Using Pharyngeal Teeth and Chewing Pads to Predict Juvenile Silver Carp Total Length in the La Grange Reach, Illinois River: Data

ilver carp (Hypophthalmichthys molitrix) are an invasive species in the Mississippi River Basin; understanding their vulnerability to predation as juveniles may inform control by native predators and predator stocking. Digestion of silver carp recovered from diets makes it difficult to determine the size classes most vulnerable to predation by native fishes. The objective of this study was to determine if total length of silver carp can be predicted from the size of their chewing pad, pharyngeal teeth, and pharyngeal arch, the structures most often found intact in diets. Juvenile silver carp (n=136: <180 mm) were collected using 60 hz pulsed- DC electrofishing and mini fyke nets in 2014 and 2015 from the La Grange Reach of the Illinois River. We dissected silver carp chewing pads (n= 136 fish) and pharyngeal teeth (n=127 fish) and measured chewing pad length and width, eight reproducible pharyngeal teeth landmarks, and four reproducible pharyngeal arch landmarks to the nearest 0.01 mm. Using simple linear regression we found that there is a strong predictive relationship between chewing pad, pharyngeal teeth, pharyngeal arch measurements and total length of silver carp. Chewing pad length and width were stronger predictors of silver carp length (r2= 0.94) than pharyngeal teeth (r2= 0.87), but both structures can be used to estimate silver carp total length.

鲢（Hypophthalmichthys molitrix）是密西西比河流域的入侵物种，明确其幼体的被捕食脆弱性，可为本土捕食者管控及捕食者人工放养提供参考。通过分析捕食者胃容物中残留的鲢鱼消化残骸，难以确定最易遭受本土鱼类捕食的体长组。本研究旨在探究能否通过鲢鱼的咀嚼垫、咽齿及咽弓的尺寸预测其总长度——这类结构在胃容物中通常保存完好。2014年至2015年，研究团队使用60Hz脉冲直流电捕鱼法（pulsed-DC electrofishing）与小型囊网（mini fyke nets），在伊利诺伊河拉格兰奇河段采集了136尾幼鲢（体长<180mm）。研究人员对全部136尾鲢鱼的咀嚼垫、127尾鲢鱼的咽齿进行了解剖，并测量了咀嚼垫的长度与宽度、8个可重复定位的咽齿地标点以及4个可重复定位的咽弓地标点，测量精度可达0.01mm。通过简单线性回归分析发现，咀嚼垫、咽齿及咽弓的测量值与鲢鱼总长度之间存在极强的预测相关性。其中，咀嚼垫的长度与宽度对鲢鱼体长的预测能力（决定系数r²=0.94）优于咽齿结构（r²=0.87），但两类结构均可用于估算鲢鱼总长度。