Effects of changes in Great Barrier Reef Marine Park Zoning plans on the 'Magnetic Shoals', off Townsville (MTSRF Project 4.8.2)

A baseline survey of 5 green zoned sites on Magnetic Shoals together with 4 adjacent blue zoned areas of the marine park. Surveys were carried out in July, September, October and November 2006 to assess any seasonal effects on the fish and benthic communities in addition to potential zoning effects. The Shoals are characterised by a mosaic of rich epibenthic filter feeding communities typically surrounded by low relief algae and seagrasses. These communities appear to be founded on loose sediments comprised of sand, rubble and foraminifera.

A preliminary assessment of the fish communities enumerated with baited video sets (BRUVS) revealed a diverse assemblage across numerous taxonomic and trophic groups. Fish communities associated with patches of habitat were typically more diverse than those from the open, low relief areas and could be discriminated at the scale of 10s of metres. This result underlined the importance of very accurate deployment of sampling gear, especially in respect of on-going temporal monitoring.

The blue sites, nominally representing controls for the no-take green sites, included habitat features not present on Magnetic Shoal. These sites were selected on cross-shelf position/depth (the strongest biological gradient on the GBR) and location. They included artificial habitat (a wreck), calcareous reefal substrate and dense filter feeding communities. Many fish species were common to sites both on Magnetic Shoal and in these blue zones yet the concept of control-treatment contrasts cannot be readily applied in this study. Temporal monitoring should focus on the trajectories of each site as simple metrics of abundance and size may be confounded by the disparity between habitats and fish-habitat associations.

Thirty percent of all fishes recorded could be classified as targeted or otherwise taken by fishers. This relatively high percentage offers an excellent foundation for monitoring the impact of fishers who have access to a broad range of well represented species.

本研究对磁滩（Magnetic Shoals）的5个绿色分区点位，以及该海洋公园内毗邻的4个蓝色分区区域开展了基线调查。本次调查于2006年7、9、10、11月开展，旨在评估分区管控效应之外，季节变化对鱼类及底栖生物群落的影响。磁滩以丰富的表栖滤食性生物群落镶嵌体为典型特征，这类群落通常被低起伏藻类与海草环绕。该类群落的基底为砂、碎石及有孔虫组成的松散沉积物。

本研究采用诱饵摄像装置（BRUVS）对鱼类群落进行计数，初步评估结果显示，其涵盖了众多分类类群与营养类群，组成极为多样。依附于生境斑块的鱼类群落，多样性通常高于开阔低起伏区域的鱼类群落，且可在数十米尺度上被区分开来。这一结果凸显了采样装备精准布设的重要性，尤其在长期时序监测中至关重要。

蓝色分区点位名义上作为禁捕绿色分区点位的对照样点，但其包含了磁滩所没有的生境特征。本研究依据跨陆架位置/深度（大堡礁（Great Barrier Reef, GBR）上最显著的生物梯度）与区位遴选了这些点位，其中涵盖人工生境（一处沉船）、钙质礁质基底以及高密度滤食性生物群落。磁滩与蓝色分区区域共享诸多鱼类物种，但本研究难以直接套用对照-处理组对比的研究范式。时序监测应聚焦各点位的动态轨迹，因为丰度与体型的简单指标可能会受生境差异及鱼类-生境关联模式差异的干扰而产生混淆。

本次记录的所有鱼类中，有30%可被归类为渔民目标捕捞或兼捕物种。这一相对较高的占比，为监测可接触到大量常见物种的渔民的捕捞影响提供了极佳的研究基础。