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

美洲胡瓜鱼（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）中检出该物种，此后其种群数量急剧增长。本研究尝试通过捕捞与捕食相结合的策略，从闪光湖中移除美洲胡瓜鱼。若该策略获得成功，便可无需使用杀鱼剂（piscicide），将其他受胡瓜鱼入侵的威斯康星州湖泊恢复至更接近自然的物种群落结构。
本数据集收录了胡瓜鱼移除行动中的捕捞组分相关数据。2001年夏末，研究团队开展了美洲胡瓜鱼种群评估工作，以补充长期生态研究（Long-Term Ecological Research, LTER）的年度监测数据。2002年春季，研究人员于冰层消融后启动移除行动，采用多种渔具开展作业；同年夏季中晚期，还通过水平刺网（horizontal gill net）延续了移除工作。2003年至2009年，研究团队借助美洲胡瓜鱼的产卵行为，将移除行动压缩至春季冰层消融后单一阶段，且仅使用诱捕笼网（fyke net）开展作业。
每次捕捞行动均记录了总捕捞重量，并针对每次移除作业的部分捕捞样本，记录了体长-体重对应关系以及性别比例。本次移除行动曾多次清除大部分成年胡瓜鱼种群，但美洲胡瓜鱼适应性极强，在大规模移除的年份后种群仍会持续反弹。因此各年度捕捞量波动范围为16千克至近2吨。研究团队观测到，胡瓜鱼的整体体型呈下降趋势，且种群中雄性个体占比逐年升高。采样频率：每年一次。