Management of coral predators, corallivores, is recommended to improve coral cover on tropical coral reefs under projected increasing levels of accumulated thermal stress, but whether corallivore ...management can improve coral cover, which is necessary for large-scale operationalisation, remains equivocal. Here, using a multispecies ecosystem model, we investigate intensive management of an invertebrate corallivore, the Crown-of-Thorns Starfish (Acanthaster cf. solaris), and show that culling could improve coral cover at sub-reef spatial scales, but efficacy varied substantially within and among reefs. Simulated thermal stress events attenuated management-derived coral cover improvements and was dependent on the level of accumulated thermal stress, the thermal sensitivity of coral communities and the rate of corallivore recruitment at fine spatial scales. Corallivore management was most effective when accumulated thermal stress was low, coral communities were less sensitive to heat stress and in areas of high corallivore recruitment success. Our analysis informs how to manage a pest species to promote coral cover under future thermal stress events.
Ecosystem‐based fishery management requires considering the effects of actions on social, natural and economic systems. These considerations are important for forage fish fisheries, because these ...species provide ecosystem services as a key prey in food webs and support valuable commercial fisheries. Forage fish stocks fluctuate naturally, and fishing may make these fluctuations more pronounced, yet harvest strategies intended to ameliorate these effects might adversely affect fisheries and communities. Here, we evaluate trade‐offs among a diverse suite of management objectives by simulating outcomes from several harvest strategies on forage fish species. We demonstrate that some trade‐offs (like those between catches and minimizing collapse length) were universal among forage species and could not be eliminated by the use of different control rules. We also demonstrate that trade‐offs vary among forage fish species, with strong trade‐offs between stable, high catches and high‐biomass periods (“bonanzas”) for menhaden‐ and anchovy‐like fish, and counterintuitive trade‐offs for sardine‐like fish between shorter collapses and longer bonanzas. We find that harvest strategies designed to maintain stability in catches will result in more severe collapses. Finally, we show that the ability of assessments to detect rapid changes in population status greatly affects control rule performance and the degree and type of trade‐offs, increasing the risk and severity of collapses and reducing catches. Together, these results demonstrate that while default harvest strategies are useful in data‐poor situations, management strategy evaluations that are tailored to specific forage fish may better balance trade‐offs.
Historical harvesting pushed many whale species to the brink of extinction. Although most Southern Hemisphere populations are slowly recovering, the influence of future climate change on their ...recovery remains unknown. We investigate the impacts of two anthropogenic pressures—historical commercial whaling and future climate change—on populations of baleen whales (blue, fin, humpback, Antarctic minke, southern right) and their prey (krill and copepods) in the Southern Ocean. We use a climate–biological coupled “Model of Intermediate Complexity for Ecosystem Assessments” (MICE) that links krill and whale population dynamics with climate change drivers, including changes in ocean temperature, primary productivity and sea ice. Models predict negative future impacts of climate change on krill and all whale species, although the magnitude of impacts on whales differs among populations. Despite initial recovery from historical whaling, models predict concerning declines under climate change, even local extinctions by 2100, for Pacific populations of blue, fin and southern right whales, and Atlantic/Indian fin and humpback whales. Predicted declines were a consequence of reduced prey (copepods/krill) from warming and increasing interspecific competition between whale species. We model whale population recovery under an alternative scenario whereby whales adapt their migratory patterns to accommodate changing sea ice in the Antarctic and a shifting prey base. Plasticity in range size and migration was predicted to improve recovery for ice‐associated blue and minke whales. Our study highlights the need for ongoing protection to help depleted whale populations recover, as well as local management to ensure the krill prey base remains viable, but this may have limited success without immediate action to reduce emissions.
We predict impacts of historical commercial whaling (black bars, top), and future climate change, including changing sea‐surface temperature (shown in red, top), primary productivity and sea‐ice extent, on populations of baleen whales and their prey (krill and copepods) across the Southern Hemisphere. Despite initial recovery from commercial harvesting, models predict concerning declines for whale populations due to climate change by 2,100 for populations of blue (blue bars, bottom), fin (green, bottom), humpback (purple, bottom) and Southern right whales (orange, bottom) as a consequence of reduced krill prey (grey line) from warming.
Stakeholders increasingly expect ecosystem assessments as part of advice on fisheries management. Quantitative models to support fisheries decision‐making may be either strategic (‘big picture’, ...direction‐setting and contextual) or tactical (focused on management actions on short timescales), with some strategic models informing the development of tactical models. We describe and review ‘Models of Intermediate Complexity for Ecosystem assessments’ (MICE) that have a tactical focus, including use as ecosystem assessment tools. MICE are context‐ and question‐driven and limit complexity by restricting the focus to those components of the ecosystem needed to address the main effects of the management question under consideration. Stakeholder participation and dialogue is an integral part of this process. MICE estimate parameters through fitting to data, use statistical diagnostic tools to evaluate model performance and account for a broad range of uncertainties. These models therefore address many of the impediments to greater use of ecosystem models in strategic and particularly tactical decision‐making for marine resource management and conservation. MICE are capable of producing outputs that could be used for tactical decision‐making, but our summary of existing models suggests this has not occurred in any meaningful way to date. We use a model of the pelagic ecosystem in the Coral Sea and a linked catchment and ocean model of the Gulf of Carpentaria, Australia, to illustrate how MICE can be constructed. We summarize the major advantages of the approach, indicate opportunities for the development of further applications and identify the major challenges to broad adoption of the approach.
The crown-of-thorns starfish Acanthaster planci (COTS) has contributed greatly to declines in coral cover on Australia's Great Barrier Reef, and remains one of the major acute disturbances on ...Indo-Pacific coral reefs. Despite uncertainty about the underlying causes of outbreaks and the management responses that might address them, few studies have critically and directly compared competing hypotheses. This study uses qualitative modelling to compare hypotheses relating to outbreak initiation, explicitly considering the potential role of positive feedbacks, elevated nutrients, and removal of starfish predators by fishing. When nutrients and fishing are considered in isolation, the models indicate that a range of alternative hypotheses are capable of explaining outbreak initiation with similar levels of certainty. The models also suggest that outbreaks may be caused by multiple factors operating simultaneously, rather than by single proximal causes. As the complexity and realism of the models increased, the certainty of outcomes decreased, but key areas that require further research to improve the structure of the models were identified. Nutrient additions were likely to result in outbreaks only when COTS larvae alone benefitted from nutrients. Similarly, the effects of fishing on the decline of corals depended on the complexity of interactions among several categories of fishes. Our work suggests that management approaches which seek to be robust to model structure uncertainty should allow for multiple potential causes of outbreaks. Monitoring programs can provide tests of alternative potential causes of outbreaks if they specifically monitor all key taxa at reefs that are exposed to appropriate combinations of potential causal factors.
Short‐lived, fast‐growing species that contribute greatly to global capture fisheries are sensitive to fluctuations in the environment. Uncertainties in exact stock–environment relationships have ...meant that environmental variability and extremes have been difficult to integrate directly into fisheries management. We applied a management strategy evaluation approach for one of Australia's large prawn stocks to test the robustness of harvest control rules to environmental variability. The model ensemble included coupled environmental‐population models and an alternative catchability scenario fitted to historical catch per unit effort data. We compared the efficacy of alternative management actions to conserve marine resources under a variable environment while accounting for fisher livelihoods. Model fits to catch per unit effort were reasonably good and similar across operating models (OMs). For models that were coupled to the environment, environmental parameters for El Niño years were estimated with good associated precision, and OM3 had a lower AIC score (77.61) than the base model (OM1, 80.39), whereas OM2 (AIC 82.41) had a similar AIC score, suggesting the OMs were all plausible model alternatives. Our model testing resulted in a plausible subset of management options, and stakeholders selected a permanent closure of the first fishing season based on overall performance of this option; ability to reduce the risk of fishery closure and stock collapse; robustness to uncertainties; and ease of implementation. Our simulation approach enabled the selection of an optimal yet pragmatic solution for addressing economic and conservation objectives under a variable environment with extreme events.
Rediseño de las Estrategias de Captura para el Manejo de Pesquerías Sustentables de Caraa una Variabilidad Ambiental Extrema
Resumen
Las especies de vida corta y rápido crecimiento que contribuyen enormemente a la captura mundial de las pesquerías son sensibles a las fluctuaciones en el ambiente. La incertidumbre en torno a las relaciones exactas entre el ambiente y el stock ha representado una dificultad para integrar directamente la variabilidad y los extremos ambientales a la gestión de las pesquerías. Aplicamos un enfoque de evaluación de estrategia de manejo (EEM) para uno de los stocks de camarones de Australia y así analizar la solidez de las reglas de control de captura para la variabilidad ambiental. El ensamblado modelo incluyó modelos ambientales‐poblacionales emparejados y un escenario alternativo de capturabilidad ajustado a los datos históricos de esfuerzo de captura por unidad. Comparamos la eficiencia de acciones alternativas de manejo para conservar los recursos marinos bajo un ambiente variable teniendo en cuenta el sustento de los pescadores. Los ajustes del modelo para el esfuerzo de captura por unidad fueron razonablemente buenos y similares en los modelos operantes (MO). Para los modelos que estuvieron emparejados con el ambiente, los parámetros ambientales para los años de El Niño estuvieron estimados con una buena precisión asociada, y el MO3 tuvo un puntaje AIC menor (77.61) que el modelo base (MO1, 80.39), mientras que el MO2 (AIC 82.41) tuvo un puntaje AIC similar, lo que sugiere que los MO eran todos modelos plausibles alternativos. Nuestro análisis de los modelos resultó en un subconjunto plausible de opciones de manejo, y los actores seleccionaron un cierre permanente de la primera temporada de pesca con base en el desempeño general de esta opción, la habilidad para reducir el riesgo del cierre de la pesquería y el colapso del stock, la solidez ante las incertidumbres y la facilidad de implementación. Nuestra estrategia de simulación permitió la selección de una solución óptima pero pragmática para abordar los objetivos económicos y de conservación bajo un ambiente variable con eventos extremos.
Article Impact statement: Simulation testing shows a seasonal closure protects fisher livelihoods and the stock in years with extreme environmental conditions.
【摘要】
寿命短、生长快的物种对全球捕捞渔业贡献巨大, 但对环境的波动十分敏感。这些物种种群与环境关系之间的不确定性意味着难以将环境的可变性和极端情况直接纳入渔业管理之中。本研究对澳大利亚的一个大型对虾种群采用了管理策略评估 (MSE) 的方法, 以检验控制捕捞的规则应对环境变化的稳健性。该模型组合包括环境‐种群耦合模型和拟合单位捕捞量渔获的历史数据的可捕量替代方案。我们在考虑渔民生计的同时, 比较了在多变环境下保护海洋资源的替代管理行动的有效性。单位捕捞量渔获的模型拟合结果相当好, 且在不同的操控模型 (operating models, OMs) 中都相近。在与环境耦合的模型中, 厄尔尼诺年的环境参数估算后的关联精度很高, OM3 的 AIC 值 (77.61) 低于基础模型 (OM1, 80.39), 而 OM2(AIC 82.41) 的 AIC 值与 OM1 相近, 表明这些操控模型都是合理的替代选择。我们的模型测试还得到了一部分合理的管理方案, 利益相关者根据管理方案的总体表现、降低渔业关闭和种群崩溃风险的能力、面对不确定性的稳健性以及实施管理的便利性等因素, 选择了在第一个捕捞季永久禁渔。本研究提出的模拟方法使我们能够选择一个最优且实际的解决方案, 从而在可能发生极端事件的可变环境中实现经济和保护目标。 【翻译: 胡怡思; 审校: 聂永刚】
The nature and impact of fishing on predators that share a fished resource is an important consideration in ecosystem-based fisheries management. Krill (
Euphausia superba
) is a keystone species in ...the Antarctic, serving as a fundamental forage source for predators and simultaneously being subject to fishing. We developed a spatial multispecies operating model (SMOM) of krill-predator fishery dynamics to help advise on allocation of the total krill catch among 15 small-scale management units (SSMUs) in the Scotia Sea, with a goal to reduce the potential impact of fishing on krill predators. The operating model describes the underlying population dynamics and is used in simulations to compare different management options for adjusting fishing activities (e.g., a different spatial distribution of catches). The numerous uncertainties regarding the choice of parameter values pose a major impediment to constructing reliable ecosystem models. The pragmatic solution proposed here involves the use of operating models that are composed of alternative combinations of parameters that essentially try to bound the uncertainty in, for example, the choice of survival rate estimates as well as the functional relationships between predators and prey. Despite the large uncertainties, it is possible to discriminate the ecosystem impacts of different spatial fishing allocations. The spatial structure of the model is fundamental to addressing concerns of localized depletion of prey in the vicinity of land-based predator breeding colonies. Results of the model have been considered in recent management deliberations for spatial allocations of krill catches in the Scotia Sea and their associated impacts on dependent predator species.
Many baleen whales were commercially harvested during the 20th century almost to extinction. Reliable assessments of how this mass depletion impacted whale populations, and projections of their ...recovery, are crucial but there are uncertainties regarding the status of Southern Hemisphere whale populations. We developed a Southern Hemisphere spatial “Model of Intermediate Complexity for Ecosystem Assessments” (MICE) for phytoplankton, krill (Euphausia superba) and five baleen whale species, to estimate whale population trajectories from 1890 to present. To forward project to 2100, we couple the predator–prey model to a global climate model. We used the most up to date catch records, fitted to survey data and accounted for key uncertainties. We predict Antarctic blue (Balaenoptera musculus intermedia), fin (Balaenoptera physalus) and southern right (Eubalaena australis) whales will be at less than half their pre‐exploitation numbers (K) even given 100 years of future protection from whaling, because of slow growth rates. Some species have benefited greatly from cessation of harvesting, particularly humpbacks (Megaptera novaeangliae), currently at 32% of K, with full recovery predicted by 2050. We highlight spatial differences in the recovery of whale species between oceanic areas, with current estimates of Atlantic/Indian area blue (1,890, <1% of K) and fin (16,950, <4% of K) whales suggesting slower recovery from harvesting, whilst Pacific southern right numbers are <7% of K (2,680). Antarctic minke (Balaenoptera bonaerensis) population trajectories track future expected increases in primary productivity. Population estimates and plausible future predicted trajectories for Southern Hemisphere baleen whales are key requirements for management and conservation.
The decline of coral cover on Australia's Great Barrier Reef (GBR) has largely been attributed to the cumulative pressures of tropical cyclones, temperature-induced coral bleaching, and prédation by ...crown-of-thorns starfish (CoTS). In such a complex system, the effectiveness of any management intervention will become apparent only over decadal time scales. Systems modeling approaches are therefore essential to formulating and testing alternative management strategies. For a network of reefs, we developed a metacommunity model that incorporated the cumulative pressures of tropical cyclones, coral bleaching, prédation, and competition between corals. We then tested the response of coral cover to management interventions including catchment restoration to reduce discharge onto the reef during cyclone-induced flood events and enhanced protection of trophic networks supporting prédation of CoTS. Model results showed good agreement with long-term monitoring of the GBR, including cyclical outbreaks of CoTS driven by predator-prey dynamics on the network of reefs. Testing of intervention strategies showed that catchment restoration would likely improve coral cover. However, strategies that combined catchment restoration with enhanced CoTS predation were far more effective than catchment restoration alone. La declinación de la cobertura de coral en la Gran Barrera Arecifal (GBA) en Australia se ha atribuido en su mayoría a las presiones acumuladas de los ciclones tropicales, el blanqueamiento de corales influenciado por la temperatura, y la depredación por parte de la estrella de mar corona de espinas (ECdE). En un sistema tan complejo, la efectividad de cualquier intervención de manejo se volverá evidente solamente después de varias escalas de tiempo en décadas. Por lo tanto, los métodos de modelado de sistemas son esenciales para formular y evaluar las estrategias alternativas de manejo. Desarrollamos un modelo de metacomunidadpara una red de arrecifes que incorporó las presiones acumulativas de los ciclones tropicales, el blanqueamiento del coral, la depredación, y la competencia entre corales. Después probamos la respuesta de la cobertura de coral ante las intervenciones de manejo, incluyendo la restauración de la zona de influencia para reducir la descarga sobre el arrecife durante los eventos de inundación inducidos por los ciclones y la protección mejorada de las redes tróficas que respaldan la depredación de la ECdE. Los resultados del modelo mostraron buena concordancia con el monitoreo a largo plazo de la GBA, incluyendo brotes cíclicos de ECdE conducidos por las dinámicas de depredador-presa en la red de arrecifes. La prueba de las estrategias de intervención mostró que la restauración de la zona de influencia probablemente aumentaría la cobertura de coral. Sin embargo, las estrategias que combinaron la restauración de la zona de influencia con la depredación aumentada de la ECdE fueron mucho más efectivas que la restauración de la zona de influencia por sí sola. 澳大利亚大堡礁珊瑚覆盖率的下降很大程度上是受到热带气旋、温度引起的珊瑚白化和棘冠海星捕食的 累积影响。在这样ー个复杂系統中，管理干预措施的有效ñ 需要数十年才能显现。因此,用系统建模的方法来制 定和检验替代的管理策略显得至关重要。我们针对珊瑚礁网络发展了ー个聚合群落模型，整合了热带气旋、珊 琐白化、捕食和珊瑚间竞争的累积压力。接下来我们检测了珊瑚覆盖率对管理干预的响应,这些干预措施包括 通过流域恢复来减少气旋引发的洪水排放到珊瑚礁区域, 以及加强保护来维持棘冠海星捕食的食物网。模型结 果与大堡礁长期监测的情況一致，可以模拟出珊瑚礁网络中由捕食者-猎物动力学导致的棘冠海星周期性爆发。 对干预措施的检测表明，流域恢复可以提高珊瑚樵覆盖率。不过，流域恢复与增强棘冠海星捕食相结合的策略比 只考虑流域恢复要有效得多。
Integrated pest management (IPM) leverages our understanding of ecological interactions to mitigate the impact of pest species on economically and/or ecologically important assets. It has primarily ...been applied in terrestrial settings (e.g., agriculture), but has rarely been attempted for marine ecosystems. The crown‐of‐thorns starfish (CoTS), Acanthaster spp., is a voracious coral predator throughout the Indo‐Pacific where it undergoes large population increases (irruptions), termed outbreaks. During outbreaks CoTS act as a pest species and can result in substantial coral loss. Contemporary management of CoTS on the Great Barrier Reef (GBR) adopts facets of the IPM paradigm to manage these outbreaks through strategic use of direct manual control (culling) of individuals in response to ecologically based target thresholds. There has, however, been limited quantitative analysis of how to optimize the implementation of such thresholds. Here we use a multispecies modeling approach to assess the performance of alternative CoTS management scenarios for improving coral cover trajectories. The scenarios examined varied in terms of their ecological threshold target, the sensitivity of the threshold, and the level of management resourcing. Our approach illustrates how to quantify multidimensional trade‐offs in resourcing constraints, concurrent CoTS and coral population dynamics, the stringency of target thresholds, and the geographical scale of management outcomes (number of sites). We found strategies with low target density thresholds for CoTS (≤0.03 CoTS min−1) could act as “Effort Sinks” and limit the number of sites that could be effectively controlled, particularly under CoTS population outbreaks. This was because a handful of sites took longer to control, which meant other sites were not controlled. Higher density thresholds (e.g., 0.04–0.08 CoTS min−1), tuned to levels of coral cover, diluted resources among sites but were more robust to resourcing constraints and pest population dynamics. Our study highlights trade‐off decisions when using an IPM framework and informs the implementation of threshold‐based strategies on the GBR.
PDF
