Farming new species and promoting polyculture can enhance aquaculture sustainability. This implies to define the rearing conditions that meet the ecological requirements of a target species and/or to ...assess if different species can live in the same farming environment. However, there is a large number of rearing conditions and/or taxon combinations that can be considered. In order to minimise cumbersome and expensive empirical trials to explore all possibilities, we introduce a tool, AquaDesign. It is based on a R-script and package which help to determine farming conditions that are most likely suitable for species through in silico assessment. We estimate farming conditions potentially suitable for an aquatic organism by considering the species niche. We define the species n-dimensional niche hypervolume using a correlative approach in which the species niche is estimated by relating distribution data to environmental conditions. Required input datasets are mined from several public databases. The assistant tool allows users to highlight (i) abiotic conditions that are most likely suitable for species and (ii) combinations of species potentially able to live in the same abiotic environment. Moreover, it offers the possibility to assess if a particular set of abiotic conditions or a given farming location is potentially suitable for the monoculture or the polyculture of species of interest. Our tool provides useful pieces of information to develop freshwater aquacultures. Using the large amount of biogeographic and abiotic information available in public databases allows us to propose a pragmatic and operational tool even for species for which abiotic requirements are poorly or not available in literature such as currently non-produced species. Overall, we argue that the assistant tool can act as a stepping stone to promote new aquatic productions which are required to enhance aquaculture sustainability.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Polyculture is a potentially interesting rearing practice for future aquaculture developments. Nevertheless, it may result in beneficial as well as detrimental consequences for fish production. One ...way to maximize the benefits of polyculture is to combine species with high levels of compatibility and complementarity. This requires the development of a ranking procedure, based on a multi-trait assessment, that highlights the most suitable species combinations for polyculture. Moreover, in order to ensure the relevance of such a procedure, it is important to integrate the socio-economic expectations by assigning relative weights to each trait according to the stakeholder priorities. Here, we proposed a ranking procedure of candidate fish polycultures (i.e., species combinations that could be potentially interesting for aquaculture) based on a multi-trait assessment approach and the stakeholder priorities. This procedure aims at successively (i) weighting evaluation results obtained for each candidate polyculture according to stakeholder priorities; (ii) assessing differentiation between candidate species combinations based on these weighted results; and (iii) ranking differentiated candidate polycultures. We applied our procedure on three test cases of fish polycultures in recirculated aquaculture systems. These test cases each focused on a target species (two on Sander lucioperca and one on Carassius auratus), which were reared in two or three different alternative candidate fish polycultures. For each test case, our procedure aimed at ranking alternative combinations according to their benefits for production and/or welfare of the target species. These benefits were evaluated based on survival rate as well as morphology, behavioral, and physiological traits. Three scenarios of stakeholder priorities were considered for weighting evaluation results: placing a premium on production, welfare, or both for the target species. A comparison of our procedure results between these scenarios showed that the ranking changed for candidate polycultures in two test cases. This highlights the need to carefully consider stakeholder priorities when choosing fish polycultures.
Gallic and pelargonic acids are naturally found in a variety of plants and food products. Despite their extensive use in man-made applications, little is known regarding their potential risks to ...aquatic vertebrates. The aim of this work was to assess the acute toxicity of these polyphenolic and fatty acid compounds to the zebrafish. In order to get insights into sublethal effects, the enzyme activity of usual biomarkers related to oxidative stress and biotransformation were also assessed in fish. These latter included total superoxide dismutase, catalase as well as total glutathione peroxidase for antioxidant defence mechanisms and glutathione S-transferase for biotransformation related enzyme. Gallic acid was practically non-toxic (96-h lethal concentration (LC₅₀) > 100 mg/L) whereas pelargonic acid was slightly toxic (96-h LC₅₀of 81.2 mg/L). Moreover, biomarker analyses indicated enhanced superoxide dismutase activity in fish exposed to 20, 40 and 100 mg/L of gallic acid compared to control. A dose-dependent induction of glutathione peroxidase and glutathione S-transferase was reported following gallic acid exposure at the tested concentrations of 10, 20 and 40 mg/L, with the exception of 100 mg/L of substance where basal activity levels were reported. In the case of pelargonic acid, there was no change in antioxidant enzyme activity while an inhibition of glutathione S-transferase was observed from organisms exposed to 45, 58 and 76 mg/L of test solution. The results concerning sublethal effects on biological parameters of zebrafish highlighted thereby the need for further investigations following chronic exposure to both organic acids.
Animal production systems (APSs) have long been transformed through intensification, specialization and geographical concentration, leading them to become major anthropogenic drivers of pollution, ...climate change, and biodiversity loss. Agroecology, organic farming and sustainable intensification have been proposed as alternative models to invert those trends. Diversity is highly valued in agroecology and organic farming, in which it is assumed not only to increase farm performance but also to strengthen farm resilience. Here, we examine how the diversity of system components and interactions among these components can increase productivity, resource-use efficiency and farm resilience in aquaculture, rabbit, monogastric and ruminant systems. In doing so, we reveal that the same processes can occur in very different systems. For instance, the higher performance of multi-species aquaculture or ruminant grazing systems results from (i) the complementary feeding habits of animal species that exploit resources from different ecological niches more efficiently; and (ii) facilitation or competitive exclusion, which results in a species increasing or decreasing resource availability for another species. The benefits of diversity are observed not only in relatively extensive systems but also in intensive indoor systems. For instance, genetic diversity is associated with herd and social immunity in rabbit production, while trade-offs between life functions play a major role in dairy herd performance. In the last section, we discuss how management options nested in system component diversity and their interactions can enhance system resilience. Strategic and tactical management of APS diversity can promote farm buffering and adaptive capabilities, respectively, via the abovementioned processes. By stabilizing the farm financial situation and facilitating access to short supply channels, transformative changes, such as a diversification of the animal species bred or development of a processing enterprise on farm, expand options for increasing the resilience of APSs to market price fluctuations and climatic shocks. However, the need for new technical skills and sometimes high initial investments can act as strong inhibitors of farm diversification. We conclude with a description of some of the research or action that is needed for these principles to be more widely implemented in commercial farms.
Physical enrichment of structures has been used for the last decades in aquaculture to improve fish production and welfare. Until now, this enrichment has been practiced in fish monoculture but not ...in fish polyculture. In this study, we developed a polyculture of two freshwater species (pikeperch and sterlet) in recirculated systems (tank of 2.4 m3) with or without physical structures for enrichment. Two types of structures were used: a cover plank on a part of the tank decreasing the light intensity and vertical pipes modifying the water flow. The experiment was conducted in triplicate for a three-month period with juvenile fishes (143 ± 41 g and 27.3 ± 2.2 cm for pikeperch and 133 ± 21 g and 32.8 ± 1.6 cm for sterlet). Behavioural (space occupation and abnormal behaviours) and morphological (total length, final weight, Fulton condition factor, coefficient of variation of the final weight, percentage of biomass gain and specific growth rate) traits were measured. The pikeperch changed their space occupation and showed a preference for low light areas. Sterlet also changed their space occupation: they did not use the cover and occurred mainly in the part of the tank without enrichment. There was no difference for the frequency of abnormal behaviours for pikeperch and sterlet between the two sets (with or without enrichment). There was no statistical difference between the two sets for all the morphological and growth parameters no matter the species and the rearing modality.
Fishponds built across streams can greatly affect their functioning, especially through loss of ecological continuity but also changes in water availability and trophic resources. Yet, their ...consequences on communities and stream functioning remain largely understudied. We investigated effects of fishpond dams on the trophic ecology of macroinvertebrate communities in temporary low-order streams using C and N stable isotopes. Food resources and macroinvertebrates were sampled in one upstream and one downstream site of two temporary streams, one stream without (reference stream) versus one with a fishpond (impacted stream) and used for isotopic analyses. Results suggested moderate effects of fishponds on the upstream tributaries. In contrast, at the downstream impacted site, ten times higher macroinvertebrate biomass and modifications in the trophic niches were recorded, likely due to changes in resource availability/quality and dam-related hydrology. By modifying the food sources as well as water fluxes, fishpond dams tend to alter macroinvertebrate communities but also shift the trophic dynamics downstream. This assessment stresses the need for exploring their impacts on food webs and nutrient fluxes at larger downstream distances to better understand their effects before drawing conclusions in regard to their management.
Polyculture offers an alternative to monoculture in recirculated aquaculture systems (RAS). Nevertheless, RAS polyculture can potentially result in beneficial as well as detrimental consequences. ...This places a premium on assessing consequences of a particular polyculture prior to its implementation in farming production. In fish aquaculture, most of previous assessments of polyculture consequences have been carried out through multi-trait approach by analysing independently species traits related to a single biological function. Yet, polyculture can impact many biological functions and the overall consequences are the result of multiple interactions from different functions. Therefore, an integrative analysis is required to synthesise the polyculture consequences at the multi-trait levels. Here we propose a multi-trait evaluation framework (i.e. considering traits related to multiple functions), for the polyculture consequence assessment. We analyse this framework through multivariate analysis prior integrating results for each trait. As test case, we used pikeperch (Sander lucioperca), reared in monoculture and in polyculture with European perch (Perca fluviatilis), common carp (Cyprinus carpio) and black-bass (Micropterus salmoides). Our results revealed the importance of applying multi-trait framework to obtain a reliable assessment of fish polycultures. The divergence that might occur in the expression of some traits in the same polyculture has been highlighted to support this argument. Through the integration method, it was possible to find the suitable combination(s) of fish and to exclude the unsuitable ones. For future researches, we suggest to support the multi-trait assessment by weighting the traits involved in the multivariate analysis.
•Aquaculture could become more efficient and sustainable through fish polyculture.•Applying a multi-trait approach allow to obtain a reliable assessment of fish polyculture.•The traits involved in the polyculture consequences assessment should be related to multiple functions.
ABSTRACT
Human population growth has increased demand for food products, which is expected to double in coming decades. Until recently, this demand has been met by expanding agricultural area and ...intensifying agrochemical‐based monoculture of a few species. However, this development pathway has been criticised due to its negative impacts on the environment and other human activities. Therefore, new production practices are needed to meet human food requirements sustainably in the future. Herein, we assert that polyculture practices can ensure the transition of aquaculture towards sustainable development. We review traditional and recent polyculture practices (ponds, recirculated aquaculture systems, integrated multi‐trophic aquaculture, aquaponics, integrated agriculture–aquaculture) to highlight how they improve aquaculture through the coexistence and interactions of species. This overview highlights the importance of species compatibility (i.e. species that can live in the same farming environment without detrimental interactions) and complementarity (i.e. complementary use of available resources and/or commensalism/mutualism) to achieve efficient and ethical aquaculture. Overall, polyculture combines aspects of productivity, environmental protection, resource sharing, and animal welfare. However, several challenges must be addressed to facilitate polyculture development across the world. We developed a four‐step conceptual framework for designing innovative polyculture systems. This framework highlights the importance of (i) using prospective approaches to consider which species to combine, (ii) performing integrated assessment of rearing environments to determine in which farming system a particular combination of species is the most relevant, (iii) developing new tools and strategies to facilitate polyculture system management, and (iv) implementing polyculture innovation for relevant stakeholders involved in aquaculture transitions.
Stable isotope analysis is frequently used as a complementary method of dietary analysis, to describe trophic relationships and assess food-web structure. These studies allow a precise determination, ...based on the calculation of a diet-tissue fractionation factor. The fractionation factor, determined for whole organisms or specific tissues, may vary substantially
in natura. In the present study,
δ
13C and
δ
15N were assessed in lipid-free tissues (spleen, liver, viscera, scales, gills, spine, white muscle, brain) and in available energy reserves (proteins, glycogen, lipids) of Eurasian perch (
Perca fluviatilis) reared under controlled conditions and fed for 4 months with the same artificial diet. Some discrepancies in
δ
15N and
δ
13C data were observed among tissues, respectively up to 3.43‰ and 2.54‰ for
δ
15N and
δ
13C. The
15N signature in organs depends on their metabolic activity. Despite a significant
δ
13C enrichment from feed to tissues, the lipids in spine, liver and viscera exhibit a certain stability.
The increase in anthropogenic nutrient loading affecting many freshwater ecosystems combined with global warming may lead to cyanobacterial blooms on an increasingly frequent basis. Among the various ...physicochemical and biological methods which have been proposed to rapidly control blue-green algae growth, the use of plant-derived substances such as allelochemicals has gained great interest as an environment-friendly approach. The primary aim of this work was to evaluate the efficiency of gallic and nonanoic acid application to preemptively inhibit cyanobacterial growth in lentic hydrosystems. In order to address the process feasibility under realistic exposure scenarios, thirteen outdoor freshwater mesocosms (unit volume: 3m3) were designed, each containing phytoplankton (including local blue-green algae species) and various non-target organisms from higher trophic levels (Physa, Lymnaea, Gammarus, and Scardinius erythrophthalmus). After an 8-week mesocosm stabilization period, a full factorial design based on the presence/absence of gallic acid (GA) and nonanoic acid (NA) (including a control group) was implemented into the exposure tanks. Regular monitoring of major phytoplankton taxa was conducted during a 28-day experiment using an on-line fluorometer. The main results suggested that gallic acid was more efficient than nonanoic acid at limiting cyanobacterial growth at concentrations as low as 1mgL−1. Successive gallic acid applications (at 1, 2 and 4mgL−1) at the early stages of cyanobacterial growth did not allow the complete elimination of blue-green algae from the mesocosms. However, the specificity of the allelopathic effect of gallic acid towards cyanobacteria was compatible with the maintenance of a primary productivity in the treated tanks as indicated by the photoautotrophic growth of other algal taxa. Finally, no biomarker induction signal could be reported in non-target species. Further gallic acid application trials in lentic systems such as small freshwater ponds may help to design innovative allelopathy-based aquatic ecotechnologies.
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•Gallic and nonanoic acid allelopathy potential was evaluated against microalgae•An outdoor mesocosm was designed using a multi-species approach•Only gallic acid use at the early stages of cyanobacterial population growth seemed efficient•Biomarker evaluation indicated no adverse effect of compounds on non-target species
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