Modeling Variation in Mass-Length Relations and Condition Indices of Lake Trout and Chinook Salmon in Lake Huron: A Hierarchical Bayesian Approach (original) (raw)
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Marine Ecology Progress Series, 2008
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Declines in body size of sockeye salmon associated with increased competition in the ocean
Proceedings of the Royal Society B: Biological Sciences
Declining body sizes have been documented for several species of Pacific salmon; however, whether size declines are caused mainly by ocean warming or other ecological factors, and whether they result primarily from trends in age at maturation or changing growth rates remain poorly understood. We quantified changes in mean body size and contributions from shifting size-at-age and age structure of mature sockeye salmon returning to Bristol Bay, Alaska, over the past 60 years. Mean length declined by 3%, corresponding to a 10% decline in mean body mass, since the early 1960s, though much of this decline occurred since the early 2000s. Changes in size-at-age were the dominant cause of body size declines and were more consistent than trends in age structure among the major rivers that flow into Bristol Bay. Annual variation in size-at-age was largely explained by competition among Bristol Bay sockeye salmon and interspecific competition with other salmon in the North Pacific Ocean. Warm ...
Canadian Journal of Fisheries and Aquatic Sciences, 2007
We examined statewide time series (1940s–2002) of mean length at ages 2, 3, and 4 for seven fish species sampled from Michigan and Wisconsin inland lakes for temporal trends. We used a components of variance approach to examine how total variation in mean length at age was partitioned into lake-to-lake, coherent temporal, ephemeral temporal, trend, and residual variation. Using these estimated variance components, we simulated the effects of different variance structures on the power to detect trends in mean length at age. Of the 42 data sets examined, only four demonstrated significant regional (statewide) trends: age 4 largemouth bass (Micropterus salmoides) from Wisconsin lakes increased about 0.7 mm·year–1 in mean length at age, and ages 2, 3, and 4 walleye (Sander vitreus) from Wisconsin lakes decreased between 0.5 and 0.9 mm·year–1 in mean length at age. The structure of variation differed substantially among data sets, and these differences strongly affected the power to dete...
Biostatistical implications of individual variability in growth in rainbow trout and Atlantic salmon
Aquaculture, 2001
The relationship between specific growth rate and initial body weight in fish was analysed by Ž multivariate analysis using data sets from growth studies on rainbow trout initial weight between . Ž . 10 and 30 g, n s 546 and Atlantic salmon initial weight between 10 and 20 g, n s 355 . We demonstrate that individuals can be pooled into different classes according to their growth characteristics. Classes with similar initial mean weight can have very different mean specific growth rate. Indeed, we found the mean specific growth rate ratio between classes with similar initial mean weight to be between 1.5 and 5.8 in rainbow trout and between 1.2 and 1.9 in Atlantic salmon. We conclude that the constitution of replicates with homogeneous initial weight is not assurance of homogeneous specific growth rate among replicates. The consequences of such variability in growth on experimental designs and power of analysis-of-variance models are discussed. q
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North Pacific Anadromous Fish Commission Bulletin, 2016
Temporal and spatial variation in the growth condition of Pacifi c salmon (Oncorhynchus spp.) were investigated using the prey-density function for consumption. Zooplankton prey density was estimated from an ecosystem model, NEMURO, embedded in a 3D physical model for the years 1948-2007. This study focused on three species of Pacifi c salmon (chum (O. keta), pink (O. gorbuscha), and sockeye (O. nerka)), all of which are zooplankton feeders. The prey dependence function for consumption of Pacifi c salmon varies on a decadal time scale, and its empirical orthogonal function fi rst mode was correlated with the Pacifi c Decadal Oscillation. The variation in the prey dependence function for consumption in the Bering Sea and the Western Subarctic Gyre was correlated with the variation in the carrying capacity of chum, pink, and sockeye salmon, indicating that these are key areas for connecting climate variability to the carrying capacity of Pacifi c salmon. In these areas, prey density increased after the 1976/77 regime shift, in synchrony with the increase in primary production due to enhanced nutrient supply through deepening of the mixed layer and/or stronger Ekman upwelling.
Fish and Fisheries, 2019
Successful management of wildlife involves an understanding of fluctuations in abundance, survival, productivity, and body size or condition. Demographic metrics are shaped by a wide range of factors related to environmental conditions, interactions with humans and population dynamics related to density, interactions with other species and other factors. Multidecadal, accurate, species-specific accounting of these metrics enables managers to compare them to environmental and anthropogenic conditions to accurately forecast future abundance and viability (
Influence of Salmon Abundance and Ocean Conditions on Body Size of Pacific Salmon
After the North Pacific ocean climate change in 1976–77, most species of Pacific salmon (Oncorhyn-chus spp.) in North America and Asia increased in abundance and declined in body size up until the early 1990s. Several authors attributed this decline in body size of chum salmon (O. keta) to increasing population density of chum salmon in the ocean. In the mid-1990s, the body size of adult chum salmon increased in several streams in North America in spite of high population numbers. To determine if these increases in body size were restricted to local areas or more widespread geographically in North America, we examined data on the abundance and mean body size of salmon from commercial catches in waters from northern Alaska south to the state of Oregon among three time periods (1960–76, 1977–94, 1995–2006). Trends in body size indicate that northern and southern pop-ulations of chum, pink, and sockeye, and coho in Washington and Oregon experienced increased body size in the mid-1990s....
Ecological Modelling, 2004
Variability in animal growth from one population to another is of keen interest to population ecologists wishing to understand the inherent within species variability and explore meaningful environmental covariates. Yet most studies investigating growth of animals within a population are usually analyzed in isolation from, or at best, compared qualitatively across populations. Here, we introduce statistical methods that permit simultaneous quantitative analysis of the growth of 245 populations of largemouth bass (Micropterus salmoides) across the North American Continent. Growth in length at age is modeled using a nonlinear mixed effect model and we used Bayesian hierarchical meta-analysis as a natural approach to estimate parameters, investigate growth variability among populations and to elucidate meaningful biological covariates for this species. Growth of M. salmoides across North America varied by more than 120% in terms of maximum attainable size (L ∞ ; 36-80 cm) and by more than 88% in terms of instantaneous growth rates (K; 0.091 to 0.670 per year). Results from this method also confirm the theoretical, but often untested, view that growth parameters L ∞ and K are negatively correlated in fish populations; Bayesian credibility intervals ranged from −0.56 to −0.72 with the posterior mode of −0.65. The Bayesian hierarchical growth model showed less variability in growth parameters and lower correlations among parameters than those from standard techniques used in population ecology suggesting that the absolute value of the correlation between L ∞ and K may be lower than the general perception in the ecological literature, often in the range of −0.8 to −0.9. Finally, growth parameters were negatively correlated with latitude suggesting that population productivity most likely declines the higher in latitude a population is found for this species. Published by Elsevier B.V. dynamics models that are used to derive sustainable harvests for managing stocks . Since von Bertalanffy's (1938) pioneering work on the theory of organic growth, the relationship between fish length and age has been often described by a three-parameter nonlinear relationship, the functional form of which is attributed to that author. The von Bertalanffy growth model still presides as the dominant paradigm of 0304-3800/$ -see front matter. Published by Elsevier B.V.
Atlantic salmon stocks are declining in European and North American rivers (ICES 2006). French rivers are located at the southern edge of the species distribution in Europe, providing a good opportunity to study life history variants in a changing environment (local and global) where unfavorable conditions may occur rapidly. In these rivers, almost all juveniles smoltify at age 1 (Smolt1) or age 2 (Smolt2), and adults return to rivers to spawn after 1 or 2 sea winters (1SW or 2SW). In the present work, we focus on the age at smoltification as an integrated parameter of changes occurring during the juvenile period in rivers. More precisely, variations in the mean age at smoltification (MAS) were studied in 23 rivers of the Armoricain Massif (western France) belonging to three geographical regions: northern Brittany, southern Brittany, and lower Normandy.
Marine and Coastal Fisheries, 2016
The productivity of Bristol Bay, Alaska, Sockeye Salmon Oncorhynchus nerka increased during the mid-1970s. This increase is believed to be partially due to an increase in early marine growth associated with the 1976-1977 cool-to-warm shift in summer sea surface temperature (SST). The body size of juvenile salmon during their first year at sea is believed to regulate their ability to survive over winter. The back-calculated smolt length, first-year ocean growth, and total juvenile length of Sockeye Salmon from five Bristol Bay river systems (Egegik, Kvichak, Naknek, Ugashik, and Wood) and two smolt ages were used to examine trends and factors influencing total juvenile length, compensatory growth, and size-selective mortality in the first year in the ocean from 1962 to 2007. Juvenile length increased in relation to summer sea temperature, the 1977-2001 and 2002-2007 warm temperature regimes, smolt length, and compensatory growth. Compensatory growth-an inverse relationship between first-year ocean growth and smolt size-increased over time as well as after the 1976-1977 climate regime shift, was more common in age-1.0 fish than in age-2.0 juveniles, and was important in determining the length of juvenile Sockeye Salmon from the Wood River (the shorter fish among rivers and smolt ages). The coefficient of variation in length did not change with SST, suggesting that size-selective mortality occurred prior to the end of the first year at sea for all 10 fish groups. The predictor variables that were significant in the models varied among river systems and smolt ages. This study demonstrated that the frequency of compensatory growth and the total lengths of juvenile Sockeye Salmon during their first year at sea increased with summer SST (range, 7.5-10.5°C) in the eastern Bering Sea, a possible mechanism for the increased productivity of Bristol Bay Sockeye Salmon associated with warmer sea temperatures.