Ken Cook, fish biologist, used knowledge of PH levels to win the 1991
BASS MASTER CLASSIC on Chesapeake Bay. He reportedly spends most tournament practice days determining what PH levels exist at the pending tournament site. When a bass tournament officially starts, Cook usually knew where to find the action. Penny Berryman paralleled much the same technique on a Corps inland lake winning the 1992 Bass’n Gal Classic on Mark Twain Lake in N.E. Missouri.
My first exposure at fishing according to PH 
levels was when crappie fishing Truman Lake with Guy Winters and Tony Silvers from Camdenton. Winters constantly checked PH and light refraction readings with a Combo-C-Lector. When its readings changed, we changed depths and jig colors according to what it designated. The process
produced limits of crappie for all of us including a 15 incher caught by Winters. This was the morning after a major thunderstorm moved through central Missouri and while the area continued to be locked in the grip of a major low and a bottomed out barometer.
You do not need a college degree in fish biology to understand or make use of PH data. PH in chemistry simply measures acidity or alkalinity of solutions on a scale of one-through- 14 with seven representing a neutral point. Any reading above seven confirms alkalinity and acidic below that level.
Fish become stressed in acidic water, and also when PH reaches too
high a level. Bass are most comfortable at PH levels between 7.5 - 8.5 with 7.0 - 9.0 the preferred maximum limits of their comfort zone.
When PH is acidic or too basic (more than 9.0 PH), bass experience trouble getting oxygen from water. The resultant stress curbs their feeding forays.
Carbon dioxide only makes up three-percent of air volume but is highly soluble in water creating PH levels in normal rain approximating 5.3 to 5.6. This slightly acidic condition compounds when polluted air containing sulphur dioxide turns rain into a much stronger acid called “acid rain.”
Photosynthesis by submerged plants removes carbon dioxide dissolved in water replacing it with oxygen and calcium carbonate. This causes PH levels to rise clarifying why fish exit weed-beds, shallows and backs of coves as the sun’s impact progressively raises PH above the comfort zone. Smaller fish can and do remain, but larger ones are driven out when influenced by the latter condition.
In the 1991 Classic, Cook discovered satisfactory PH levels in creeks with wood structure early in the morning. However, as the sun rose so did PH levels in the latter. PH levels became ideal after that at tributaries’ mouths in the Bay.
He fished structure where he interpreted that PH levels told him to - and the rest is history.
A meter determines PH from the surface proceeding downward at
one foot increments by virtue of a probe attached to a cable. The “PH break-line” is where the greatest change occurs in one foot of depth. Remember, PH levels can and do alter dramatically as the sun rises.
When fishing water either above 9.0 or under 7.0 PH, fish slowly while seeking a break-line with two-tenths or greater change at that level. Bass can survive in waters ranging from 4.0 to 10.0 (albeit uncomfortably) outside their comfort zone.
Though stressed, fish must feed. Under these conditions, slow
presentations make it easier for them to justify energy to chase the lure. Fish too fast and they probably will not react. This same presentation should be used in winter conditions.
Understanding PH and how it affects fish behavior helps clarify an old “saw” that 90% of fish are in 10% of the water. Fishing structure at depths determined by PH break-lines guarantees more fish per hour than randomly casting a stretch of water.