Cover vs. Structure
When talking about bass
habitat, it’s important to get
the terminology correct. One
of the most common misun-
derstandings occurs when
anglers use the words cover
and structure interchange-
ably. They are not the same
thing, and understanding the
difference is key to being
able to accurately and effec-
tively describe and analyze
habitat.
A piece of structure is
anything that stands out – it
affects the macro shape of
the shoreline or bottom.
Points, humps, reefs, break
lines, creek channels, drains,
ditches and saddles are all
pieces of structure.
Cover is anything that a
bass can hide in or on,
patrol, or otherwise hang out
around that may or may not
be located on a piece of
structure. Think rocks, logs,
docks, lily pads, laydowns,
brush piles, fish attractors
and even non-permanent
things such as shade lines or
baitfish balls.
Once you know how to
categorize fishable cover and
structure, you can start to
inventory what’s in your local
fisheries. From there, we turn
to research and experience
on the water to start to
understand how bass use the
cover and structure in differ-
ent seasons and conditions.
What Research Shows
There have been numer-
ous studies about how bass
use cover, where they live in
a body of water and how
much traveling they do. Not
surprisingly, most of this data
identifies trends that you’re
already subconsciously
exploiting just about every
time you’re on the water. For
instance, studies have shown
that when vegetation is
abundant, bass tend to use it
preferentially. When coarse
woody debris such as lay-
downs, logs and flooded tim-
ber is available, you’re more
likely to encounter a bass
than when it’s not present.
Rocky areas attract more
bass than non-rocky, similar-
ly shaped structure.
This type of critical think-
ing, though illustrated with
well-known examples, helps
to show how understanding
cover and structure – the
habitat – can narrow down a
fishery to its highest-percent-
age areas.
Although much of this
research falls in line with
what anglers experience,
there is also data showing
some more unexpected habi-
tat-related observations that
might help anglers in certain
situations:
• A study at Missouri’s
Table Rock Lake found that
bass selected boat docks as
cover at twice the rate of nat-
ural woody debris.
Interestingly, another study
found that docks aren’t near-
ly as likely to hold a bass in a
shallow, vegetated Florida
lake.
• Although a major posi-
tive indicator of bass pres-
ence, too much vegetation
can also be a deterrent, as
one study found that bass are
more effective at feeding and
more commonly found in
looser vegetation than dense
vegetation.
• Across multiple studies,
bass of all species predomi-
nantly spend the majority of
their time shallower than 25
feet regardless of the season.
Those same studies also
showed that spotted and
smallmouth bass often
choose habitat in slightly
deeper water than large-
mouth bass.
APRIL-MAY 2020 | MAJORLEAGUEFISHING.COM | FLWFISHING.COM
Tying it Together
So, you understand the
difference between structure
and cover, you’re thinking
critically about what’s avail-
able in your local lakes or
rivers, and you’re consider-
ing both seasonal and
regional paradigms. Now
you’re on the right track.
In the next column, we’ll
tie habitat to another impor-
tant factor in finding bass: the
availability of prey species.
dock post on the same day.
They don’t all use the same
type of habitat at the same
time, and what’s ideal for
one bass could be less ideal
for another.
That being said, an
understanding of how to
describe available habitat in
your local fishing holes, and
an appreciation of how it
interacts with the water qual-
ity and prey abundance,
allows you to up your odds of
locating more bass in a given
day.
HSI: HABITAT SUITABILITY
INDEX
As with most facets of wildlife interaction, scientists have created a
way to numerically measure the relative suitability of habitat for any
given species. It’s called the Habitat Suitability Index (HSI), and it serves
as a way to describe the relative quality of a particular habitat against
others based upon a predetermined set of factors.
HSI is measured on a scale of zero to one, with measurement of
zero being a habitat completely unsuitable for life, and a measurement
of one being ideal in every aspect. Depending on the number of factors
chosen, measuring habitat suitability can be simple or very complex. For
example, if you only considered dissolved oxygen, you’d measure suit-
ability simply by whether there is enough oxygen for a bass to live – and
then map it across a waterbody.
If you add in factors such as water temperature, depth, water clarity,
and presence or absence of prey, and take measurements of all these
details at numerous points around a lake, you could use that data to
create a “map” of the most suitable places for a bass or any other
species to hang out. Many DNR scientists create and use HSI data dur-
ing the course of their management research.
Check your local DNR office’s public records to see if you can find
detailed habitat analysis for the lakes you most commonly fish.
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