Introduction
Aquaculture industry is growing at an astounding rate, overtaking capture fishery production and foresighted to represent 60% of global finfish production by 2030. The increasing demand for healthy and less expensive protein has catalysed intensification and favoured an ideal environment for several production-related problems to flourish, impact ing the environment, the animals and human health . One of the best-understood risks that aquaculture intensification poses is the heavy use of antibiotics and the concerning consequence of increasing antimicrobial resistance (AMR). On farms, fishes’ welfare is compromised by poor health, nutrition, and rearing practices with implications in susceptibility to stress and diseases. As a result, the w eakened immune systems increase the possibility of disease outbreaks and lead to prophylactic and therapeutic antibiotic overuse . Managing antibiotic use associated with the prevention and control of aquatic animal diseases is, therefore, necessary to secure the business venture and product brand . Research on alternatives and sustainable management strategies against infection become crucial and imperative to safeguard the different actors of the aquaculture chain. Bearing this in mind, this research introduc es environmentally friendly alternatives to boost the fish’s immune system . A nutritional strategy including diets supplemented with natural immunostimulants, and a thermal strategy relying on physiological requirements and environmental availability, will be developed to increase fish’s fitness towards challenging situations and reduce the use of antibiotics and mitigate their consequences. Overall, such alternatives will boost the welfare of the fish and leverage the industry with forthcoming management protocols to promote a more resilient and sustainable aquaculture -secure future.
Material and Methods
In a first approach, gilthead seabream will be infected with the bacteria Tenacibaculus Maritimum to characterize the bacterial infection through Label-free shotgun proteomic (LC-MS/MS) analysis and identify possible disease biomarkers. In this experiment, the fish behavior will be observed through cameras displayed in the tanks and the optimal temperature of non-infected seabream will be assessed in thermal gradient tanks. Furthermore, hematologic, histological, and microbiological analyses will be performed. In the second experiment, seabream will be subjected to infection and allowed to swim along a thermal gradient or being exposed to a constant temperature (obtained previously). Post-infection fish behavior and thermal preference will be evaluated through video recording. At last, seabream will be subjected to a nutritional therapy where will be fed with two experimental diets with natural immunostimulants against a commercial diet. After this, fish will be infected with the bacteria to assess the diet’s impact on fish disease behavioral phenotype and proteome. Biochemical parameters of plasma (cortisol, lactate, and glucose) and liver glycogen will be assessed.
Expected outcomes
Dietary supplementation with balanced natural immunostimulants and environmental thermal gradient availability improves welfare and enhance fitness of fish under challenging farming systems. Such strategies may well be promising avenues to tailor aquaculture management protocols to boost aquaculture sustainability and consumer’s safety.
Acknowledgements
This work received Portuguese national funds from FCT- Foundation for Science and Technology through project UID/04326/2020 and integrates the project BIOIMMUNE (Refª MAR-02.05.01-FEAMP-0052, “Natural Antimicrobials and Pyrexia as Alternative Strategies for Antibiotic Use to Prevent Pathogens and Improve Welfare in Aquaculture”) financed by Mar2020, in the framework of the program Portugal 2020 . Raquel Carrilho acknowledges a FCT PhD scholarship, Refª 2021.06786.BD.