Shifting Distributions of Adult Atlantic Sturgeon Amidst Post-Industrialization and Future Impacts in the Delaware River: a Maximum Entropy Approach

Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) experienced severe declines due to habitat destruction and overfishing beginning in the late 19th century. Subsequent to the boom and bust period of exploitation, there has been minimal fishing pressure and improving habitats. However, lack of recovery led to the 2012 listing of Atlantic sturgeon under the Endangered Species Act. Although habitats may be improving, the availability of high quality spawning habitat, essential for the survival and development of eggs and larvae may still be a limiting factor in the recovery of Atlantic sturgeon. To estimate adult Atlantic sturgeon spatial distributions during riverine occupancy in the Delaware River, we utilized a maximum entropy (MaxEnt) approach along with passive biotelemetry during the likely spawning season. We found that substrate composition and distance from the salt front significantly influenced the locations of adult Atlantic sturgeon in the Delaware River. To broaden the scope of this study we projected our model onto four scenarios depicting varying locations of the salt front in the Delaware River: the contemporary location of the salt front during the likely spawning season, the location of the salt front during the historic fishery in the late 19th century, an estimated shift in the salt front by the year 2100 due to climate change, and an extreme drought scenario, similar to that which occurred in the 1960’s. The movement of the salt front upstream as a result of dredging and climate change likely eliminated historic spawning habitats and currently threatens areas where Atlantic sturgeon spawning may be taking place. Identifying where suitable spawning substrate and water chemistry intersect with the likely occurrence of adult Atlantic sturgeon in the Delaware River highlights essential spawning habitats, enhancing recovery prospects for this imperiled species.

大西洋鲟（Atlantic sturgeon，学名Acipenser oxyrinchus oxyrinchus）自19世纪末起，因栖息地破坏与过度捕捞遭遇种群数量急剧下滑。在捕捞开发的兴衰周期结束后，该物种面临的捕捞压力已大幅降低，栖息地质量也逐步改善。但种群迟迟未能恢复，因此大西洋鲟于2012年被列入《濒危物种法》（Endangered Species Act）保护名录。尽管栖息地整体状况有所好转，但高质量产卵栖息地的可获得性——这对鱼卵与幼体的存活及发育至关重要——仍是制约其种群恢复的关键限制因素。为估算特拉华河（Delaware River）内成年大西洋鲟在河流栖息阶段的空间分布，本研究在其可能的产卵季采用了最大熵（MaxEnt）模型与被动生物遥测技术相结合的分析方法。研究结果显示，底质组成与距盐锋（salt front）的距离，对特拉华河内成年大西洋鲟的栖息位置存在显著影响。为拓展本研究的适用范围，我们将模型投射至四种模拟特拉华河盐锋位置变化的场景中：一是当前可能产卵季的盐锋位置，二是19世纪末历史捕捞时期的盐锋位置，三是预计因气候变化至2100年时盐锋的迁移位置，四是与1960年代类似的极端干旱场景。因疏浚作业与气候变化导致的盐锋上移，可能已破坏了该物种的历史产卵栖息地，且目前仍威胁着大西洋鲟潜在的产卵区域。通过识别特拉华河内适宜产卵底质、水体化学特性与成年大西洋鲟潜在栖息区域的重叠区域，可明确核心产卵栖息地，从而提升这一濒危物种的种群恢复前景。