Case Studies in Fisheries Conservation and Management: Applied Critical Thinking and Problem Solving
Case 22: Successful Use of a Protected Slot Length Limit to Improve Largemouth Bass Size Structure: But What Happens to the Panfish?
Protected slot length limits (e.g., all fish between 30 and 38 cm must be immediately released) have been used to restructure high-density, slow-growing largemouth bass populations in small impoundments (Dean and Wright 1992; Flickinger et al. 1999; Noble and Jones 1999). When anglers have been willing to harvest the small largemouth bass, the regulation results in improved bass size structure. Typically, the management goal is to reduce density of sub-slot fish, improve growth rates, and increase size structure.
In this case study, you will be asked to think beyond population-level management to the community or assemblage level. As the largemouth bass is a top-level predator in many small impoundments, might changes in bass abundance be related to abundance and resulting size structure of prey species?
Watkins Mill Lake (Figure 22.1) is a 42-ha impoundment located 50 km northeast of Kansas City, Missouri. It has a maximum depth of 12.2 m, and secchi transparency measurements typically ranged from 0.6 to 1.2 m at the time of this study. The 770-ha watershed includes pasture, row crops, and forest. The fish community included largemouth bass, bluegills, white crappie, channel catfish, and gizzard shad. The largemouth bass population was managed with a 38-cm minimum length limit (all fish less than 38 cm had to be immediately released) beginning in Year 1 of this study, with the 30- to 38-cm protected slot length limit (Figure 22.2) being imposed prior to the fish community sampling in Year 4.