Sustainable and safe fisheries for Rio de Janeiro, Brazil: Movement patterns and pollutant accumulation by corvina (Micropogonias furnieri)

大多数鱼类在其生命周期中进行运动模式，确定这些个体发育运动(即它们去哪里和在什么生命阶段)和确定连通性(即它们混合的程度)是为了养护和开发管理目的理解其生态的关键。这对商业开发的物种尤其重要，因为这可以提供(1)关键生命阶段的保护区(如苗圃、摄食或产卵区)和(2)当地粮食安全和在当地社区的持续就业。可以使用重新捕获和无线电跟踪单独标记的鱼来重建运动模式，但这些方法劳力密集，在后勤上难以实施和/或昂贵。此外，它们在小鱼上的应用可能会受到限制。最近，基于观察到的水化学的空间差异，如耳石(钙化的“耳石”)等钙质结构的微量元素化学已被用来了解鱼类在这些地点之间的运动模式。这项技术的优点是它不受大小限制，每条鱼都已经有了自己的内部标签。水生系统一直被认为是持久性和生物累积性毒物(PBT)的理想最终汇，如金属和有机卤化物。由于一些特征，包括化学稳定性和对蛋白质或脂肪的亲和力，一些多溴联苯能有效地生物积累，并随着营养水平的增加(即，随着食物链的向上移动)而经历生物放大作用(即浓缩)。因此，大型高营养级捕食者，如鱼类和水生哺乳动物，是研究的关键群体，可能在它们的体内积累高浓度的PBT。如果人类摄取了足够的数量，如果这些PBT的转移可能会对健康构成重大风险，在本研究中，提出了一种双重方法来研究来自瓜纳巴拉湾(里约热内卢)的白口黄鱼(或Corvina)的PBTS。首先，将研究耳石中元素的浓度，以研究Corvina的运动模式；其次，将测量不同年龄/大小的鱼在海湾不同位置捕获的肌肉PBT浓度，以确定个体发育对PBTS的摄取和积累。瓜纳巴拉湾是一个城市化的河口，具有极其重要的社会和经济意义，但也是巴西污染最严重的河口之一。尽管如此，瓜纳巴拉湾的鱼类种群支持个体渔业(3 700名渔民，上岸19000吨，年度首次销售480万美元)，而Corvina约占年渔获量的20%。对于巴西的温带地区，已经证明，随着成鱼在沿海水域觅食并进入河口产卵，这种鱼的个体发育栖息地发生了变化。幼鱼在河口居住数年，然后迁徙到沿海水域，补充成鱼。该项目将解决以下问题：(1)瓜纳巴拉湾幼年Corvina的运动模式是什么？(3)成年鱼在半咸水和海水之间的运动模式是什么？(4)瓜纳巴拉湾和沿海水域中肌肉中的多溴联苯浓度是多少？(5)肌肉中的多溴联苯浓度随年龄/大小的变化而变化？(即在河口居留期间的堆积速度是多少？一旦成年鱼在更清洁的沿海水域觅食，它们的浓度是否会降低？)

Most fish species undertake movement patterns during their life cycle and defining these ontogenetic movements (i.e. where they go and at what life stage) and determining connectivity (i.e. the extent to which they intermix) are key to understanding their ecology for both conservation and exploitation management purposes. This is especially important for commercially-exploited species as this can allow provision of (1) protected areas for key life stages (e.g. nursery, feeding or spawning areas) and (2) local food security and continuity of employment in the local community. Movement patterns can be reconstructed using tag-recapture and radio-tracking of individually-tagged fish but these methodologies are labour-intensive, logistically difficult to implement and/or costly. In addition, their application to small fish can be limited. Recently, based on the observed spatial differences in water chemistry, the trace element chemistry of calcareous structures such as otoliths (calcified "ear stones") has been used to understand movement patterns of fishes among these locations. The advantage of this technique is that it is not size-restricted and each fish already carries its own internal tag. Aquatic systems have been considered ideal final sinks for persistent and bioaccumulative toxicants (PBTs), such as metals and organohalogen compounds. Due to some features that include chemical stability and affinity for proteins or lipids, some PBTs are efficiently bioaccumulated and end up undergoing biomagnification (i.e. are concentrated) with increasing trophic level (i.e. as you move up the food chain). Therefore, large high trophic level predators such as fish and aquatic mammals, are critical groups to study and may accumulate high PBT concentrations in their bodies. If eaten by Man in sufficient quantities, the transfer if these PBTs may present a significant health risk In this study, a dual approach to study PBTs in whitemouth croaker (or corvina), Micropogonias furnieri, from Guanabara Bay (Rio de Janeiro) is proposed. Firstly, the elemental concentrations in the otoliths will be studied in order to examine the movement patterns of corvina and, secondly, muscle PBT concentrations will be measured in fish of different ages/sizes caught in different locations of the Bay in order to determine uptake rate and accumulation of PBTs over ontogeny. Guanabara Bay is an urbanized estuary of utmost social and economic importance but also one of the most polluted in Brazil. Despite this, the fish populations of Guanabara Bay support artisanal fisheries (3700 fishers, landings 19000 tonnes, $4.8M annual first sale) and corvina comprises about 20% of the annual catch value. For temperate regions of Brazil, it has been demonstrated that this fish species displays ontogenetic habitat shifts with the adult fish feeding in coastal waters and moving into estuaries to spawn. The juvenile fish reside in estuaries for several years before moving out to coastal waters to recruit into the adult stock. The project will address the following questions: (1) What are the movement patterns of juvenile corvina in Guanabara Bay? (i.e. do juveniles of all ages/sizes mix freely within the Bay or do they show size-specific changes in salinity/habitat preference?)(2) At what age/size do adolescent corvinas move from the estuary into coastal waters? (3) What are the movement patterns of adult fish between brackish and marine water? (4) What are the muscular PBT concentrations of corvina in Guanabara Bay and coastal waters? (5) How do muscular PBT concentrations change with age/size? (i.e. what is the rate of accumulation during the estuarine residency period? and do concentrations reduce in adult fish once they are feeding in cleaner coastal waters?)