Impact of Putative Probiotics on Growth, Behavior, and the Gut Microbiome of Farmed Arctic Char (Salvelinus alpinus)

Abstract

Beneficial bacteria promise to promote the health and productivity of farmed fish species. However, the impact on host physiology is largely strain-dependent, and studies on Arctic char (Salvelinus alpinus), a commercially farmed salmonid species, are lacking. In this study, 10 candidate probiotic strains were subjected to in vitro assays, small-scale growth trials, and behavioral analysis with juvenile Arctic char to examine the impact of probiotic supplementation on fish growth, behavior and the gut microbiome. Most strains showed high tolerance to gastric juice and fish bile acid, as well as high auto-aggregation activity, which are important probiotic characteristics. However, they neither markedly altered the core gut microbiome, which was dominated by three bacterial species, nor detectably colonized the gut environment after the 4-week probiotic treatment. Despite a lack of long-term colonization, the presence of the bacterial strains showed either beneficial or detrimental effects on the host through growth rate enhancement or reduction, as well as changes in fish motility under confinement. This study offers insights into the effect of bacterial strains on a salmonid host and highlights three strains, Carnobacterium divergens V41, Pediococcus acidilactici ASG16, and Lactiplantibacillus plantarum ISCAR-07436, for future research into growth promotion of salmonid fish through probiotic supplementation.

Enhancement of Soybean Meal Alters Gut Microbiome and Influences Behavior of Farmed Atlantic Salmon (Salmo salar)

“…The fish fed the US diet displayed a trend toward being the least bold and having lower repeatability of the trait of boldness, which could lead to reduced welfare, trends that were less pronounced for the treated ETS and USP diets. Previous studies have shown that manipulating the fish gut microbiome can modulate behavior via the gut–brain axis [ 47 ], and a recent study on farmed Arctic charr ( Salvelinus alpinus ) [ 124 ] showed evidence of bacterial strains influencing the response to stress and growth, where fish fed with E. thailandicus 04-394 and L. brevis ISCAR-07433 displayed an increase in motility and slower growth, which can be interpreted as a lower stress coping ability. Selecting for personality has been identified as a valuable tool to reduce chronic stress in captive fish, where bolder individuals are usually more resistant to chronic stress [ 125 ].…”

The gut microbiome of farmed Arctic char (Salvelinus alpinus) is shaped by feeding stage and nutrient presence

“…Juvenile Arctic char ( S. alpinus ) were collected from an ongoing feeding trial (Knobloch et al 2022 ) at 104 days posthatch (dph) (T0, N = 22), 132 dph (T1, N = 15), and 157 dph (T2, N = 15). Before the beginning of the feeding trial (T0), one fish was collected from each of the 22 experimental tanks.…”

“…At T1 and T2, five fish were collected from each of the three replicate control tanks. All fish had received the same control diet, consisting of fish meal, fish oil, gelatinized wheat, minerals, and vitamins as described in Knobloch et al ( 2022 ), and were reared under identical conditions with a continuous freshwater exchange and a water temperature of 8.6 ± 0.5°C. The fish were fasted 12 h prior to weighing and sample collection.…”

“…Similar to Atlantic salmon, Mycoplasma was also among the dominant gut symbionts. In an aquaculture environment, the gut microbiota of Arctic char has been studied to determine the impact of feeds and probiotics on the microbial community (Nyman et al 2017 , Knobloch et al 2022 ). However, it is not yet known which bacteria constitute the resident gut microbiota in farmed Arctic char or what role they might play in maintaining health, well-being and productivity of the fish.…”

Antimicrobial Activity, Genetic Relatedness, and Safety Assessment of Potential Probiotic Lactic Acid Bacteria Isolated from a Rearing Tank of Rotifers (Brachionus plicatilis) Used as Live Feed in Fish Larviculture

“…In aquaculture, probiotics can be defined as live micro-organisms, usually bacteria or yeasts, that, when administered through feed or the rearing environment, confer beneficial effects to the host such as protection against ichthyopathogens, the stimulation of the immune system, competition for adhesion sites in the mucosa, improved tolerance to stress, host nutrition enhancement, and water quality improvement [14][15][16][17][18]. Usually, both the host and the rearing environment have been regarded as the most suitable sources for the isolation of probiotic candidates for larviculture.…”