Bits & Pieces: Angler Behavior, Effects of Live-Bait Release, & Bass Vision

This article originally appeared in the August-September 2022 issue of In-Fisherman.

Select Science: Angler Choices & Walleye Fishing Success

The potential for fishing success starts with understanding the nature of the fish we seek, being in the right area on the right waterbody at the right time, and using an effective presentation for the species at hand. This is the foundation of In-Fisherman’s formula for fishing success: F (Fish) + L (Location) + P (Presentation) = S (Success). Finding a waterbody with good numbers (and sizes) of fish is the fundamental starting point. Beyond that, where on the water we choose to fish, when we fish, and what presentation we choose to use ultimately affect our fishing outcomes.

Along these lines, researchers at Ohio State University and the Ohio Department of Natural Resources determined factors that drive fishing success in a large, complex recreational fishery.* The fishery was walleyes on Lake Erie, and they analyzed data from over 92,000 angler interviews conducted during 1989-2017, along with fishery demographics data, to determine how angler behaviors affect catch outcomes.

The set of variables used in the analyses included angler type (launched from a ramp, fished from a dock, or hired a charter), lake basin area fished (west, west-central, or east-central), time (year, month, weekend or weekday, time of day), fishing method (casting or trolling), trip length (hours fished), harvest regulations in effect, fish population demographics (population size, average walleye age, forage fish abundance), and various interactions among these factors. Separate analyses focused on total walleye catch, length of harvested walleyes, and overall fishing success (defined as catching 5 or more walleyes during a trip, with an average walleye length of 19 inches or longer).

The researchers found that angler behaviors were strongly associated with catch outcomes, and were more influential than fish population demographic, environmental, or harvest regulation factors. Factors strongly associated with increased walleye catch included the use of trolling, 15-inch minimum length limit, fishing in the west basin, using a charter, and fishing during the summer. Weekday trips also experienced slightly better catches. Catch decreased with time of day, number of anglers in a group, trip length (quickly filling a bag limit might result in shorter trips), and mean age of walleyes.

Catches also depended on interactions among factors. While increased catches overall were strongly associated with trolling, for example, the effectiveness of casting or trolling varied by month. In spring, when walleyes are congregated at west basin spawning sites, casting and trolling had similar catches; during late spring and summer, when walleyes disperse to the central and east basins, anglers who trolled caught more fish.

Fishing in the spring and trolling were strongly associated with catching larger walleyes. The researchers suggest that relative to casting, which has been shown to select for smaller male walleyes, trolling may catch a larger proportion of larger females. Using a charter service and fishing on weekends were also weakly associated with increased length of harvested walleyes.

Overall fishing success (catching 5 walleyes with a mean length of 19 inches or longer), was greater for anglers who trolled and fished on charter trips. Anglers who trolled were twice as likely to have fishing success, and charter trips were over 100 percent more likely to achieve success. Fishing success decreased as the number of anglers in a group increased from 1 to 10, and as trip length increased from 1 to 13 hours. An interaction between month and basin areas showed that as seasons progressed from spring to fall, probability of success shifted from the west basin to the east-central basin area.

The researchers discuss several ways this study can benefit fishery management. Findings can be used to help educate anglers to make informed choices to maximize total walleye catch, size of fish caught, or a combination of the two. Findings also can help fishery managers focus efforts on conditions that most affect catch outcomes that are important to anglers, and help fishery agencies guide angler expectations to match current fishery conditions.

–Rob Neumann

*Bade, A. P., Dippold, D. A., Schmidt, B. A., DuFour, M. R., Hartman, T. J., Ludsin, S. A. 2022. Angler choices that help catch lots of big fish. Fisheries 47(5):200-212.

Conservation Connections: Live Baitfish Use and Release

Aquatic invasive species are among the greatest threats to biodiversity in freshwater systems. Invasives have been introduced to new waters primarily by humans through distributions of infested water, equipment, and organisms into systems that are otherwise inaccessible to invasives through natural pathways. International shipping, manmade connections between waters (e.g., canal systems), and unintentional or intentional releases (e.g., aquarium fishes), are a few examples. Once invasives are established, they can continue to be spread through secondary transfer to other regional waters. An example of secondary spread is the movement of zebra mussels to unimpacted waters via contaminated boats and trailers.

Angling has been identified as a high-risk pathway for secondary spread of invasive fishes, according to a group of University of Minnesota researchers who recently studied patterns of live baitfish use and release in Minnesota.* They point out that high rates of live baitfish use and transfer, coupled with the potential for spreading invasive species and pathogens, has resulted in most states, including Minnesota, and provinces prohibiting release of live baitfish. Some states such as Minnesota also prohibit importation of baitfish for angling. The researchers report that most baitfish in Minnesota are harvested from wild populations and about 40 percent are raised in aquaculture settings.

To better understand patterns of live baitfish use and release in Minnesota, the researchers sent a mail survey to a sample of licensed anglers, coupled with on-the-water interviews of anglers. Survey questions targeted activities during the 2018-2019 fishing season, and included questions on baitfish procurement, use, species, baitfish disposal, trip frequency, and reasons that factor into decisions regarding baitfish disposal methods.

Overall, 72 percent of mail survey respondents reported that they used live baitfish, with 94 percent purchasing their fish and 6 percent self-harvesting baitfish from the wild. Livebait users fished an average of 28 trips per year, more trips than non-baitfish users. Anglers who harvested their own bait from the wild took more fishing trips per year than those who bought baitfish.

Of the anglers who used baitfish, 48 percent reported that they disposed of baitfish in the trash or on land, while about 20 percent released their leftover baitfish into a waterbody. Among the smaller group of anglers who harvested their baitfish from the wild, 36 percent reported they released their baitfish into a different waterbody than where harvested.

For anglers who didn’t release their live baitfish, their most common reported reasons were the desire to reuse baitfish (18 percent), concern for the environment (14 percent), to follow the law (9 percent), and perceived social norms (7 percent). For those who released their baitfish, reasons included convenience of release (32 percent) and desire not to waste bait (12 percent). Baitfish releasers also cited concern for the environment (34 percent) and perceived social norms (7 percent), likely under the impression they were providing forage for gamefish and bolstering populations of baitfish in the lake.

The researchers conclude illegal baitfish release is widespread and relatively common among anglers in Minnesota, and that it’s likely that millions of fishing trips are taken each year where live baitfish are released into Minnesota waters, creating significant opportunities for cross-watershed transport of baitfish and their hazards within the state. They suggest that improving awareness of regulations could help increase compliance for some anglers who are unaware of baitfish laws, and because some anglers release baitfish “out of convenience,” awareness outreach may also need to be accompanied by other support such as bait disposal facilities and increased enforcement.

–Rob Neumann

*McEachran, M. C., Hofelich Mohr, A., Lindsay, T., Fulton, D. C., and N. B. D. Phelps. 2022. Patterns of live baitfish use and release among recreational anglers in a regulated landscape. N. Am. J. Fish. Mgmt. 42:295-306.

Practical Perceptions: Bass Vision & Presentations

Dr. Keith Jones, former director of the Pure Fishing research laboratory, noted that, "Many fish, including black bass, appear to be more in tune with objects moving horizontally than vertically.” He sug­gests bass may maintain a sharper memory for lures retrieved across their visual fields than lures drifting or falling from above.

His opinion was based on research by two Japanese scientists working on bass vision.* Their mea­surements show that in largemouth bass the visual axis, along which the lens moves for focusing, lies in a roughly horizontal plane. Cone-cell density in the largemouths’ retina is highest in this plane.

Since cone cells are the primary receptors of motion, and the largemouths' cell pattern favors the horizontal axis over the vertical, he believes bass are probably most sensitive to motion in this plane. Moreover, Dr. Jones notes a tendency for vertebrate brains to “match mem­ory capacity with sensory strengths.” We remember what we sense most strongly.

This eye orientation and memory link may help explain why bass seem to learn to identify and avoid various widely used crankbaits, while ‘they have a harder time identifying and avoiding jigs and plastic lures that are often presented as dropping baits. It may also explain why dropping and slow-sinking baits don’t seem to need as lifelike an appearance as crankbaits.

–Ralph Manns

*Kawamura, G., and T. Kishimoto. 2002. Color vision, accom­modation, and visual acuity in the largemouth bass. Fisheries Science 68:1041-1064.

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