DR09 · Atchafalaya bass size-limit evidence case
Version: 1.0.0
Checked: 2026-10-21

Purpose
This is an attributed synthesis of agency-reported historical observations and published basin research. It asks what the historical 14-inch minimum-length rule achieved and what the existing record can establish before the 2026 rule is evaluated. It does not reanalyze raw fish samples, estimate a regulation effect, or predict catches.

Sources and units
- LDWF, Evaluation of the 14-Inch Minimum Length Limit for Largemouth Bass in the Atchafalaya Basin and Surrounding Waters, official PDF endpoint: https://www.wlf.louisiana.gov/assets/Resources/Publications/Freshwater_Inland_Fish/2011_Evaluation_of_the_14-Inch_Minimum_Length_Limit_for_Largemouth_Bass_in_the_Atchafalaya_Basin_and_Surrounding_Waters_Louisiana.pdf
- LDWF, Atchafalaya Basin Management Plan Part B (2023), especially regulation history, relative-weight Figure 5 and age/growth Figure 6: https://www.wlf.louisiana.gov/assets/Resources/Publications/Freshwater_Inland_Fish/Inland-Waterbody-Management-Plans/Atchafalaya-Basin-MP-B-2023.pdf
- LDWF, 2010 Atchafalaya, Henderson and Verret Black Bass Survey: https://www.wlf.louisiana.gov/assets/Resources/Publications/Freshwater_Inland_Fish/2010_Atchafalaya_Henderson_and_Verret_Black_Bass_Survey.pdf
- LDWF, Atchafalaya Basin Management Plan Part B (2023), Figure 16 creel-survey category comparisons: https://www.wlf.louisiana.gov/assets/Resources/Publications/Freshwater_Inland_Fish/Inland-Waterbody-Management-Plans/Atchafalaya-Basin-MP-B-2023.pdf
- Louisiana Senate Concurrent Resolution 154 Study Group Report: https://www.dnr.louisiana.gov/assets/OCM/ABP/SR154.ReportA.pdf
- Alford, J.B. (2011), Managing the flood pulse for optimal fisheries production in the Atchafalaya River Basin, Louisiana (USA), River Research and Applications, doi:10.1002/rra.1610
- Louisiana Act 460 / SB 111: https://legis.la.gov/Legis/ViewDocument.aspx?d=1480143

Acquisition and audit status
The Act text and effective date are available through official Louisiana legislative pages. LDWF's 2011 and 2023 PDF endpoints returned 403/405 responses to direct opening in the research session. Search indexing exposed the reports' abstracts and specific figure/table text, including the 3.4-year age-at-14 result, the seldom-five-years statement, the agency conclusion on the old rule, and the 2005-2022 n=4,326 figure. Those values are reproduced as agency-reported facts, not independently recomputed. Complete methods, annual samples, uncertainty intervals and figure data have not been audited. The evidence page discloses this limit next to the result.

Analysis rules
1. Keep agency observations, agency conclusions, published model associations, angler preference and current law as different evidence types.
2. Do not calculate a before/after effect from aggregate records. The 2013 rule change bundled removal of the minimum with a temporary change in daily bag limit; environmental conditions and cohorts changed as well.
3. Treat the 2026 Act as the current policy in its defined area, not as an evaluated intervention. No post-August 2026 biological response is claimed.
4. Do not treat the 4,326 relative-weight sample as an annual count, a size-structure series or 4,326 independent tests.
5. The published flood-pulse associations describe relative-abundance models in a defined basin and period. They are not converted to a fishing forecast or a causal effect of regulation.

Files
- evidence.json: source-attributed timeline, reported values and explicit limits.
- policy-timeline.csv: reader-friendly policy/evidence history, derived from the same timeline.
- creel-practice.csv: LDWF-reported rounded angler outcome-category percentages from Figure 16.

No source figure or raw observation data is redistributed. This package contains no new fish-level dataset and no fitted model. For a future quantitative evaluation, obtain the complete annual LDWF electrofishing, age/growth and creel records with survey protocols and effort, then pair them with flow, stage, storm and fish-kill histories. Predefine population and angler outcomes before comparing regulation periods.