Cultivation of Brook Charr Salvelinus fontinalis: The Challenges of Disease Control and the Promise of Microbial Ecology Management

Abstract

Among salmonids, brook charr, Salvelinus fontinalis has been gaining popularity in aquaculture. However, major limitations associated with opportunistic diseases that result from unstable egg and fry-rearing conditions are experienced under intensive rearing conditions. Great losses in brook charr culture result from viral (e.g., infectious pancreatic necrosis, viral hemorrhagic septicemia virus), fungal (e.g., saprolegniosis), and bacterial (e.g., furunculosis, cold water disease, columnaris) diseases. Unfortunately, there is no effective treatment for viral diseases for brook charr, and the chemical disinfectants and antibiotics commonly used against bacterial and fungal infections are reaching their limits (pathogen resistance, microbial community disruption), making alternative and more sustainable rearing approaches essential to bolster aquaculture. In this regard, recent studies show that many microbial species (bacteria, archaea, viruses, eukaryotes-like protozoa, and unicellular fungi) are essential from the earliest life stages for the proper development and growth of fish. Based on ecological theory and work on marine fish, it has been hypothesized that current aquaculture practices favor r-strategic, opportunistic microbes that are detrimental to fish health and development. Consequently, to ensure the success and sustainability of brook charr farming, a new aquaculture paradigm involving recirculating aquaculture systems (RAS) that select a K-enriched, specialized microbial community as a preventive measure against those microbial diseases is a very promising avenue. In this review, after introducing brook charr biology, the role of microbes in brook charr rearing and the general problems of disease and low fry survival due to an imbalance in the microbial community will be discussed. Various curative and prophylactic treatment methods currently used to control these diseases and their impact on microbial ecology will be covered, and we will conclude with the rationale of microbial ecology management and its effectiveness in promoting fry survival through disease prevention. To our knowledge, this is the first literature review addressing the promises of managing microbial ecology in a sustainable way in the brook char industry.