Anadromous Brook Charr Research Articles

Metabolic and transcriptomic response of two juvenile anadromous brook charr (Salvelinus fontinalis) genetic lines towards a chronic thermal stress

Many salmonid species are particularly susceptible to chronic and acute temperature changes caused by global warming. We aimed to study the differences in metabolic and transcriptomic responses of a chronic heat stress on a control and selected (absence of early sexual maturation and growth) line of brook charr Salvelinus fontinalis (Mitchill, 1814). We exposed individuals to different temperatures for 35 days (15, 17, and 19 °C). High temperature reduced the growth rate (in length) and the Fulton condition factor. Both maximal metabolic rate and the aerobic scope were higher in fish reared at 17 °C, while they decreased in fish maintained at 19 °C. The relative gene expression of cytochrome c oxidase was lower at 19 °C than at 15 °C. The relative gene expressions of both liver and gill hsp90 was higher at the highest temperature. The standard metabolic rate, while not affected by temperature, was higher for the control line over the selected line. Only in the control line, the relative expression of catalase and of receptor of insulin-like growth factor-1 increased at 19 °C. Our results showed that the selected line was able to cope more effectively with the oxidative stress caused by the rise in temperature.

Comparative transcriptomics of anadromous and resident brook charr Salvelinus fontinalis before their first salt water transition

Abstract Most salmonid taxa have an anadromous life history strategy, whereby fish migrate to saltwater habitats for a growth period before returning to freshwater habitats for spawning. Moreover, several species are characterized by different life history tactics whereby resident and anadromous forms may occur in genetically differentiated populations within a same species, as well as polymorphism within a population. The molecular mechanisms underlying the physiological differences between anadromous and resident forms during the first transition from freshwater to saltwater environments are only partially understood. Insofar research has typically focused on species of the genus Salmo. Here, using a 16,000 cDNA array, we tested the hypothesis that ana-dromous brook charr Salvelinus fontinalis are characterized by differences in their transcriptome relative to resident brook charr before the anadromous fish migration. Families originating from parapatric populations of anadromous and resident charr were reared in controlled environments mimicking natural temperature and photoperiod, and sampled in spring, while still in fresh water. While anadromous and resident charr showed similar transcriptome profiles in white muscle, they were characterized by striking differences in their gill transcriptome profiles. Genes that were upregulated in the gills of anadromous charr were principally involved in metabolism (mitochondrial electron transport chain, glucose metabolism, and protein synthesis), development (tissue differentiation) and innate immunity. We discuss the nature of these transcriptomic differences in relation to molecular mechanisms underlying the expression of anadromous and resident life history tactics and suggest that the anadromous charr express some of the molecular processes present in other migratory salmonids.

Brook charr mortalities during extreme temperature events in Sutton River, Hudson Bay Lowlands, Canada

Fish die-offs during warming events have rarely or ever been recorded within arctic watersheds. The 2001 mortality of anadromous brook charr (Salvelinus fontinalis) in the Sutton River in the Hudson Bay Lowlands may be the first documented case of an increasing number of such events, as climate warming affects north latitude systems. Warm air temperatures (daily maximums >30°C) combined with unusual thermal stratification conditions in the upstream lake appeared to have created the lethal conditions, but changing marine environments likely triggered the event. This highly productive brook charr population depends heavily on the local marine environment, not only for food, but also to moderate the continental climate of the region. The steadily shortening ice season in Hudson Bay appears to be greatly increasing the vulnerability of anadromous stocks to warming events.

Temporal and Spatial Habitats of Anadromous Brook Charr in the Laval River and its Estuary

Anadromy in brook charr occurs across the species’ range, but few studies have examined contiguous seasonal movements and habitat utilization of freshwater and estuarine environments. We used acoustic telemetry to track movements of anadromous brook charr for 1 year in the Laval River, Quebec. Fish entered the marine environment in May and June, inhabited shallow (<1.7 m), near-shore areas (<500 m from shore), and rarely ventured beyond the headlands of the bay. They were found where salinities were 1–34 ppt and temperatures 5–18°C. There was a strong tidal periodicity to observed movements with fish running up into bays as they became inundated at high tide and then returning to deep river channels in the bays at low tide. Between late July and early September, the charr returned to freshwater and spawned in the middle and upper sections of the river in October and November. Winter habitats were dispersed over 22 km of the river including two lakes. These detailed observations are an important contribution to our understanding of the evolutionary significance of anadromy in this species. The salinity and temperature co-tolerance provides insights into the species’ post-glacial dispersal, present-day distribution, and potential habitat maps for conservation, restoration, and enhancement programmes.

Maternal genetic effects on adaptive divergence between anadromous and resident brook charr during early life history

The importance of directional selection relative to neutral evolution may be determined by comparing quantitative genetic variation in phenotype (Q(ST)) to variation at neutral molecular markers (F(ST)). Quantitative divergence between salmonid life history types is often considerable, but ontogenetic changes in the significance of major sources of genetic variance during post-hatch development suggest that selective differentiation varies by developmental stage. In this study, we tested the hypothesis that maternal genetic differentiation between anadromous and resident brook charr (Salvelinus fontinalis Mitchill) populations for early quantitative traits (embryonic size/growth, survival, egg number and developmental time) would be greater than neutral genetic differentiation, but that the maternal genetic basis for differentiation would be higher for pre-resorption traits than post-resorption traits. Quantitative genetic divergence between anadromous (seawater migratory) and resident Laval River (Québec) brook charr based on maternal genetic variance was high (Q(ST) > 0.4) for embryonic length, yolk sac volume, embryonic growth rate and time to first response to feeding relative to neutral genetic differentiation [F(ST) = 0.153 (0.071-0.214)], with anadromous females having positive genetic coefficients for all of the above characters. However, Q(ST) was essentially zero for all traits post-resorption of the yolk sac. Our results indicate that the observed divergence between resident and anadromous brook charr has been driven by directional selection, and may therefore be adaptive. Moreover, they provide among the first evidence that the relative importance of selective differentiation may be highly context-specific, and varies by genetic contributions to phenotype by parental sex at specific points in offspring ontogeny. This in turn suggests that interpretations of Q(ST)-F(ST) comparisons may be improved by considering the structure of quantitative genetic architecture by age category and the sex of the parent used in estimation.

The rise and fall of isolation by distance in the anadromous brook charr (Salvelinus fontinalis Mitchill).

Geographic patterns of genetic diversity depend on a species' demographic properties in a given habitat, which may change over time. The rates at which patterns of diversity respond to changes in demographic properties and approach equilibrium are therefore pivotal in our understanding of spatial patterns of diversity. The brook charr Salvelinus fontinalis is a coastal fish exhibiting limited marine movements, such that a stable one-dimensional isolation-by-distance (IBD) pattern should be observed over the whole range. Its range, however, recently shifted northward such that northern populations may still be in the process of reaching equilibrium. We investigated variation in IBD patterns, genetic divergence, and allelic richness at six microsatellite markers in 2087 anadromous brook charr from 59 rivers along the most likely postglacial colonization route. We observed a decrease in allelic richness, together with an increase in differentiation and a decrease in IBD in the most recently colonized northern populations, as expected following recent colonization. Contrary to expectation, however, similar patterns were also observed at the southernmost part of the range, despite the fact that these populations are not considered to be newly colonized. We propose that the loss of dispersal capabilities associated with anadromy may have caused the southernmost populations to evolve relatively independently of one another. This study thus demonstrated that changes in a species' geographic range and dispersal capabilities may contribute to shaping geographic patterns of genetic diversity.

Genetic relationships among populations of wild resident, and wild and hatchery anadromous brook charr

To determine the genetic relationship of anadromous and resident life-history types within and among drainages, and compare several hatchery strains to their progenitor populations, brook charr Salvelinus fontinalis were examined for allozyme and mitochondrial DNA variation. Greater genetic similarity of sympatric anadromous and resident charr was found compared to similar life-history forms allopatrically, suggesting the two life-history types are not reproductively isolated. Low divergence among the mtDNA haplotypes suggests that the two life-history types are members of the same evolutionary lineage. Population differentiation from mtDNA data exceeded that from estimates based on allozymes. Genetic deviations from expectations suggest that the hatchery strains were derived from few individuals. 1997 The Fisheries Society of the British Isles

Genetic relationships among populations of wild resident, and wild and hatchery anadromous brook charr

Genetic relationships among populations of wild resident, and wild and hatchery anadromous brook charr

Potential use of certain parasites of brook charr (Salvelinus fontinalis) as biological indicators in the Tabusintac River, New Brunswick, Canada

A survey of 1146 nonanadromous and anadromous brook charr (Salvelinus fontinalis) from the Tabusintac River for parasites revealed 36 species of parasites, of which 18 were freshwater and 18 were marine. Most freshwater parasites were either too common or too rare in their occurrence to be of any value as biological indicators; however, Diplostomum sp. (metacercariae), Truttaedacnitis truttae, and Salmincola edwardsii were useful as indicators of foci of infection in fresh water. Decreases in prevalences of infection with marine gastrointestinal parasites in the estuary, especially Brachyphallus crenatus, Neoechinorhynchus sp., and larvae of Hysterothylacium aduncum, provided evidence for the approximate times of arrival of anadromous charr from fresh water. Marine gastrointestinal parasites were also useful as biological indicators of anadromous charr in fresh water, but these parasites were lost after varying times. High prevalences of infection with metacercariae of the marine digenean Cryptocotyle lingua resulted in a black spot condition that proved to be the best indicator of anadromous charr in fresh water. The distributions of Azygia longa, Echinorhynchus lateralis, and Zoogonus lasius from charr in the Tabusintac River as well as the nearby Miramichi and Burnt Church estuaries suggested that estuarine wanderings among adjacent river systems do occur. Tetraphyllidea gen. sp. plerocercoids from anadromous charr in the Tabusintac River were useful in identifying offshore movements of these charr into the Gulf of St. Lawrence.

Life history and movements of anadromous brook charr, Salvelinus fontinalis, in the St-Jean River, Gaspé, Quebec

A comparison between an anadromous and a freshwater lake population of brook charr showed that anadromous charr had a lower mean length at age 2+ and 3+, a greater longevity, a greater maximal length and a greater length and age at first maturity than the freshwater population. A biased sex ratio towards females occurred only in the anadromous population. The first 2 or 3 years in the life cycle of anadromous charr is spent in the river, followed by an intermediate period of a year in the salt wedge area and then by a 2- or 3-month period in salt water before returning to the river. Bigger charr started upstream migration earlier in the season than smaller charr. Migration peaks in 1979 were synchronized with the new moon. Fish movements in the estuary were greater during spring tides than neap tides. Diel activity was highest in the day in the estuary whereas the inverse situation occurred in the river. From tags returns, it was concluded that anadromous brook charr had a strong homing tendency.

Répartition des ressources et changements saisonniers de l'alimentation d'ombles de fontaine anadromes, Salvelinus fontinalis

Resource partitioning among anadromous brook charr in an estuary included habitat and prey-type partitioning. In spring and summer, juveniles were foraging in the upper estuary on crustacea and insects while adults were eating crustacea and fish in the lower estuary. In the fall, adult charr, which were all in the river, ate little. During winter, adult charr were found in the estuary and consumed crustacea and only a few fish. The relative weights of stomach contents were similar in summer and winter, showing for the first time the importance of winter feeding for this species.

Metazoan parasites as indicators of movements of anadromous brook charr (Salvelinus fontinalis) to sea

Changes in the numbers of metazoan parasites of anadromous brook charr, Salvelinus fontinalis, during the summer 1980 were determined by examining 220 fish at different times and localities in the Moisie River, Quebec. The marine trematode Brachyphallus crenatus remained in brook charr during their movements into fresh water. Differences in the prevalence of this parasite between sampling localities in late July indicated that some charr which undergo smoltification do not go to sea although others do. Also, infection with B. crenatus enabled an estimate to be made of the percentage of charr that had been to sea entering a tributary in late August. Brook charr were also infected with Crepidostomum cooperi, Diplostomum spathaceum, Eubothrium salvelini, Proteocephalus sp., Metechinorhynchus lateralis, Echinorhynchus gadi complex, Cystidicoloides tenuissima, Hysterothylacium sp., Anisakis simplex, Acuarioidea: Seuratiinae gen. sp., Salmincola edwardsii, and glochidia larvae.