Estimated Escapement of Atlantic Salmon (<i>Salmo salar</i>) for Maximum Smolt Production in Rivers of Different Productivity

Symons, Philip E. K.

doi:10.1139/f79-022

Cited by 97 publications

(78 citation statements)

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“…Fish came out of hiding at water temperatures of 6-7°C. Based on Allen's (1969) observations that juvenile salmon growth was slow at temperatures below 7°C, Symons (1979) defined the growing season in a river as the number of days per year in which water temperature reaches or exceeds 7°C. The same definition was used by Evans et al (1985) while working on a river in southwestern Newfoundland.…”

Section: Discussionmentioning

confidence: 99%

Atlantic salmon (Salmo salar) in the regulated River Alta: effects of altered water temperature on parr growth

Jensen

2003

River Research & Apps

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The chief objective of this study was to analyse the effects of altered water temperature, due to the hydropower regulation of the River Alta, on growth of Atlantic salmon parr. The river was developed for hydroelectric purposes in 1987. A 110 m high concrete dam was built in the main river 49 km upstream from the outlet to the sea. The outlet of the power station is located 2.5 km downstream from the dam. The annual regime of water temperature has been altered downstream from the power station because of the regulation. It has decreased 1-2°C during June, July and the first half of August, while it has increased up to 3°C during late summer. During winter, water temperature has increased from 0°C to about 0.3-0.4°C. Atlantic salmon is the predominant fish species in the river. They can penetrate 46 km from the sea, up to the outlet of the power station.In this paper I have studied the relationship between growth of juvenile Atlantic salmon and water temperature in the upper part of the river. At similar temperatures, the growth rate of salmon parr in the River Alta is higher in early summer than later in the growing season. In early summer the salmon grew faster than the maximum rate predicted by a recently published model. Therefore, I adjusted the model to describe growth rates of salmon in early summer (ice break to mid-August), using data derived prior to the hydropower development (1981)(1982)(1983)(1984)(1985)(1986)).The new model proved effective at describing growth rates of fish in early summer following the hydropower development (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996). After development, growth rates decreased during early summer, but increased correspondingly later in the season. There was close agreement between these growth changes and the altered annual regime of river temperature. Overall, only minor changes in annual growth rates have been observed after the hydropower development.

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Section: Discussionmentioning

confidence: 99%

Atlantic salmon (Salmo salar) in the regulated River Alta: effects of altered water temperature on parr growth

Jensen

2003

River Research & Apps

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“…However, these observations were made during the day and it is possible that there was a temperaturedependent switch from diurnal to nocturnal foraging as shown in the laboratory by Fraser, Metcalfe & Thorpe (1993). The lower threshold for growth in the field has been given as 7°C (Symons 1979;Evans, Rice & Chadwick 1985), 6°C (Power 1969), 5·6°C (Lee & Power 1976) and 6·3-7·4°C (Jensen & Johnsen 1986;Jensen, Johnsen & Saksgard 1989). All these values are close to that of 6°C in the present study and it is notable that none of these studies differentiated between spring and autumn temperature thresholds for growth.…”

Section: Discussionmentioning

confidence: 99%

A functional model for maximum growth of Atlantic Salmon parr, Salmo salar, from two populations in northwest England

1997

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1. The chief objective was to develop a functional model for the growth of parr (0+, 1+) of Atlantic Salmon, Salmo salar, from two populations (Rivers Leven and Lune in northwest England), using a model similar to that developed previously for Brown Trout, Salmo trutta. Parr bred from Leven parents were acclimatized to nine fairly constant temperatures (two 0+, two 1+ parr per temperature) in the range 3·8–21·7 °C (variation ± 0·3 at 3·8 °C to ± 1·0 at 21·7 °C). Each fish was kept in a separate tank and fed to satiation on shrimps. The mass and length of each fish was recorded at the start and finish of a growth period of 30 days. Parr (0+, 1+) bred from Lune parents were separated into slow and fast growers, and acclimatized to six very constant temperatures. There were three slow and three fast growers at each of 5·0, 10·0, 15·0 °C for 0+ parr and each of 5·0, 10·0, 13·0, 15·0, 18·0, 20·0 °C for 1+ parr. Procedures were the same as for Leven parr except that the growth period lasted 30 days for the 18 0+ parr and 42 days for the 36 1+ parr. 2. The growth model was an excellent fit (P < 0·001) with no significant differences between parr from the two rivers, fast‐growing parr of different ages (0+, 1+), or fast‐ and slow‐growing 1+ parr. The optimum temperature for the combined data (81 parr) was 15·9 °C with a range for growth of 6·0–22·5 °C. The model failed to fit the data for slow‐growing 0+ Lune parr in experiments from November to February. Growth was reduced in these fish, even though the temperatures were suitable for growth (10, 15°C). 3. The model described approximately the growth of three year‐classes of Atlantic Salmon parr in the River Eden in northwest England. Some of the discrepancies between actual masses and those predicted from the model were consistent and possible reasons for this are discussed.

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“…We ignored survival at the egg-to-fry stages, as the genetic correlations in age-structured populations depend on differences in survival among the reproductive age classes ( Jorde and Ryman 1996). Thus, for nonmature male and female parr, we assumed a constant annual freshwater survival (s fw ) to the smolt stage of 0.38 (median value of estimates for Canadian rivers) (Symons 1979;Evans et al 1984;Myers 1984;Cunjak and Therrien 1998;Locke 1998). The majority of smolts in Newfoundland rivers spend one winter in the ocean before returning to spawn (O'Connell et al 2006a).…”

Section: Methodsmentioning

confidence: 99%

Age Structure, Changing Demography and Effective Population Size in Atlantic Salmon (Salmo salar)

2009

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Effective population size (N e ) is a central evolutionary concept, but its genetic estimation can be significantly complicated by age structure. Here we investigate N e in Atlantic salmon (Salmo salar) populations that have undergone changes in demography and population dynamics, applying four different genetic estimators. For this purpose we use genetic data (14 microsatellite markers) from archived scale samples collected between 1951 and 2004. Through life table simulations we assess the genetic consequences of life history variation on N e . Although variation in reproductive contribution by mature parr affects age structure, we find that its effect on N e estimation may be relatively minor. A comparison of estimator models suggests that even low iteroparity may upwardly bias N e estimates when ignored (semelparity assumed) and should thus empirically be accounted for. Our results indicate that N e may have changed over time in relatively small populations, but otherwise remained stable. Our ability to detect changes in N e in larger populations was, however, likely hindered by sampling limitations. An evaluation of N e estimates in a demographic context suggests that life history diversity, density-dependent factors, and metapopulation dynamics may all affect the genetic stability of these populations.

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Estimated Escapement of Atlantic Salmon (Salmo salar) for Maximum Smolt Production in Rivers of Different Productivity

Cited by 97 publications

References 0 publications

Atlantic salmon (Salmo salar) in the regulated River Alta: effects of altered water temperature on parr growth

Atlantic salmon (Salmo salar) in the regulated River Alta: effects of altered water temperature on parr growth

A functional model for maximum growth of Atlantic Salmon parr, Salmo salar, from two populations in northwest England

Age Structure, Changing Demography and Effective Population Size in Atlantic Salmon (Salmo salar)

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