CSIRO Environment, Battery Point, Hobart, Tasmania, Australia.
CSIRO NCMI, Battery Point, Hobart, Tasmania, Australia.
J Fish Biol. 2023 Jun;102(6):1455-1469. doi: 10.1111/jfb.15376. Epub 2023 Apr 20.
Egg case nurseries of the boreal skate (Amblyraja hyperborea) and Richardson's skate (Bathyraja richardsoni) were defined and mapped on a bathyal seascape (c. 500-1900 m depths) south of Tasmania, Australia, using 99 towed-camera transects (157 linear km; N = 50,858 images). In total, 738 skate egg cases were observed (present in 240 images, absent in 50,618); among 113 egg cases examined to identify parent species, 70% were A. hyperborea, 10% B. richardsoni and 20% unidentified Bathyraja species. "Recently laid" egg cases were differentiated from "aged" ones by classifying their colour and condition. The great majority (98%) of egg cases were observed in c. 1100-1400 m depths on seamounts (15 of 36 surveyed), not seamount bases or adjacent continental slope. Egg cases were associated with reefs formed by accumulated skeletal matrix of the stony coral Solenosmilia variabilis, with >90% egg cases (including most of those recently laid) observed on living S. variabilis that characterises a "coral zone" in c. 950-1350 m depths. Water in the coral zone is warmer (+0.66 to 2.37°C) than at the deep distributional limits of adult A. hyperborea and B. richardsoni (2000 and 3000 m, respectively), potentially providing for accelerated embryonic development. Co-occurrence with living coral infers an energetically favourable local-scale hydrodynamic environment for egg cases, particularly on seamount peaks, where increased water flow over egg cases would avert smothering by suspended sediment, and compensate for lower oxygen concentration compared to deeper depths occupied by adult skates. Criteria identifying egg case nurseries are strongly met for A. hyperborea at Seamount Z110 (468 egg cases of varied ages, maximum density of 5.47 m ) and to a lesser extent on five others (Seamounts K1, Z16, Hill U, Z5 and Hill V). An abundance (density) criterion for defining nurseries needs to be flexible because it is a spatially scale-dependent measure that differs between surveys according to the tools and design employed. Off Australia, coral reef egg case nursery habitat is restricted to a narrow depth range in temperate latitudes where it is scarce and impacted by historical bottom trawl fishing in many locations. There has been effective conservation of nursery habitat, however, because four of the six nursery sites identified here and extensive coral reef areas are protected within marine parks.
在澳大利亚塔斯马尼亚南部，使用 99 个拖曳式摄像机横切（157 线性公里；N=50858 张图像），在一个深海地貌（水深 500-1900 米之间）上定义和绘制了北方魟（Amblyraja hyperborea）和里查森氏魟（Bathyraja richardsoni）的卵壳托儿所，并对其进行了绘制。总共观察到 738 个魟鱼卵壳（240 张图像中有，50618 张图像中没有）；在检查的 113 个卵壳中，有 70%鉴定为北方魟，10%为里查森氏魟，20%无法鉴定为其他魟鱼。通过对其颜色和状况进行分类，将“新产”的卵壳与“旧产”的卵壳区分开来。绝大多数（98%）的卵壳见于水深约 1100-1400 米的海山（36 个调查点中的 15 个），而不是海山底部或附近的大陆坡。卵壳与由石珊瑚 Solenosmilia variabilis 积累的骨骼基质形成的珊瑚礁有关，在水深约 950-1350 米的“珊瑚区”，有超过 90%的卵壳（包括大部分新产的卵壳）附着在活体 Solenosmilia variabilis 上，这构成了一个“珊瑚区”。珊瑚区的水比北方魟和里查森氏魟成鱼分布的最深处（分别为 2000 米和 3000 米）温暖（高 0.66 至 2.37°C），这可能为胚胎发育提供了加速。与活体珊瑚同时出现推断出卵壳在局部尺度上具有有利的能量环境，特别是在海山的山顶上，那里卵壳上方的水流增加可以防止卵壳被悬浮泥沙窒息，并补偿与成魟鱼所在的更深深度相比，这里的氧气浓度较低。用于识别卵壳托儿所的标准在 Z110 海山（468 个不同年龄的卵壳，最大密度为 5.47m）的北方魟中得到了很好的满足，在其他五个海山（K1、Z16、Hill U、Z5 和 Hill V）中也得到了一定程度的满足。定义托儿所的丰度（密度）标准需要具有灵活性，因为它是一个空间尺度相关的衡量标准，根据使用的工具和设计，在不同的调查中有所不同。在澳大利亚，珊瑚礁卵壳托儿所生境仅限于温带地区狭窄的水深范围内，这里的生境数量稀少，在许多地方都受到历史上底层拖网捕捞的影响。然而，托儿所生境得到了有效的保护，因为这里确定的六个托儿所地点中有四个，以及广泛的珊瑚礁区都受到了海洋公园的保护。
