Factors associated with extirpation of the last Northern Sunfish (<i>Lepomis peltastes</i> Cope, 1870) population in western New York State, USA

The Northern Sunfish (<i>Lepomis peltastes</i> Cope, 1870) is threatened in New York state, USA, but this was not the case before 1940 when the NY Biological Survey documented the species at scattered, specialized habitats in six watersheds in the central and western parts of the state. After 1940 the historic populations could not be detected, but a new population was discovered in 1974 in lower Tonawanda Creek and the nearby Erie Canal. Northern Sunfish, and a few of their hybrids with other <i>Lepomis</i> species, were caught at these locations during irregular sampling through 2009, but no Northern Sunfish were caught after 2009. The objectives of our study were to: (1) Determine the extent of Northern Sunfish hybridization with other <i>Lepomis</i> species, and (2) Evaluate how well identifications of <i>Lepomis</i> species and their hybrids agreed among field keys, morphometric measurements and meristic counts, and genetic methods. In 2013, we collected Northern Sunfish (descended from fish captured in lower Tonawanda Creek from 2006-2009) from NY State Department of Environmental Conservation rearing ponds, plus wild Green Sunfish (<i>L. cyanellus</i> Rafinesque, 1819), Pumpkinseed (<i>L. gibbosus</i> Linnaeus, 1758), Bluegill (<i>L. macrochirus</i> Rafinesque, 1819), and suspected <i>Lepomis</i> hybrids from lower Tonawanda Creek. Ultimately, 91 fish were identified using field keys, morphometric-meristic analysis, and mtDNA and nuclear DNA analysis. Assuming genetic analysis provided accurate identification, we found 7 Bluegill × Northern Sunfish, 8 Bluegill × Pumpkinseed, 13 Bluegill × Green Sunfish, and 3 Green Sunfish × Pumpkinseed hybrids in our sample (female parent listed second in these crosses). Keyed and morphometric-meristic identifications did not differ in accuracy and averaged 81% of genetic identification accuracy. After Northern Sunfish stocking (not in our study area) and sampling from 2008 to 2018 in several watersheds with appropriate habitat and no recaptures after 2014, we conclude that the Northern Sunfish is extirpated in western New York state. While populations of Northern Sunfish (<i>Lepomis peltastes</i>) existed in several New York state watersheds before 1940, only one, discovered in 1974, persisted in small areas of lower Tonawanda Creek and the nearby Erie Canal.Despite high effort, no Northern Sunfish were captured after 2009 in the places they had occupied since 1974.Because many Northern Sunfish, all descended from wild fish in lower Tonawanda Creek and the Erie Canal, exist in two New York state hatchery ponds, we recommend attempting restoration in their former habitat by stocking. While populations of Northern Sunfish (<i>Lepomis peltastes</i>) existed in several New York state watersheds before 1940, only one, discovered in 1974, persisted in small areas of lower Tonawanda Creek and the nearby Erie Canal. Despite high effort, no Northern Sunfish were captured after 2009 in the places they had occupied since 1974. Because many Northern Sunfish, all descended from wild fish in lower Tonawanda Creek and the Erie Canal, exist in two New York state hatchery ponds, we recommend attempting restoration in their former habitat by stocking.北方太阳鱼（Northern Sunfish，学名*Lepomis peltastes* Cope, 1870）在美国纽约州境内受到生存威胁，但1940年之前并非如此——彼时纽约生物调查局（NY Biological Survey）曾在该州中西部6个流域的零散特殊生境中记录到该物种。1940年后，这些历史种群便再未被发现，但1974年在陶万达溪下游及附近的伊利运河中发现了一个新的种群。1974年至2009年期间，通过不定期采样，在上述区域捕获到了北方太阳鱼及其与其他刺盖太阳鱼属（*Lepomis*）物种的少量杂交个体，但2009年后未再捕获到任何北方太阳鱼。 本研究的目标为：（1）明确北方太阳鱼与其他刺盖太阳鱼属物种的杂交程度；（2）评估野外检索表、形态测量与可数性状计数，以及遗传学方法在刺盖太阳鱼属物种及其杂交个体鉴定中的一致性。 2013年，我们从纽约州环境保护部（NY State Department of Environmental Conservation）的繁育池塘中采集了北方太阳鱼（其亲本为2006-2009年在陶万达溪下游捕获的个体），同时采集了野生的绿色太阳鱼（*L. cyanellus* Rafinesque, 1819）、南瓜籽太阳鱼（*L. gibbosus* Linnaeus, 1758）、蓝鳃太阳鱼（*L. macrochirus* Rafinesque, 1819），以及在陶万达溪下游采集到的疑似刺盖太阳鱼属杂交个体。最终通过野外检索表、形态计量-可数性状分析、线粒体DNA与核DNA分析，共鉴定了91尾鱼类。 以遗传学鉴定结果作为准确鉴定的标准，我们共发现7尾蓝鳃太阳鱼×北方太阳鱼杂交个体、8尾蓝鳃太阳鱼×南瓜籽太阳鱼杂交个体、13尾蓝鳃太阳鱼×绿色太阳鱼杂交个体，以及3尾绿色太阳鱼×南瓜籽太阳鱼杂交个体（上述杂交组合中母本列于第二位）。野外检索表鉴定与形态计量-可数性状分析的鉴定准确率无显著差异，平均达到遗传学鉴定准确率的81%。 在（未在本研究区域内开展的）北方太阳鱼放流后，我们于2008年至2018年对多个具备适宜生境的流域进行采样，且2014年后未再次捕获到个体，据此认定北方太阳鱼已在纽约州西部区域性灭绝。 1940年之前，纽约州多个流域曾存在北方太阳鱼（*Lepomis peltastes*）种群，但仅1974年发现的那个种群在陶万达溪下游及附近伊利运河的小片区域存续。尽管投入了大量采样工作，2009年后在该种群自1974年以来占据的栖息地中未再捕获到任何北方太阳鱼。由于目前有大量北方太阳鱼个体均源自陶万达溪下游与伊利运河的野生种群，且存活于纽约州的两个孵化场池塘中，我们建议通过放流尝试在其原栖息地开展种群恢复。 1940年之前，纽约州多个流域曾存在北方太阳鱼（*Lepomis peltastes*）种群，但仅1974年发现的那个种群在陶万达溪下游及附近伊利运河的小片区域存续。尽管投入了大量采样工作，2009年后在该种群自1974年以来占据的栖息地中未再捕获到任何北方太阳鱼。由于目前有大量北方太阳鱼个体均源自陶万达溪下游与伊利运河的野生种群，且存活于纽约州的两个孵化场池塘中，我们建议通过放流尝试在其原栖息地开展种群恢复。