Data from: Shortspine thornyhead and rockfish (Scorpaenidae) distribution in response to substratum, biogenic structures and trawling

Learmonth Bank in northern British Columbia sustains an active trawl fishery that returns large bycatches of deep-sea sponges and corals. To examine effects of biogenic structures on the distribution of fish, we examined nearly 30 km of high-definition imagery from a remotely operated vehicle and documented locations of 2770 scorpaenid fish. The 2 local genera have similar abundances, averaging about 1.2 individuals 100 m–2, but have different spatial abundance patterns: shortspine thornyhead Sebastolobus alascanus are randomly distributed on featureless substrata and their abundance increases with depth. Rockfish Sebastes spp. associate with higher seafloor relief nonrandomly and select for sponges and corals over the inert substrata alone; 95% of the rockfish occurred on 27% of the seafloor surveyed. Sponges (Demospongia and Hexactinellida) were abundant on the bedrock and boulders of the bank and adjacent moraine and covered 30 to 55% of the seafloor compared with 1% of the sediment and aggregates of the surrounding basin. The majority of rockfish (80%) occurred with sponges ≥50 cm in height, and even beds of short sponges attracted 4 times as many rockfish than did substrata with no large epifauna. While over half of primnoid corals over 30 cm tall had associated rockfish, less than 2% of the seafloor had large coral, and small coral had no associated rockfish. On the adjacent seafloor with past trawling activity, Primnoa pacifica was 13 times less abundant, and large corals and sponges were rare. Thornyhead abundance doubled but rockfish had a 3-fold reduction in numbers. Our study indicates that degradation of biogenic structures is a long-term detriment to rockfish species and, although the mechanism remains unclear, our data suggest it occurs through the destruction of a habitat that is more effective for shelter than rough inert seafloor.

不列颠哥伦比亚省北部的利尔蒙特浅滩（Learmonth Bank）存在活跃的拖网渔业，伴随大量深海海绵与珊瑚的副渔获物。为探究生物成因结构对鱼类分布的影响，本研究分析了遥控水下机器人（Remotely Operated Vehicle, ROV）采集的近30公里高清影像，记录了2770条鲉科鱼类（Scorpaenid fish）的分布位置。该区域的两个本地属类丰度相近，平均密度约为1.2尾/100平方米，但空间分布模式存在显著差异：短棘刺头鲉（Sebastolobus alascanus）在无特征底质上呈随机分布，其种群丰度随水深增加而升高；平鲉属（Sebastes spp.）鱼类则非随机地聚集于海底地形起伏较高的区域，相较于单纯的惰性底质，它们更倾向于选择附着海绵与珊瑚的生境。95%的平鲉属鱼类集中分布在本次调查海域仅27%的海底区域。海绵（寻常海绵纲Demospongia与六放海绵纲Hexactinellida）在浅滩及邻近冰碛的基岩与巨砾上大量分布，覆盖了30%至55%的海底区域；而在周边盆地的沉积物与团聚体中，海绵覆盖占比仅为1%。绝大多数平鲉属鱼类（80%）栖息于高度≥50厘米的海绵生境中，即便是低矮的海绵床，所能吸引的平鲉数量也比无大型表生动物的底质区域高出4倍。尽管超过一半高度超过30厘米的原柳珊瑚科珊瑚会伴生平鲉，但海底大型珊瑚的分布占比不足2%，且小型珊瑚未发现有平鲉附着。在邻近曾开展拖网作业的海底区域，太平洋原柳珊瑚（Primnoa pacifica）的丰度仅为未受干扰区域的1/13，大型珊瑚与海绵也极为稀少。此时短棘刺头鲉的丰度翻倍，但平鲉属鱼类的种群数量降至原来的1/3。本研究表明，生物成因结构的退化对平鲉属物种存在长期负面影响；尽管具体作用机制尚不明晰，但研究数据显示，这类破坏会摧毁比粗糙惰性海底更有效的庇护栖息地，进而影响平鲉种群。