This page has information on lure depths when using most popular type lines.
This is based upon field testing in a variety of conditons.
Factors Affecting Lure Depth
Speed
The speed of the water is the biggest single factor effecting depth. Water
speed is the sum of the boat speed and the current velocity and vector. In the
Chesapeake Bay currents can vary from less than .5 knots to as much as 5 or 6
knots depending on conditions and location.
Even a slight increase in speed affects lure depth drastically. Most anglers
around the Chesapeake agree that boat speeds of 1.5 to 4 knots seem to work best
when fishing for striped bass and trout. Bluefish prefer 3.5 to 5 knots. Other
species prefer even faster presentations. I have caught tuna at 16 knots and
many fish have been caught at speeds in excess of 20 knots.
Weight
The simplest way to make a lure run deeper is to add weight. This can be
accomplished in a number of ways. Inline sinkers can be added in front of the
lure. Another way is to use a 3 way and run tandem lures. One can be heavy and
the other smaller. This allows the angler to present the correct size lure at
the correct depth.
If you troll a single weight at a given speed and line length, the depth will
be approximately the same when you troll tandem lures which total the original
weight if all other factors are unchanged.
Lure Shape
Some lures have a lip which makes them dive. Others have a shape that
inhibits the sinking of the lure.
Line Distance, Type and Diameter
Line diameter and material are big factors. The highest running lines shear
the water less efficiently. The weight of the line can also help it run deeper.
The spectrum of lines from shallow to deep are: mono, braided, multistranded
wire, single stranded wire.
Thinner lines run deeper. Line diameter is a compromise between the ability
to run deep and the strength needed for the type of fishing.
As line length is increased, the drag becomes significant. After a certain
distance of line is deployed, the gain in depth decreases dramatically as line
length increases.
Line Types
Monofilament
Mono is the most common line used in trolling. It has advantages such as knot
strength and durability but does not run as deep as other lines.
Braided
Braided line is popular when trolling for striped bass, trout and bluefish.
It runs much deeper than mono and not run as deep as wire line.
Single Strand Stainless Wire
This is inexpensive and runs deep. It kinks and breaks unexpectedly. It is
used in high speed ocean trolling for tuna and wahoo at times.
Single Strand Monel Wire
Monel is expensive to use and requires some getting used to. For low speed
trolling some anglers prefer this as a deep line. Monel runs as deep as
stainless and deeper than other lines at low speeds.
Multi Strand Stainless Wire
Multistrand wire runs deeper than mono or braided and is very resistant to
abrasion. It is often used around structure such as bridge pilings.
Prediciting Depths
In the field lure depth prediction is simply impossible. The factors are
complicated and ever changing. As the boat travels over the water, the current
velocity and direct are constantly changing. As a boater travels up current the
boat speed and current oppose, making the lures rise, when the boat reverses
direction the 2 forces combine and lures sink. This action is ever changing.
Even a small increase in speed makes a big difference. One way to get a feel
for things is to note boat speed and let a test weight out in a shallow area
with a hard bottom. If the current is significant, you can easily see
differences in how much line it takes to hold bottom when reversing direction.
This only works at low speeds, perhaps 2-4 knots.
The table below is a good starting point for wire line. Other lines will
react differently.