Physical, chemical and perceived stressors can all evoke non-specific responses in fish, which are considered adaptive to enable the fish to cope with the disturbance and maintain its homeostatic state. If the stressor is overly severe or long-lasting to the point that the fish is not capable of regaining homeostasis, then the responses themselves may become maladaptive and threaten the fish's health and well-being. Physiological responses to stress are grouped as primary, which include endocrine changes such as in measurable levels of circulating catecholamines and corticosteroids, and secondary, which include changes in features related to metabolism, hydromineral balance, and cardiovascular, respiratory and immune functions. In some instances, the endocrine responses are directly responsible for these secondary responses resulting in changes in concentration of blood constituents, including metabolites and major ions, and, at the cellular level, the expression of heat-shock or stress proteins. Tertiary or whole-animal changes in performance, such as in growth, disease resistance and behavior, can result from the primary and secondary responses and possibly affect survivorship.Fishes display a wide variation in their physiological responses to stress, which is clearly evident in the plasma corticosteroid changes, chiefly cortisol in actinopterygian fishes, that occur following a stressful event. The characteristic elevation in circulating cortisol during the first hour after an acute disturbance can vary by more than two orders of magnitude among species and genetic history appears to account for much of this interspecific variation. An appreciation of the factors that affect the magnitude, duration and recovery of cortisol and other physiological changes caused by stress in fishes is important for proper interpretation of experimental data and design of effective biological monitoring programs.

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Stress in Fishes: A Diversity of Responses with Particular Reference to Changes in Circulating Corticosteroids

The ocean moderates anthropogenic climate change at the cost of profound alterations of its physics, chemistry, ecology, and services. Here, we evaluate and compare the risks of impacts on marine and coastal ecosystems—and the goods and services they provide—for growing cumulative carbon emissions under two contrasting emissions scenarios. The current emissions trajectory would rapidly and significantly alter many ecosystems and the associated services on which humans heavily depend. A reduced emissions scenario—consistent with the Copenhagen Accord’s goal of a global temperature increase of less than 2°C—is much more favorable to the ocean but still substantially alters important marine ecosystems and associated goods and services. The management options to address ocean impacts narrow as the ocean warms and acidifies. Consequently, any new climate regime that fails to minimize ocean impacts would be incomplete and inadequate.

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Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios

The evolution of intrinsic growth rate has received less attention than other life history traits, and has been studied differently in plants, homoiotherms, and poikilotherms. The benefits of rapid growth are obvious, so the problems is to explain the costs and tradeoffs that cause organisms to grow below their physiological maximum. Four prevailing themes emerge from the literature: (1) slow growth is adaptive for dealing with nutrient stress, (2) the tradeoff between growth rate and development limits growth in species that require mature function early in life, (3) rapid growth evolves when a minimum size must be reached quickly, such as for sexual maturation or overwintering, and (4) rapid growth may evolve to compensate for slowed growth owing to environmental conditions. Evidence for each of these themes is detailed for plants, homoiotherms, and poikilotherms. In addition, empirical evidence is reviewed for costs of rapid growth, including increased fluctuating asymmetry, reduced immune capacity, and reduced ability to respond to environmental stress.

https://www.biology.ucr.edu/people/postdocs/reprints/01arendt_qrb%20.pdf

Adaptive intrinsic growth rates: an integration across taxa

The Dynamic Energy Budget theory unifies the commonalties between organisms, as prescribed by the implications of energetics, and links different levels of biological organisation (cells, organisms and populations). The theory presents simple mechanistic rules that describe the uptake and use of energy and nutrients and the consequences for physiological organization throughout an organism's life cycle. All living organisms are covered in a single quantitative framework, the predictions of which are tested against a variety of experimental results at a range of levels of organisation. The theory explains many general observations, such as the body size scaling relationships of certain physiological traits, and provides a theoretical underpinning to the method of indirect calorimetry. In each case, the theory is developed in elementary mathematical terms, but a more detailed discussion of the methodological aspects of mathematical modelling is also included.

Dynamic Energy and Mass Budgets in Biological Systems

:plications for our ability to sample and identify all the ecologically relevant members of microbial communities in other high-diversity habitats, such as soils (22), microbial mats (23), and communities where low-abundance taxa may play crucial roles, such as the human microbiome. It provides a comparative population structure analysis with statistically significant descriptions of diversity and relative abundance of microbial populations. These large estimates of phylogenetic diversity at every taxonomic level present a challenge to large-scale microbial community genomic surveys. Metagenomic studies seek to inventory the full range of metabolic capabilities that define ecosystem function or to determine their context within assembled genomic scaffolds. Our results suggest that even the largest of published metagenomic investigations inadequately represent the full extent of microbial diversity, as they survey only the most highly abundant taxa (11).

/pdf/genetic-effects-of-captive-breeding-cause-a-rapid-cumulative-2b03q5mtpc.pdf

Genetic Effects of Captive Breeding Cause a Rapid, Cumulative Fitness Decline in the Wild

Captive breeding and release programs, widely used to supplement populations of declining species, minimize juvenile mortality to achieve rapid population growth However, raising animals in benign environments may promote traits that are adaptive in captivity but maladaptive in nature In chinook salmon, hatchery rearing relaxes natural selection favoring large eggs, allowing fecundity selection to drive exceptionally rapid evolution of small eggs Trends toward small eggs are also evident in natural populations heavily supplemented by hatcheries, but not in minimally supplemented populations Unintentional selection in captivity can lead to rapid changes in critical life-history traits that may reduce the success of supplementation or reintroduction programs

/pdf/rapid-evolution-of-egg-size-in-captive-salmon-3faa95eh0q.pdf

Rapid Evolution of Egg Size in Captive Salmon

We performed two breeding experiments with chinook salmon (Oncorhynchus tshawytscha) to explore maternal effects on offspring size. We estimated the magnitude of maternal effects as the differences between sire-offspring and dam-offspring regression slopes. Early in life, offspring size is largely influenced by maternal size, but this influence decreases through early development, with the maternal effect becoming negative at intermediate offspring ages (corresponding to a period of reduced growth of progeny hatching from large eggs) and converging on zero as offspring age. Also, egg size was positively correlated with early survival, but negatively correlated with maternal fecundity.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1999.tb05424.x

Maternal effects on offspring size: variation through early development of chinook salmon.

The viability of Pacific salmon populations could be compromised by the effects of climate change given their limited ability to adapt to increased temperatures.

/pdf/adaptive-potential-of-a-pacific-salmon-challenged-by-climate-1kuvdbfxgt.pdf

Adaptive potential of a Pacific salmon challenged by climate change

Genetic, environmental and interaction effects on the incidence of jacking in Oncorhynchus tshawytscha (chinook salmon)

/pdf/genetic-environmental-and-interaction-effects-on-the-2k14ih4nkk.pdf

Detailed analysis of variation in reproductive success can provide an understanding of the selective pressures that drive the evolution of adaptations. Here, we use experimental spawning channels to assess phenotypic and genotypic correlates of reproductive success in Chinook salmon (Oncorhynchus tshawytscha). Groups of 36 fish in three different sex ratios (1:2, 1:1 and 2:1) were allowed to spawn and the offspring were collected after emergence from the gravel. Microsatellite genetic markers were used to assign parentage of each offspring, and the parents were also typed at the major histocompatibility class IIB locus (MHC). We found that large males, and males with brighter coloration and a more green/blue hue on their lateral integument sired more offspring, albeit only body size and brightness had independent effects. There was no similar relationship between these variables and female reproductive success. Furthermore, there was no effect of sex ratio on the strength or significance of any of the correlations. Females mated non-randomly at the MHC, appearing to select mates that produced offspring with greater genetic diversity as measured by amino-acid divergence. Females mated randomly with respect to male genetic relatedness and males mated randomly with respect to both MHC and genetic relatedness. These results indicate that sexual selection favours increased body size and perhaps integument coloration in males as well as increases genetic diversity at the MHC by female mate choice.

/pdf/the-mhc-and-non-random-mating-in-a-captive-population-of-2fokhsak8w.pdf

John W. Heath

Papers

Rapid Evolution of Egg Size in Captive Salmon

Maternal effects on offspring size: variation through early development of chinook salmon.

Adaptive potential of a Pacific salmon challenged by climate change

Genetic, environmental and interaction effects on the incidence of jacking in Oncorhynchus tshawytscha (chinook salmon)

The MHC and non-random mating in a captive population of Chinook salmon