Relatively little research exists for lentic populations of Flathead Catfish Pylodictis olivaris, particularly in northern states, such as Iowa, where there are currently no harvest restrictions but where the interest in trophy opportunities is growing. We assessed size structure, age structure, growth, condition, and survival for Flathead Catfish populations in Lake Red Rock and Rathbun Lake to increase our understanding of populations in Iowa and determine parameter values to be used in simulating potential regulations. Using low-frequency electrofishing, we captured Flathead Catfish during July and August 2019; all fish were measured and weighed, and a pectoral spine was collected for age estimation. Archived data collected in 2010–2013 were also included in analyses. Reducing harvest by using two potential protected slot limits (PSLs; 305–381 and 381–432 mm) or a maximum length limit (no restrictions on fish < 381 mm and a reduced bag limit for fish >381 mm) was simulated to determine effects on the percentage of quality- and preferred-size fish. Simulations indicated that both PSLs and the maximum length limit produced a greater percentage of quality- and preferred-size fish than a “no regulation” scenario, with PSLs being more effective at low exploitation (0.05) and the maximum length limit being more effective at higher exploitation rates (>0.10). An understanding of the current status of Flathead Catfish populations will allow managers to better manage these populations via informed decision making and help to protect them as their popularity with anglers increases.

中文翻译：

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爱荷华州大型水库改善鲇鱼尺寸结构的潜在法规评估

对扁头鲶鱼Pylodictis olivaris 的静息种群的研究相对较少，特别是在爱荷华州等北部各州，那里目前没有收获限制，但对奖杯机会的兴趣正在增长。我们评估了红岩湖和 Rathbun 湖平头鲶鱼种群的大小结构、年龄结构、生长、状况和存活率，以增加我们对爱荷华州种群的了解，并确定用于模拟潜在法规的参数值。使用低频电捕鱼，我们在 2019 年 7 月和 8 月捕获了平头鲶鱼；对所有鱼进行测量和称重，并收集胸椎用于年龄估计。2010-2013 年收集的存档数据也包括在分析中。通过使用两个潜在的受保护槽位限制（PSL；305-381 和 381-432 毫米）或最大长度限制（对小于 381 毫米和减少的鱼袋限制（> 381 毫米），以确定对质量和首选尺寸鱼的百分比的影响。模拟表明，PSL 和最大长度限制比“无管制”情景产生了更高比例的优质和首选尺寸的鱼，PSL 在低开发 (0.05) 时更有效，最大长度限制在更高的开发率（>0.10）。了解扁头鲶鱼种群的现状将使管理人员能够通过明智的决策更好地管理这些种群，并在垂钓者越来越受欢迎时帮助保护它们。模拟表明，PSL 和最大长度限制比“无管制”情景产生了更高比例的优质和首选尺寸的鱼，PSL 在低开发 (0.05) 时更有效，最大长度限制在更高的开发率（>0.10）。了解扁头鲶鱼种群的现状将使管理人员能够通过明智的决策更好地管理这些种群，并在垂钓者越来越受欢迎时帮助保护它们。模拟表明，PSL 和最大长度限制比“无管制”情景产生了更高比例的优质和首选尺寸的鱼，PSL 在低开发 (0.05) 时更有效，最大长度限制在更高的开发率（>0.10）。了解扁头鲶鱼种群的现状将使管理人员能够通过明智的决策更好地管理这些种群，并在垂钓者越来越受欢迎时帮助保护它们。