RAPID: Human-Driven Trophic Cascades: Mesopredator Release and Recreational Fishing in Estuaries

人类活动通过开发直接影响生物的自然种群，并通过改变物种之间的相互作用间接影响。这个项目正在调查捕鱼对河口食物网的影响。在牡蛎礁食物链中，新定居的牡蛎被螃蟹吃掉，而螃蟹又被鱼吃掉。更多的鱼类捕食者意味着更少的螃蟹和更多的牡蛎。鱼类也减少了螃蟹的觅食，这进一步有利于牡蛎。虽然小规模的实验研究已经测量了鱼类排斥对牡蛎礁的影响，但捕鱼、鱼类种群和牡蛎礁之间的联系需要进行河口规模的实验。与COVID-19大流行相关的居家令减少了整个河口的捕鱼活动。该项目结合了经验实验和2019冠状病毒相关限制之前、期间和之后的渔业监测数据，调查捕捞活动的变化如何影响牡蛎礁食物网。该数据集建立在10多年的已有观测基础上，包括百年一遇的洪水、飓风和现在的大流行，这是在没有其他干扰的情况下调查低捕捞压力影响的难得机会。本研究的更广泛影响是为优化海洋资源的管理和保护提供数据。牡蛎礁是发挥生态系统功能的重要栖息地，如水过滤和海岸线稳定，但它们也作为商业渔业收获。在墨西哥湾沿岸，人们对用于娱乐和捕鱼的河口系统很感兴趣。海豚岛海洋实验室的公众展示和推广活动将包括该项目的成果，以提高人们对人类活动对当地生态系统影响的认识。顶级捕食者的消失会使生态系统更容易受到入侵，改变栖息地内部和栖息地之间的营养流动，阻碍干扰后的恢复，从而破坏生态系统的稳定。过度捕捞减少了高级捕食者的丰度，导致中级捕食者或中等捕食者的丰度增加。中掠食者的释放会增加基础营养水平的捕食压力，包括基础物种。在河口，鳍鱼，其中许多是商业和娱乐垂钓者的目标，提供了一个重要的营养环节，它们的移除或实验排除可以触发中掠食者的释放。然而，人们对渔业改变社区的程度仍然知之甚少。一个多世纪以来，墨西哥湾沿岸的河口系统几乎经历了持续而广泛的开发，渔业压力暂时缓解的少数例子与其他自然灾害同时发生。COVID-19大流行减少了捕鱼活动，并提供了一个独特的研究机会。在一个模型系统——牡蛎礁中，研究人员采用了前后控制影响（BACI）设计，研究了捕捞压力对自上而下控制的影响。将捕捞活动和鱼类资源评估与实地实验进行比较，以确定顶级捕食者的摄食活动、中捕食者的丰度以及牡蛎的补充和生长。为了衡量河口食物网结构的变化，将这些数据与10多年来已有的结果进行比较，以将捕鱼活动的影响与飓风和洪水等自然灾害相关的混杂因素隔离开来。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Human activity affects natural populations of organisms directly through exploitation and indirectly by changing how species interact with each other. This project is investigating the effect of fishing on an estuarine food web. In the oyster reef food chain, newly settled oysters are eaten by crabs, and the crabs are in turn eaten by fish. More fish predators mean fewer crabs and more oysters. Fish also reduce foraging by crabs, which further benefits oysters. Although small-scale experimental studies have measured the impact of fish exclusion on oyster reefs, the links between fishing, fish populations and oyster reefs require an estuary-scale experiment. Stay-at-home orders associated with the COVID-19 pandemic has curtailed fishing activity throughout estuaries. This project combines empirical experiments and fisheries monitoring data from before, during and after COVID-19-related restrictions to investigate how changes in fishing activity influence oyster reef food webs. Building on 10+ years of preexisting observations the dataset encompasses a 100-year flood, a hurricane, and now a pandemic, a rare opportunity to investigate the effects of low fishing pressure in the absence of other disturbances. The broader impacts of this study contribution of data towards optimizing management and conservation of marine resources. Oyster reefs are essential habitat that perform ecosystem services such as water filtration and shoreline stabilization, but they are also harvested as a commercial fishery. Interest in estuarine systems for recreation and fishing is high along the Gulf of Mexico. Public displays and outreach activities at the Dauphin Island Sea Lab will include results from this project to increase awareness of the effect of human activity on local ecosystems.The loss of top predators can destabilize ecosystems by making them more prone to invasions, altering nutrient fluxes within and between habitats, and impeding recovery after disturbances. Overfishing reduces the abundance of higher order predators, leading to higher abundances of intermediate consumers or mesopredators. Mesopredator release can increase predation pressure on basal trophic levels, including foundation species. In estuaries, fin fish, many of which are targeted by both commercial and recreational anglers, provide an important trophic link and their removal or experimental exclusion can trigger mesopredator release. However, the extent that fishing alters communities remains poorly understood. Estuarine systems along the Gulf of Mexico have experienced nearly continuous and widespread exploitation for over a century, and the few examples of temporary releases from fishing pressure have co-occurred with other natural disasters. The COVID-19 pandemic has curtailed fishing and has provided a unique research opportunity. Using a Before After Control Impact (BACI) design, the effects of fishing pressure on top-down control is being investigated in a model system, oyster reefs. Fishing activity and fish stock assessments are compared with field experiments to determine top predator feeding activity, mesopredator abundances, and recruitment and growth of oysters. To gauge changes in the structure of estuarine food webs, the data are being compared with 10+ years of preexisting results to isolate the effect of fishing activity from confounding factors associated with natural disasters like hurricanes and floods.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.