Winter biology of stream fishes.
Our knowledge of the winter behaviour and ecology of fishes in rivers is largely based on research with salmonids (Cunjak 1988a, 1996; Cunjak & Power 1986a; Heggenes et al. 1995, 1999; Linnansaari et al. 2008,2009) with relatively little work on other species (Cunjak 1986; Cunjak & Power 1986b; Keeler et al. 2007). Generally, salmonids tend to select habitats with abundant in-stream cover where energy expenditure is minimized but where food is available and there is refuge from adverse physical conditions (Cunjak & Power 1986b, 1987a; Cunjak et al. 1998; Linnansaari et al 2008). Energetically, it appears that species lose most of their fat reserves in early winter coincident with acclimation to declining temperatures (Cunjak 1988b; Cunjak & Power 1987b; Cunjak et al. 1987). Location of suitable habitat may require significant in-stream movement.
Cunjak & Randall (1993) were the first to show that salmon parr moved significant distances in ice-covered streams. That study preceded subsequent work on movements by adult, post-spawned Atlantic salmon (Komadina-Douthwright et al. 1997; Caissie et al 1997) that documented moves >30 km, often into tidal water, perhaps in response to ice (Cunjak & Caissie 1994; Cunjak et al. 1998). Non-mobile stages (i.e. eggs) and sedentary fishes (e.g. cottids) are especially susceptible to severe physical disturbances such as those caused by mid-winter ice break-up and scour (Cunjak et al. 1998; Edwards & Cunjak 2006).
Based on recent technological advancements in my lab using passive integrated transponder (PIT) technology (Coucherousset et al. 2005; Linnansaari et al. 2007; Linnansaari & Cunjak 2007) it is now possible to track tagged individuals beneath an ice cover with minimal disturbance, and understand winter habitat selection and movement patterns (Roussel et al 2004; Linnansaari et al. 2009). In most of Canada and northern Eurasia where winter is the dominant season, understanding environmental complexities (hydraulics, thermal dynamics, ice) and the habitat requirements of aquatic biota are essential for conservation and successful resource management (Cunjak 1996; Cunjak et al. 1998; Linnansaari et al. 2008, 2009).
Assessing anthropogenic impacts to riverine biota.
This applied aspect of my research program is centred around the Catamaran Brook Research Project (CBRP), a long-term (20 y), multi-disciplinary project focused on measuring Atlantic salmon population dynamics, fish ecology and ecosystem processes, and for quantifying forestry impacts in a sub-basin of the Miramichi River (Cunjak et al. 1993; Cunjak 1995). I initiated the project in 1990, and continue to direct the research. Timber harvest representing <10% of the area caused no significant changes in basin-wide hydrologic parameters (e.g., annual water yield, seasonal runoff). However, increases in summer stormflow peaks were detected at the sub-basin scale where >23% of a catchment was harvested (Caissie et al. 2002). No discernible impact to the abundance of fish populations (Cunjak et al. 2004; Edwards & Cunjak 2006), egg survival (Flanagan 2003) or aquatic fungi (Garnett et al 2000) has been detected at whole basin or stream reach scales.
The project structure encourages short-term studies such as in-stream flow models (Bourgeois et al. 1996), stable isotope analyses of food webs (Doucett et al. 1996), biology of non-salmonids (Reebs et al. 1995, 2008; Edwards & Cunjak 2006), hydro-graph separation (Caissie et al. 1995), woody debris dynamics (Clement et al. 2008) and developing new techniques (e.g., PIT) to study movements and growth (Roussel et al. 2000; Coucherousset et al. 2005; Linnansaari & Cunjak 2007; Sigourney et al. 2008). To date, 15 universities and colleges have been involved; >100 scientific papers and 35 theses written. Techniques and knowledge gained from the CBRP have been used to study salmonid ecology in France (Charles et al. 2004), Norway (Linnansaari et al 2009) and the USA (Sigourney et al. 2008), and to investigate the impacts to incubating eggs from agriculture-based sedimentation in PEI (Cunjak et al. 2002) and from flow regulation in NB (Flanagan 2003MSc) and BC (Long 2006MSc).
Natural environmental stressors influencing fish behaviour and survival in rivers.
The influence of elevated water temperature on the behaviour and physiology of juvenile Atlantic salmon has been studied in rivers over a broad latitudinal range (McCormick et al. 1999; Lund et al. 2002) and has relevance for salmon survival according to predicted climate changes for the region. Recently, Breau et al (2007) used our PIT system to identify aggregation behaviour and habitat use of coolwater refugia by wild salmon parr in the Miramichi River when water temperatures were >24oC. Ultimately, such research will provide better information for improving salmon management and river conservation (Dodson et al. 1998) and is the basis for a recent NSERC CRD research grant. This research aims to establish the importance of density-independent (environmental) variables in regulating stream fish populations in contrast to density-dependent factors (Imre et al. 2005, 2009).
My earlier research showed that declining temperatures in early winter were physiologically and energetically demanding (Cunjak 1988; Cunjak & Power 1987) and necessitated adaptive behavioural strategies to survive seasonal stressors (Cunjak & Power 1986, Cunjak 1996). Cunjak et al. (1998) used hydro-climatological data in a case study of salmon population dynamics to link egg survival and winter streamflow, and the effect of ice break-up on survival of salmon. Related research has linked natural flood events to changes in habitat quality (St. Hilaire et al. 2005) and growth (Arndt et al. 2002). In Newfoundland, we demonstrated how different temperature regimes influenced the timing of fry drift and smolt movement and growth (Bujold & Cunjak 2004; Dietrich et al. 2004).