Linking Omega-3 Polyunsaturated Fatty Acids in Natural Diet with Brain Size of Wild Consumers

Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) are key structural lipids and their dietary intake is essential for brain development of virtually all vertebrates. The importance of n-3 LC-PUFA has been demonstrated in clinical and laboratory studies, but little is known about how differences in availability of n-3 LC-PUFA in natural prey influence brain development of wild consumers. The numerous consumers foraging on the interface of aquatic and terrestrial food webs can differ substantially in their intake of n-3 LC-PUFA, which may lead to differences in brain development, yet, this hypothesis remains to be tested. Here we use the previously demonstrated shift towards higher reliance on n-3 LC-PUFA deprived terrestrial prey of native brown trout Salmo trutta living in sympatry with invasive brook trout Salvelinus fontinalis to explore this hypothesis. We found that the content of n-3 LC-PUFA in muscle tissues of brown trout decreased with increasing consumption of n-3 LC-PUFA deprived terrestrial prey. Brain volume was positively related to content of the n-3 LC-PUFA, docosahexaenoic acid, in muscle tissues of brown trout. Our study thus suggests that increased reliance on low quality diet of n-3 LC-PUFA deprived subsidies can have a significant negative impact on brain development of wild trout. Our findings are important, because ongoing global change is predicted to reduce the availability of dietary n-3 LC-PUFA across food webs and we showed here a first evidence of how brain of wild vertebrate consumers response to scarcity of n-3 LC-PUFA content in natural prey.

Study and development of methods for obtaining intergeneric hybrids of salmonids (Salmonidae (Jarocki or Schinz, 1822)) for achieving the effect of heterosis and increasing their productivity

Purpose. To study the possibility of obtaining highly productive intergeneric salmonid hybrids between rainbow trout and brook trout; brown trout and brook trout; rainbow trout and brown trout, as well as to develop methodological approaches and determine of optimal variants of hybrid crosses. Findings. In order to obtain intergeneric hybrids, we used six variants of hybrid crosses with brood fish of three salmonids belonging to three families (Salmo, Oncorhynhus, Salvelinus). The study used age-4 female rainbow trout with average body weight of 3296.8 g, Fork length was 62.6 cm, and the average working fecundity was 7420 eggs. Age-3 rainbow trout males had an average body weight of 1613 g and an average body length of 49.8 cm; age-3 brown trout females had an average body weight of 453.8 g and average working fecundity of 1540 eggs, and males had an average weight of 458.7 g; age-3 brook trout females had an average weight of 809.7 g and a length of 38.9 cm with working fecundity of 1732 eggs, and age-4 males had an average weight of 1212.8 g and an average body length of 46.0 cm. Twelve variants of fertilization were used: six variants at normal water temperature and six variants after a temperature shock. Under natural conditions, the creation of intergeneric hybrids is almost impossible, except for variants between brown trout and brook trout, which is due to the similarity of their biology. However, the efficiency of this cross is low and economically impractical for fish farmers. When applying the temperature shock during fertilization, hybrids proved to be the most effective, where females were rainbow trout, and males were brook trout and brown trout. The average weight of young-of-the-year intergeneric hybrids was, depending on the species of fish, from 8 to 54 g. The highest results were obtained for the creation of hybrids where following broodstock was used: ♂brook trout Х ♀brown trout; ♂brown trout Х ♀rainbow trout. In these variants of crossbreeding, the survival rate of young-of-the-year during the period of cultivation was 94.8 and 92.8%, respectively. In particular, the above hybrids did not suffer from infectious diseases during the growing period. Originality. New data on the development of methods for obtaining viable offspring of newly created hybrids were obtained, and the optimal variants of crossing between females and males of these salmonids were determined. Practical value. The results can be used for artificial breeding of salmonids in specialized farms that will allow obtaining high quality products and reducing their costs. Key words:rainbow trout, brown trout, brook trout, incubation, free embryos, larvae, fry, young-of-the-year.

Linking brain size in wild stream-dwelling brown trout with dietary supply of omega-3 fatty acids

1. Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) are key structural lipids and their dietary intake is essential for brain development of virtually all vertebrates. The importance of n-3 LC-PUFA has been demonstrated in clinical and laboratory studies, but little is known about how differences in availability of n-3 LC-PUFA in natural prey influence brain development of wild consumers. The availability of n-3 LC-PUFA in the prey communities is driven by primary producers and it is therefore distributed heterogeneously, but predictably across ecosystems, being higher in aquatic than in terrestrial food webs. Consequently, the numerous consumers foraging on the interface of aquatic and terrestrial food webs can differ substantially in their intake of n-3 LC-PUFA, which may lead to in brain development, yet, this hypothesis still remains to be tested. 2. Here we use the previously demonstrated shift towards higher reliance on n-3 LC-PUFA deprived terrestrial prey of native brown troutSalmo trutta living in sympatry with invasive brook troutSalvelinus fontinalis to explore this hypothesis. 3. We found that the content of n-3 LC-PUFA in muscle tissues of brown trout decreased with increasing consumption of n-3 LC-PUFA deprived terrestrial prey. Brain volume was positively related to content of the n-3 LC-PUFA, docosahexaenoic acid, in muscle tissues of brown trout. 4. Our study thus suggests that increased reliance on low quality diet of n-3 LC-PUFA deprived subsidies from terrestrial food web can have a significant negative impact on brain development of wild trout. These findings provide the first evidence of an intra-specific link between n-3 LC-PUFA content in natural prey and brain size of wild vertebrate consumers. 5. Ongoing global change is predicted to reduce the availability of dietary n-3 LC-PUFA across food webs. Therefore, our findings emphasise the need for further research on how wild consumers adapt to the shortage of dietary n-3 LC-PUFA in order to maintain optimal development and functioning of their brain, which is crucial for their fitness.

Food web incorporation of marine-derived nutrients after the reintroduction of endangered inner Bay of Fundy Atlantic salmon (Salmo salar)

Inner Bay of Fundy Atlantic salmon (Salmo salar) are endangered anadromous fish that have the potential to provide marine-derived nutrients (MDNs) to freshwater ecosystems depending on their population abundance. Salmon have been reintroduced to the Upper Salmon River, but not the adjacent Point Wolfe River, in Fundy National Park, New Brunswick, Canada. This study determined whether stocking of adult salmon increased the productivity of the river. To examine the incorporation of MDNs, biofilm, leaf litter, Perlidae, Heptageniidae and brook trout (Salvelinus fontinalis) were sampled pre- and post-spawning in 2015-2017 from down- and up-stream of a natural barrier in both rivers and analyzed for carbon (δ13C) and nitrogen (δ15N) isotopes. After salmon spawning in each year, all organisms at the downstream site of the stocked river increased in δ13C and δ15N, with the greatest enrichment in brook trout (δ13C -23.97 to -21.10‰, δ15N +6.36 to +10.73‰). The proportion of MDNs in brook trout after salmon spawning (2015: 23.4%, 2016: 40.7%, 2017: 37.4%) also increased with higher numbers of released adult salmon. Results support the importance of salmon restoration for increasing the proportion of MDNs and productivity in rivers in Atlantic Canada.