Direct effects of climate change on productivity of European aquaculture

Aquaculture managers and industry must take into account the impact of climate change on production and environmental quality to ensure that sector growth is sustainable over the coming decades, a key requirement for food security. The potential effects of climate change on aquaculture range from changes to production capacity in existing cultivation areas to changes in the areas themselves, which may become unsuitable for particular species, but also suitable for new species. The prediction of where and how such changes may occur is challenging, not least because the cultivated species may themselves exhibit plasticity, which makes it difficult to forecast the degree to which different locations and culture types may be affected. This work presents a modelling approach used to predict the potential effects of climate change on aquaculture, considering six key finfish and shellfish species of economic importance in Europe: Atlantic salmon (Salmo salar), gilthead seabream (Sparus aurata), sea bass (Dicentrarchus labrax), Pacific oyster (Crassostrea gigas), blue mussel (Mytilus edulis) and Mediterranean mussel (Mytilus galloprovincialis). The focus is on effects on physiology, growth performance and environmental footprint, and the resultant economic impact at the farm scale. Climate projections for present-day conditions; mid-century (2040–2060) and end-of-century (2080–2100) were extracted from regionally downscaled global climate models and used to force bioenergetic models. For each of those time periods, two different carbon concentration scenarios were considered: a moderate situation (IPCC RCP 4.5) and an extreme situation (IPCC RCP 8.5). Projected temperature changes will have variable effects on growth depending on the species and geographic region. From the case studies analysed, gilthead bream farmed in sea cages in the western Mediterranean was the most vulnerable, whereas offshore-suspended mussel culture in SW Portugal was least affected. Most of the marine finfish simulated were projected to have decreased feeding efficiency in both mid-century and end-of-century climate scenarios. Bivalve shellfish showed a decreasing trend with respect to most productivity parameters as climate change progresses, under both emission scenarios. As a general trend across species and regions, economic uncertainty is expected to increase under all future projections

Treatment planning systems dosimetry auditing project in Portugal

BACKGROUND AND PURPOSE: The Medical Physics Division of the Portuguese Physics Society (DFM_SPF) in collaboration with the IAEA, carried out a national auditing project in radiotherapy, between September 2011 and April 2012. The objective of this audit was to ensure the optimal usage of treatment planning systems. The national results are presented in this paper. MATERIAL AND METHODS: The audit methodology simulated all steps of external beam radiotherapy workflow, from image acquisition to treatment planning and dose delivery. A thorax CIRS phantom lend by IAEA was used in 8 planning test-cases for photon beams corresponding to 15 measuring points (33 point dose results, including individual fields in multi-field test cases and 5 sum results) in different phantom materials covering a set of typical clinical delivery techniques in 3D Conformal Radiotherapy. RESULTS: All 24 radiotherapy centers in Portugal have participated. 50 photon beams with energies 4-18 MV have been audited using 25 linear accelerators and 32 calculation algorithms. In general a very good consistency was observed for the same type of algorithm in all centres and for each beam quality. CONCLUSIONS: The overall results confirmed that the national status of TPS calculations and dose delivery for 3D conformal radiotherapy is generally acceptable with no major causes for concern. This project contributed to the strengthening of the cooperation between the centres and professionals, paving the way to further national collaborations

Sustainable shellfish aquaculture in Saldanha Bay, South Africa

The carrying capacity for bivalve shellfish culture in Saldanha Bay, South Africa, was analysed through the application of the well-tested EcoWin ecological model, in order to simulate key ecosystem variables. The model was set up using: (i) oceanographic and water-quality data collected from Saldanha Bay, and (ii) culture-practice information provided by local shellfish farmers. EcoWin successfully reproduced key ecological processes,simulating an annual mean phytoplankton biomass of 7.5 μg Chl a l–1 and an annual harvested shellfish biomass of about 3 000 tonnes (t) y–1, in good agreement with reported yield. The maximum annual carrying capacity of Small Bay was estimated as 20 000 t live weight (LW) of oysters Crassostrea gigas, or alternatively 5 100 t LW of mussels Mytilus galloprovincialis, and for Big Bay as 100 000 t LW of oysters. Two production scenarios were investigated for Small Bay: a production of 4 000 t LW y–1 of mussels, and the most profitable scenario for oysters of 19 700 t LW y–1.The main conclusions of this work are: (i) in 2015–2016, both Small Bay and Big Bay were below their maximum production capacity; (ii) the current production of shellfish potentially removes 85% of the human nitrogen inputs; (iii) a maximum-production scenario in both Big Bay and Small Bay would result in phytoplankton depletion in the farmed area; (iv) increasing the production intensity in Big Bay would probably impact the existing cultures in Small Bay; and (v) the production in Small Bay could be increased, resulting in higher income for farmers. Keywords: blue mussel, carrying capacity, ecological model, EcoWin, Pacific oyster, phytoplankton biomass, production scenario, water qualit

Buoyancy-stirring interactions in a subtropical embayment: a synthesis of measurements and model simulations in Maputo Bay, Mozambique

Maputo Bay, on the coast of Mozambique, is a tidally energetic, subtropical embayment in a region subjected to strong seasonal rainfall. Data from moored current meters, tide gauges and monthly bay-wide surveys were used to characterise the evolution of the density structure on seasonal, fortnightly and semi-diurnal time-scales and its relation to tidal forcing. The bay is subjected to large seasonal variations in freshwater input (10–103 m3 s–1) and pronounced fortnightly variations in tidal amplitude with a spring:neap tide ratio varying between 3.6 and 9.0 with a corresponding variation in tidal stirring power input (10–3–1 W m–3). During the dry season, the water column was continuously fully mixed with weak horizontal density gradients. In contrast, during the wet season, freshwater buoyancy induced marked horizontal salinity gradients and stratification, which was pronounced around the time of neap tides. This stratification was largely eroded at spring tides but semi-diurnal, periodic stratification was still evident. A potential energy anomaly model was used to demonstrate that this periodic component of stratification was largely a result of tidal straining acting locally, with an additional contribution of stratified water advected from outside the bay during the last stages of the flood tide. Simulations using the Delft3D-Flow hydrodynamic model gave a realistic account of the tidal regime in the bay, but achieved only qualitative success in the hindcasting of the changes in water column structure and horizontal exchange. The model indicated a wet season salinity deficit of 2–3 times that of the observed values and wet season temperatures were ~2–3 °C higher than those observed. The model also underestimated the intensity of stratification in the wet season. These shortcomings all suggest an overestimate of vertical mixing by the model’s turbulence closure scheme.publishe

A model for sustainable management of shellfish polyculture in coastal bays

International audienc

Modelling of interactions between inshore and offshore aquaculture

Offshore aquaculture is the subject of intense debate, focusing on feasibility, sustainability, and the potential for effective expansion in the context of competing uses of the coastal zone, and a world requirement for an additional thirty million tonnes of aquatic products by 2050.A modelling framework that integrates the SWAT model for the watershed, Delft3D for ocean circulation, and the EcoWin model for long-term (10year) ecological simulations, was developed for integrated analysis of catchment, inshore waters, and offshore aquaculture, providing an approach that addresses production, environmental effects, and disease interactions. This framework was tested using a case study in SE Portugal, for a system-scale modelling domain with an ocean area of 470km2 and a coastal watershed area of 627km2.This domain contains an inshore area of 184km2 (Ria Formosa) subject to multiple (often conflicting) uses, including aquaculture of the high value (farmgate price>10€kg-1) clam Tapes decussatus, and one of the first offshore aquaculture parks in the world, located at distance of 3.6nm from the coast, at a water depth of 30-60m, with an area of 15km2. The park contains 60 leases, of which at most 70% are for finfish cage culture, and at least 30% for bivalve longline culture.A substantial part of the dissolved nutrients required to drive primary production that constitutes the food source for clams originates from the coastal catchment. Although stakeholder perception is that nutrients are mainly linked to point-source discharges from wastewater treatment plants, watershed modelling indicates that 55% of the nitrogen and 70% of the phosphorus loads are from diffuse sources.The residence time of waters in the inshore area is low (1-2. days), and consequently pelagic primary production takes place offshore, and drives inshore clam production. The longline culture of Mediterranean mussels (Mytilus galloprovincialis) in the offshore park reduces inshore food availability for clams: simulations suggest that a 3% decrease in clam yields will occur due to offshore mussel cultivation, at a cost of 1.2. million. €. This is offset by revenue from offshore culture, but is a source of stakeholder conflict.Potential disease spread between the offshore and inshore systems was analysed using a particle tracking model, and allowed the development of a risk exposure map. This illustrates the challenges posed by hydrodynamic connectivity with respect to biosecurity of aquaculture and fisheries, both inshore and offshore.The model framework was also used for optimisation of stocking density, and analysis of combined culture of finfish and shellfish, both in terms of production and environmental effects. In the offshore aquaculture park, the models suggest that integrated multi-trophic aquaculture (IMTA) of gilthead bream (Sparus aurata) and Mediterranean mussels allows for an increased harvestable biomass of mussels, particularly at higher stocking densities, and offsets some of the negative externalities of finfish culture.By quantifying issues such as reduced yields for inshore stakeholders due to offshore activity, and illustrating the need for strong governance to offset disease risks, dynamic models make a valuable contribution in assessing the feasibility of offshore aquaculture, and the general principles that should underpin licensing and regulation of this sector.We stress the need to go beyond the conventional spatial planning toolset in order to ensure an ecosystem approach to aquaculture, and the opportunities that exist for applying a systems framework in an information economy, where the capital costs of software and data have been sharply reduced