Department of Fisheries, Animal and Veterinary Sciences, University of Rhode Island, 9 East Alumni Avenue, Kingston, Rhode Island, 02881, USA.
Department of Marine Science and Technology, Faculty of Fisheries and Marine Science, Institut Pertanian Bogor (IPB), Jalan Rasamala, Bogor, Darmaga, 16680, Indonesia.
Ecol Appl. 2021 Jul;31(5):e02345. doi: 10.1002/eap.2345. Epub 2021 May 4.
Marine food webs are structured through a combination of top-down and bottom-up processes. In coral reef ecosystems, fish size is related to life-history characteristics and size-based indicators can represent the distribution and flow of energy through the food web. Thus, size spectra can be a useful tool for investigating the impacts of both fishing and habitat condition on the health and productivity of coral reef fisheries. In addition, coral reef fisheries are often data-limited and size spectra analysis can be a relatively cost-effective and simple method for assessing fish populations. Abundance size spectra are widely used and quantify the relationship between organism size and relative abundance. Previous studies that have investigated the impacts of fishing and habitat condition together on the size distribution of coral reef fishes, however, have aggregated all fishes regardless of taxonomic identity. This leads to a poor understanding of how fishes with different feeding strategies, body size-abundance relationships, or catchability might be influenced by top-down and bottom-up drivers. To address this gap, we quantified size spectra slopes of carnivorous and herbivorous coral reef fishes across three regions of Indonesia representing a gradient in fishing pressure and habitat conditions. We show that fishing pressure was the dominant driver of size spectra slopes such that they became steeper as fishing pressure increased, which was due to the removal of large-bodied fishes. When considering fish functional groups separately, however, carnivore size spectra slopes were more heavily impacted by fishing than herbivores. Also, structural complexity, which can mediate predator-prey interactions and provisioning of resources, was a relatively important driver of herbivore size spectra slopes such that slopes were shallower in more complex habitats. Our results show that size spectra slopes can be used as indicators of fishing pressure on coral reef fishes, but aggregating fish regardless of trophic identity or functional role overlooks differential impacts of fishing pressure and habitat condition on carnivore and herbivore size distributions.
海洋食物网是通过自上而下和自下而上的过程相结合而形成的。在珊瑚礁生态系统中，鱼类的大小与生活史特征有关，基于大小的指标可以代表能量在食物网中的分布和流动。因此，大小谱可以成为一种有用的工具，用于研究捕捞和生境条件对珊瑚礁渔业健康和生产力的影响。此外，珊瑚礁渔业通常数据有限，大小谱分析可以是一种相对具有成本效益和简单的方法来评估鱼类种群。丰度大小谱被广泛使用，量化了生物体大小和相对丰度之间的关系。然而，以前的研究表明，无论是从分类学角度还是从整体角度来看，将所有鱼类都归为一类，而不考虑其生活史特征和体型大小-丰度关系，这种方法无法评估鱼类的丰度。这导致人们对不同摄食策略、体型大小-丰度关系或可捕性的鱼类如何受到自上而下和自下而上的驱动因素的影响了解甚少。为了解决这一差距，我们在印度尼西亚的三个地区量化了肉食性和草食性珊瑚礁鱼类的大小谱斜率，这些地区代表了捕捞压力和生境条件的梯度。结果表明，捕捞压力是大小谱斜率的主要驱动因素，随着捕捞压力的增加，斜率变得更加陡峭，这是由于大型鱼类的减少。然而，当分别考虑鱼类功能群时，肉食性鱼类的大小谱斜率受到捕捞的影响大于草食性鱼类。此外，结构复杂性可以调节捕食者-猎物相互作用和资源供应，对草食性鱼类的大小谱斜率有相对重要的影响，因此在结构更复杂的生境中，斜率更平缓。研究结果表明，大小谱斜率可以作为衡量珊瑚礁鱼类捕捞压力的指标，但无论其营养身份或功能角色如何，将鱼类归为一类都会忽略捕捞压力和生境条件对肉食性和草食性鱼类分布的不同影响。
