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Papers by Richard Cunjak

Journal of Fish Biology, Jun 13, 2022

Deformities in fish embryos are important for their survival in later life stages. However, a con... more Deformities in fish embryos are important for their survival in later life stages. However, a consistent way to refer to and classify salmonid embryo deformities does not exist. Expanding on reports of alevin deformities, we developed a classification tool for distinguishing the deformities observed in a collection of preserved Atlantic salmon (Salmo salar) embryos. Deformities were classified based on the deformed body part and a qualitative subtype. This classification tool uses external morphology, requires minimal equipment and can be applied from the first appearance of optic vesicles to hatch.

HAL (Le Centre pour la Communication Scientifique Directe), Aug 13, 2006

Blackwell Science Ltd eBooks, Nov 26, 2007

ABSTRACT IntroductionThe geographic regionOverview of forestry regulations in Atlantic CanadaThe ... more ABSTRACT IntroductionThe geographic regionOverview of forestry regulations in Atlantic CanadaThe Catamaran Brook Habitat Research ProjectThe Copper Lake Buffer Zone StudySummary and recommendations

Canadian Journal of Zoology, 2017

Individuals travelling through landscapes may use the presence of conspecifics to evaluate habita... more Individuals travelling through landscapes may use the presence of conspecifics to evaluate habitat quality. Juvenile Atlantic salmon Salmo salar (L. 1758) are usually territorial and exhibit some degree of density-dependent regulation in wild populations. They are also vulnerable to heat stress and may need to locate a thermal refuge to offset metabolic costs above certain temperature thresholds. During July 2010, a heat wave resulted in water temperatures in the Miramichi River system exceeding 30º C. During this period, salmon parr were observed aggregating in cold-water refugia at densities several orders of magnitude greater than usual. We tested whether groups of wild-caught salmon parr held at high densities (160 m-2) would have an attractant effect on free-swimming parr at three sites differing in temperature between 16.5-24° C. While neither temperature nor site influenced the number of parr we observed, there were significantly more parr in close proximity (< 1 m) to the artificial aggregations than to the controls. These results suggest that social cues from high density aggregations of conspecifics during extreme temperature events may advertise the location of thermal refugia to others. Understanding how heat-stressed salmon locate refugia may prove valuable to ongoing conservation efforts given the likelihood of increasingly frequent and extreme high-temperature events.

Journal of Fish Biology, Aug 1, 2017

Carbon and nitrogen stable-isotope ratios were compared of fin and muscle tissue from 15 fish spe... more Carbon and nitrogen stable-isotope ratios were compared of fin and muscle tissue from 15 fish species collected from seven headwater rivers in eastern and western Thailand. In addition, two-source stable-isotope mixing models were used to derive estimates of each fish's reliance on allochthonous and autochthonous energy based on fin and muscle tissues. Across the dataset, fish fin was enriched in 13 C relative to muscle by c. 1•5‰. Variation in 15 N between tissues was below statistically significant levels. Estimates of autochthonous resource use calculated from fin tissue were on average 15% greater than those calculated from muscle. Linear mixed-effects models indicated that inter-tissue variation in estimates of resource use was predominantly related to inter-tissue variation in 13 C. Fish fin is a credible and desirable alternative to tissues such as muscle or liver which require destructive sampling of fishes. Care must be taken, however, when estimating resource use or interpreting previous estimates of resource use derived from different tissues.

Journal of Fish Biology, Dec 12, 2017

Changes in the isotopic composition (13 C and 15 N) in biofilm, macro-invertebrates and resident ... more Changes in the isotopic composition (13 C and 15 N) in biofilm, macro-invertebrates and resident salmonids were used to characterize temporal dynamics of marine derived nutrients (MDNs) incorporation between stream reaches with and without MDN inputs. Five Atlantic rivers were chosen to represent contrasting MDN subsidies: four rivers with considerable numbers of anadromous fishes; one river with little MDN input. Rainbow smelt Osmerus mordax, alewife Alosa pseudoharengus, sea lamprey Petromyzon marinus and Atlantic salmon Salmo salar, were the primary anadromous species for the sampled rivers. Regardless of the spatial resolution or the pathway of incorporation, annual nutrient pulses from spawning anadromous fishes had a positive effect on isotopic enrichment at all trophic levels (biofilm, 1•2-5•4‰; macro-invertebrates, 0•0-6•8‰; fish, 1•2-2•6‰). Community-wide niche space shifted toward the marine-nutrient source, but the total ecological niche space did not always increase with MDN inputs. The time-integrated marine-nutrient resource contribution to the diet of S. salar parr and brook trout Salvelinus fontinalis ranged between 16•3 and 36•0% during anadromous fish-spawning periods. The high degree of spatio-temporal heterogeneity in marine-nutrient subsidies from anadromous fishes lead to both direct and indirect pathways of MDN incorporation into stream food webs. This suggests that organisms at many trophic levels derive a substantial proportion of their energy from marine resources when present. The current trend of declining anadromous fish populations means fewer nutrient-rich marine subsidies being delivered to rivers, diminishing the ability to sustain elevated riverine productivity.

Journal of Fish Biology, Sep 1, 1986

Brook trout, Salvelinus fontinalis, were sampled from two sites on the Koksoak River system in no... more Brook trout, Salvelinus fontinalis, were sampled from two sites on the Koksoak River system in northern Quebec to determine seasonal physiological changes in hematology and proximate body composition. Water content increased over the winter at both sites, whereas body lipids decreased. The relationship was most pronounced in the anadromous trout of the Caniapiscau River compared with the smaller resident trout of a tributary stream. Serum protein levels decreased significantly over the winter with the greatest depletion being realized by Caniapiscau River trout. Despite the severity of the winter stream environment in the north, the extent of depletion was similar to that encountered in temperate latitudes, suggesting compensatory physiological mechanisms within the species’ latitudinal range. By mid‐summer both populations had restored their depleted energy stores, especially the anadromous trout which accumulated the greatest amount of lipids after feeding in the estuary. Serum glucose levels were maintained at high levels during the winter, then declined in the summer. Differences between the two sites for the degree of physiological change are discussed in relation to specific overwintering strategies and life history variation.

Hydrobiologia, Nov 23, 2012

Freshwater Biology, Apr 1, 2019

1. Embryos of many valued salmonid species incubate in the hyporheic zone of boreal streams over ... more 1. Embryos of many valued salmonid species incubate in the hyporheic zone of boreal streams over winter. Influence of individual winter-related environmental variables on salmonid embryo success has been previously investigated. However, how multiple variables act together to influence embryo incubation remains poorly understood. 2. Using a naturally spawning population of Atlantic salmon (Salmo salar) in the Miramichi River basin (New Brunswick, Canada), we related variation in the abiotic embryo incubation habitat in different streams (spatial) and over the course of two winters (temporal) to embryo mortality between fertilisation and hatch. Over two years (2013-2014 and 2014-2015), we introduced fertilised eggs to six simulated salmon redds in each of three riffles in each of five active spawning reaches (n redds = 90) with a range of hyporheic conditions. Embryo mortality was quantified at an early sampling event (March; pre-freshet and during late embryonic development) and a late sampling event (May; post-freshet and post-hatch). We extracted 22 abiotic predictor variables for statistical analyses from continuous records of hyporheic environmental conditions, collected for the duration of the incubation period in each study reach. 3. Through partial least squares regression analyses, 37.6% of the total variation in mortality was explained by the predictor variables. Each group of predictor variables explained similar proportions of variation (water temperature: 8.4%, water level: 7.4%, dissolved oxygen: 7.1%, ice conditions: 7.2%, and substrate characteristics: 7.5%), which suggests that mortality is influenced by multiple interacting abiotic conditions, rather than a single variable in isolation, and that the factors contributing to ideal salmonid incubation habitats are complex and interconnected. 4. Our research highlights the value of a multi-faceted research perspective and provides a baseline from which future changes in threatened salmonid populations can be measured and compared in an effort to identify relevant species-or population-specific differences.

Canadian Journal of Zoology, Nov 1, 1988

Young Arctic char (Salvelinus alpinus) were observed in a stream tank located on the bank of the ... more Young Arctic char (Salvelinus alpinus) were observed in a stream tank located on the bank of the Koroc river, northern Quebec. Early in the summer, char were most active from dusk to dawn, and at midday, mainly over gravel or sand. Some nocturnal feeding activity was evident. As the summer progressed, this diel periodicity in activity became less pronounced; char exhibited increasing diurnal activity, most of it over rubble substrata. Char preferred rubble for resting throughout the summer. Invertebrate drift decreased from July through August so that, although fish were active more of the time, the rate of feeding during periods of activity declined.

Journal of Fish Biology, Oct 1, 2004

Atlantic salmon Salmo salar fry and parr were subjected to 5 min of forced activity and the subse... more Atlantic salmon Salmo salar fry and parr were subjected to 5 min of forced activity and the subsequent changes in oxygen consumption and ammonia excretion rates were evaluated over a 24 h period. In a second experiment, individual Atlantic salmon fry and parr were freeze‐clamped in liquid nitrogen, before, immediately following a 5 min activity period, or after periods of recovery up to 2 h. Samples were analysed for whole body phosphocreatine (PCr), ATP and lactate. Five minutes of forced activity resulted in significant increases in both oxygen consumption and ammonia excretion rates. Changes in the oxygen consumption rates were greater in the parr compared with the fry. In contrast, the post‐exercise ammonia excretion rates were nearly twice as high for the fry compared with the parr. Exercise also caused a marked decrease in PCr levels (c. 47 and 65% in fry and parr, respectively), no change in ATP levels and a significant increase in lactate levels in Atlantic salmon fry and parr. Recovery of PCr occurred quickly (between 15 and 30 min) in fry and parr. Although the post‐activity levels of lactate were lower in fry (c. 3 μmol g−1) compared with parr (c. 14 μmol g−1), lactate levels returned to control levels within 60 min in fry, but it took >2 h for this metabolite to recover in parr. Compared with parr, these findings show that Atlantic salmon fry possess a reduced anaerobic capacity, and these results are consistent with the theoretical and experimental evidence that smaller fish support burst swimming through aerobic processes.

Ecosystems, Jun 1, 2003

Rainbow smelt (Osmerus mordax) is a recent invader to the lakes of the Hudson Bay drainage in nor... more Rainbow smelt (Osmerus mordax) is a recent invader to the lakes of the Hudson Bay drainage in northwestern Ontario, Canada. In some systems, the invasion has been linked to an increase in mercury (Hg) concentration in native predatory fish. This increase may be due to the fact that rainbow smelt are trophically elevated and thus accumulate more Hg than native forage fish species. To test this hypothesis, we compared the trophic positions and Hg concentrations of rainbow smelt and native forage fish in a series of smelt-invaded and reference lakes in northwestern Ontario. A comparison of forage fish ␦ 15 N (an index of trophic position) between the smelt-invaded and reference lakes indicated that rainbow smelt moved into a trophic niche that was unoccupied prior to their arrival. Relationships between ␦ 15 N and body size and between Hg concentration and body size differed among the forage species. This indicates that the response of predator Hg concentrations to smelt invasion depends on both the species and size composition of their preversus post-invasion diet. At a standardized body mass of 10 g, rainbow smelt were significantly trophically elevated relative to most native forage species, but they did not have significantly higher muscle Hg concentrations. Relationships between Hg concentration and ␦ 15 N were weak, both within and among forage fish species. This study shows that trophic elevation on a fine scale (within the forage fish community) may not result in increased contaminant bioaccumulation. It further challenges the general assumptions of food web theory and contaminant bioaccumulation.

Freshwater Science, Sep 1, 2015

ABSTRACT

Canadian Journal of Zoology, Jul 1, 1995

Baited and unbaited minnow traps were set in Catamaran Brook and the Little Southwest Miramichi R... more Baited and unbaited minnow traps were set in Catamaran Brook and the Little Southwest Miramichi River, New Brunswick, and checked every 4 h to determine the diel activity pattern of four species of stream-dwelling fish (threespine stickleback (Gasterosteus aculeatus), juvenile white sucker (Catostomus commersoni), blacknose dace (Rhinichthys atratulus), and lake chub (Couesius plumbeus)). Secondary goals were to determine whether the presence of bait inside minnow traps affected the diel patterns of captures and to compare patterns of lake chub captures in minnow traps with movement through a nearby fish-counting fence. All fish except lake chubs were diurnal, although strict diurnality was less obvious when bait was present in the traps. Lake chubs, which are normally diurnal in the laboratory, were captured mostly near dawn or dusk in unbaited traps, throughout the day in baited traps, and mostly at night at the fish-counting fence. We infer that chubs are active mostly at dawn or dusk, except (i) when strong food cues are present, in which case their activity may extend into the day, and (ii) during the spawning migration, when they move mostly at night. Relative inactivity by chubs during the day may be caused by the presence of piscivorous birds such as kingfishers and common mergansers, whose hunting efficiency may be higher under brighter light.

Canadian Journal of Zoology, Oct 1, 2010

Ecologically related polymorphisms occur in many northern freshwater fish populations and are dis... more Ecologically related polymorphisms occur in many northern freshwater fish populations and are distinguished by alternate phenotypes consistently associated with differential use of habitats or resources. We tested for polymorphism in walleye (Sander vitreus (Mitchill, 1818)) in the south basin of Lake Winnipeg, where evidence suggests that ''dwarf'' and ''normal'' growth forms may coexist. Morphometric comparisons of these growth forms at similar size demonstrated significant differences in the relative sizes of head, snout, eye, and mouth, collectively suggesting dwarf individuals inhabit a more benthic niche than normal morphs. Stable isotope analysis did not support this morphometric interpretation, however, as d 13 C and d 15 N isotope signatures were similar between similar-sized individuals of both forms, but differed from those of large normal walleye. Walleye from Lake Winnipeg do not seem to exhibit a simple resource polymorphism where different ecotypes are associated with alternate habitats throughout their life history, nor do they exhibit characteristics of a simple mating polymorphism. We suggest the walleye from Lake Winnipeg represent two growth forms sharing a common juvenile habitat followed by the normal form shifting into an alternative adult niche. Résumé : Des polymorphismes de nature écologique se produisent dans plusieurs populations boréales de poissons d'eau douce et se caractérisent par le fait que les différents phénotypes sont associés à une utilisation particulière des habitats ou des ressources. Nous avons vérifié le polymorphisme chez le doré (Sander vitreus (Mitchill, 1818)) dans le bassin sud du lac Winnipeg, où il y a des indications de coexistence de formes de croissance « naines » et « normales ». Des comparaisons morphométriques de ces formes de croissance à des tailles semblables montrent des différences significatives dans les tailles relatives de la tête, du museau, de l'oeil et de la bouche qui, considérées conjointement, laissent croire que les individus nains occupent une niche plus benthique que les individus normaux. Une analyse des isotopes stables n'appuie, cependant, pas cette interprétation morphométrique puisque les signatures isotopiques d 13 C et d 15 N sont semblables chez les individus de même taille des deux formes, mais elles diffèrent de celles des dorés normaux de grande taille. Les dorés du lac Winnipeg ne semblent pas posséder un simple polymorphisme des ressources dans lequel les différents écotypes sont associés à des habitats différents pendant tout leur cycle biologique; ils n'ont pas non plus les caractéristiques d'un simple polymorphisme d'accouplement. Nous croyons que les dorés du lac Winnipeg comprennent deux formes de croissance qui partagent un habitat commun durant leur période juvénile et qu'ensuite la forme normale va occuper une niche adulte différente.

Ecology of Freshwater Fish, Mar 1, 1999

– Habitat is important in determining stream carrying capacity and population density in young At... more – Habitat is important in determining stream carrying capacity and population density in young Atlantic salmon and brown trout. We review stream habitat selection studies and relate results to variable and interacting abiotic and biotic factors. The importance of spatial and temporal scales are often overlooked. Different physical variables may influence fish position choice at different spatial scales. Temporally variable water flows and temperatures are pervasive environmental factors in streams that affect behavior and habitat selection. The more frequently measured abiotic variables are water depth, water velocity (or stream gradient), substrate particle size, and cover. Summer daytime, feeding habitats of Atlantic salmon are size structured. Larger parr (>7 cm) have a wider spatial niche than small parr. Selected snout water velocities are consistently low (3–25 cm. s−1). Mean (or surface) water velocities are in the preferred range of 30–50 cm. s−1, and usually in combination with coarse substratum (16–256 mm). However, salmon parr demonstrate flexibility with respect to preferred water velocity, depending on fish size, intra‐ and interspecific competition, and predation risk. Water depth is less important, except in small streams. In large rivers and lakes a variety of water depths are used by salmon parr. Summer daytime, feeding habitat of brown trout is also characterized by a narrow selection of low snout water velocities. Habitat use is size‐structured, which appears to be mainly a result of intraspecific competition. The small trout parr (<7 cm) are abundant in the shallow swift stream areas (<20–30 cm depths, 10–50 cm. s−1 water velocities) with cobble substrates. The larger trout have increasingly strong preferences for deep‐slow stream areas, in particular pools. Water depth is considered the most important habitat variable for brown trout. Spatial niche overlap is considerable where the two species are sympatric, although young Atlantic salmon tend to be distributed more in the faster flowing and shallow habitats compared with trout. Habitat use by salmon is restricted through interspecific competition with the more aggressive brown trout (interactive segregation). However, subtle innate differences in behavior at an early stage also indicate selective segregation. Seasonal changes in habitat use related to water temperatures occur in both species. In winter, they have a stronger preference for cover and shelter, and may seek shelter in the streambed and/or deeper water. At low temperatures (higher latitudes), there are also marked shifts in habitat use during day and night as the fish become nocturnal. Passive sheltering in the substrate or aggregating in deep‐slow stream areas is the typical daytime behavior. While active at night, the fish move to more exposed holding positions primarily on but also above the substrate. Diurnal changes in habitat use take place also in summer; brown trout may utilize a wider spatial niche at night with more fish occupying the shallow‐slow stream areas. Brown trout and young Atlantic salmon also exhibit a flexible response to variability in streamflows, wherein habitat selection may change considerably. Important topics in need of further research include: influence of spatial measurement scale, effects of temporal and spatial variability in habitat conditions on habitat selection, effects of interactive competition and trophic interactions (predation risk) on habitat selection, influence of extreme natural events on habitat selection use or suitability (floods, ice formation and jams, droughts), and individual variation in habitat use or behavior.

Cold Regions Science and Technology, Sep 1, 2017

Anchor ice is a type of river ice that occurs on river beds in supercooled, turbulent water. Its ... more Anchor ice is a type of river ice that occurs on river beds in supercooled, turbulent water. Its formation and release can affect the water level, discharge, bed roughness, and morphology of rivers in cold regions. Despite these important effects, the number of anchor ice events documented in the literature has historically remained small because of the ephemeral nature of anchor ice. The purpose of this study was to determine the hydrometeorological factors that control anchor ice formation, release, and morphology, as well as to determine the impact of hydropower regulation on the anchor ice regime of small streams. In total, 161 anchor ice formation and release events were examined in 2 regulated streams and 1 unregulated stream in north-central New Brunswick, Canada, using hourly or half-hourly ice observations and nearcontinuously measured environmental variables. The day after formation, anchor ice accumulations either completely released, stayed in place to form multi-day accumulations, or were incorporated into the surface ice cover of the stream. 98% of anchor ice accumulations completely released on days when there was a net heat gain to the water surface and the air temperature was >-15 °C, indicating a strong thermal control on anchor ice release. The release of one accumulation could not be attributed to either thermal effects or to the 'plucking' of the substrate, suggesting the need for further study of the strength of ice-pebble bonds. Finally, the regulated and unregulated streams had different ice regimes: the regulated stream experienced a greater number of anchor ice events, which occurred with a different seasonal pattern compared to the unregulated streams.

Journal of Animal Ecology, May 23, 2005

While density-dependent mortality and emigration have been widely reported in stream salmonid pop... more While density-dependent mortality and emigration have been widely reported in stream salmonid populations, density-dependent growth is less frequently detected. A recent study suggests that density-dependent growth in stream salmonids occurs at low densities, whereas density-dependent mortality and emigration occur at high densities. 2. To test the hypothesis that density-dependent growth occurs primarily at low rather than at high densities, we examined the relationship between average fork length and population density of young-of-the-year (YOY) Atlantic salmon at the end of the growing season using a 10-year data set collected on Catamaran Brook, New Brunswick. We tested whether (1) average body size decreases with increasing density; (2) the effect of density on average body size is greatest at low densities; (3) growth rate will decrease most rapidly at low effective densities [ Σ (fork length) 2 ]; (4) density-dependent growth is weaker over space than over time; and (5) the strength of density-dependent growth increases with the size of the habitat unit (i.e. spatial scale) when compared within years, but not between years. 3. There was a strong negative relationship between the average body size and population density of YOY Atlantic salmon in the autumn, which was best described by a negative power curve. Similarly, a negative power curve provided the best fit to the relationship between average body size and effective density. Most of the variation in average body size was explained by YOY density, with year, location and the density of 1+ and 2+ salmon accounting for a minor proportion of the variation. 4. The strength of density-dependent growth did not differ significantly between comparisons over space vs. time. Consistent with the last prediction, the strength of densitydependent growth increased with increasing spatial scale in the within-year, but not in the between-year comparisons. 5. The effect of density on growth was strongest at low population densities, too low to expect interference competition. Stream salmonid populations may be regulated by two mechanisms: density-dependent growth via exploitative competition at low densities, perhaps mediated by predator-induced reductions in drift rate, and density-dependent mortality and emigration via interference competition at high densities.

Journal of Fish Biology, May 29, 2019

We used stable isotopes of carbon, hydrogen and nitrogen to quantify the trophic position and res... more We used stable isotopes of carbon, hydrogen and nitrogen to quantify the trophic position and resource use of larval sea lamprey Petromyzon marinus, four benthic macroinvertebrate functional feeding guilds (scraper, shredder, collector and predator) and other fishes in three