§ FG Field Guide 50 topics · evergreen

The data behind
every good day.

Eight environmental variables that explain why fish bit — or didn't. Each guide covers what the number means, how to read it, and what to do with it on the water.

All guides
01
Water Temperature
Optimal ranges, thermocline depth, seasonal patterns, and how bass metabolism shifts with every degree.
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02
Barometric Pressure
Why the 24-hour trend matters more than the absolute reading, and how fronts create the best — and worst — bites of the year.
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03
Water Clarity
The FNU turbidity scale explained. How to match lure color and presentation to clear, stained, and muddy water.
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04
Solunar Theory
Major and minor feeding windows derived from moon position. The science, the debate, and how to use them in practice.
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05
Tide Phase
Rising, falling, high slack, low slack — what each phase does to bait position and how to fish the transitions.
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06
Water Level Trend
Rising water pulls bass shallow into new cover. Falling water concentrates them on main-lake structure. The 3-day trend tells you which world you're fishing.
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07
Wind & Cloud Cover
Wind concentrates bait on windward banks. Overcast skies pull bass shallow. Together they create the best topwater window of the day.
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08
Moon Phase
Full moon, new moon, spawn timing, night feeding patterns. How the 29.5-day lunar cycle shows up in your catch log.
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09
Dissolved Oxygen & The Bite
Understand how dissolved oxygen, not just temperature, dictates bass depth and feeding zones, concentrating them vertically.
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10
Lake Stratification & Turnover
Learn how summer heat stratifies lakes into thermal layers, affecting bass behavior, and how fall turnover re-oxygenates the water column.
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11
Daylight Length & The Bass Calendar
Day length, not just temperature, drives bass's annual calendar. Equinoxes and solstices trigger spawning, feeding, and winter behaviors.
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12
Cold Fronts & Bite Recovery
Post-cold front bass behavior: Understand the science behind pressure changes, feeding shutdowns, and how to fish the bite recovery.
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13
Spawn Temperature Thresholds
Understand how water temperature, from 55°F to 72°F, triggers bass spawn phases and how latitude and depth shift timing.
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14
Forage Cycles & The Shad Year
Explore the annual cycle of threadfin and gizzard shad and its profound influence on bass behavior and location through the seasons.
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15
Aquatic Vegetation Types
Aquatic vegetation types—hydrilla, milfoil, lily pads, eelgrass, coontail, pondweed—dictate bass location, forage, and water quality indicators.
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16
Bottom Composition & Cover
Understand how bottom composition like rock, gravel, sand, clay, and mud impacts bass behavior and location.
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17
Current and Water Flow
Understand how water current dictates bass positioning and behavior. Learn to read flow patterns in rivers and reservoirs, and leverage real-time data for better fishing.
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18
Tributary Inflow & The Mud Line
Rainfall creates tributary inflow. This inflow forms a temperature and turbidity "mud line" where it meets the main lake. This edge concentrates baitfish and offers bass prime ambush points.
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19
Light Penetration & Secchi Depth
Secchi depth defines how deep light penetrates water. This sets the visible hunting range for bass, influencing their behavior and your lure choices.
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20
Wind Direction & The Windward Bank
Wind direction is crucial for bass. Learn why windward banks concentrate plankton and baitfish, creating prime, challenging feeding grounds for bass.
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21
Cloud Cover & Sky Type
Understand how cloud cover and sky type impact bass feeding. Optimize shallow water fishing based on light penetration.
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22
The Shad Spawn Window
Understand the brief, explosive spring shad spawn bite. Learn why water temperature and first light trigger this feeding frenzy and how to find it.
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23
Tannin-Stained Water
Understand how tannins affect water color and light penetration, influencing bass behavior differently than turbidity. Use Bassai data to refine your approach.
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24
Algae Blooms & Water Quality
Understand how algae blooms impact bass fishing by affecting water quality, dissolved oxygen, and pH, and learn to identify pre- and post-bloom feeding windows.
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25
Drought & Falling Water
Understand how extended drought concentrates bass on main-lake structure, exposes new shorelines, and alters spring spawning.
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26
Flood Conditions & High-Water Bass
Learn how rising water levels push bass into new territory and how to fish crawfish patterns effectively during flood conditions.
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27
River vs Reservoir vs Natural Lake
Understand how habitat influences largemouth and smallmouth bass behavior in rivers, reservoirs, and natural lakes. Log your data.
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28
The Sunrise Window
The sunrise window is a crucial summer feeding period. Bass leverage low light, cool water, and exposed baitfish for a highly productive, short-duration bite.
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29
Air Temperature vs Water Temperature
Understand why water temperature, not air temp, dictates bass behavior. Learn about thermal lag and how Bassai data reveals true patterns.
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30
Lake Elevation & Pool Stage
Understand how lake elevation and pool stage impact bass location and behavior, informed by USGS data.
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31
Bedding Bass & Spawn Beds
Understand bass spawning cycles, temperature triggers, identifying beds, and ethical angling practices for the bedding phase.
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32
Ice-Out & The First Bite
Understand post ice-out bass behavior and master cold-water finesse tactics for 38-45°F conditions.
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33
Post-Spawn Recovery
Understand the post-spawn slump in bass fishing, including duration, recovery feeding windows, and the transition to summer staging areas.
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34
Water pH & Bass Behavior
Understand how water pH affects bass behavior and feeding. Learn the ideal range and how to infer pH shifts from your Bassai log.
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35
Moon Rise & Moon Set Windows
Moonrise and moonset windows offer subtle cues for bass activity. Use these solunar periods as a tiebreaker when primary conditions align, informed by your logged data.
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36
Lake Age & Reservoir Stage
Understand how reservoir age, from new impoundments to aging lakes, affects bass populations, behavior, and fishing patterns.
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37
Frontal Passages & Sky Reading
Decipher bass behavior during weather fronts. Understand how barometric pressure and sky cues reveal pre-frontal feeding windows, during-front pauses, and post-frontal shutdowns.
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38
Nighttime Bass Behavior
Understand how bass senses and behavior change after dark. Learn about lunar, seasonal, and structural influences on nighttime feeding.
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39
Rainfall & The Watershed Lag
Understand how rainfall impacts bass fishing days after a storm by learning about watershed lag and tracking upstream USGS gauges.
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40
Shoreline Orientation & Sun Angle
Understand how sun angle and shoreline direction affect lake temps and bass behavior throughout the seasons for better fishing.
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41
Fetch & Wave Action
Understand how wind fetch, the distance wind travels over water, influences wave action, water mixing, and baitfish location for bass.
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42
Thermal Refuges in Summer
Summer's high water temperatures force bass to seek thermal refuges. Understand the types of cooler-water habitats they frequent, shaping their behavior and patterns for informed angling.
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43
Lake-Effect Weather
Large lakes create localized weather patterns — wind shifts, fog, and storms. Learn how these 'lake effects' diverge from regional forecasts.
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44
Lake Trophic State: Clear, Green, or Murky
Understand lake productivity spectrums—oligotrophic, mesotrophic, eutrophic—to refine bass fishing strategies and adapt your approach.
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45
Finding the Thermocline on Sonar
How to identify the thermocline on sonar, why bass and baitfish relate to it in summer, and its seasonal depth changes.
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46
Relative Weight: Is This Lake Healthy?
Relative Weight (Wr) measures a bass's condition, revealing a lake's health. Learn how to interpret Wr and adapt your strategy to skinny or fat fish.
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47
Year-Class Strength & The Boom Lake
Understand how environmental factors shape dominant year classes of bass, influencing fishing patterns and population structure for years.
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48
Reading a USGS Streamgage
Understand river bass behavior by decoding USGS streamgage data. Learn how gauge height, discharge, hydrographs, and trends inform angling strategy.
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49
The Bluegill Spawn & Bed Raids
Understand bluegill spawn triggers, bed identification, and bass behaviors. Refine your fishing approach using Bassai data during this critical period.
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50
Crawfish Molt & Seasonal Color
Crawfish molt cycles dictate their color and vulnerability. Learn why bass key in on soft-shell craws and how to match your baits to local, seasonal patterns.
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Also on Bassai
All data fields explained → About Bassai → Support →
About these guides

The Field Guide is written and maintained by the Bassai Field Guide Team — the small independent team in Cordova, Tennessee that builds Bassai. Each guide explains one environmental variable the app records: what the number means, how to read it, and how to use it on the water. The guides describe conditions and patterns — they don’t predict catches. Reading the water is still the angler’s call.