A comparison of the effects of water-level policies on the availability of walleye spawning habitat in a boreal reservoir

Papenfuss JT, Cross T, Venturelli PA. 2018. A comparison of the effects of water-level policies on the availability of walleye spawning habitat in a boreal reservoir. Lake Reserv Manage. 34:321–333. Water levels in reservoirs can affect the quantity and quality of the habitat that is available for spawning fish and their eggs. We studied how a change in the water-level management policy (“rule curve”) in 2000 affected the availability of walleye (<i>Sander vitreus</i>) spawning habitat in 3 lakes (Kabetogama, Namakan, and Sand Point) that make up a large, boreal reservoir between Canada and the United States. According to observed water-level data, available spawning habitat on known Lake Kabetogama spawning sites increased 95% (<i>P</i> &lt; 0.01) with the 2000 rule curve, but did not change on Namakan or Sand Point lake spawning sites. However, when using modeled water-level data to control for confounding weather events, habitat availability at known spawning sites increased significantly (<i>P</i> &lt; 0.01) on all 3 lakes (179%, 92%, and 93%, respectively). Habitat availability improved because the 2000 rule curve increased mean spring water levels by 0.5 m, and water levels rose more slowly (2.2 vs. 3.0 cm/d) during egg incubation. Our findings suggest that, although water-level management on large reservoirs can be a challenge, carefully designed policies can improve walleye spawning habitat conditions and help to achieve fisheries management goals.

Papenfuss JT、Cross T、Venturelli PA于2018年发表的研究《水库水位政策对寒带水库玻璃梭鲈产卵栖息地可获得性的影响比较》，刊载于《Lake Reserv Manage》34卷：321–333页。
水库水位会影响产卵鱼类及其鱼卵栖息环境的数量与质量。本研究以加美边境由三座湖泊（卡贝托加马湖、纳马坎湖、桑德波因特湖）构成的大型寒带水库为研究对象，探究2000年出台的水位管理政策（rule curve）对玻璃梭鲈（walleye，<i>Sander vitreus</i>）产卵栖息地可获得性的影响。
基于实测水位数据，卡贝托加马湖已知产卵位点的可利用产卵栖息地在2000年政策实施后提升了95%（P < 0.01），但纳马坎湖与桑德波因特湖的产卵位点栖息地未发生显著变化。
然而，当采用模拟水位数据以控制混杂性天气因素的干扰时，三座湖泊的已知产卵位点栖息地可获得性均出现显著提升（P < 0.01），增幅分别为179%、92%与93%。
栖息地可获得性得以改善的原因在于，2000年的水位管理政策将春季平均水位提升了0.5米，且鱼卵孵化期内水位上升速率放缓（2.2 cm/d 对比 3.0 cm/d）。
本研究结果表明，尽管大型水库的水位管理面临诸多挑战，但经过精心设计的管理政策可改善玻璃梭鲈的产卵栖息环境，助力达成渔业管理目标。