Orrell Danielle L, Sadd Daniel, Jones Kirsty L, Chadwick Kate, Simpson Tiffany, Philpott Darcy E, Hussey Nigel E
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
Ascension Island Government Conservation & Fisheries Directorate, Ascension Island Government, ASN 1ZZ.
J Fish Biol. 2025 May;106(5):1377-1399. doi: 10.1111/jfb.15744. Epub 2024 Apr 17.
Rock hind (Epinephelus adscensionis) and spotted moray (Gymnothorax moringa) are ubiquitous mesopredators that co-occur in the nearshore waters of Ascension Island in the South Atlantic Ocean, where they have significant cultural and subsistence value, but management of their non-commercial take is limited. This isolated volcanic system is home to high biomass and low species diversity, which poses two key questions: How can two mesopredators that perform similar ecological roles coexist? And if these two species are so ecologically similar, can they be managed using the same approach? Here, we combined acoustic telemetry, stomach content analysis, and stable isotope analysis to (i) explore space use and diet choices within and between these two species and (ii) to assess appropriate species-specific management options. Although rock hind had high residency and small calculated home ranges (0.0001-0.3114 km), spotted moray exhibited shorter periods of residency (<3 months) before exiting the array. Vertical space use differed significantly across the 20-month tracking period, with individual differences in vertical space observed for both species. A hierarchical generalized additive model using 12-h averaged depth data identified that rock hind occurred lower in the water column than spotted moray, with both species occupying moderately deeper depths at night versus day (+1.6% relative depth). Spotted moray depth was also significantly predicted by lunar illumination. Aggregating samples by species and tissue type, Bayesian ecological niche modeling identified a 53.14%-54.15% and 78.02%-97.08% probability of niche overlap from fin clip and white muscle, respectively, whereas limited stomach content data indicated a preference for piscivorous prey. Variability in niche breadth between years suggests these species may exploit a range of prey items over time. These findings indicate that although these two species perform a similar ecological role by feeding on prey occupying the same trophic levels, subtle differences in movement behaviors between them suggest a one-rule-fits-all management approach is not likely the most effective option.
岩礁石斑鱼（Epinephelus adscensionis）和斑点海鳝（Gymnothorax moringa）是常见的中层食肉动物，共同出现在南大西洋阿森松岛的近岸水域，在那里它们具有重要的文化和生存价值，但对其非商业性捕捞的管理却很有限。这个孤立的火山系统拥有高生物量和低物种多样性，这引发了两个关键问题：两种发挥相似生态作用的中层食肉动物如何共存？如果这两个物种在生态上如此相似，能否采用相同的方法进行管理？在这里，我们结合声学遥测、胃内容物分析和稳定同位素分析，以（i）探索这两个物种内部和之间的空间利用和饮食选择，以及（ii）评估适当的针对特定物种的管理选项。尽管岩礁石斑鱼具有较高的居留性且计算出的家域较小（0.0001 - 0.3114千米），但斑点海鳝在离开阵列之前表现出较短的居留期（<3个月）。在20个月的跟踪期内，垂直空间利用存在显著差异，两个物种在垂直空间上均观察到个体差异。使用12小时平均深度数据的分层广义相加模型表明，岩礁石斑鱼在水柱中的出现深度比斑点海鳝低，两个物种在夜间相对于白天占据的深度都略深（相对深度增加1.6%）。斑点海鳝的深度也受到月照的显著影响。按物种和组织类型汇总样本，贝叶斯生态位建模分别确定了来自鳍条和白肌的生态位重叠概率为53.14% - 54.15%和78.02% - 97.08%，而有限的胃内容物数据表明它们偏好食鱼性猎物。不同年份生态位宽度的变化表明，随着时间推移，这些物种可能会利用一系列猎物。这些发现表明，尽管这两个物种通过捕食处于相同营养级的猎物发挥相似的生态作用，但它们之间运动行为的细微差异表明，一刀切的管理方法不太可能是最有效的选择。
