Biocomplexity at North Temperate Lakes LTER; Whole Lake Manipulations: Rainbow Smelt Removal 2001 - 2009

Rainbow smelt (Osmerus mordax) are a harmful invasive species in lakes of northern Wisconsin. Smelt were first detected in Sparkling Lake, Vilas county, WI in 1980 and their population has since increased dramatically. We attempt to remove rainbow smelt from Sparkling Lake through a combined strategy of harvest and predation. If successful, such a strategy might be employed to restore other Wisconsin lakes invaded by smelt to a more natural species assemblage without resorting to piscicides. The data sets presented here report the harvest component of smelt removal. An assessment of the rainbow smelt population, supplementing annual LTER data, was performed during the late summer of 2001. The spring removal effort began in 2002 at ice out using multiple gear types. In 2002, the removal effort also continued from mid to late summer using horizontal gill nets. However, from 2003-2009 we took advantage of smelt spawning behavior and our efforts were condensed to a spring removal at ice-off and we utilized only fyke nets. The total weight of each catch was recorded and length-weights as well as sex ratios were documented for a subset of the catch from each removal event. The removal effort resulted in the removal of the majority of the adult population multiple times. However, smelt are a robust species and the population continuously rebounded from large removal years. As a result, catches have fluctuated from 16kg to nearly two tons. We have observed an overall reduction in fish size and an increase in the proportion of males to females. Sampling Frequency: annually

彩虹胡瓜鱼（Rainbow smelt，Osmerus mordax）是威斯康星州北部湖泊中的有害入侵物种。1980年，研究人员首次在威斯康星州维拉斯县的闪光湖（Sparkling Lake）中检测到该物种，此后其种群数量急剧攀升。本研究尝试通过捕捞与捕食协同的综合防控策略，清除闪光湖中的彩虹胡瓜鱼。若该策略取得成功，或可推广应用于其他受彩虹胡瓜鱼入侵的威斯康星州湖泊，使其恢复至更自然的物种群落结构，且无需使用杀鱼剂（piscicides）。本数据集所呈现的内容，即为彩虹胡瓜鱼清除行动中捕捞环节的相关数据。2001年夏末，研究人员开展了彩虹胡瓜鱼种群评估工作，以补充年度长期生态研究（Long-Term Ecological Research, LTER）数据。2002年春季的清除行动于冰融期启动，采用了多种渔具类型；同年夏季中至下旬，研究人员亦通过水平刺网（horizontal gill nets）持续开展清除作业。但在2003年至2009年间，研究人员借助彩虹胡瓜鱼的产卵行为，将清除行动压缩至春季冰融期，且仅使用芬克网（fyke nets）进行捕捞。每次捕捞行动均记录了总渔获重量，并针对每次清除行动的部分渔获样本，记录了体长-体重关系以及性别比例数据。此次清除行动多次移除了成年种群的绝大多数个体，但彩虹胡瓜鱼为适应性极强的物种，种群在大规模捕捞年份后会持续反弹回升。因此，年捕捞量在16千克至近2吨之间波动。研究人员同时观测到，渔获个体的整体体型呈下降趋势，且种群雌雄比例中雄性占比有所提升。采样频率：每年一次。