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.

Effects of Androgens, Estrogens, and Cortisol on the Skin, Stomach, Liver, Pancreas, and Kidney in Gonadectomized Adult Sockeye Salmon (Oncorhynchus nerka)

1971 ◽  
Vol 28 (4) ◽  
pp. 485-490 ◽  
Author(s):  
J. R. McBride ◽  
A. P. van Overbeeke
Keyword(s):  
Islets Of Langerhans ◽  
Sockeye Salmon ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Skin Atrophy ◽  
Histological Changes ◽  
Male And Female ◽  
Liver And Kidney ◽  
Marked Atrophy

A study was made of the histological changes occurring in the skin, stomach, liver, pancreas and kidney of adult gonadectomized male and female sockeye salmon in response to hormone treatments. The males received 11-ketotestosterone, 17α-methyltestosterone or cortisol for 4 or 7 weeks, and the females received estradiol, estradiol cypionate, or cortisol for 8 weeks.In the males, androgen injection evoked a highly significant increase in the thickness of the epidermis, a marked atrophy of the stomach, and a degeneration in the liver and kidney. In the pancreas, the exocrine portion showed characteristics of cytolysis in the acini, whereas the islets of Langerhans were hypertrophied. These changes were generally more pronounced after 7 weeks than after 4 but, in the skin, no further increase in the thickening of the epidermis was noted after the 4th week of treatment. No differences between responses of these tissues to 11-ketotestosterone and 17α-methyltestosterosne were detected.Estrogen administration in the females evoked similar, albeit weaker, responses in the skin, stomach, pancreas, and kidney than those recorded in the androgen-treated males. The liver of the females exhibited the characteristics of a hyperactive organ, which probably reflects estrogen-induced vitellogenesis.The effects of cortisol were similar in both sexes: little, if any, change was noted in the skin; atrophy or degeneration was observed in the stomach, liver, kidney, and in the exocrine portion of the pancreas, and the islets of Langerhans were hypertrophied. The cortisol-induced alterations were not, however, as pronounced as those noted in either the androgen- or estrogen-treated fish.These changes are discussed in relation to the changes observed in normal sexually maturing and reproducing Pacific salmon.

Long term trends in total nitrogen of a vertisol subjected to zero-tillage, nitrogen application and stubble retention

Soil Research ◽  
1992 ◽  
Vol 30 (2) ◽  
pp. 223 ◽  
Author(s):  
RC Dalal
Keyword(s):  
Management Practices ◽  
N Recovery ◽  
Zero Tillage ◽  
Fertilizer N ◽  
Total N ◽  
Leaching Losses ◽  
Stubble Retention ◽  
Long Term Trends ◽  
Apparent N Recovery

The effects of conservation practices, zero-tillage and stubble retention, on long-term trends in total N (0-0.1 m depth) of a Vertisol used mainly for wheat cropping were studied in a semi-arid subtropical environment (28�12'S. and 152�06' E.) in Queensland. Trends in total N content of a Vertisoi (65% clay, pH 7.2) were discerned during a 22-year period of management practices including: zero-tillage (ZT) and conventional tillage (CT); stubble retention (SR) and stubble burning (SB); and fertilizer N application of nil (Nl), 23 kg N ha-1 yr-1 (N2) and 69 kg N ha-1 yr-1 (N3). Soil total N (0-0.1 m) declined under all treatments at an overall rate of 25f 2 kg N ha-1 yr-1 although after 22 years soil under ZT, SR and N3 treatments still contained higher soil total N than under CT, SB and N1 treatments. Apparent fertilizer N recovery in the soil-plant system was poor (34 64%) under CTSB, CTSR and ZTSB and ZTSR treatments, because N removed by the wheat crop was equivalent to less than 20% of fertilizer N in the first 12 years of management practices, due mainly to disease. Deep leaching losses of NO3-N was the likely factor for poor recovery of N. The ZTSR treatment showed better apparent N recovery than the CTSB treatment, most likely due to greater immobilization of fertilizer N, more N uptake in grain due to additional available soil water and hence less leaching losses of NO3-N. Under the current cultural practices, soil total N (0-0.1 m) may decline further to reach a steady state (about 1000 kg N ha-1). However, the apparent N recovery in the soil-plant system can be increased by disease control (for example, resistant cultivars and winter-summer crop rotations) and optimum utilisation of soil water (opportunity cropping) to minimize NO3-N leaching losses and to maximise production of crop biomass.

A hierarchical model for salmon run reconstruction and application to the Bristol Bay sockeye salmon (Oncorhynchus nerka) fishery

2006 ◽  
Vol 63 (7) ◽  
pp. 1564-1577 ◽  
Author(s):  
Lucy Flynn ◽  
André E Punt ◽  
Ray Hilborn
Keyword(s):  
Hierarchical Structure ◽  
Sockeye Salmon ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Model Development ◽  
Bristol Bay ◽  
Process Error ◽  
The Hierarchical Structure ◽  
River Test ◽  
Run Timing

The goal of spreading the annual catch of a Pacific salmon (Oncorhynchus spp.) run proportionally across all segments of the migration is rendered difficult or impossible because of the interannual variability in both run size and run timing. This problem is particularly acute in the case of the fishery for sockeye salmon (Oncorhynchus nerka) in Bristol Bay, Alaska, for which traditional run reconstruction models are not applicable because of the extreme temporal compression of the run. We develop a run reconstruction model appropriate for sockeye salmon in Bristol Bay by accounting for the hierarchical structure of the problem and by including process error. Our results indicate that the hierarchical structure is, in fact, not necessary, whereas the process error parameters are needed to fit the data. We suggest further model development without the hierarchical structure, including incorporating in-river test fishing data. The results of our method can be used to address questions regarding environmental or intrinsic drivers of run timing and the possibility of artificial selection on run timing.

Spawning success of males using alternative mating tactics in sockeye salmon, Oncorhynchus nerka

1997 ◽  
Vol 54 (8) ◽  
pp. 1785-1795 ◽  
Author(s):  
C J Foote ◽  
G S Brown ◽  
C C Wood
Keyword(s):  
Sockeye Salmon ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Relative Size ◽  
Mating Strategies ◽  
Older Individuals ◽  
Alpha Male ◽  
Gonad Size ◽  
Sperm Volume ◽  
Spawning Success

Protein electrophoresis was used to determine the relative spawning success of jack sockeye salmon, Oncorhynchus nerka, males when they joined spawnings of larger, older individuals in experimental enclosures in the natal stream, Pierre Creek, Babine Lake, British Columbia. We attempted to relate the results to distance of the jack from female before spawning and relative size of the jack to the alpha male. Further, we measured the relationships between relative gonad size and available sperm volume to body size to determine if sperm competition could also play a role in determining the relative spawning success of males. Jack spawning success was variable (3-93%) and not significantly different from that of large males, even though they were further from the female before spawning, had smaller gonads, and had less available sperm. Jack males were adept at sneaking, usually commencing spawning within a split second of the alpha male and always on the opposite, free, side of the spawning female. The results are related to various theories on the evolution of alternative mating strategies and tactics in Pacific salmon.

The role of long-term sites in agroecological research: A case study

1995 ◽  
Vol 75 (1) ◽  
pp. 123-133 ◽  
Author(s):  
H. H. Janzen
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Management Practices ◽  
Cropping Systems ◽  
Simulation Models ◽  
Sample Collection ◽  
Productivity Measurement ◽  
Sampling Protocols ◽  
Long Term Studies

Gradual, episodic or subtle changes in agroecosystems can be definitively measured only in long-term studies. The objective of this paper is to illustrate the benefits and limitations of long-term agroecological sites using a crop rotation study (Rotation ABC) established at Lethbridge, Alberta in 1910. Long-term agroecological sites, envisioned as part of a continuum of research levels, seek to determine the persistence of cropping systems with respect to their effects on soil resources and the larger environment. Examples of research findings arising from such sites include the documentation of long-term changes in agricultural productivity, measurement of organic matter changes over time, calculation of long-term nutrient budgets, and verification of simulation models. For example, soil organic matter concentrations in Rotation ABC were found to decline abruptly within the first few decades of cultivation and then approach a new steady state. Despite the continual removal of N in harvested grain, soil N concentrations also appear to have stabilized, suggesting an accession of N approximately equivalent to the amount harvested. Common limitations of long-term sites like that at Lethbridge include: rudimentary experimental design, evolving management practices, incidental changes at the sites, and variation in sampling protocols. The successful use of long-term agroecological sites depends on well-defined objectives, simplicity of design, adequate scale, consistent data and sample collection, and collaboration among sites. The primary justification for the establishment and maintenance of long-term agroecological sites may be their future role in answering questions not yet envisioned. Key words: Soil organic matter, long-term studies, crop rotations, sustainability, fertilizer

The reactions to macro-economic crises in Nordic health system policies: Denmark, Finland and Sweden, 1980–2013

2014 ◽  
Vol 10 (1) ◽  
pp. 61-81 ◽  
Author(s):  
Juhani Lehto ◽  
Karsten Vrangbæk ◽  
Ulrika Winblad
Keyword(s):  
Health System ◽  
Economic Crisis ◽  
Management Practices ◽  
Growth Period ◽  
External Shocks ◽  
Economic Crises ◽  
Long Term Trends ◽  
Paradigmatic Change ◽  
Relationship Of

AbstractDenmark, Finland and Sweden have experienced two major recessions during the last 25 years. The adjustments to the earlier crisis in the late 1980s (Denmark) and early 1990s (Finland and Sweden) resembled the policies in many other European countries during the present crisis. The analysis of relationship of deep economic crises and growth period between them to the health system policies and institutions in the three countries from the 1980s to 2013 is based on a categorisation of reactions to external shocks as path conforming or path breaking. The results of the empirical long-term trends show that the reactions to deep recessions have been mainly temporary adjustments and acceleration of changes already prepared before economic crisis. The economic crisis in the three countries has not been ‘good enough’ to enable paradigmatic changes in the Nordic public, decentralised and equity-oriented health systems. Changes such as the slow privatisation in care funding and production and the adoption of new management practices indicate an ongoing paradigmatic change related to longer-term societal, ideological and political developments rather than directly to economic crises or growth.

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.

Homing in Wild Sockeye Salmon (Oncorhynchus nerka) Populations as Inferred from Differences in Parasite Prevalance and Allozyme Allele Frequencies

1987 ◽  
Vol 44 (11) ◽  
pp. 1963-1971 ◽  
Author(s):  
T. P. Quinn ◽  
C. C. Wood ◽  
L. Margolis ◽  
B. E. Riddell ◽  
K. D. Hyatt
Keyword(s):  
British Columbia ◽  
Sockeye Salmon ◽  
Pacific Salmon ◽  
Oncorhynchus Nerka ◽  
Genetic Differences ◽  
Allele Frequencies ◽  
Wild Populations ◽  
Central Coast ◽  
Barkley Sound ◽  
Quantitative Estimates

Although it is widely accepted that adult Pacific salmon (Oncorhynchus spp.) spawn in their natal stream, there are few quantitative estimates of homing precision in wild populations. The prevalence of two myxosporean parasites, Myxobolus neurobius and Henneguya salminicola, indicated very precise homing in certain sockeye salmon (O. nerka) populations in British Columbia (Long and Owikeno lakes on the central coast and Sproat, Great Central, and Henderson lakes on Barkley Sound, Vancouver Island). These populations were also sampled for electrophoretic differences at 23 loci. Genetic differences were found among all five populations, and estimates of straying from these data corroborated the parasitological evidence that straying is rare (< 1%).

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