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.
The objective of this task was to establish a baseline on which to build, via ongoing temporal surveys, an understanding of the responses of biological communities (fish and benthos) to differential zoning of human use on inshore "shoals". Areas closed to fishing (green zones) on Magnetic Shoals were compared with adjacent areas open to fishing (non-green zones). Marine Protected Areas (MPAs) are typically predicted to acquire measurable changes in the size, demographics and species composition of fishes (Russ 2002) and this study was designed to capture such changes which might be effected by the re-zoning. In addition, changes in the structure and complexity of the associated benthic communities are documented.
Shoal locations:Green - Rap2, Rap12, Rap13, Rap14, Rap15Blue - Rap4, Rap16, RapMP (Mackerel Patch).This is one component in a series of surveys conducted as part of this MTSRF project, see also separate metadata records on:Southern mid-shelf Shoals (East and West Warregos; Karamea and Barcoo Banks)Reef base shoals (Capricorn-Bunker, Pompey and Swains Groups) Shoals off Cardwell Shoals off Cairns.Note that the 'Northern Shoals' of Cardwell, Cairns, and Magnetic Shoals have individual records as each region was analysed separately.

本研究对磁浅滩（Magnetic Shoal）的5个绿色分区禁捕站点，以及该海洋公园内毗邻的4个蓝色分区开放捕捞区域开展了基线调查。调查于2006年7、9、10、11月进行，旨在评估分区政策对鱼类及底栖生物群落的潜在影响，同时分析季节效应的作用。

磁浅滩以丰富的表生滤食性群落镶嵌体为典型特征，这类群落通常被低起伏藻类和海草环绕，其基底多为砂、碎石和有孔虫组成的松散沉积物。通过带诱饵远程水下视频系统（Baited Remote Underwater Video Stations, BRUVS）对鱼类群落进行初步计数调查，结果显示不同分类学和营养类群的鱼类组成均具有较高多样性。与特定生境斑块相关联的鱼类群落，其多样性通常高于开阔低起伏区域，且在数十米的尺度上即可区分群落组成。这一结果凸显了采样设备精准布设的重要性，尤其在长期时序监测工作中尤为关键。

蓝色站点名义上作为绿色禁捕站点的对照样地，但包含了磁浅滩所没有的生境特征。本次站点选择依据跨陆架位置/水深（大堡礁（Great Barrier Reef, GBR）上最显著的生物梯度）与区位条件，涵盖了人工生境（一艘沉船）、钙质礁基质以及密集的滤食性群落。尽管磁浅滩与蓝色分区区域共有诸多鱼类物种，但本研究难以直接应用对照-处理组的对比分析框架。时序监测应聚焦于各站点的群落动态，因为简单的丰度和体型指标可能会因生境差异以及鱼类与生境的关联模式不同而产生混淆。

本次记录的鱼类中，有30%可归类为渔业目标捕捞物种或被渔民捕获的其他物种。这一相对较高的占比为监测访问该区域的渔民的捕捞影响提供了良好基础，因为该区域拥有种类丰富且分布广泛的物种。

本任务的目标是建立基线数据，以便通过后续的时序调查，深入理解近岸浅滩区域人类活动分区差异对生物群落（鱼类与底栖生物）的响应。研究对比了磁浅滩的禁捕绿色区域与毗邻的开放捕捞非绿色区域。通常认为海洋保护区（Marine Protected Areas, MPAs）可使鱼类的体型、种群结构及物种组成发生可检测的变化（Russ 2002），本研究旨在捕捉因分区调整可能引发的这类变化。此外，本研究还记录了相关底栖生物群落的结构与复杂性变化。

浅滩站点信息：
绿色分区站点：Rap2、Rap12、Rap13、Rap14、Rap15
蓝色分区站点：Rap4、Rap16、RapMP（鲭鱼滩涂）

本调查为MTSRF项目系列调研的组成部分，其他相关元数据记录可参阅：
- 中陆架南部浅滩（东西沃雷戈浅滩；卡拉米亚沙洲与巴库沙洲）
- 礁基浅滩（摩羯座-邦克尔群岛群、庞培群岛与斯温群岛群）
- 卡德韦尔近海浅滩
- 凯恩斯近海浅滩
注：卡德韦尔、凯恩斯与磁浅滩的“北部浅滩”均有独立记录，因各区域均单独开展了分析。