School of Aquatic and Fishery Sciences, University of Washington, 1122 Northeast Boat Street, Seattle, Washington, 98195, USA.
School of Environmental and Forest Sciences, University of Washington, 4000 15th Avenue Northeast, Seattle, Washington, 98195, USA.
Ecol Appl. 2020 Apr;30(3):e02061. doi: 10.1002/eap.2061. Epub 2020 Jan 21.
Ecosystem-based management requires consideration of overlapping resource use between humans and other consumers. Pacific salmon are an important resource for both fisheries and populations of wildlife around the Pacific rim, including coastal brown bears (Ursus arctos); salmon consumption has been positively linked to bear density, body size, and reproductive rate. As a case study within the broader context of human-wildlife competition for food, we used 16-22 yr of empirical data in four different salmon-bearing systems in southwestern Alaska to explore the relationship between sockeye salmon (Oncorhynchus nerka) availability and consumption by bears. We found a negative relationship between the annual biomass of salmon available to bears and the fraction of biomass consumed per fish, and a saturating relationship between salmon availability and the total annual biomass of salmon consumed by bears. Under modeled scenarios, bear consumption of salmon was predicted to increase only with dramatic (on the order of 50-100%) increases in prey availability. Even such large increases in salmon abundance were estimated to produce relatively modest increases in per capita salmon consumption by bears (2.4-4.8 kg·bear ·d , 15-59% of the estimated daily maximum per capita intake), in part because bears did not consume salmon entirely, especially when salmon were most available. Thus, while bears catching salmon in small streams may be limited by salmon harvest in some years, current management of the systems we studied is sufficient for bear populations to reach maximum salmon consumption every 2-4 yr. Consequently, allocating more salmon for brown bear conservation would unlikely result in an ecologically significant response for bears in these systems, though other ecosystem components might benefit. Our results highlight the need for documenting empirical relationships between prey abundance and consumption, particularly in systems with partial consumption, when evaluating the ecological response of managing prey resources for wildlife populations.
基于生态系统的管理需要考虑人类和其他消费者之间资源的重叠使用。太平洋鲑鱼是环太平洋地区渔业和野生动物种群的重要资源，包括沿海棕熊（Ursus arctos）；鲑鱼的消费与熊的密度、体型和繁殖率呈正相关。作为人类与野生动物争夺食物这一更广泛背景下的案例研究，我们使用了来自阿拉斯加西南部四个不同鲑鱼承载系统的 16-22 年的经验数据，来探讨红大麻哈鱼（Oncorhynchus nerka）的可利用性与熊的捕食之间的关系。我们发现，熊可利用的鲑鱼的年度生物量与每只鱼消耗的生物量之间呈负相关，而鲑鱼的可利用性与熊每年消耗的鲑鱼总生物量之间呈饱和关系。在模拟的场景中，只有在猎物的可利用性发生巨大（50-100%）增加的情况下，熊对鲑鱼的捕食才会增加。即使鲑鱼数量大量增加，估计熊的人均鲑鱼消费量也只会适度增加（2.4-4.8 公斤·熊 -1 ·天，占估计的每日最大人均摄入量的 15-59%），部分原因是熊不完全食用鲑鱼，尤其是在鲑鱼最丰富的时候。因此，虽然在一些年份，溪流中的熊可能会受到鲑鱼捕捞的限制，但我们研究的系统目前的管理足以使熊群在每 2-4 年达到最大的鲑鱼消费。因此，为棕熊保护分配更多的鲑鱼不太可能导致这些系统中熊的生态响应具有重要意义，尽管其他生态系统组成部分可能会受益。我们的研究结果强调了在评估管理猎物资源对野生动物种群的生态响应时，需要记录猎物丰度和消耗之间的经验关系，特别是在部分消耗的系统中。
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