Aquatic and Riparian Habitat Assessment
Several species of wildlife that warrant specific attention occur in Pollett watershed: Atlantic salmon, American eels, and wood turtles. Of these, the locations of documented encounters with salmon and eels are presented in (Figure 3-10). Due to their smaller home range, encounters with wood turtles are considered to be sensitive information, and so are being withheld here. Atlantic salmon (Salmo salar) Inner Bay of Fundy (iBoF) populations were listed as endangered under the Species at Risk Act in 2003 (DFO, 2010; SARA Registry, 2013a), and the species is considered to be extirpated from the Petitcodiac River system, except for those introduced in stocking programs (AMEC, 2005).
Figure 3-10: Locations of Atlantic salmon and American eels within the Pollett River watershed.
American eels (Anguilla rostrata) were designated as “Special Concern” by COSEWIC in 2006 (COSEWIC, 2006). Their status was re-examined and raised to “Threatened” in May 2012 (COSEWIC, 2014). This species is being considered for listing under the federal Species at Risk Act, but currently it has no status (SARA Registry, 2013b). Wood turtles (Glyptemys insculpta) were designated as “Special Concern” by COSEWIC in 1996 which was raised to “Threatened” in 2007 (COSEWIC 2007; COSEWIC 2011). This species is listed as “threatened” under the Species at Risk Act (SARA Registry, 2012). Guidelines for projects in areas with these species are in Appendix A.
The decline in numbers of iBoF salmon is a marked contrast to the abundance described by early settlers. Though numbers of this species had been decreasing for some time (Elson 1962) construction of the Moncton to Riverview causeway in 1968 eliminated fish passage for adult salmon and smolts and effectively (but for ongoing intervention) extirpated the species from a river system that represented 20% of the total iBoF population (Locke, et al. 2003).
The survival and development of fry released along the Pollett in 2009, 2011 and 2012 were monitored by annual electrofishing at the release sites, and operation of a Rotary Screw Trap (RST) or “smolt wheel” near the mouth of the river during the smolt runs in 2011, 2012, 2013, and 2014 ; with plans for additional work in 2015. Release sites (Figure 3-10) included locations upstream of Gordon Falls, where quality habitat exists, even though there is some question if salmon would be unable to access it naturally. The decision was made to use that portion of the river as well since such areas could provide nursery habitat for juveniles (who then migrate out as smolts), despite them possibly being unable to return that far upstream as adults. Electrofishing in 2013 captured 28 salmon parr on the Pollett. The RST was operated 7 days per week that year, from April 30th to June 25th (except for 5 days lost to high water), and caught 172 smolts. In 2014 only 6 parr were found by electrofishing, which was not surprising as the last release of salmon fry was in 2012. This decline was consistent with lack of natural salmon spawning in the river. The RST was operated 7 days per week in 2014, from May 8th to June 9th (except for 1 day due to low water), There were 351 smolts caught during their downstream migration either in the RST or nearby fyke nets.
American eels were encountered at numerous sites while electrofishing, and in the RST. The RST data has catch, length and weight available; however since eels were not the target of the electrofishing effort (which was sampling salmon) their presence or absence was not specifically quantified or documented at these locations. However, a reasonable interpretation of the observations is that at most sites they were present more often than not.
In the decades that the causeway gates were closed downstream on the Petitcodiac, eels had more success than salmon did navigating the fishway and accessing the upper reaches of the river, such as the Pollett. Aside from that, being catadromous, instead of anadromous like salmon, made the eel population less vulnerable as they are not as dependent upon accessing any given river. Their spawning takes place in the Sargasso Sea, and so young eels already arrive at and reside in different rivers than those in which their parents had lived (COSEWIC, 2006). This allowed for a steady stream of incoming eels, despite the causeway.
The Petitcodiac Watershed Alliance reported observing a wood turtle on a tributary stream while conducting field work in 2009 (Petitcodiac Watershed Alliance 2009). Wood turtles were seen also while Fort Folly Habitat Recovery crews were doing smolt monitoring most years; electrofishing in 2012; and while conducting geomorphic assessments in 2013. Wood turtles were searched for through a series of targeted surveys conducted by the Petitcodiac Watershed Alliance along the Pollett River in 2014. Wood turtles are terrestrial turtles that require forest cover, clean water courses, and access to gravel or sand for nesting.
Water quality on the Pollett was assessed by the Petitcodiac Watershed Alliance as part of their habitat assessment project in 2009 (Petitcodiac Watershed Alliance 2009). During the months of July, August and September they measured Dissolved Oxygen (DO), Conductivity (CON), pH, and Temperature (TEMP) at numerous locations within the watershed. They also maintained a fixed monitoring site near the mouth of the river, a short distance downstream of the site used in subsequent years for the Rotary Screw Trap during the smolt run. Both the basin wide results and those for this monitoring site are presented in Table 3-2.
Table 3-2: Water Quality on the Pollett River in 2009 (Petitcodiac Watershed Alliance 2009)
Across the basin, Dissolved Oxygen readings were taken at 45 different sites and averaged 10 mg/L, which is well within the desired range of 7 to 11 mg/L for streams with cold water fish such as salmon. Conductivity was measured at 50 different locations during this period, and ranged from a low of 27.8 to a high of 55.3 µS, increasing along a gradient from low values high in the watershed to higher values lower in the watershed. Temperature readings were taken 48 times, the lowest being 11.2 °C taken one morning in September and the highest being 21.4 °C in the afternoon of a hot day in July. It is worth noting that the fixed monitoring station got up to 24 °C on day in August. Values for pH were measured 50 times, with little variance. With the exception of the high August temperature recorded at the fixed site, water quality on the river appears to be reasonably good and not a limiting factor for fish.
Rapid Geomorphic Assessment (RGA) and Rapid Stream Assessment (RSAT)
The following is taken from the report prepared by Parish Geomorphic based on the Rapid Geomorphic Assessment (RGA) and Rapid Stream Assessment (RSAT) data collected by Fort Folly Habitat Recovery on the Pollett River, New Brunswick during the summer of 2013. Figure 3-11 depicts the three main assessed reaches divided by their respective sub‐reach ranges. The total length of watercourse assessed was approximately 57 kilometres (km); the entire Pollett River system drains an area of approximately 314 square kilometres (km2).
Figure 3-11: Pollett River watershed and assessed reaches
The RGA and RSAT data were used to determine the geomorphic condition and stability of the assessed sections of the Pollett River. In order to interpret the geomorphic data, the watercourse is highlighted according to sub‐reach stability and dominant geomorphic processes. The geomorphic processes identified were aggradation, degradation, channel widening, and planform adjustment.
Channel aggradation may occur when the sediment load to a river increases (due to natural processes or human activities) and it lacks the capacity to carry it. Piles of sediment in the river can re‐direct flows against the banks, leading to erosion and channel widening.
Some indicators of aggradation include:
- Shallow pool depths
- Abundant sediment deposition on point bars
- Extensive sediment deposition around obstructions, channel constrictions, at upstream ends of tight meander bends, and in the overbank zone
- Most of the channel bed is exposed during typical low flow periods
- High frequency of debris jams
- Coarse gravels, cobbles, and boulders may be embedded with sand/silt and fine gravel
- Soft, unconsolidated bed
- Mid‐channel and lateral bars
Degradation occurs as the river cuts deeper into the land and decreases its gradient. This can occur from a rapid removal of streambed material due to an increase in discharge, water velocity, or a decrease in sediment supply. Bed lowering can move in both an upstream (as a headcut or nick point) and/or downstream direction.
Indicators of degradation include:
- Elevated tree roots
- Bank height increases as you move downstream
- Absence of depositional features such as bars
- Head cutting of the channel bed
- Cut face on bar forms
Channel worn into undisturbed overburden/bedrock
Widening typically follows or occurs in conjunction with aggradation or degradation. With aggradation, banks collapse when flows are forced on the outside, and the river starts to widen. Wide, shallow watercourses have a lower capacity to transport sediment and flows continue to concentrate towards the banks. Widening can also be seen with degradation, as it occurs with an increase in flows or decrease in sediment supply. Widening ultimately occurs because the stream bottom materials eventually become more resistant to erosion(harder to move) by the flowing waters than the materials in the stream banks.
Indicators of widening include:
- Active undermining of bank vegetation on both sides of the channel, and many unstable bank overhangs that have little vegetation holding soils together
- Erosion on both right and left banks in riffle sections
- Recently exposed tree roots
- Fracture lines at the top of banks that appear as cracks parallel to the river, which is
- evidence of landslides and mass failures
- Deposition on mid‐channel bars and shoals
- Urbanization and storm water outfalls leading to higher rate and duration of runoff and channel enlargement typically in smaller watershed with a high percentage (>10%) of impervious surface (urban land use).
These are the changes that can be seen from the air when looking down at the river. The river’s pattern has changed. This can happen because of channel management activities (such as straightening the bends of the river with heavy equipment). Planform changes also occur during floods. When there is no streambank vegetation with roots to hold soil in place, rivers cut new channels in the weak part of the bank during high water. Planform adjustments typically are responses to aggradation, degradation, or widening geomorphic phases.
Indicators of planform change include:
- Flood chutes, which are longitudinal depressions where the stream has straightened and cut a more direct route usually across the inside of a meander bend
- Channel avulsions, where the stream has suddenly abandoned a previous channel alignment
- Change or loss in bed form structure, sometimes resulting in a mix of plane bed and pool‐riffle forms
- Island formation and/or multiple channels
- Additional large deposition and scour features in the channel length typically occupied by a single riffle/pool sequence (may result from the lateral extension of meander bends)
- Thalweg not lined up with planform. In meandering streams, the thalweg typically travels from the outside of a meander bend to the outside of the next meander bend.
- During planform adjustments, the thalweg may not line up with this pattern.
Watercourse Channel Stability
The stream geomorphic condition is a key piece of data obtained from the Rapid Geomorphic Assessment. This is based on the degree of departure of the channel from its reference stream type and is evaluated by the magnitude and combination of adjustments underway in the stream channel. Upon completion of the field inspection, indicators were tallied by category and used to calculate an overall reach stability index. There are three stability classes that refer to a relative sensitivity to altered sediment and flow regimes:
In Regime: The channel morphology is within a range of variance for streams of similar hydrographic characteristics – evidence of instability is isolated or associated with normal river meander propagation processes (considered stable or least sensitive).
Transitional or Stressed: Channel morphology is within the range of variance for streams of similar hydrographic characteristics but the evidence of instability is frequent (considered moderately sensitive).
In Adjustment: Channel morphology is not within the range of variance and evidence of instability is wide spread (considered most sensitive).
The RSAT provides a more qualitative assessment of the overall health and functions of a reach in order to provide a quick assessment of stream conditions and the identification of restoration needs on a watershed scale. This system integrates visual estimates of channel conditions and numerical scoring of stream parameters using six categories:
- Channel Stability
- Erosion and Deposition
- Instream Habitat
- Water Quality
- Riparian Conditions
- Biological Indicators
Once a condition has been assigned a score, these scores are totalled to produce an overall rating that is based on a 50 point scoring system, divided into three classes:
The majority of RSAT classes determined on the Pollett River were in the moderate range with some in a High class of RSAT stability. Figure 3-12 outlines RSAT classes of the Pollett River.
Figure 3-12: Pollett River RSAT classes