Behavioural plasticity of lake charr (Salvelinus namaycush) x brook charr (S. fontinalis) F1 hybrids in response to varying social environment

Lake x brook F₁ hybrid charr were observed in heterogeneous groups with lake charr or brook charr to assess the effects of different species on hybrid social behaviour. Levels of behavioural plasticity were low in relation to the behavioural differences between the parental and hybrid types. Feeding behaviour showed the most dramatic change, with higher levels in the lake charr treatment and lower levels in the brook charr treatment than controls, suggesting social facilitation. Even though only two measures varied significantly between treatments, there was a tendency for the frequencies and durations of all agonistic measures to increase in the presence of lake charr and decrease with brook charr. A cost-benefit argument is presented to account for this trend.     

Genetics of social behaviour in charrs (Salvelinus species)

Juvenile brook charr (Salvelinus fontinalis) are territorial and have high levels of agonistic behaviour. Juvenile lake charr (S. namaycush) rarely show any indication of territoriality and have very low levels of agonistic behaviour. The inheritance of behaviour in their reciprocal hybrids was investigated by multivariate stepwise discriminant analysis. Lateral display, charge, chase, and forage composed the first canonical axis (87.2% of total dispersion). Pooled hybrid means were closer to that of brook charr, suggesting either directional dominance or modification of the behaviour of hybrids in response to water flow. The mean values of reciprocal hybrids were skewed towards the maternal parent, suggesting a maternal effect in the phenotypic expression of behaviour in these fish.     

Chemical Alarm Signals Enhance Survival of Brook Charr (Salvelinus fontinalis) During Encounters with Predatory Chain Pickerel (Esox niger)

A diversity of aquatic organisms release chemical alarm signals when attacked or captured by a predator. These alarm signals are thought to warn other conspecifics of danger and, consequently, may benefit receivers by increasing their survival. Here we experimentally investigated the differences in behaviour and survival of hatchery-reared juvenile brook charr Salvelinus fontinalis that had been exposed to either brook charr skin extract (experimental treatment) or a control of swordtail skin extract (control treatment). Charr exposed to conspecific skin extract exhibited a significant reduction in movement and/or altered their foraging behaviour in the laboratory when compared with charr exposed to swordtail skin extract. We also exposed charr to either water conditioned by a single brook charr disturbed by a predatory bird model or water conditioned by a single undisturbed brook charr. Charr exposed to disturbance signals reduced activity significantly more than charr exposed to chemical stimuli from undisturbed charr. These results demonstrate the existence of both damage-released alarm signals and disturbance signals in brook charr. Wild brook charr also responded to damage-released alarm cues under natural conditions. Charr avoided areas of a stream with minnow traps labelled with conspecific alarm cues vs. control cues. During staged encounters with chain pickerel Esox niger in the laboratory, predator-naive charr fry were better able to evade the predator if they were previously warned by an alarm signal, thus suggesting a survival benefit to receivers. Collectively, these results demonstrate that the presence of alarm signals in brook charr has important implications for understanding predator–prey interactions.     

Comparative ontogeny of photobehavioural responses of charrs (Salvelinus species)

Synopsis The development of photobehavioural responses in brook (Salvelinus fontinalis) and lake (S. namaycush) charr was studied by monitoring the intrasubstrate movements and concurrent photoresponse behaviour of incubated embryos and alevins. Photoresponse behaviour of both F-1 hybrids of the parent species was also recorded. All embryos initially moved downward in the substrate, however brook charr descended farther and faster into the substrate than did lake charr. Photoresponse tests demonstrated a similar pattern of photoresponse transformation from a photonegative to a photopositive state in both species. However, photoresponse reversal was faster, more extensive and occurred later in brook charr than in lake charr. Patterns of photoresponse change in F-1 hybrids were intermediate between those of the parent species. Photoresponse shifts preceded the onset of alevin emergence in both species. occurring when differential development of various morphological characters existed. Developmental states of characters were synchronously maximal towards the end of alevin emergence. Intermediate measures of morphological development were observed for F-1 hybrids. Possible functions and mechanisms of photoresponse transitions are discussed in relation to ecological differences between the species.     

Conservation and variation in the agonistic repertoire of the brook stickleback, <Emphasis Type="Italic">Culaea inconstans</Emphasis> (Kirtland)

Interpopulation variability in behaviour is thought to play a role in the production of biological diversity on this planet. The brook stickleback, Culaea inconstans, is a prime candidate for investigations of such variability because mtDNA sequences indicate that it diverged into two distinct lineages 3.6–4.8 mya; more than enough time for differences to evolve. In this paper we show that, despite long periods of allopatry, the brook stickleback’s agonistic repertoire has remained quite conservative. Existing variability represents shifts in the mean population frequencies (performance parameter) of some displays, rather than changes in the composition of the agonistic repertoire itself (presence or absence of behavioural elements).     

Behaviour of Arctic charr Salvelinus alpinus during an induced mating season in captivity: how male relative size influences male behavioural investment and female preference over time

The behaviour of sexually mature Arctic charr Salvelinus alpinus specimens (fifth farm generation) was observed in captivity for four consecutive days. Only agonistic interactions between males of different size were facilitated on the first 2 days, while both agonistic and courtship interactions were possible from the third day up to the end of the experiment. The reliability of behavioural analysis was assessed in order to reduce the possibility of observer errors within the generated datasets. The behavioural investment of big males, small males and females was analysed using general linear models (two‐way repeated measures ANOVAs with time and male size as factors). A peak in the agonistic interactions between males occurred during the first day of interactions, where the agonistic investment of big males was significantly higher than that of small males. This resulted in an increased investment in submissive behaviour by the small males, who consistently performed submissive behaviours from the second day of interactions up to the end of the trial. Big males were found to invest significantly more than small males in courtship behaviours for the duration of the trial. Even though females performed inter‐sexual behaviours towards both big and small males for the entire observation period, female interaction rate towards big males was higher than towards small males. This study suggests that both male investment in mating behaviour and female preference might be related to male characteristics such as body length and that S. alpinus behavioural patterns and mate choice cues might be strongly context‐related and characterized by high levels of behavioural plasticity (i.e. presence–absence of certain behavioural units or potential reversal of a mate choice cue) within the same species. Finally, in light of this, some conservation measures are discussed. In particular, effective management plans should take into account the high level of behavioural plasticity likely to be occurring in this species.     

Obituary of Vadim Dimitrovitch Vladykov, 1898–1986

Synopsis The behaviour and ecology of lake charr Salvelinus namaycush, brook charr S. fontinalis, and Atlantic salmon Salmo salar, are reviewed to assess the susceptibility of these species to mortality from exposure to episodic pH depressions and accompanying changes in water quality. Critical life history periods are identified from an examination of: spawning site characteristics, timing of acidic pulses, changes in the sensitivity of developing fish to acidic water, and the ability of these species to detect and avoid deleterious chemical conditions. The three species appeared to be most vulnerable to pH depressions during Snowmelt as: alevins emerging from the redd (brook charr); free embryos in the interstitial spaces of the spawning rubble (lake charr); and embryos during hatching and juveniles during smoltification (Atlantic salmon). Factors that may modify the toxic effects of or the behavioural responses to low pH included: water temperature, acclimation and body energy reserves. The effect of site-specific or episodic mortality of early life history stages on recruitment to the population could not be evaluated due to the lack of information on compensatory mechanisms.     

Influence of spring and summer water temperature on brook charr, Salvelinus fontinalis, growth and age structure in the Ford River, Michigan

Synopsis The influence of late spring and summer water temperatures on brook charr, Salvelinus fontinalis, growth and age structure was evaluated from 1984 to 1991 in the Ford River, Michigan. Temperature was monitored and brook charr sampled for vital statistics from late May through September using fyke nets and weirs at four locations within a 25.8 km section of stream. Scale analysis was used to determine captured brook charr age, past length at age and relative annual growth rates. Late spring and summer water temperature patterns varied between years with the greatest variability occurring in May and June. Age and size structure also varied between years and was significantly related to temperature. Years with cooler late spring and summer temperature patterns were dominated by older (age 2 and 3), larger brook charr, while years with warmer spring and summer temperature patterns were dominated by younger (age 1), smaller brook charr. Spring and summer temperature did not appear to have a significant effect on the growth of age 0 or age 1 brook charr. However, temperature was negatively related to brook charr growth from age 2 on. As spring and summer water temperatures are critical to brook charr growth and survival, it is important that a streams thermal regime be considered when establishing management goals for this species.     

Isolation and cross‐familial amplification of 41 microsatellites for the brook charr (Salvelinus fontinalis)

The brook charr (Salvelinus fontinalis; Osteichthyes: Salmonidae) is a phenotypically diverse fish species inhabiting much of North America. But relatively few genetic diagnostic resources are available for this fish species. We isolated 41 microsatellites from S. fontinalis polymorphic in one or more species of salmonid fish. Thirty‐seven were polymorphic in brook charr, 15 in the congener Arctic charr (Salvelinus alpinus) and 14 in the lake charr (Salvelinus namaycush). Polymorphism was also relatively high in Oncorhynchus, where 21 loci were polymorphic in rainbow trout (Oncorhynchus mykiss) and 16 in cutthroat trout (Oncorhynchus clarkii) but only seven and four microsatellite loci were polymorphic in the more distantly related lake whitefish (Coregonus clupeaformis) and Atlantic salmon (Salmo salar), respectively. One duplicated locus (Sfo228Lav) was polymorphic at both duplicates in S. fontinalis.     

Growth and food of young-of-the-year brook charr,Salvelinus fontinalis,in lake and creek environments

Synopsis Growth and diet of brook charr,Salvelinus fontinalis, during their first weeks of exogenous feeding were compared between the nearshore zone of a central Ontario lake and its small, inlet creeks. Food selection was related to size and age of charr and possibly availability of food items. Mean growth was similar between habitats despite differences in consumed food types and caloric values. Differences in social behaviour may have been responsible for different patterns of growth between habitats. The importance of creek habitats to the dynamics and fitness of lake populations of brook charr are suggested.     

Clusters in social behaviour of female domestic cats (Felis silvestris catus) living in confinement

Associations between different agonistic and affiliative behavioural patterns of female domestic cats (Felis silvestris catus) were studied. In three groups of intact cats living in confinement frequencies of fourteen agonistic and affiliative behavioural patterns were recorded. The technique of factor analysis (Principal Components Analysis followed by varimax rotation on a dyads X behavioural patterns matrix) was used to detect clusters in these behavioural patterns. Five factors (or types of interindividual relationships) were extracted per group. They accounted collectively for at least 77% of the total variance present in the data. Although differences existed between groups with respect to behavioural patterns included in each factor, four clusters of behaviours could be discriminated: (I) social rubbing, lordosis and rolling in front of partner (sexual behaviour), (II) allogrooming, social sniffing, nosing, sniffing rear and treading (inspection-affiliative behaviour), (III) offensive behaviour and staring, and (IV) defensive behaviour and staring. The role of these clusters in group living is discussed.     

Temporal Persistence of Resource Polymorphism in Brook Charr, Salvelinus Fontinalis

Resource polymorphisms are believed to be an important intermediate step in competitive sympatric speciation. Reports of resource polymorphisms in fishes are becoming more common, but tests of the temporal persistence of resource polymorphisms remain scarce. We examined the temporal persistence of a body shape dimorphism reported previously for stream dwelling young-of-the-year brook charr, Salvelinus fontinalis, inhabiting slow vs. fast running water. In the year of our study, we found no difference in body shape between individuals in slow vs. fast flowing water, although fish in fast flowing water were of greater standard length than those in slower flowing water. We conclude that the resource polymorphism reported earlier for brook charr in streams is not stable temporally.     

Effects of Partially Anadromous Arctic Charr (Salvelinus alpinus) Populations on Ecology of Coastal Arctic Lakes

Little research has been conducted on effects of iteroparous anadromous fishes on Arctic lakes. We investigated trophic ecology, fish growth, and food web structure in six lakes located in Nunavut, Canada; three lakes contained anadromous Arctic charr (Salvelinus alpinus) whereas three lakes did not contain Arctic charr. All lakes contained forage fishes and lake trout (Salvelinus namaycush; top predator). Isotope ratios (δ¹³C, δ¹⁵N) of fishes and invertebrates did not differ between lakes with and without anadromous Arctic charr; if anadromous Arctic charr deliver marine-derived nutrients and/or organic matter to freshwater lakes, these inputs could not be detected with δ¹³C and/or δ¹⁵N. Lake trout carbon (C):nitrogen (N) and condition were significantly higher in lakes with Arctic charr (C:N = 3.42, K = 1.1) than in lakes without Arctic charr (C:N = 3.17, K = 0.99), however, and ninespine stickleback (Pungitius pungitius) condition was significantly lower in lakes with Arctic charr (K = 0.58) than in lakes without Arctic charr (K = 0.64). Isotope data indicated that pre-smolt and resident Arctic charr may be prey for lake trout and compete with ninespine stickleback. Linear distance metrics applied to isotope data showed that food webs were more compact and isotopically redundant in lakes where Arctic charr were present. Despite this, lake trout populations in lakes with Arctic charr occupied a larger isotope space and showed greater inter-individual isotope differences. Anadromous Arctic charr appear to affect ecology and feeding of sympatric freshwater species, but effects are more subtle than those seen for semelparous anadromous species.     

Behavioural Divergence in Allopatric and Sympatric Gerbil Species (Rodentia: Gerbillinae)

Southern African gerbils comprise 3 genera, each genus represented by morphologically- and ecologically-similar species. All species are monomorphic, with social systems varying from asocial (Desmodillus auricularis) to colonial (Tatera species). This study compares the behaviour patterns of an allopatric species, T. afra, 2 sympatric species, T. leucogaster and T. brantsii, and a species of a different genus, D. auricularis which is sympatric with T. leucogaster and T. brantsii. Interactions between males and females of the same species were staged and quantified in terms of the frequencies of each of 23 behavioural acts. D. auricularis performed 2 acts, namely “sidle” and “fight” which have not been identified in Gerbillurus or Tatera interactions. Sequences of behaviour were similar in all species, and involved females moving away from males, which followed, sniffed the anogenital region and attempted to mount the females. Females responded by presenting, if receptive, or agonistic behaviour such as aggressive or upright postures. Exploration of the terrarium accounted for a large proportion of the behaviour during the 20 min encounter, and watching the opponent also occurred frequently. Discriminant function analysis successfully separated all 4 species on the basis of behaviour frequencies. Individuals were assigned to the correct species with an accuracy of 80%, indicating that each species exhibits species-specific patterns of behaviour. D. auricularis displayed more agonistic and sexual behaviour and less huddling behaviour than any of the Tatera species. The sympatric species-pair, T. leucogaster and T. brantsii, exhibited more significant difference in behaviour than either of the allopatric species-pairs, T. afra and T. brantsii, and T. afra and T. leucogaster. Divergence in behaviour patterns has occurred in allopatric species, but divergence is more marked in species which are sympatric. It is not known whether divergence between T. leucogaster and T. brantsii occurred during a period of allopatry, or whether divergence has occurred due to selection against hybrids in sympatry.     

The influence of groundwater withdrawal and land use changes on brook charr (<Emphasis Type="Italic">Salvelinus fontinalis</Emphasis>) thermal habitat in two coldwater tributaries in Michigan,U.S.A.

Brook charr (Salvelinus fontinalis) is a sentinel fish species which requires clean, cold water habitats. As such, many jurisdictions in the United States where brook charr are present use this species as an indicator of ecosystem health. In Michigan, groundwater-dominated streams are currently being impacted by increased groundwater withdrawal and land use/land cover changes which alter stream temperatures and their flow, and thus have the potential to significantly influence brook charr production and behavior. We quantified the influence of groundwater withdrawal and land use alteration on thermal habitat availability for brook charr using a groundwater modeling tool that estimated changes in baseflow to a stream segment based on changes to the groundwater system due to groundwater withdrawal and changes in rates of recharge related to landscape changes within a watershed. Projected stream temperature changes were calculated using a stream temperature modeling tool and compared to the range of temperature preferenda for brook charr in order to evaluate the potential impact of policy decisions regarding water extraction and land use/cover changes. The models predicted relatively small changes in both stream baseflow and consequently, stream temperature, with increased groundwater withdrawal rates. Land use/land cover alterations which we analyzed were shown to either mitigate or enhance the loss of brook charr thermal habitat as a result of groundwater withdrawal, depending on its relationship to recharge dynamics. This study emphasizes the importance of collaboration between water, land, and fisheries managers to ensure brook charr population viability, productivity, and sustainability in the face of environmental change, increasing water use and development in the watershed.     

Production of brook charr and ouananiche in a large rapid,tributary of the Caniapiscau River,northern Quebec

Synopsis The age structures of brook charr (Salvelinus fontinalis) and ouananiche (Salmo salar) stocks inhabiting a large rapid the river Méo, tributary to the Caniapiscau River were used to compare population stability and production of these species in north central Quebec. The brook chart stock was stable whereas ouananiche showed considerable variation in year class strength. Stock estimates were not significantly different for the two species although the brook charr estimate was 1.5 that of the ouananiche. Production estimates differed by a greater margin because of different growth patterns. Brook chair production was estimated at 19.4 kg ha⁻¹ yr⁻¹. Above age 2+ it was 11.4 kg ha⁻¹ yr⁻¹ which compares with 4.8 kg ha⁻¹ yr⁻¹ for the same age groups of ouananiche.     

Electrocommunication behaviour during social interactions in two species of pulse‐type weakly electric fishes (Mormyridae)

This study compares electrocommunication behaviour in groups of freely swimming weakly electric fishes of two species, Marcusenius altisambesi and Mormyrus rume. Animals emitted variable temporal sequences of stereotyped electric organ discharges (EOD) that served as communication signals. While the waveform of individual signals remained constant, the inter‐discharge interval (IDI) patterns conveyed situation‐specific information. Both species showed different types of group behaviour, e.g. they engaged in collective (group) foraging. The results show that in each species, during different behavioural conditions (resting, foraging and agonistic encounters), certain situation‐specific IDI patterns occurred. In both species, neighbouring fishes swimming closely together interacted electrically by going in and out of synchronization episodes, i.e. periods of temporally correlated EOD production. These often resulted in echo responses between neighbours. During group foraging, fishes often signalled in a repetitive fixed order (fixed‐order signalling). During foraging, EOD emission rates of M. altisambesi were higher and more regular than those of M. rume. The two species also differed in the quantity of group behaviours with M. altisambesi being more social than M. rume, which was reflected in the lack of specific agonistic IDI patterns, more fixed‐order signalling and more communal resting behaviour in M. altisambesi.     

Water temperature, light intensity and zooplankton density and the feeding activity of juvenile brook charr (Salvelinus fontinalis)

SUMMARY 1. The objective of this study was to evaluate the effects of zooplankton biomass (as a measure of density), fish biomass, light intensity and water temperature on the attack rate and swimming characteristics (i.e. swimming speed and angle of turn) of juvenile (1+) brook charr (Salvelinus fontinalis) in field enclosures. We used a portable underwater camera system in a series of pelagic enclosures to quantify the feeding behaviour of brook charr over a gradient of natural conditions. 2. In simple linear or non‐linear regression models we found (i) that attack rate and angle of turn were positively related to water temperature, (ii) that attack rate and swimming speed were positively related to zooplankton biomass and light intensity and (iii) that attack rate was positively related to swimming speed. In multiple regression models, fish biomass, light intensity and variance of the angle of turn accounted for 87% of the variation in attack rate. Light intensity and water temperature accounted for 86% of the variation in swimming speed. Fish gut fullness and attack rate accounted for 83% of the variation in the variance of the angle of turn executed by fish. 3. The increase in the number of attacks as zooplankton biomass increases conforms to the general positive functional response observed in other fish species. Our results also support the hypothesis that swimming speed increases with prey biomass. We did not observe a plateau in attack rate as zooplankton biomass increased. As our experiments were performed under natural biotic and abiotic conditions, factors other than zooplankton biomass might affect or limit this response, such as water temperature and light intensity. 4. Because zooplankton biomass was correlated with water temperature and light intensity, it was not possible to evaluate the independent contribution of these factors on the attack rate and swimming characteristics (swimming speeds and angle of turn) of brook charr. However, this study highlighted the impact of these factors on the feeding behaviour of juvenile brook charr when feeding in the pelagic habitat under natural conditions, and their importance in future models of optimal foraging and fish habitat quality.     

Genetic Diversity and Hybridisation between Native and Introduced Salmonidae Fishes in a Swedish Alpine Lake

Understanding the processes underlying diversification can aid in formulating appropriate conservation management plans that help maintain the evolutionary potential of taxa, particularly under human-induced activities and climate change. Here we assessed the microsatellite genetic diversity and structure of three salmonid species, two native (Arctic charr, Salvelinus alpinus and brown trout, Salmo trutta) and one introduced (brook charr, Salvelinus fontinalis), from an alpine lake in sub-arctic Sweden, Lake Ånn. The genetic diversity of the three species was similar and sufficiently high from a conservation genetics perspective: corrected total heterozygosity, H’_T = 0.54, 0.66, 0.60 and allelic richness, A_R = 4.93, 5.53 and 5.26 for Arctic charr, brown trout and brook charr, respectively. There were indications of elevated inbreeding coefficients in brown trout (G_IS = 0.144) and brook charr (G_IS = 0.129) although sibling relationships were likely a confounding factor, as a high proportion of siblings were observed in all species within and among sampling locations. Overall genetic structure differed between species, Fst = 0.01, 0.02 and 0.04 in Arctic charr, brown trout and brook charr respectively, and there was differentiation at only a few specific locations. There was clear evidence of hybridisation between the native Arctic charr and the introduced brook charr, with 6% of individuals being hybrids, all of which were sampled in tributary streams. The ecological and evolutionary consequences of the observed hybridisation are priorities for further research and the conservation of the evolutionary potential of native salmonid species.     

Characterization of Charr Chromosomes Using Fluorescence in Situ Hybridization

The chromosomal locations of several families of tandem repetitive DNA sequences and the 5S rDNA were determined using fluorescence in situ hybridization (FISH) in the five North American charr species: Salvelinus namaycush, S. fontinalis, S. alpinus, S. malma, and S. confluentus. The pattern of hybridization of three centromeric repetitive sequences previously isolated from S. namaycush and S. alpinus was unique in each species. Dual-color FISH experiments showed that in several species many of the centromeres had the EcoRI-DraI family in addition to either the AluI-RsaI type A or type B families. The EcoRI-DraI family which was found only at the centromeres of acrocentric chromosomes in S. namaycush, S. fontinalis and S. malma was also found at centromeres of selected metacentrics in S. alpinus (one pair) and S. confluentus (four pairs) whose chromosomes have undergone additional centric fusions compared to the other species. The locations of 5S rDNA sequences were different in each species except for the two most closely related (S. alpinus and S. malma). Two whole-arm chromosome paint probes, one specific for the short and the other for the long arm of the lake charr sex chromosomes, hybridize to the same chromosome pair in all species. Results with other paint probes suggest that independent centric fusions have occurred in S. alpinus and S. confluentus which is consistent with the phylogenetic tree obtained previously for Salvelinus with cytogenetic and DNA data.