In this research article, the authors utilize a comprehensive dataset spanning 22 years and encompassing various disciplines. The data is derived from Catamaran Brook, a river within the North-Watch study area located in Miramichi, Canada. The primary objective of the study is to explore the intricate relationship between Atlantic salmon and the hydrological factors inherent to the Miramichi basin, considering the boreal-temperate Canadian climate.
The hydrology of Catamaran Brook exhibits distinct patterns characterized by two periods of high flow (spring and autumn) and two periods of low flow (summer and winter), as illustrated in Figure 2. While high flow events can occur throughout the year, the peak flows are typically observed during the spring snowmelt freshet. Within the dataset spanning over 20 years, the maximum recorded discharge of 13 m3/s was documented twice, specifically on May 3, 1991, and December 14, 2010.
To delineate the high and low flow periods, a 30-day discharge running mean was employed. As a result, the winter low flow period typically takes place around February 21 (day 52), while the spring flood occurs approximately on April 28 (day 118), as depicted in Figure 2. The summer low flow period is observed around August 30 (day 242), while the autumn high flow period transpires around November 11 (day 315).
“Fig. 2. Streamflow characteristics of Catamaran Brook (1990–2010) showing high and low flow periods. The dark line shows mean discharge whereas the light lines show both minimum and maximum values”.
The monitoring activities conducted for Atlantic Salmon include the following:
Fish-counting fence: A fish-counting fence near the stream mouth was operated annually from May to November between 1990 and 2008. Its purpose was to enumerate and measure all fish entering and leaving Catamaran Brook. Atlantic salmon smolts, typically three years old when emigrating, were recorded. On average, approximately 972 smolts were estimated to emigrate from Catamaran Brook each year. Additionally, around 110 adult salmon entered Catamaran Brook each autumn for spawning.
Annual electrofishing surveys: Electrofishing surveys were conducted in 26 to 32 study sites from the headwaters to the lower reaches of the brook. These surveys took place in the summer and autumn from 1990 to 2010. A multiple-sweep depletion method was employed to estimate fish abundance, distribution, species diversity, and density. The same sites were surveyed each year, with the size of each site determined by the entire habitat type it represented (such as pool, riffle, run, flat). Consequently, the wetted area of a site varied across years based on discharge conditions during sampling. A total of 17 fish species have been captured in Catamaran Brook, with Atlantic salmon being the most abundant and having the highest biomass. Each year, approximately 100,000 wild juvenile salmon (of all ages) rear in Catamaran Brook.
Daily estimates of emigrating salmon fry: Counts of emigrating salmon fry were obtained from 2 to 4 drift-traps set in the stream mouth from late May to early July, covering the years 1994 to 2002. It is estimated that between 7,000 and 33,000 salmon fry emigrate from the brook each spring
Winter conditions can significantly impact stream fishes at the individual, population, and community levels. The survival of Atlantic salmon eggs, which represent a non-mobile stage existing entirely during the cold season, is particularly influenced by winter physical conditions. Based on linear regression analysis of the initial six years of data collected from Catamaran Brook, the results suggest a positive relationship between the survival of Atlantic salmon eggs (until the summer fry stage) and winter streamflow. This relationship was further supported by an extended research period of 11 years, with available egg survival data showing a significant positive correlation. It should be noted, however, that extreme high winter flows associated with ice-break-up events can also act as major physical disturbances in rivers, potentially causing significant mortality among stream fishes.
“Fig. 4. Relationship between winter discharge (1 December to 31 March) and A) salmon egg survival, 1990–2000, B) % change in autumn-to-summer density of juvenile Atlantic salmon (composite of all age classes), 1990–2002, in the Lower Reach of Catamaran Brook, and C) estimated smolt totals, 1990–2008, in Catamaran Brook. Note that the winter 95/95 data point was removed from all three plots because it was an ice-affected anomaly”.
Previous studies have suggested a potential link between winter streamflow and the juvenile (parr) stage of Atlantic salmon. During winter, juvenile salmon exhibit photonegative behavior and seek shelter beneath coarse substrates during the daytime. Since individual shelters are rarely shared, the availability of suitable daytime sheltering locations becomes a limited resource controlled by stream discharge and its direct impact on the total wetted streambed and habitat availability. This hypothesis finds support in seasonal electrofishing data spanning 13 years (1990-2002) collected from 8 to 10 sites in the Lower Reach of Catamaran Brook, where sample sizes for different age-classes are sufficient for analysis. Figure 4b demonstrates that the percent reduction in average density of salmon parr from autumn to the following summer is least when winter streamflow is high. Conversely, the density change declines significantly as average winter flow decreases.
The destructive consequences of mid-winter mechanical ice break-ups on the survival of juvenile salmon and other fish species are highly unpredictable but have significant implications for fish community dynamics. These "rare" or extreme flow events may become more frequent in the future, as predicted under various climate-warming scenarios.
In this research article, the authors utilize a comprehensive dataset spanning 22 years and encompassing various disciplines. The data is derived from Catamaran Brook, a river within the North-Watch study area located in Miramichi, Canada. The primary objective of the study is to explore the intricate relationship between Atlantic salmon and the hydrological factors inherent to the Miramichi basin, considering the boreal-temperate Canadian climate. The hydrology of Catamaran Brook exhibits distinct patterns characterized by two periods of high flow (spring and autumn) and two periods of low flow (summer and winter), as illustrated in Figure 2. While high flow events can occur throughout the year, the peak flows are typically observed during the spring snowmelt freshet. Within the dataset spanning over 20 years, the maximum recorded discharge of 13 m3/s was documented twice, specifically on May 3, 1991, and December 14, 2010. To delineate the high and low flow periods, a 30-day discharge running mean was employed. As a result, the winter low flow period typically takes place around February 21 (day 52), while the spring flood occurs approximately on April 28 (day 118), as depicted in Figure 2. The summer low flow period is observed around August 30 (day 242), while the autumn high flow period transpires around November 11 (day 315).
“Fig. 2. Streamflow characteristics of Catamaran Brook (1990–2010) showing high and low flow periods. The dark line shows mean discharge whereas the light lines show both minimum and maximum values”.
The monitoring activities conducted for Atlantic Salmon include the following:
Winter conditions can significantly impact stream fishes at the individual, population, and community levels. The survival of Atlantic salmon eggs, which represent a non-mobile stage existing entirely during the cold season, is particularly influenced by winter physical conditions. Based on linear regression analysis of the initial six years of data collected from Catamaran Brook, the results suggest a positive relationship between the survival of Atlantic salmon eggs (until the summer fry stage) and winter streamflow. This relationship was further supported by an extended research period of 11 years, with available egg survival data showing a significant positive correlation. It should be noted, however, that extreme high winter flows associated with ice-break-up events can also act as major physical disturbances in rivers, potentially causing significant mortality among stream fishes.
“Fig. 4. Relationship between winter discharge (1 December to 31 March) and A) salmon egg survival, 1990–2000, B) % change in autumn-to-summer density of juvenile Atlantic salmon (composite of all age classes), 1990–2002, in the Lower Reach of Catamaran Brook, and C) estimated smolt totals, 1990–2008, in Catamaran Brook. Note that the winter 95/95 data point was removed from all three plots because it was an ice-affected anomaly”.
(A) Egg Survival :
CODE: https://github.com/Salmon-Ecology-Library/Functional-Relationships/blob/main/code/Cunjak%202013.R DATA: https://github.com/Salmon-Ecology-Library/Functional-Relationships/blob/main/data/cunjak_et_al_2013.csv PLOT: https://github.com/Salmon-Ecology-Library/Functional-Relationships/blob/main/plots/cunjak_et_al_2013.png
Previous studies have suggested a potential link between winter streamflow and the juvenile (parr) stage of Atlantic salmon. During winter, juvenile salmon exhibit photonegative behavior and seek shelter beneath coarse substrates during the daytime. Since individual shelters are rarely shared, the availability of suitable daytime sheltering locations becomes a limited resource controlled by stream discharge and its direct impact on the total wetted streambed and habitat availability. This hypothesis finds support in seasonal electrofishing data spanning 13 years (1990-2002) collected from 8 to 10 sites in the Lower Reach of Catamaran Brook, where sample sizes for different age-classes are sufficient for analysis. Figure 4b demonstrates that the percent reduction in average density of salmon parr from autumn to the following summer is least when winter streamflow is high. Conversely, the density change declines significantly as average winter flow decreases.
The destructive consequences of mid-winter mechanical ice break-ups on the survival of juvenile salmon and other fish species are highly unpredictable but have significant implications for fish community dynamics. These "rare" or extreme flow events may become more frequent in the future, as predicted under various climate-warming scenarios.