Cognitive and Behavioural Ecology Program, Psychology Department, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada.
Canadian Wildlife Service, Dartmouth, Nova Scotia, Canada.
PLoS One. 2023 Jul 14;18(7):e0288650. doi: 10.1371/journal.pone.0288650. eCollection 2023.
Spatial planning for marine areas of multi-species conservation concern requires in-depth assessment of the distribution of predators and their prey. Northern Gannets Morus bassanus are generalist predators that predate several different forage fishes depending on their availability. In the western North Atlantic, gannets employ different dive tactics while in pursuit of different prey types, performing deep, prolonged U-shaped dives when foraging on capelin (Mallotus villosus), and rapid, shallow, V-shaped dives when foraging on larger pelagic fishes. Therefore, much can be inferred about the distribution and abundance of key forage fishes by assessing the foraging behaviour and space-use of gannets. In this study, we aimed to quantify space-use and to determine areas of suitable foraging habitat for gannets in pursuit of different prey types using habitat suitability models and kernel density utilization distributions. We deployed 25 GPS/Time-depth recorder devices on parental Northern Gannets at Cape St. Mary's, Newfoundland, Canada from 2019 to 2021. To assess the influence of environmental variables on gannets foraging for different prey types, we constructed three different habitat suitability models: a U-shaped dive model, and two V-shaped dive models (early and late chick-rearing). Suitable foraging habitat for capelin, deduced by the U-shaped dive model, was defined by coastal, shallow waters with flat relief and sea surface temperatures (SST) of 11-15° C. Suitable habitat for early V-shaped dives was defined by shallow and coastal waters with steep slope and SST of 12-15°C and ~18°C, likely reflecting the variability in environmental preferences of different prey species captured when performing V-shaped dives. Suitable habitat for late V-shaped dives was defined by shallow coastal waters (<100m depth), as well as waters deeper than 200 m, and by SST greater than 16°C. We show that space-use by gannets can vary both within and between years depending on environmental conditions and the prey they are searching for, with consequences for the extent of potential interaction with anthropogenic activities. Further, we suggest regions defined as suitable for U-shaped dives are likely to be critical habitat of multi-species conservation concern, as these regions are likely to represent consistent capelin spawning habitat.
对具有多种保护物种的海洋区域进行空间规划需要深入评估捕食者及其猎物的分布情况。北方塘鹅（Morus bassanus）是一种杂食性捕食者，会根据其可获得性捕食多种不同的觅食鱼类。在北大西洋西部，塘鹅在追逐不同猎物类型时会采用不同的潜水策略，在捕食毛鳞鱼（Mallotus villosus）时会进行深度较长的 U 形潜水，而在捕食较大的远洋鱼类时会进行快速、浅的 V 形潜水。因此，通过评估塘鹅的觅食行为和空间利用情况，可以推断出关键觅食鱼类的分布和丰度。在这项研究中，我们旨在使用栖息地适宜性模型和核密度利用分布来量化空间利用，并确定塘鹅在追逐不同猎物类型时的适宜觅食栖息地区域。我们在加拿大纽芬兰省圣玛丽海角部署了 25 个 GPS/时间深度记录器设备，用于跟踪 2019 年至 2021 年期间的亲北方塘鹅。为了评估环境变量对塘鹅捕食不同猎物类型的影响，我们构建了三种不同的栖息地适宜性模型：U 形潜水模型，以及两种 V 形潜水模型（早育雏和晚育雏）。U 形潜水模型推断出的毛鳞鱼适宜觅食栖息地是沿海浅水区，具有平坦的地形和 11-15°C 的海面温度。适合早期 V 形潜水的栖息地是由浅海和沿海地区组成，坡度陡峭，海面温度为 12-15°C 和 18°C 左右，这可能反映了在进行 V 形潜水时捕获的不同猎物物种的环境偏好变化。适合晚期 V 形潜水的栖息地是由浅海（<100m 水深）和水深超过 200m 的水域以及大于 16°C 的海水温度组成。我们表明，塘鹅的空间利用情况会根据环境条件和它们正在寻找的猎物而在年内和年际之间发生变化，这对它们与人为活动之间潜在的相互作用程度有影响。此外，我们建议将 U 形潜水定义为适宜区域可能是具有多种保护物种的关键栖息地，因为这些区域可能代表着毛鳞鱼产卵栖息地的一致性。
