Development of a large-scale juvenile density model to inform the assessment and management of Atlantic salmon (Salmo salar) populations in Scotland

Malcolm, I. A.; Millidine, K. J.; Glover, R. S.; Jackson, Faye; Millar, Colin P.; Fryer, R. J.

doi:10.1016/j.ecolind.2018.09.005

Cited by 14 publications

(21 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(2019) and Malcolm et al . (, ) have indicated positive trends in p over time. In this study, year reflected temporal trends in p that could not be explained by the available covariates but could reflect undocumented improvements in equipment or user training.…”

Section: Discussionmentioning

confidence: 94%

“…Previous studies have illustrated the importance of incorporating estimates of capture probability in S. salar assessments based on fish abundance (Malcolm et al ., ; Malcolm et al ., ; Millar et al ., ). This study demonstrates the additional risks of using uncalibrated single‐pass or timed‐electrofishing data to assess temporal trends in fish abundance.…”

Section: Discussionmentioning

confidence: 99%

“…The study did not explore potential trends in p that could introduce systematic bias over time, probably because the underlying dataset was collected over only 6 years, compared with the 50 year dataset analysed in this study. It is clear that in the case of longer time series, there is a need for regular (preferably annual) calibration of p (Malcolm et al ., ), although specific requirements in terms of sample size would depend on the availability of pre‐existing multi‐pass data and consistency of trends among sampling locations. Importantly, this study also suggests that it would not be possible to perform a post hoc correction of single pass electrofishing data where there were no comparable multi‐pass data for the same time period.…”

Section: Discussionmentioning

confidence: 99%

“…The electrofishing data in this paper were collected during a period of declining adult returns and juvenile production and had capture probabilities that were high and increased over time ( §3.1). However, a wide range of scenarios is possible including stable or increasing abundances and declining or low levels of capture probability (Malcolm et al, 2019b). The effect of changes in capture probability on estimated trends in abundance from uncalibrated data can be explored theoretically through the following stylised model.…”

Section: Bias In Trends In Abundance From Uncalibrated Datamentioning

confidence: 99%

“…Equation 15). Although the data underpinning this study were collected by an organisation that has a high p compared with many other organisations in Scotland (Malcolm et al, 2019b;Millar et al, 2016), changes in fry and parr abundance over a 50 year period would still be positively biased by c.…”

Section: Trends In Fork Lengthmentioning

confidence: 99%

See 4 more Smart Citations

These are not the trends you are looking for: poorly calibrated single‐pass electrofishing data can bias estimates of trends in fish abundance

Glover

Fryer

Soulsby

et al. 2019

Journal of Fish Biology

Self Cite

View full text Add to dashboard Cite

There is increasing interest in the potential of single‐pass and timed electrofishing to assess status and trends in fish populations. However, where capture probability varies over time, there is a risk that uncalibrated electrofishing data could fail to detect, or provide biased estimates of trends. This study analysed a long‐term electrofishing dataset collected over 50 years in an intensively studied catchment where egg deposition and emigrant production declined by c. 82% and 35% over the same time. The electrofishing data were used to illustrate the effects of changing capture probability on estimated trends in juvenile Atlantic salmon Salmo salar abundance. Temporal variability in capture probability was modelled. Trends in abundance were then estimated from uncalibrated single‐pass electrofishing count data and compared with estimates from data calibrated for capture probability. The calibrated data revealed significant declines in S. salar fry (age 0) and parr (age ≥ 1) abundance. However, the trend estimates from the uncalibrated data were positively biased and not significant. Exploration of alternative (realistic) scenarios with different trends in true abundance and capture probability suggests that uncalibrated electrofishing data can provide very misleading estimates of trends. The problem is exacerbated in data where capture probability is low. It is recommended that single‐pass and timed electrofishing methods should not be used to assess trends in fish populations without regular (annual) calibration.

show abstract

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Bias In Trends In Abundance From Uncalibrated Datamentioning

confidence: 99%

Section: Trends In Fork Lengthmentioning

confidence: 99%

See 3 more Smart Citations

These are not the trends you are looking for: poorly calibrated single‐pass electrofishing data can bias estimates of trends in fish abundance

Glover

Fryer

Soulsby

et al. 2019

Journal of Fish Biology

Self Cite

View full text Add to dashboard Cite

show abstract

Quantifying the relative importance of stock level, river temperature and discharge on the abundance of juvenile Atlantic salmon (Salmo salar)

et al. 2020

Self Cite

View full text Add to dashboard Cite

Fisheries scientists need to understand the relationships between river temperature, discharge and production of juvenile salmonids to inform evidence‐based management and regulation of rivers and to understand the potential effects of climate change. These relationships can be determined by characterising interannual variability in abundance and environmental conditions from long‐term monitoring data and assessing their inter‐relationships. Two major challenges are (1) the requirement to separate the relative effects of stock level and environment which both affect interannual variability in abundance and (2) obtaining long‐term environmental time‐series that do not suffer from temporal biases. This study built on recent advances in hydrological, river‐temperature and juvenile salmonid modelling to investigate the influence of temperature and discharge on interannual variability in Atlantic salmon (Salmo salar) fry (age: 0 years) and parr (age: 1 year) production. The study used a unique long‐term dataset (>50 years) with detailed age‐differentiated census data collected for multiple life‐stages. The study shows that most of the interannual variability in recruitment was explained by stock level. Discharge had a comparatively small effect on fry recruitment, but a greater effect than artificial stocking. Discharge had no discernible effect on parr recruitment. Temperature had no effect on recruitment of either life‐stage. This study suggests that salmon are well adapted to current environmental variability in natural upland rivers in Scotland, but reductions in discharge during spawning and emergence could negatively affect fry recruitment with consequences for regulation of river flows. The study highlights the importance of high‐quality census data for accurately determining the effects of environmental variability on recruitment.

show abstract

A deterministic river temperature model to prioritize management of riparian woodlands to reduce summer maximum river temperatures

Jackson

Hannah

Ouellet

et al. 2021

Hydrological Processes

Self Cite

View full text Add to dashboard Cite

show abstract

Development of a large-scale juvenile density model to inform the assessment and management of Atlantic salmon (Salmo salar) populations in Scotland

Cited by 14 publications

References 54 publications

These are not the trends you are looking for: poorly calibrated single‐pass electrofishing data can bias estimates of trends in fish abundance

These are not the trends you are looking for: poorly calibrated single‐pass electrofishing data can bias estimates of trends in fish abundance

Quantifying the relative importance of stock level, river temperature and discharge on the abundance of juvenile Atlantic salmon (Salmo salar)

A deterministic river temperature model to prioritize management of riparian woodlands to reduce summer maximum river temperatures

Contact Info

Product

Resources

About