The body of work relating to the gut microbiota of fish is dwarfed by that on humans and mammals. However, it is a field that has had historical interest and has grown significantly along with the expansion of the aquaculture industry and developments in microbiome research. Research is now moving quickly in this field. Much recent focus has been on nutritional manipulation and modification of the gut microbiota to meet the needs of fish farming, while trying to maintain host health and welfare. However, the diversity amongst fish means that baseline data from wild fish and a clear understanding of the role that specific gut microbiota play is still lacking. We review here the factors shaping marine fish gut microbiota and highlight gaps in the research.

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The Gut Microbiota of Marine Fish.

The gastrointestinal (GI) microbiota of vertebrates plays critical roles in nutrition, development, immunity and resistance against invasive pathogens. In the past decade, research of the GI microbiota of mammals has drastically increased our knowledge on the microbiota and their relationship with health and disease. However, our understanding of fish intestinal microbiota is limited. This review provides an overview of research on fish gut microbiota, including microbial composition, formation, factors that affect the GI microbes and characteristics of fish intestinal microbiota compared with human and mice. Further, the updated research on gnotobiotic zebrafish is elaborated and the insights gained on functions of the fish intestinal microbiota are discussed. Understanding the intestinal microbiota of fish will guide the development of probiotics, prebiotics and hopefully probiotic effectors as novel additives to improve the health of fish.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/raq.12191

Progress in fish gastrointestinal microbiota research

Utilisation of dietary carbohydrates in farmed fishes: New insights on influencing factors, biological limitations and future strategies

Along with the intensification of culture systems to meet the increasing global demands, there was an elevated risk for diseases outbreak and substantial loss for farmers. In view of several drawbacks caused by prophylactic administration of antibiotics, strict regulations have been established to ban or minimize their application in aquaculture. As an alternative to antibiotics, dietary administration of feed additives has received increasing attention during the past three decades. Probiotics, prebiotics, synbiotics and medicinal plants were among the most promising feed supplements for control or treatments of bacterial, viral and parasitic diseases of fish and shellfish. The present review summarizes and discusses the topic of potential application of probiotics as a means of disease control with comprehensive look at the available literature. The possible mode of action of probiotics (Strengthening immune response, competition for binding sites, production of antibacterial substances, and competition for nutrients) in providing protection against diseases is described. Besides, we have classified different pathogens and separately described the effects of probiotics as protective strategy. Furthermore, we have addressed the gaps of existing knowledge as well as the topics that merit further investigations. Overall, the present review paper revealed potential of different probiont to be used as protective agent against various pathogens.

/pdf/probiotics-as-means-of-diseases-control-in-aquaculture-a-4l72ns3bh5.pdf

Probiotics as Means of Diseases Control in Aquaculture, a Review of Current Knowledge and Future Perspectives.

The growth and survival of Penaeus vannamei postlarvae was measured at temperatures of 20, 25, 30 and 35 °C and salinities of 20, 30, 35, 40 and 50%.. Groups of 30 animals were used in each combination of conditions, in triplicate. The results clearly show that juveniles of this species have their best survival between temperatures of 20 and 30 °C and salinities above 20%.. Best growth was obtained between temperatures of 25 and 35 °C, with little difference being noted among salinities. Survival and growth coincide best at around 28 to 30 °C and 33 to 40%.. Calculated overall production was shown to be best in these conditions. The results demonstrate a high coincidence between the experimentally determined optimum conditions for production and the prevailing conditions in the coastal environment from which the animals originated.

The effects of salinity and temperature on the growth and survival rates of juvenile white shrimp, Penaeus vannamei, Boone, 1931

It is well known that healthy gut microbiota is essential to promote host health and well-being. The intestinal microbiota of endothermic animals as well as fish are classified as autochthonous or indigenous, when they are able to colonize the host's epithelial surface or are associated with the microvilli, or as allochthonous or transient (associated with digesta or are present in the lumen). Furthermore, the gut microbiota of aquatic animals is more fluidic than that of terrestrial vertebrates and is highly sensitive to dietary changes. In fish, it is demonstrated that [a] dietary form (live feeds or pelleted diets), [b] dietary lipid (lipid levels, lipid sources and polyunsaturated fatty acids), [c] protein sources (soybean meal, krill meal and other meal products), [d] functional glycomic ingredients (chitin and cellulose), [e] nutraceuticals (probiotics, prebiotics, synbiotics and immunostimulants), [f] antibiotics, [g] dietary iron and [h] chromic oxide affect the gut microbiota. Furthermore, some information is available on bacterial colonization of the gut enterocyte surface as a result of dietary manipulation which indicates that changes in indigenous microbial populations may have repercussion on secondary host–microbe interactions. The effect of dietary components on the gut microbiota is important to investigate, as the gastrointestinal tract has been suggested as one of the major routes of infection in fish. Possible interactions between dietary components and the protective microbiota colonizing the digestive tract are discussed.

https://biblio.ugent.be/publication/8517580/file/8525700.pdf

Effect of dietary components on the gut microbiota of aquatic animals. A never‐ending story?

Groups of juvenile tench (7.02 ± 0.28 g) were reared under four different light regimes; blue light, red light (80 Wm−2 12L:12D photoperiod) white light (912 ± 210 lux, 80 Wm−2, 12L:12D photoperiod) and no light (0 lux) (0L:24D). Visibility of fish out of shelters was used as an indicator of activity and was monitored by video recording. Blood plasma cortisol concentrations were also measured. Fish under blue or white light were significantly less active during the photophase than those under red or no light (P < 0.01). Red light produced similar activity patterns to fish receiving 24 h darkness. Plasma cortisol concentrations were also significantly influenced (P < 0.05) with the fish under white light having the highest plasma cortisol concentration (317 ± 62 ng cm−3) compared to fish in the dark treatment (106 ± 36 ng cm−3). Thus, the provision of coloured light filters increases activity in juvenile tench and may reduce their intrinsic stress level.

Light colour influences the behaviour and stress physiology of captive tench ( Tinca tinca )

https://myresearchspace.uws.ac.uk/ws/files/10750094/2018_07_29_Bardera_et_al_Shrimp.pdf

The importance of behaviour in improving the production of shrimp in aquaculture

A proteomics strategy for determining the synthesis and degradation rates of individual proteins in fish

https://myresearchspace.uws.ac.uk/ws/files/12280283/2019_06_11_Bardera_et_al_The_Effect.pdf

Matthew A.G. Owen

Papers

Effect of dietary components on the gut microbiota of aquatic animals. A never‐ending story?

Light colour influences the behaviour and stress physiology of captive tench ( Tinca tinca )

The importance of behaviour in improving the production of shrimp in aquaculture

A proteomics strategy for determining the synthesis and degradation rates of individual proteins in fish

The effect of short-term feed-deprivation and moult status on feeding behaviour of the Pacific white shrimp (Litopenaeus vannamei)