Daniele Brigolin

Modelling the biomass yield and the impact of seabream mariculture in the Adriatic and Tyrrhenian Seas (Italy)

An individual-based model for Sparus aurata was developed, taking into account the effects on the growth rate of water temperature, food availability and diet composition. The model was identified on the basis of the recent literature regarding the physiological ecology of this species. It was subsequently calibrated and validated by using original field data collected at two Italian fish farms located, respectively, in the Adriatic and Tyrrhenian Seas. The mass budget of uneaten food and faeces was computed using the model at each farm: the optimal ingestion rate of a fish was computed based on its wet weight and the temperature of the water, while the faeces estimation considered the different digestibility of lipids, carbohydrates and proteins in the diet. From an applied perspective, the future use of this growth model in relation to mariculture site selection and monitoring might typically be to estimate both the yield and the amount of uneaten food and faeces discharged from a fish cage. This second output represents a useful input for deposition models which are routinely used in the field of mariculture monitoring by different EU countries. The integration of growth and deposition models in a single system could provide a useful tool for the site-selection and monitoring of finfish mariculture operations in Mediterranean environments.

Linking food web functioning and habitat diversity for an ecosystem based management : a Mediterranean lagoon case-study

We propose a modelling approach relating the functioning of a transitional ecosystem with the spatial extension of its habitats. A test case is presented for the lagoon of Venice, discussing the results in the context of the application of current EU directives. The effects on food web functioning due to changes related to manageable and unmanageable drivers were investigated. The modelling procedure involved the use of steady-state food web models and network analysis, respectively applied to estimate the fluxes of energy associated with trophic interactions, and to compute indices of food web functioning. On the long term (hundred years) temporal scale, the model indicated that the expected loss of salt marshes will produce further changes at the system level, with a lagoon showing a decrease in the energy processing efficiency. On the short term scale, simulation results indicated that fishery management accompanied by seagrass restoration measures would produce a slight transition towards a more healthy system, with higher energy cycling, and maintaining a good balance between processing efficiency and resilience. Scenarios presented suggest that the effectiveness of short term management strategies can be better evaluated when contextualized in the long term trends of evolution of a system. We also remark the need for further studying the relationship between habitat diversity and indicators of food web functioning.

Optimization of shellfish production carrying capacity at a farm scale

In this paper, we investigate the relationship between the production and ecological carrying capacity of shellfish cultured species (mussels, oysters, clams, etc.) and the spatial distribution of shellfish density within a licensed area. In order to achieve this goal, we used an analytical model for simulating the impact of a shellfish farm on the concentration of suspended particles or dissolved substances, namely dissolved oxygen in steady-state conditions. The results show that the impact depends on the spatial distribution of the rearing density within the licensed area. In particular, we found a family of non-homogeneous distribution of rearing density which allow one to increase the biomass yield in respect to the homogeneous one, while complying with constraints on suspended particles or dissolved substances. These results may be relevant for enhancing both the production and ecological carrying capacity of shellfish farms.

Making space for shellfish farming along the Adriatic coast

Making space for shellfish farming along the Adriatic coast Daniele Brigolin*, Erika Maria Diletta Porporato, Giuseppe Prioli, and Roberto Pastres Department of Environmental Sciences, Informatics and Statistics, Universit a Ca’ Foscari Venezia, Via Torino 155, Venice Mestre 30170, Italy Bluefarm S.r.l, Via delle Industrie 15, Venezia Marghera 30175, Italy M.A.R.E. S.c. a r.l. – 47841, via Enrico Toti 2, Cattolica (RN), Italy *Corresponding author: tel: þ39 042348528; fax: þ39 0412348594; e-mail: brigo@unive.it

The Influence of the Spatial Scale on the Fishery Landings-SST Relationship

Possible effects of the spatial scale of analysis on the relationship between fishery landings and the water temperature in the Mediterranean Sea have been investigated using the FAO capture database (1970-2010). The analysis was performed by dividing species in three thermal affinity categories: cold, temperate and hot species. Results showed significant changes in fishery landings composition during the last four decades, in terms of the relative contribution of cold, temperate and hot species to landings; moreover, the presence of a strong influence of water warming in determining the landings temporal pattern has been confirmed. This relationship, however, resulted to be not homogenous across the tested spatial scales (entire Mediterranean basin, three main sub-basins, eight FAO areas). The best models (based on the Akaike Information Criterion), were the ones fitted at the finer spatial definition (i.e. the eight FAO areas) for all the three thermal affinity categories. The recorded relationship showed clear differences in terms of direction, depending on both areas and thermal affinity groups. Cold species showed a negative relationship with the increasing water temperature in all the FAO areas, being partially replaced by temperate ones, with the exception of the Adriatic and Black Sea (the coldest areas in the Mediterranean basin), where a moderate increase in the water temperature is still favoring the cold affinity group. This kind of results could be useful within the context of the management plans definition, within a context of climate changes.

An R package for simulating growth and organic wastage in aquaculture farms in response to environmental conditions and husbandry practices

A new R software package, RAC, is presented. RAC allows to simulate the rearing cycle of 4 species, finfish and shellfish, highly important in terms of production in the Mediterranean Sea. The package works both at the scale of the individual and of the farmed population. Mathematical models included in RAC were all validated in previous works, and account for growth and metabolism, based on input data characterizing the forcing functions—water temperature, and food quality/quantity. The package provides a demo dataset of forcings for each species, as well as a typical set of husbandry parameters for Mediterranean conditions. The present work illustrates RAC main features, and its current capabilities/limitations. Three test cases are presented as a proof of concept of RAC applicability, and to demonstrate its potential for integrating different open products nowadays provided by remote sensing and operational oceanography.

Modelling the impacts of Semi-Intensive aquaculture on the foodweb functioning of a Nile Delta coastal lake

Nutrient loadings are an important component of aquaculture impacts as they can lead to cascade effects at the ecosystem level. An evaluation of these effects on foodweb functioning is presented and discussed for the case study of Lake Burullus in the Nile Delta, Egypt, where semi-intensive aquaculture in earthen ponds has grown remarkably in recent decades. Estimations of nutrient loads into the lakes brackish water, from agriculture and fish ponds, were assessed. A biogeochemical model was set up and calibrated to simulate the loads from nitrogen, phosphorus and phytoplankton, with and without fish ponds. The biogeochemical model was coupled offline to a foodweb model to test the effects of additional nutrient loads from aquaculture on the lakes foodweb functioning. The results obtained by comparing the present conditions of aquaculture development with a no-aquaculture scenario allowed us to identify a set of indicators of foodweb functioning which are sensitive to changes in nutrient loads from aquaculture. The limited changes in phytoplankton concentration with respect to changes in nutrient loads suggested that primary production in Lake Burullus is presently controlled largely by factors other than nutrient influxes from aquaculture. This study emphasises the potential benefits of using a combination of biogeochemical and foodweb models to assess the cumulative effects of nutrient loading from aquaculture on a receiving water body.