Long-term changes in rearing habitat and downstream movement by juvenile sockeye salmon (Oncorhynchus nerka) in an interconnected Alaska lake system

2008 ◽  
Vol 17 (3) ◽  
pp. 443-454 ◽  
Author(s):  
P. A. H. Westley ◽  
R. Hilborn ◽  
T. P. Quinn ◽  
G. T. Ruggerone ◽  
D. E. Schindler
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Lake System ◽  
Long Term Changes ◽  
Downstream Movement

Factors Affecting Rainbow Trout (Salmo gairdneri) Predation on Migrant Fry of Sockeye Salmon (Oncorhynchus nerka)

1976 ◽  
Vol 33 (1) ◽  
pp. 19-24 ◽  
Author(s):  
R. M. Ginetz ◽  
P. A. Larkin
Keyword(s):  
Rainbow Trout ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Development Stage ◽  
Salmo Gairdneri ◽  
Factors Affecting ◽  
Light Intensities ◽  
Salmon Fry ◽  
Lower Stream ◽  
Downstream Movement

Predation of rainbow trout (Salmo gairdneri) on migrant sockeye salmon (Oncorhynchus nerka) fry in experimental streams was higher on fry at an earlier development stage, in moonlight by contrast to cloudy night light intensities, at lesser turbidities, and at lower stream velocities. At dusk light intensities, from.05 to.30 ft-c, mortality from predation was inversely related to light intensity. The longer the period of exposure of fry to naturally declining light intensities prior to downstream movement, the lower was the loss to predators. Exposure of predators to high light intensities prior to the downstream movement of fry resulted in decreased fry mortality. Fry that had survived exposure to predators in an experimental stream 1 and 2 days previous were less vulnerable to predation than "naive" fry. Successive exposures further decreased the loss to predation. Fry enumerated at a counting fence suffered less predation than fry not enumerated. Experienced fry moved downstream more rapidly than naive fry.In laboratory aquaria, experienced fry formed compact schools prior to and in response to stimuli, while naive fry formed loose schools or did not school. Experienced fry were less active in responding to stimuli. Enumerated fry resembled experienced fry; nonenumerated fry resembled naive fry.Various techniques of enhancing sockeye salmon fry survival during downstream migration are suggested by these results.

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.

Long-term zooplankton responses to nutrient and consumer subsidies arising from migratory sockeye salmon (Oncorhynchus nerka)

Oikos ◽  
2011 ◽  
Vol 120 (9) ◽  
pp. 1317-1326 ◽  
Author(s):  
Guangjie Chen ◽  
Daniel T. Selbie ◽  
Bruce P. Finney ◽  
Daniel E. Schindler ◽  
Lynda Bunting ◽  
...  
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka

Identification of Sockeye Salmon (Oncorhynchus nerka) Stocks in the Stikine River Based on Egg Size Measurements

1985 ◽  
Vol 42 (11) ◽  
pp. 1696-1701 ◽  
Author(s):  
P. C. Craig
Keyword(s):  
Body Weight ◽  
Egg Size ◽  
Sockeye Salmon ◽  
Pattern Analysis ◽  
Oncorhynchus Nerka ◽  
Egg Mass ◽  
Stock Identification ◽  
Mass Measurements ◽  
Lake System ◽  
Identification Method

The Stikine River in southeastern Alaska supports two principal stocks of sockeye salmon (Oncorhynchus nerka). An expedient means of separating these stocks when they enter freshwater is by egg size and egg mass measurements. Eggs of sockeye that spawn in the Tahltan Lake system are smaller than sockeye spawning elsewhere in the Stikine drainage, a difference supported by an independent stock identification method (scale pattern analysis). Tahltan females have only slightly developed ovaries (1–3% of body weight) and small eggs (2.0–3.5 mm) when they enter freshwater; they enter the river earlier (2–3 wk) and travel farther upstream to spawn than non-Tahltan sockeye. The latter group has more developed ovaries (5–16% of body weight) and larger eggs (3.5–6.2 mm) when they enter the river. Thus, an assessment of egg sizes of sockeye caught in the river can provide on-site information about stock composition and run timing. These data and escapement counts at Tahltan Lake indicate that the total escapement to the Stikine in 1983 was 61 000 to 71 000 sockeye of which 45–53% were Tahltan stock and 47–55% spawned eleswhere in the drainage.

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.

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.

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.

Early marine growth of juvenile Fraser River sockeye salmon (Oncorhynchus nerka) in relation to juvenile pink (Oncorhynchus gorbuscha) and sockeye salmon abundance

2012 ◽  
Vol 69 (9) ◽  
pp. 1499-1512 ◽  
Author(s):  
Skip McKinnell ◽  
Maxine Reichardt
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Pink Salmon ◽  
Oncorhynchus Gorbuscha ◽  
First Year ◽  
Fraser River ◽  
Pink Salmon Oncorhynchus Gorbuscha ◽  
Strait Of Georgia ◽  
Average Survival

Mortality of salmon in the ocean is considered to be greatest during the first few months and that its magnitude is an inverse of growth. First year marine growth (M1) in two Fraser River sockeye salmon ( Oncorhynchus nerka ) populations was positively correlated, reflecting a shared oceanic experience as postsmolts. M1 declined abruptly in both populations after 1977, corresponding to a well-documented change in climate. The reduction in average M1 was not accompanied by a detectable reduction in average survival. In both populations, M1 was significantly greater in even years when juvenile pink salmon ( Oncorhynchus gorbuscha ) are abundant in the Strait of Georgia, suggesting that interspecific competition there has little effect on M1. All correlations of M1 with regional pink salmon or sockeye salmon abundances, lagged to align ocean entry years, were negative, but few (pink) or none (sockeye) were statistically significant. The negative correlations were due to the long-term changes (pink salmon abundance increasing, sockeye M1 smaller). Odd year dominance of juvenile pink salmon in northern British Columbia, Canada, is persistent and corresponds with the biennial pattern of M1 variation in Fraser River sockeye salmon and may be the source of the significant odd–even year line effect on M1.

Density and Distribution of Young Sockeye Salmon (Oncorhynchus nerka) throughout a Multibasin Lake System

1958 ◽  
Vol 15 (5) ◽  
pp. 961-982 ◽  
Author(s):  
W. E. Johnson
Keyword(s):  
Population Density ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Catch Per Unit Effort ◽  
Lake System ◽  
Unit Effort ◽  
Limited Dispersal ◽  
Discrete Populations

Estimates of density (based on catch per unit effort with tow nets) of fingerling sockeye salmon populations in a large (174 sq. mile) multibasin lake system were carried out during 1955, 1956 and 1957. Density and distribution of fingerling sockeye throughout the lake system are related to density and distribution of the spawning parent populations. Discrete populations associated with discrete basins point to a limited dispersal as a result of the multibasin nature of the lake system. In one example, higher population density appears to result in greater dispersal.

A 500-year context for the recent surge in sockeye salmon (Oncorhynchus nerka) abundance in the Alagnak River, Alaska

2006 ◽  
Vol 63 (7) ◽  
pp. 1439-1444 ◽  
Author(s):  
Daniel E Schindler ◽  
Peter R Leavitt ◽  
Susan P Johnson ◽  
Curtis S Brock
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Mixing Model ◽  
Population Variability ◽  
Transient Phenomenon ◽  
Bristol Bay ◽  
Lower Abundance

Returns of sockeye salmon (Oncorhynchus nerka) to the Alagnak River in Bristol Bay, Alaska, during the last 3 years were unprecedented in the last five decades. Enumerated run sizes averaged about 1 million fish from 1955 to 2002 but surged unexpectedly to average 5.4 million fish in 2003–2005. These huge returns currently pose a challenge to management of Bristol Bay sockeye for several reasons, including that it is unclear whether the recent surge in abundance is a new phenomenon or if it has arisen as part of interdecadal population variability. To answer this question we used changes in lake sedimentary δ15N coupled with an isotope-mixing model to estimate historical abundances of sockeye salmon populations in this ecosystem. Our analyses show that periods of high salmon abundance have occurred every ~100 years during the last five centuries, interspersed by prolonged periods of substantially lower abundance. We suggest that the recent high returns are an expression of the long-term variability that is characteristic of this stock and will be a relatively transient phenomenon.

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