By Drew Dutterer
TrophyCatch—FWC’s trophy bass conservation and citizen-science program—relies on photographic documentation of a bass’s weight for program qualification. Originally, the program required participants to photo document both weight and length of entrant bass to qualify for Lunker and Trophy levels and Hall of Fame level bass required on-site verification by a Florida Fish and Wildlife Conservation Commission (FWC) biologist. But due to concerns over excessive program participation guidelines, TrophyCatch has since transitioned to requiring only a single weight-documentation photograph for all three tiers of recognition. This simplification reduced handling of bass, reduced their time out of water, and made it easier for anglers to participate. However, by lifting the requirement of length-documentation photos, it left
TrophyCatch biologists with less information to help verify reported weights of entrant bass.
This led FWC researchers to begin investigating alternative methods of verifying length and weight of trophy bass. Using photographs, they developed techniques now referred to as trophy bass photo analytics. In a nutshell, biologists use an object of known size in the photo (e.g., a standard 12-inch ruler) to scale dimensions within the focus of the photo, which can then be applied elsewhere in the shot. Similar to existing equations that use length and girth to estimate a bass’s weight, trophy bass photo analytics allows biologists to measure a bass’s length, body depth, or cross-sectional area in a photo, and these values can then be input into linear models that estimate weight.
The trophy bass photo analytics models are informed by data from nearly 200 bass that were photographed, weighed, and measured in the field by biologists during 2014–2015. To make sure that these methods were applicable to bass of nearly all sizes, they included bass from 2.2–13.1 lbs; however, 65% of the bass were ≥ 8 lbs, since the project’s focus was to help verify weights of trophy bass.
Obviously, the accuracy of these techniques is largely dependent on the quality of the photo. The bass must be centered in the photo and perpendicular to the axis of the shot. If parts of the bass are angled toward or away from the camera they cannot be accurately scaled. As well, an object of know dimensions must also be centered and at the same focal depth in the photo as the bass. However, when all these conditions have been met, trophy bass photo analytics generates reasonably accurate estimates of bass size. For bass used in the study, our models estimated empirical total length to within ±30 mm for 85% of the observations, and we can estimate the weight to within ±500 g 79% of the time.
At this time, TrophyCatch submission approval team has incorporated trophy bass photo analytics as a tool in its submission validation process. If photo composition meets the criteria for the technique and if the validity of the submission is dubious, the process has been applied, and results have given the approval team greater confidence in approving or not approving some bass. In the future, the TrophyCatch team will be considering amending rules for photo documentation that ensure more submissions fit photo analytics criteria, especially for larger bass, which receive that greatest visibility and prizes.