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.

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.

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.

Preseason Forecasts of Sockeye Salmon (Oncorhynchus nerka): Comparison of Methods and Economic Considerations

1988 ◽  
Vol 45 (8) ◽  
pp. 1346-1354 ◽  
Author(s):  
Robert C. Bocking ◽  
Randall M. Peterman
Keyword(s):  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Linear Method ◽  
Economic Benefits ◽  
Nonlinear Method ◽  
Bristol Bay ◽  
Economic Implications ◽  
Gill Net ◽  
Forecasting Method

We compared the ability of two methods to forecast observed abundances of sockeye salmon (Oncorhynchus nerka) in Bristol Bay, Alaska, stocks from 1956 through 1980. We determined that the commonly used linear forecasting method, based on untransformed abundances of sibling age classes, overestimated sockeye abundances more frequently than did a nonlinear method. Furthermore, the nonlinear method produced mean forecasts that were closer to actual abundances of returns than forecasts from the linear method. We therefore recommend use of the nonlinear method. We also quantified significant economic implications of incorrect preseason forecasts for Bristol Bay sockeye. Deviations of actual escapements from the target are correlated with errors in the preseason forecast. Thus, large errors in preseason forecasts can influence potential long-term harvests and resulting economic benefits. In addition, annual changes in prices of set and drift gill net permits for fishermen were correlated with forecasted annual change in the abundance of sockeye recruits. This result is consistent with the hypothesis that preseason forecasts of sockeye salmon returns affect expectations by fishermen of economic rents (related to profits). Overestimates of abundance of recruits by current methods may thus subsequently lead to overinvestment by fishermen seeking to increase their share of expected rents.

A widespread decrease in productivity of sockeye salmon (Oncorhynchus nerka) populations in western North America

2012 ◽  
Vol 69 (8) ◽  
pp. 1255-1260 ◽  
Author(s):  
Randall M. Peterman ◽  
Brigitte Dorner
Keyword(s):  
Sockeye Salmon ◽  
Spatial Scales ◽  
Oncorhynchus Nerka ◽  
Geographic Area ◽  
Fraser River ◽  
Western North America ◽  
Southeast Alaska ◽  
The Past ◽  
Large Geographic Area ◽  
Marine Areas

We used data on 64 stocks of sockeye salmon ( Oncorhynchus nerka ) from British Columbia (B.C.), Washington, and Alaska to determine whether recent decreases in abundance and productivity observed for Fraser River, B.C., sockeye have occurred more widely. We found that decreasing time trends in productivity have occurred across a large geographic area ranging from Washington, B.C., southeast Alaska, and up through the Yakutat peninsula, Alaska, but not in central and western Alaska. Furthermore, a pattern of predominantly shared trends across southern stocks and opposite trends between them and stocks from western Alaska was present in the past (1950–1985), but correlations have intensified since then. The spatial extent of declining productivity of sockeye salmon has important implications for management as well as research into potential causes of the declines. Further research should focus on mechanisms that operate at large, multiregional spatial scales, and (or) in marine areas where numerous correlated sockeye stocks overlap.

Historical Shark Meat Consumption and Trade Trends in a Global Richness Hotspot

2019 ◽  
Vol 10 (1) ◽  
pp. 97-103
Author(s):  
Márcio L. V. Barbosa-Filho ◽  
Rachel Ann Hauser-Davis ◽  
Salvatore Siciliano ◽  
Thelma L. P. Dias ◽  
Rômulo R. N. Alves ◽  
...  
Keyword(s):  
Meat Consumption ◽  
Northeastern Brazil ◽  
Historical Trends ◽  
The Past ◽  
Coastal Species ◽  
Biological Studies ◽  
Artisanal Fisher ◽  
Consumption Frequency ◽  
Sustainable Fishery

Shark catches have increased worldwide, threatening the survival of several species. This study describes historical trends concerning shark consumption and commercialization by artisanal fishers in northeastern Brazil. Semi-structured questionnaires were applied and respondents pointed out that sharks used to be locally regarded as low-quality fish in the past and rejected by fish consumers, with low fisher consumption frequency. However, this has changed in recent decades, as a total of 95.4% (n=62) of the questionnaire respondents reported currently consuming shark meat, while 61.5% (n=40) highlighted its high quality. In addition, most interviewees (90.8%; n=59) reported decreasing numbers of sharks caught over time, following worldwide trends, leading to decreased fisher access to shark meat. Because of this, most respondents (70.7%, n=46) now consider it more advantageous to sell the sharks they catch than to consume them. In addition, the local commercialization of these fish is currently based on immature coastal species (<1 m). Thus, economic and biological studies on local shark populations are suggested in order to preserve local fisher culture and ensure food security for artisanal fisher communities and a long-term sustainable fishery and conservation of exploited species.

Selective predation by brown bears (Ursus arctos) foraging on spawning sockeye salmon (Oncorhynchus nerka)

2000 ◽  
Vol 78 (6) ◽  
pp. 974-981 ◽  
Author(s):  
Gregory T Ruggerone ◽  
Renn Hanson ◽  
Donald E Rogers
Keyword(s):  
Sockeye Salmon ◽  
Ursus Arctos ◽  
Oncorhynchus Nerka ◽  
The Body ◽  
Upstream Migration ◽  
Selective Predation ◽  
Bristol Bay ◽  
Brown Bears ◽  
Risk Of Predation ◽  
Salmon Population

Selective predation by and predation rates of brown bears (Ursus arctos) foraging on spawning sockeye salmon (Oncorhynchus nerka) in a small shallow creek in the Wood River lake system near Bristol Bay, Alaska, were quantified during 1986 and 1990–1992. Bears killed a high proportion of spawning salmon when few salmon entered the creek (92% of 505 fish) and a much smaller proportion when the spawning population reached a historical high (16% of 15 631 fish). Selective predation on salmon that differed in length, sex, and spawning condition was measured by tagging salmon at the mouth of the creek immediately prior to upstream migration and then recovering dead tagged fish during daily surveys of the entire creek. The relative frequencies of large, medium-sized, and small salmon killed by bears indicated that the risk of predation was more than 150% greater for large than for small salmon. A higher proportion of the male salmon population was killed and a greater proportion of male bodies were consumed than female salmon. Selectivity for male salmon increased as the spawning season progressed, possibly because male salmon weakened earlier and lived longer in a weakened state than female salmon. Male salmon were attacked mostly along the dorsal hump area, whereas female salmon tended to be attacked along the abdomen, where eggs could be exposed. Bears selectively killed female salmon prior to spawning during 1 of the 3 years, but only 6.1–7.8% of the female spawning populations were killed prior to spawning. These data support the hypothesis that selective predation by bears may influence the body morphology of spawning salmon.

Genetic Differences in the Early Development and Growth of Sympatric Sockeye Salmon and Kokanee (Oncorhynchus nerka), and their Hybrids

1990 ◽  
Vol 47 (11) ◽  
pp. 2250-2260 ◽  
Author(s):  
Chris C. Wood ◽  
Chris J. Foote
Keyword(s):  
Egg Size ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Genetic Effect ◽  
Genetic Differences ◽  
Hybrid Progeny ◽  
Yolk Absorption ◽  
The Difference ◽  
Male Genotype ◽  
Better Than

Anadromous (sockeye salmon) and nonanadromous (kokanee) Oncorhynchus nerka spawn sympatrically yet appear genetically distinct in a number of rivers in British Columbia. To investigate whether genetic differences are maintained by selection against -hybrid" progeny, we raised pure and reciprocal crosses of Shuswap River sockeye and kokanee under controlled hatchery conditions. Sockeye eggs were larger and survived slightly better than kokanee eggs, regardless of male type, both to the eyed egg stage and as young fry. We observed no differences in survival among cross types during the remainder of the 460 d study. Rate of yolk absorption was similar in pure sockeye and pure kokanee alevins, but significantly faster in alevins sired by sockeye than those sired by kokanee. This indicates a male genetic effect which compensates for the difference in egg size. Hybrid alevins developed differently because egg size is mismatched with the male genotype. Growth rates of fry were significantly more variable within pure kokanee families than within pure sockeye families Hybrid crosses survived as well as pure crosses under the study conditions. However, any progeny resulting from hybrid crosses in nature may sustain higher mortality than those from pure crosses.

scholarly journals Quasi-1500-Year-Cycle Signal in Length-of-Day Change

2021 ◽  
Vol 56 (2) ◽  
pp. 10-17
Author(s):  
Lihua MA
Keyword(s):  
Rotation Rate ◽  
Time Span ◽  
Historical Documents ◽  
Data Series ◽  
Earth’S Rotation ◽  
Time Varying ◽  
Length Of Day ◽  
The Past ◽  
Continuous Sequence

Abstract Length-of-day (LOD) change, i.e., variations in Earth’s rotation rate, includes the long-term slowdown trend, as well as periodic and irregular fluctuations. The current continuous sequence of the LOD change covers a time span of <400 years. Using astronomical records in ancient historical documents, combined with a modern astronomical ephemeris, it is possible to obtain ancient LOD change. Some scholars have given a discontinuous LOD data series for the past 4000 years. In this paper, the author uses the Lomb–Scargle periodogram to study the LOD series and finds a significant quasi-1500-year-cycle signal. Furthermore, with weighted wavelet Z-transform, time-varying characteristics of the cycle in the LOD change are obtained.

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