Smallmouth Bass — Research & Methodology
Last updated: 2026-06-24
This page documents the current live Smallmouth Bass profile, the open-access URLs behind each driver, verbatim quotes, and what is research-backed vs. what is left out on purpose. We keep proprietary calibration details private, but we are upfront about where the evidence is strong and where it rests on a single study.
How It Works
The Smallmouth Bass rating is deliberately simple. It is a single daily number on the 1.0–5.0 scale, built by adding research-backed points to a baseline. There is no hourly chart and no solunar Major/Minor windows — the smallmouth evidence does not support a time-of-day or moon-based story, so we do not pretend it does.
The formula is plain: rating = 1.0 (baseline) + water-temperature points + season points. Two drivers, both grounded in real catch and biology data. That is the entire model.
Rating Structure
- Baseline (1.0): The floor of the scale. On the coldest days the rating genuinely sits here — when water is cold enough, smallmouth feeding largely shuts down, and the number reflects that honestly.
- Water-temperature points (primary, about 74% of the dynamic range): The main mover. Zero points below a cold floor of 7.2°C (~45°F), then a straight-line rise as water warms, flattening out at a plateau (the maximum) at 22°C (~72°F). There is no peak in the middle and no roll-off at the hot end — within the range our model covers, warmer means a higher rating, then flat.
- Season points (small residual, spring spawn bump): A modest bump during the spring spawn, keyed to water temperature rather than a fixed calendar month, so it shifts earlier in the south and later in the north. It fades to zero by 22°C — before the warm plateau — so summer warmth is never counted twice.
- One daily number: Today, Forecast, and the logbook all show the same single Smallmouth Bass rating for the day. There is no best-stretch window or hourly curve for this species.
What Drives the Rating
- Water temperature — Primary driver. Below ~7.2°C (45°F) the bite largely stops and the rating sits at the floor; it rises linearly as water warms and plateaus at ~22°C (72°F). The input is an estimated water temperature derived from recent air temperature.
- Season (spring spawn) — A small bump during the spring spawn window. It is keyed to spring water temperature (a spawn-temperature window), so it lands around March in Texas and late May/June in Minnesota. It fades out before the summer plateau to avoid double-counting warmth.
What Is NOT Used
- Moon phase — Excluded. No direct-catch evidence supports a moon effect for smallmouth in our corpus.
- Barometric pressure — Excluded. No supporting direct-catch evidence.
- Time of day — Excluded. No reliable smallmouth-specific signal, so there is no hourly chart.
- River flow / current — Deferred, not dismissed. There is real evidence that flat (stable) water out-fishes rising water, but the app does not yet have a river-flow data feed, so we do not include it rather than guess.
Honest Single-Source Disclosure
We want to be clear about this up front. The magnitude of the warm-water catch slope — how much the rating climbs per degree — rests on one study: Wolter & Neuswanger (Wisconsin DNR), built from 1,487 guided river trips, which found a significant positive relationship between water temperature and angler catch rate. The direction of that effect (warmer open-water season means more catch) is consistent with other seasonal angler-catch records, but no second study measures the slope itself. We disclose this rather than oversell it. By contrast, the cold-water shutdown — feeding largely stopping in cold water — is the most robust, multi-source part of the model.
Study Limitations
- Warm-slope magnitude is single-source: The size of the temperature-to-catch slope comes from one study (Wolter & Neuswanger, 1,487 guided trips). Its direction is consistent with a small number of seasonal angler-catch records that point the same way, but its exact magnitude is not independently confirmed. We flag this openly.
- Water temperature is an estimate: The temperature input is estimated from air temperature, and the estimator is tuned for lakes — yet smallmouth are often riverine. We tested the estimator against real river gauges and found it moves the final rating only about 0.2 points on rivers (near-zero bias), so the "river fish, lake-tuned estimate" concern is largely contained, but it is still an estimate, not a direct reading.
- Spawn timing uses a temperature prior: The spring-spawn bump uses a latitude-aware temperature window, which is a reasonable prior drawn from the spawning literature — not a per-lake measurement of when your specific water spawns.
- Winter ratings sit at the floor by design: When estimated water is below the 7.2°C (45°F) feeding cutoff, the rating is 1.0. Across the real measured data used for calibration, 28.4% of days fell below that cutoff. That is honest biology — cold water shuts the bite down — not a bug or a chart-tuned floor.
Ratings are relative indicators, not guarantees. We use the evidence-backed direction of effects and calibrate magnitude for a stable 1–5 scale. The model was calibrated on 23,003 paired daily air-and-water-temperature observations from 39 USGS gauges (2022–2023), locked on 2026-06-24, producing an average rating of about 2.5 across the year.
Variables
Every variable is classified as research-backed, deferred, or excluded.
| Variable | Status | Evidence | Notes |
|---|---|---|---|
| Water temperature | Research-backed (direction multi-source; magnitude single-source) | 1 direct-angling regression (Wolter & Neuswanger); direction corroborated | Primary driver, ~74% of the dynamic range. Zero below 7.2°C (45°F), linear rise, plateau at 22°C (72°F). No hot-end roll-off. Estimated from recent air temperature. Slope magnitude is single-source and disclosed. |
| Season (spring spawn) | Research-backed (small residual) | Spawn-temperature literature (Armour) + spring exploitation peak (Slone et al.) | Small bump keyed to spring water temperature, latitude-aware. Fades to 0 by 22°C to prevent double-counting summer warmth. |
| River flow / current | Deferred (real evidence, no data feed) | Flat-water vs. rising-water catch difference (Wolter & Neuswanger) | Flat (stable) water out-fishes rising water, but the app has no river-flow feed yet. Left out rather than estimated. |
| Moon phase | Excluded | No direct-catch evidence | No smallmouth-specific catch evidence supports a moon effect in our corpus. |
| Barometric pressure | Excluded | No direct-catch evidence | No supporting direct-catch evidence found. |
| Time of day | Excluded | No reliable signal | No dependable smallmouth-specific time-of-day signal, so there is no hourly chart. |
Key Quotes (Verbatim)
Water Temperature — Wolter & Neuswanger 2017 (Wisconsin DNR)
"Smallmouth bass demonstrated a significant positive relationship between water temperature and catch rate. This result matches the observed higher catch rates in peak summer months."
— p.22 (P<0.05; observed water-temperature range approximately 45–80°F)
This is the single direct angler-catch × water-temperature regression behind the slope magnitude (n=1,487 guided trips). Direction is corroborated by other seasonal-catch records; the magnitude itself is single-source and disclosed above.
River Flow — Wolter & Neuswanger 2017 (deferred driver)
"Catch rates for smallmouth were significantly higher under flat water conditions compared to rising water (Figure 12)."
— p.21 (flat water ~0.90 fish/hour; rising water ~0.76 fish/hour)
Real evidence that flat (stable) flow out-fishes rising flow. Deferred from the live model because the app has no river-flow data feed yet.
Spawn Temperature Window — Armour 1993 (US Fish & Wildlife Service)
"The bulk of spawning in 15.6–21.1° C range with peak at 17.8° C."
— Table 3, p.6
"For example, if 40 degree-days accumulated by 1 May, the date on which the 15° C level initially occurred, the estimated peak of spawning would be about 7 May (Fig. 5)."
— p.16
Thermal regimes for smallmouth bass: spawning roughly 15–21°C, with temperature (not calendar date) driving onset — which is why the season bump is keyed to a temperature window that shifts by latitude.
USGS publication (open access)
Spring Exploitation Peak — Slone 2024 (Iowa State M.S. thesis; published 2025, NAJFM)
"Weekly exploitation rates ranged from 0 to 11.9% and were highest in late May and early June and decreased through late September."
— 2024 thesis, p.vii
"Most harvest occurred during June."
— 2024 thesis, p.20
Tagging of 2,165 smallmouth bass shows angler exploitation peaking late May / early June — the spring spawn-congregation signal the small season bump captures.
Open-access published version (Slone et al. 2025, NAJFM)
Full Source List
| Authors / Year | Title | Role | Link |
|---|---|---|---|
| Wolter & Neuswanger 2017 (Wisconsin DNR) | Smallmouth Bass and Muskellunge Fisheries in Northwestern Wisconsin Rivers: A Guide to the Future Project (5-year report) — 1,487 guided angler trips; catch rises with water temperature | Water-temperature slope (primary); flat-vs-rising flow (deferred) | |
| Armour 1993 (US Fish & Wildlife Service) | Evaluating Temperature Regimes for Protection of Smallmouth Bass — thermal regimes: spawning (~15–21°C), growth, winter survival thresholds | Spawn-temperature window (season) | USGS |
| Slone 2024 (Iowa State M.S. thesis; publ. 2025, NAJFM) | Lake Oahe tagging of 2,165 smallmouth bass — weekly angler exploitation peaks late May / early June | Spring spawn-congregation signal (season) | Article |
Changelog
- 2026-06-24: Smallmouth Bass rating launched (direct-points; water temp + spring spawn; calibration locked on real USGS data; warm-slope single-source disclosed).