Ramón Filgueira

A Box Model for Ecosystem-Level Management of Mussel Culture Carrying Capacity in a Coastal Bay

The carrying capacity of shellfish aquaculture is determined by the interaction of cultured species with the ecosystem, particularly food availability to suspension feeders. A multiple box dynamic ecosystem model was constructed to examine the carrying capacity for mussel (Mytilus edulis) aquaculture in Tracadie Bay, Prince of Edward Island, Canada. Criteria for carrying capacity were based on chlorophyll concentration. The model was run in two different years (1998 and 1999) in which time series for three points inside the bay and a point outside the bay were available. This data set allows spatial validation of the ecosystem model and assessment of its sensitivity to changes in boundary conditions. The model validation process indicated that the differential equations and parameters used in the simulation provided robust prediction of the ecological dynamics within the bay. Results verified that mussel biomass exerts top-down control of phytoplankton populations. The model indicates that conditions observed during 1999 are more sensitive to grazing pressure from aquaculture than was observed during 1998, highlighting the importance of inter-annual variability in carrying capacity of the bay. This result is important from a management perspective because it emphasizes application of a precautionary policy and prediction in regulation of aquaculture activity in the bay. Retrospective scenarios showed that although the bay could yield greater mussel biomass production, stress on the environment would lead the ecosystem outside of its natural range of variation. Despite the spatial simplicity employed in the present model, it provides substantial management capability as well as an ecosystem-oriented approach to shellfish aquaculture.

A physical-biogeochemical coupling scheme for modeling marine coastal ecosystems

Abstract Ecological modeling of dynamic systems such as marine environments may require detailed spatial resolution when the modeled area is greatly influenced by complex physical circulation. Therefore, the simulation of a marine ecosystem must be underlain by a physical model. However, coupling hydrodynamic and biogeochemical models is not straightforward. This paper presents a modeling technique that can be used to build generic and flexible fully-spatial physical–biogeochemical models to study coastal marine ecosystems using a visual modeling environment (VME). The model core is constructed in Simile, a VME that has the capacity to create multiple instances of submodels that can be interconnected, producing a fully-spatial simulation. The core is designed to assimilate a choice of different hydrodynamic models by means of matrices, enhancing its compatibility with different software. The biogeochemical model can be modified by means of a graphical interface, which facilitates sharing within the scientific community. This paper demonstrates the application of the coupling scheme to mussel aquaculture in Tracadie Bay (PEI, Eastern Canada). The model was run for two different years, 1998 and 1999, and indicated that mussel biomass exerts a top-down control of phytoplankton populations, causing a maximum chlorophyll depletion of 61.0% and 80.3% for 1998 and 1999 respectively. The difference between both years highlights the importance of inter-annual variability, which is significant from an ecosystem-level perspective because it reveals the relevance of applying a precautionary policy in the management of aquaculture activity. Therefore, the proposed core developed in Simile is a generic and flexible tool for modeling long-term processes in coastal waters, which is able to assimilate a choice of hydrodynamic models, constituting a novel approach for generating fully-spatial models using visual modeling environments.

Implementation of marine spatial planning in shellfish aquaculture management: modeling studies in a Norwegian fjord

Shellfish carrying capacity is determined by the interaction of a cultured species with its ecosystem, which is strongly influenced by hydrodynamics. Water circulation controls the exchange of matter between farms and the adjacent areas, which in turn establishes the nutrient supply that supports phytoplankton populations. The complexity of water circulation makes necessary the use of hydrodynamic models with detailed spatial resolution in carrying capacity estimations. This detailed spatial resolution also allows for the study of processes that depend on specific spatial arrangements, e.g., the most suitable location to place farms, which is crucial for marine spatial planning, and consequently for decision support systems. In the present study, a fully spatial physical-biogeochemical model has been combined with scenario building and optimization techniques as a proof of concept of the use of ecosystem modeling as an objective tool to inform marine spatial planning. The object of this exercise was to generate objective knowledge based on an ecosystem approach to establish new mussel aquaculture areas in a Norwegian fjord. Scenario building was used to determine the best location of a pump that can be used to bring nutrient-rich deep waters to the euphotic layer, increasing primary production, and consequently, carrying capacity for mussel cultivation. In addition, an optimization tool, parameter estimation (PEST), was applied to the optimal location and mussel standing stock biomass that maximize production, according to a preestablished carrying capacity criterion. Optimization tools allow us to make rational and transparent decisions to solve a well-defined question, decisions that are essential for policy makers. The outcomes of combining ecosystem models with scenario building and optimization facilitate planning based on an ecosystem approach, highlighting the capabilities of ecosystem modeling as a tool for marine spatial planning.

Informing Marine Spatial Planning (MSP) with numerical modelling: A case-study on shellfish aquaculture in Malpeque Bay (Eastern Canada)

A moratorium on further bivalve leasing was established in 1999-2000 in Prince Edward Island (Canada). Recently, a marine spatial planning process was initiated explore potential mussel culture expansion in Malpeque Bay. This study focuses on the effects of a projected expansion scenario on productivity of existing leases and available suspended food resources. The aim is to provide a robust scientific assessment using available datasets and three modelling approaches ranging in complexity: (1) a connectivity analysis among culture areas; (2) a scenario analysis of organic seston dynamics based on a simplified biogeochemical model; and (3) a scenario analysis of phytoplankton dynamics based on an ecosystem model. These complementary approaches suggest (1) new leases can affect existing culture both through direct connectivity and through bay-scale effects driven by the overall increase in mussel biomass, and (2) a net reduction of phytoplankton within the bounds of its natural variation in the area.

Integrating the Concept of Resilience into an Ecosystem Approach to Bivalve Aquaculture Management

Bivalve aquaculture has become increasingly important for marine protein production and is an alternative to exploiting natural resources. Its further and sustainable development should follow an ecosystem approach, to maintain both biodiversity and ecosystem functioning. The identification of critical thresholds to development remains difficult. The present work aims at combining the calculation of the system’s ecological carrying capacity (ECC) with the ecosystem view of resilience for a bay system exposed to bivalve (scallop) aquaculture. Using a trophic food-web model, a stepwise further expansion of culture activities was simulated, and the impact on the system was evaluated twofold: First, a recently developed approach to estimating ECC was used, and second, a resilience indicator was calculated, which is based on the distribution of consumption flows within the trophic network (sensu Arreguín-Sanchez in Ecol Model 272: 27–276, 2014). Results suggest that a culture expansion beyond present-day scale would (a) cause a shift in community composition towards a system dominated by secondary consumers, (b) lead to the loss of system compartments, affecting ecosystem functioning, and (c) result in a decrease in resilience, emphasizing the need to regulate aquaculture activities. The applicability and potential of this presented method in the context of an ecosystem-based approach to aquaculture is discussed. This work aims at adding to the ongoing discussion on sustainable bivalve aquaculture and is expected to help guide aquaculture management.

Lack of interaction between finfish aquaculture and lobster catch in coastal Nova Scotia.

A recent study in coastal Nova Scotia (Loucks et al., 2014) used data from commercial lobster fishers (Lobster Fishing Area 33) to characterize catches in PortMouton Bay. A net pen fish farmoperated during part of their study period but was fallowed in other years. Loucks et al. attempted to relate lobster catch in the entirety of the bay to fish farm activities. They suggest that some effect of organic loading dues to fish feces or food waste was affecting lobster abundance in all of Port Mouton Bay. In this response, we reviewmultiple components of the Loucks et al. (2014) study, documenting serious problems in the following areas: spatial survey design, statistical analysis, relationship to lobster landings data, temperature effects on the lobster fishery, and scope of potential impacts. We undertake additional analysis of fishery data on regional catches to provide alterative explanations for dynamics of the fishery. A proper assessment of their study and data is essential, because fish farming is contentious in coastal waters, and documented far-field effects, especially on capture fisheries would be significant. The results of our analysis lead to the conclusion that there is no evidence of any relationship between fish farming activities and the lobster fishery in Port Mouton Bay. In Loucks et al. (2014), Port Mouton Bay was divided into 5 unequal regions (Fig. 1), and lobster landings within each region were voluntarily reported by licensed commercial fishers during the last 2 weeks of May, the endof thefishing seasonwhich begins at the endof November. Comparison of CPUE (catch per unit effort; Fig. 2) and % ovigerous females among spatial sampling regions is fundamental to the Loucks et al. (2014) study. Because their region 2 includes the fish farm, they conclude that this region shows the greatest impact of the farm and persistently lower lobster catches. The first issue we discuss related to spatial design is the uneven sector size. While regions 2–5 were similarly sized (382.6 ± 41.1 ha), region 1 was more than double the size of the next largest region at 1073.7 ha (Fig. 1, Table 1). Reasons for this discrepancy are not discussed. This introduces a potential source of bias into comparisons of CPUE among regions. As the distribution of mobile species such as lobster is spatially heterogeneous, the size of the sampling region can be predicted to have a strong influence on the estimation of local abundance. Larger areas of embayments are more likely to have a larger quantity and variety of habitat types, potentially supporting a larger lobster population subject to fishing. A second substantial spatial issue concerns the presentation of trapping effort. While overall effort per year is presented, the article fails to discuss the regional distribution of effort. As the authors state, “...lobster catch rates can be biased if the spatial distribution or extent of fishing changes through time”. Unfortunately, given the lack of information

Far-Field and Near-Field Effects of Marine Aquaculture

Abstract Aquaculture for finfish, bivalves, and seaweed is an important and growing food producing sector globally. However, culturing of species in the marine environment implies multiple interactions between farmed species and their environment. This has led to concerns over the ecological effects of aquaculture, which include benthic organic loading, changes to water quality, habitat modification, disease spread, and introduction of exotic or invasive species, interaction with wild species, coastal eutrophication, and marine litter. Over the years, governments and international organizations have recognized the need to identify, mitigate, and reduce these ecological effects. The Food and Agriculture Organization of the United Nations proposes an Ecosystem Approach to Aquaculture (EAA), which implies recognizing its effects at multiple spatial scales, including near-field effect (farm scale) and far-field (bay scale and global scale) effect. This chapter reviews ecological effects of finfish, bivalve, and seaweed aquaculture in marine coastal waters, and describes the mitigation efforts currently used to improve its sustainable management.

The use of kernel density estimation with a bio-physical model provides a method to quantify connectivity among salmon farms: spatial planning and management with epidemiological relevance.

Connectivity in an aquatic setting is determined by a combination of hydrodynamic circulation and the biology of the organisms driving linkages. These complex processes can be simulated in coupled biological-physical models. The physical model refers to an underlying circulation model defined by spatially-explicit nodes, often incorporating a particle-tracking model. The particles can then be given biological parameters or behaviors (such as maturity and/or survivability rates, diel vertical migrations, avoidance, or seeking behaviors). The output of the bio-physical models can then be used to quantify connectivity among the nodes emitting and/or receiving the particles. Here we propose a method that makes use of kernel density estimation (KDE) on the output of a particle-tracking model, to quantify the infection or infestation pressure (IP) that each node causes on the surrounding area. Because IP is the product of both exposure time and the concentration of infectious agent particles, using KDE (which also combine elements of time and space), more accurately captures IP. This method is especially useful for those interested in infectious agent networks, a situation where IP is a superior measure of connectivity than the probability of particles from each node reaching other nodes. Here we illustrate the method by modeling the connectivity of salmon farms via sea lice larvae in the Broughton Archipelago, British Columbia, Canada. Analysis revealed evidence of two sub-networks of farms connected via a single farm, and evidence that the highest IP from a given emitting farm was often tens of kilometers or more away from that farm. We also classified farms as net emitters, receivers, or balanced, based on their structural role within the network. By better understanding how these salmon farms are connected to each other via their sea lice larvae, we can effectively focus management efforts to minimize the spread of sea lice between farms, advise on future site locations and coordinated treatment efforts, and minimize any impact of farms on juvenile wild salmon. The method has wide applicability for any system where capturing infectious agent networks can provide useful guidance for management or preventative planning decisions.

Past, Present, and Future: Performance of Two Bivalve Species Under Changing Environmental Conditions

Globally, the production of marine bivalves has been steadily increasing over the past several decades. As the effects of human population growth are magnified, bivalves help provide food security as a source of inexpensive protein. However, as climate change alters sea surface temperatures (SST), the physiology, and thus the survival, growth, and distribution of bivalves are being altered. Challenges with managing bivalves may become more pronounced, as the uncertainty associated with climate change makes it difficult to predict future production levels. Modelling techniques, applied to both climate change and bivalve bioenergetics, can be used to predict and explore the impacts of changing ocean temperatures on bivalve physiology, and concomitantly on aquaculture production. This study coupled a previously established high resolution climate model and two dynamic energy budget models to explore the future growth and distribution of two economically and ecologically important species, the eastern oyster (Crassotrea virginica), and the blue mussel (Mytilus edulis) along the Atlantic coast of Canada. SST was extracted from the climate model and used as a forcing variable in the bioenergetic models. This approach was applied across three discreet time periods: the past (1986-1990), the present (2016-2020), and the future (2046-2050), thus permitting a comparison of bivalve performance under different temporal scenarios. Results show that the future growth is variable both spatially and interspecifically. Modelling outcomes suggest that warming ocean temperatures will cause an increase in growth rates of both species as a result of their ectothermic nature. However, as the thermal tolerance of C. virginica is higher than M. edulis, oysters will generally outperform mussels. The predicted effects of temperature on bivalve physiology also provided insight into vulnerabilities (e.g. mortality) under future SST scenarios. Such information is useful for adapting future management strategies for both farmed and wild shellfish. Although this study focused on a geographically specific area, the approach of coupling bioenergetic and climate models is valid for species and environments across the globe.

The effect of environmental conditions on Atlantic salmon smolts’ (Salmo salar) bioenergetic requirements and migration through an inland sea

The timing of the juvenile Atlantic salmon ocean-entry is considered a critical stage in the species’ life-history. Entry into the ocean at suboptimal times can have negative survival impacts on entire smolt cohorts. Previous studies have identified smolt residency time in the Bras d’Or Lakes as highly variable and correlated with body condition. This study combines energetic modelling using Dynamic Energy Budget (DEB) theory with acoustic telemetry to mechanistically link smolt bioenergetics to their migration strategy within the Bras d’Or. This study examines two main questions: 1) what is the relationship between smolts’ bioenergetics and smolts’ migration strategy, and 2) what effect would warmer water temperature have on smolts’ energetic requirements? Simulation results indicate that smolts requiring more food are more likely to exit the Bras d’Or during the observation period. The results also suggest higher lake temperature would result in faster depletion of smolt energy reserves, which is predicted to favour smolts migrating to the ocean sooner.