lifetime!
2000 Interactive Broadcasting Corporation