Long-term trends in age-specific recruitment of sockeye salmon (Oncorhynchus nerka) in a changing environment

2004 ◽  
Vol 61 (12) ◽  
pp. 2455-2470 ◽  
Author(s):  
Carrie A Holt ◽  
Randall M Peterman
Keyword(s):  
Kalman Filter ◽  
Sockeye Salmon ◽  
Large Scale ◽  
Oncorhynchus Nerka ◽  
Age At Maturity ◽  
Age Class ◽  
Sibling Models ◽  
Long Term Trends ◽  
Forecasting Errors

Sibling – age-class (sibling) models, which relate abundance of one age-class of adult sockeye salmon (Oncorhynchus nerka) to abundance of the previous age-class in the previous year, are commonly used to forecast abundance 1 year ahead. Standard sibling models assume constant parameters over time. However, many sockeye salmon populations have shown temporal changes in age-at-maturity. We therefore developed a new Kalman filter sibling model that allowed for time-varying parameters. We found considerable evidence for long-term trends in parameters of sibling models for 24 sockeye salmon stocks in British Columbia and Alaska; most trends reflected increasing age-at-maturity. In a retrospective analysis, the Kalman filter forecasting models reduced mean-squared forecasting errors compared with standard sibling models in 29%–39% of the stocks depending on the age-class. The Kalman filter models also had mean percent biases closer to zero than the standard models for 54%–94% of the stocks. Parameters of these sibling models are positively correlated among stocks from different regions, suggesting that large-scale factors (e.g., competition among stocks for limited marine prey) may be important drivers of long-term changes in age-at-maturity schedules in sockeye salmon.

Uncertainties in population dynamics and outcomes of regulations in sockeye salmon (Oncorhynchus nerka) fisheries: implications for management

2008 ◽  
Vol 65 (7) ◽  
pp. 1459-1474 ◽  
Author(s):  
Carrie A. Holt ◽  
Randall M. Peterman
Keyword(s):  
Sockeye Salmon ◽  
Management Practices ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Simulation Models ◽  
Age At Maturity ◽  
Sources Of Uncertainty ◽  
Future Assessment ◽  
Long Term Trends

Fisheries managers usually have multiple options available but are often unclear on how to choose among them owing to uncertainties in biological and management components of fisheries systems. We evaluated the performance of current and possible future assessment and management practices for sockeye salmon ( Oncorhynchus nerka ) in British Columbia and Alaska by using a computer model that included major biological and management components and their associated uncertainties (interannual variability in recruitment, age-at-maturity, and sex ratio, as well as uncertainty in observations of spawner abundances, forecasts of recruitment, and outcomes from implementing management regulations). One option for management practices that we evaluated was designed to make the forecasting model more realistic by accounting for long-term trends in age-at-maturity. A second option was designed to reduce deviations between management targets and actual or “realized” harvest levels. We found that compared with practices that ignore those sources of uncertainty, the second option produced annual catches that were higher, on average, and less variable over time while maintaining recruitment above critical conservation levels. Contrary to our expectations, the first modification did not result in comparable benefits. Our results demonstrate the value of using simulation models to evaluate potential modifications to Pacific salmon management practices.

Patterns of covariation in length and age at maturity of British Columbia and Alaska sockeye salmon (Oncorhynchus nerka) stocks

1999 ◽  
Vol 56 (6) ◽  
pp. 1046-1057 ◽  
Author(s):  
Brian J Pyper ◽  
Randall M Peterman ◽  
Michael F Lapointe ◽  
Carl J Walters
Keyword(s):  
British Columbia ◽  
Survival Rate ◽  
Body Length ◽  
Sockeye Salmon ◽  
Large Scale ◽  
Oncorhynchus Nerka ◽  
Regional Scale ◽  
Survival Rates ◽  
Age At Maturity ◽  
Environmental Processes

We examined patterns of covariation in age-specific adult body length and in mean age at maturity among 31 sockeye salmon (Oncorhynchus nerka) stocks from western Alaska to southern British Columbia. Positive covariation in body length was prevalent across stocks of all regions (e.g., correlations (r) from 0.2 to 0.6), suggesting either that growth periods critical to final body length of sockeye salmon occur while ocean distributions of these stocks overlap or that large-scale environmental processes influence these stocks similarly while they do not overlap. We also found stronger covariation among body length of stocks within regions (r from 0.4 to 0.7), indicating that unique regional-scale processes were also important. Mean age at maturity also showed positive covariation both among and within regions, but correlations were weaker than those for length. We also examined patterns of covariation between length and mean age at maturity and between these variables and survival rate. Although length and mean age at maturity were negatively correlated, there was little evidence of covariation between these variables and survival rate, suggesting that environmental processes that influence marine survival rates of sockeye salmon are largely different from those affecting size and age at maturity.

Use of the Kalman filter to reconstruct historical trends in productivity of Bristol Bay sockeye salmon (Oncorhynchus nerka)

2003 ◽  
Vol 60 (7) ◽  
pp. 809-824 ◽  
Author(s):  
Randall M Peterman ◽  
Brian J Pyper ◽  
Brice W MacGregor
Keyword(s):  
Kalman Filter ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Time Varying ◽  
Historical Trends ◽  
Bristol Bay ◽  
Fish Stocks ◽  
The Past ◽  
Better Than

Fisheries scientists and managers are concerned about potential long-term, persistent changes in productivity of fish stocks that might result from future climatic changes or other alterations in aquatic systems. However, because of large natural variability and measurement error in fisheries data, such changes are usually difficult to detect until long after they occur. Previous research using numerous Monte Carlo simulation trials showed that a Kalman filter performed better than standard estimation techniques in detecting such trends in a timely manner. Therefore, we used historical data along with a Kalman filter that included a time-varying Ricker a parameter to reconstruct changes in productivity (recruits per spawner at a given spawner abundance) of eight Bristol Bay, Alaska, sockeye salmon (Oncorhynchus nerka) stocks over the past 40 years. Productivity generally increased for most stocks but varied widely for others and dramatically decreased in another. Such large changes in productivity are important for management. They greatly affected optimal spawner abundances and optimal exploitation rates, suggesting that in the future, scientists should consider using models with time-varying productivity parameters.

Large-scale, long-term trends in British river macroinvertebrates

2012 ◽  
Vol 18 (7) ◽  
pp. 2184-2194 ◽  
Author(s):  
Ian P. Vaughan ◽  
Steve J. Ormerod
Keyword(s):  
Large Scale ◽  
Long Term Trends

scholarly journals Reply to “Comment on ‘Bias Correction, Quantile Mapping, and Downscaling: Revisiting the Inflation Issue’”

2014 ◽  
Vol 27 (4) ◽  
pp. 1821-1825 ◽  
Author(s):  
Douglas Maraun
Keyword(s):  
Large Scale ◽  
Weather Forecasting ◽  
Small Scale ◽  
Quantile Mapping ◽  
Spatiotemporal Structure ◽  
Weather Forecasts ◽  
Long Term Trends ◽  
Climate Signals ◽  
Local Variability

Abstract In his comment, G. Bürger criticizes the conclusion that inflation of trends by quantile mapping is an adverse effect. He assumes that the argument would be “based on the belief that long-term trends and along with them future climate signals are to be large scale.” His line of argument reverts to the so-called inflated regression. Here it is shown, by referring to previous critiques of inflation and standard literature in statistical modeling as well as weather forecasting, that inflation is built upon a wrong understanding of explained versus unexplained variability and prediction versus simulation. It is argued that a sound regression-based downscaling can in principle introduce systematic local variability in long-term trends, but inflation systematically deteriorates the representation of trends. Furthermore, it is demonstrated that inflation by construction deteriorates weather forecasts and is not able to correctly simulate small-scale spatiotemporal structure.

A Comparison of Sockeye Salmon Catches at Rivers Inlet and Skeena River, B.C., with Particular Reference to Age at Maturity

1958 ◽  
Vol 15 (3) ◽  
pp. 331-354 ◽  
Author(s):  
Harold Godfrey
Keyword(s):  
Sockeye Salmon ◽  
Environmental Influence ◽  
Size Variation ◽  
Age At Maturity ◽  
River Systems ◽  
Age Composition ◽  
Age Class ◽  
Skeena River ◽  
Two Populations

Age composition, size and sex data for sockeye salmon catches (1912–1954) at Rivers Inlet and Skeena River, B.C. were compared. For both river systems there were indications of 4- and 5-year cycles of abundance among the 4- and 5-year-old fish, respectively; but the two populations were not necessarily in phase. Tests for correlation between the numbers of parental and offspring fish strongly suggested the dominance of hereditary over environmental influence in determining age at maturity. The two stocks showed much similarity in annual size variation, among each sex and age-class.

Thermal limits and ocean migrations of sockeye salmon (Oncorhynchus nerka): long-term consequences of global warming

1998 ◽  
Vol 55 (4) ◽  
pp. 937-948 ◽  
Author(s):  
D W Welch ◽  
Y Ishida ◽  
K Nagasawa
Keyword(s):  
Pacific Ocean ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Step Function ◽  
Thermal Limits ◽  
The North ◽  
The Pacific ◽  
Different Temperatures ◽  
The Pacific Ocean

Ocean surveys show that extremely sharp thermal boundaries have limited the distribution of sockeye salmon (Oncorhynchus nerka) in the Pacific Ocean and adjacent seas over the past 40 years. These limits are expressed as a step function, with the temperature defining the position of the thermal limit varying between months in an annual cycle. The sharpness of the edge, the different temperatures that define the position of the edge in different months of the year, and the subtle variations in temperature with area or decade for a given month probably all occur because temperature-dependent metabolic rates exceed energy intake from feeding over large regions of otherwise acceptable habitat in the North Pacific. At current rates of greenhouse gas emissions, predicted temperature increases under a doubled CO2 climate are large enough to shift the position of the thermal limits into the Bering Sea by the middle of the next century. Such an increase would potentially exclude sockeye salmon from the entire Pacific Ocean and severely restrict the overall area of the marine environment that would support growth.

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