Largemouth Bass Population Structure Changes and Harvest Under a Slot Length Limit

Effects of changing harvest regulations on largemouth bass Micropterus salmoides from a 254-mm minimum length limit and 10-fish daily bag limit to a slot length limit of 356-457 mm and later to a 5-fish daily bag limit were monitored on Calaveras and Monticello reservoirs, Texas. Electrofishing was used to monitor changes in size structure at both reservoirs and density as catch per unit of effort (CPUE) at Monticello Reservoir only. A creel survey was used to monitor angler harvest at Calaveras Reservoir. In both reservoirs, RSD 203-355 decreased while RSD 356-457 and RSD 457 increased. In Monticello Reservoir, electrofishing CPUE of largemouth bass 203-355 mm declined, while CPUE of largemouth bass 356-457 mm and ≥457 mm increased. However, the total CPUE of all stock-size largemouth bass remained similar to pre-slot length limit levels. Calaveras anglers responded to length limit changes by harvesting largemouth bass below the slot length limit. Initially, number harvested increased while weight harvested decreased. After 4 years, total harvest by weight increased to pre-slot length limit levels. After 7 years, mean weight of largemouth bass harvested had increased from 0.74 kg to 2.03 kg. The reduction in the bag limit did not distribute the harvest among more anglers or effect the proportion of anglers who caught 5 largemouth bass. Carefully chosen slot length limits can be effective for improving the quality of largemouth bass fishing in larger reservoirs.

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