摘要:

Atlantic salmon (Salmosalar) is an excellent species on which to focus synthetic, integrative investigations because it is an economically important species that captures the public imagination, is heavily impacted by humans, uses several ecosystems over its life, and is the subject of a large body of extant literature. The following 24 papers were solicited to provide the biological basis for effective and innovative approaches that biologists, managers, and social scientists can use to develop policies that sustain Atlantic salmon and related species. Together these papers highlight the need for and benefits of (a) synthesizing within populations, (b) choosing the appropriate scale, (c) comparing across populations using rigorous, focused, question-oriented methods, (d) integrating across disciplines, (e) incorporating the human perspective, (f) linking multiple ecosystems, and (g) applied problem solving. To show how Atlantic salmon can guide research and conservation efforts for other species in other systems, we review the justification for the supplement and summarize the defining concepts that emerge from the volume.

ISSN:0706-652X    

DOI:10.1139/d98-000

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The Atlantic salmon (Salmo salar) is a model species for studying scale issues (i.e., the extent, duration, and resolution of a study or natural process) in ecology. Major shifts in behavior and habitat use over ontogeny, along with a relatively long life span and large dispersal and migration distances, make scale issues critical for effective conservation, management, and restoration of this species. The scale over which a process occurs must be linked to the research design and we illustrate this with a discussion of resource tracking by Atlantic salmon. Identifying scale inconsistencies (e.g., when a process is evident at one scale but not another) is shown to be an effective means by which some scale-dependent processes are understood. We review the literature to assess the temporal and spatial scales used in Atlantic salmon research and find most current studies appear to sacrifice spatial and temporal extent for increased resolution. Finally,we discuss research strategies for expanding the temporal and spatial scales in salmon research, such as conducting multiple scales studies to elucidate scale inconsistencies, identifying mechanisms, and using techniques and approaches to generalize across studies and over time and space.

ISSN:0706-652X    

DOI:10.1139/d98-017

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Based upon published and unpublished data compiled for 275 populations, we describe large-scale spatial and temporal patterns in Atlantic salmon,Salmo salar, life history and model these data to evaluate how changes to life history influence optimal growth rate thresholds for sea age at maturity. Population means (ranges in parentheses) describe the following for salmon throughout its range: smolt length = 14.8 cm (10.5-21.5 cm); smolt age = 2.91 years (1.04-5.85 years); egg-to-smolt survival = 1.5% (0.2-3.2%); grilse length = 56.8 cm (48.5-70.0 cm); sea age at maturity = 1.60 years (1.00-2.64 years); smolt-to-grilse survival = 7.4% (1.3-17.5%). Growth rate thresholds specify the length increase between the smolt and grilse stages above which reproduction after one winter at sea is favoured over later maturity. Our simulations indicated that increased growth generally favours earlier, but never delayed, maturity. Optimal growth rate thresholds for sea age at maturity are highly sensitive to survival but only moderately sensitive to fecundity, smolt size, and smolt age. Depending on an individual's growth rate at sea, early maturity is favoured by decreased smolt age or by increased smolt length, fecundity, or survival (freshwater or marine). We suggest that future Atlantic salmon life history research focus upon reaction norms and growth rate thresholds for age at maturity, demographic and genetic consequences of male parr maturation, and the origin and maintenance of coexisting anadromous and nonanadromous life history polymorphisms.

ISSN:0706-652X    

DOI:10.1139/d98-004

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

We took a hierarchical approach to understanding Atlantic salmon (Salmo salar) life history patterns by first comparing salmonids to other teleosts, next comparing Atlantic salmon to other salmonids, and finally, mapping correlations among individual life history traits within Atlantic salmon. The combination of anadromy, large eggs, nest construction and egg burial by females, and large size at maturity differentiates salmonids from most other teleosts. Within the family Salmonidae, there is considerable variation in all traits but Atlantic salmon are generally in the middle of the range. Within Atlantic salmon, we were able to map correlations among individual life history traits, but we found that we still lacked an understanding comprehensive and quantitative enough to allow us to predict how the entire life history should respond to environmental changes. Thus, we proposed several general courses of action: (i) use models to synthesize complex patterns and relationships, (ii) collect long time series of data in individual systems, and (iii) design experiments to assess phenotypic plasticity and how environmental influences differ from genetic effects and constraints.

ISSN:0706-652X    

DOI:10.1139/d98-007

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The breeding system of Atlantic salmon (Salmo salar) is shaped both by natural selection for offspring production and by sexual selection for access to mating opportunities. These evolutionary forces operate with differing intensities in the two sexes to shape their breeding behaviour and tactics. Female breeding success is largely dependent on egg production, access to breeding territories, and nest quality and survival. By contrast, male breeding success is largely determined by access to ovipositing females. As such, the breeding system of Atlantic salmon is similar to that of other members of the subfamily Salmoninae. However, early male maturity, a common pattern within the Salmoninae, reaches its greatest expression in both terms of frequency and magnitude of the mature male size difference in Atlantic salmon. Despite generalities, spawning populations of Atlantic salmon are not static, as they exhibit spatial and temporal variability in demography (e.g., spawner density, sex ratio, age at maturity, and body size). Events, both natural and anthropogenic (e.g., exploitation, habitat alteration, and climatic changes), affect this variability and ultimately shape the breeding system.

ISSN:0706-652X    

DOI:10.1139/d98-009

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A variety of movements characterize the behavioral plasticity of Atlantic salmon (Salmosalar) in fresh water, including movements of fry from redds, establishment of feeding territories, spawning movements of sexually mature male parr, movement to and from winter habitat, and smolt migration in spring. Smolting is an adaptive specialization for downstream migration, seawater entry, and marine residence. While still in fresh water, smolts become silvery and streamlined, lose their positive rheotaxis and territoriality, and begin schooling. Physiological changes include increased salinity tolerance, olfactory sensitivity, metabolic rate, scope for growth, and altered hemoglobin and visual pigments. Through their impact on the neuroendocrine system, photoperiod and temperature regulate physiological changes, whereas temperature and water flow may initiate migration. Smolt survival is affected by a limited period of readiness (a physiological "smolt window") and the timing of seawater entry with environmental conditions such as temperature, food, and predators (an ecological "smolt window"). Smolt development is adversely affected by acidity, pollutants, and improper rearing conditions, and is often more sensitive than other life stages. Unfortunately, the migration corridor of smolts (mainstems of rivers and estuaries) are the most heavily impacted by pollution, dams, and other anthropogenic activities that may be directly lethal or increase mortality by delaying or inhibiting smolt migration.

ISSN:0706-652X    

DOI:10.1139/d98-011

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Atlantic salmon (Salmo salar) exhibit extreme diversity in the age of smolt migration and sexual maturation, both within and among populations. Theoretical analyses reveal the adaptive significance of such variation, but models of the underlying physiological and behavioral mechanisms are also needed. I summarize one such proximate model that suggests that smolting and maturation are only triggered if expected performance trajectories exceed threshold levels during sensitive periods. The probability of a threshold being exceeded is therefore dependent on an individual fish's ability to acquire and utilize resources efficiently, which in turn depends on a range of physiological and behavioral traits. Spatial variation in life histories is chiefly caused by differences in growth opportunity, although there is evidence of geographical variation in genetically determined expected growth trajectories. Simulations show that small changes in young fry growth rates can have pronounced effects on mean smolt age and sex ratio, by influencing the proportion of males that fail to exceed the threshold for early smolting and mature as parr (and so are less likely to survive to smolting). More sophisticated proximate models should allow powerful predictions of smolt production based on simple environmental parameters, due to their influence on growth trajectories and hence life history decisions.

ISSN:0706-652X    

DOI:10.1139/d98-005

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Atlantic salmon (Salmosalar) are distributed over large areas in the north Atlantic Ocean. They usually move very quickly from freshwater to oceanic areas, whereas there is considerable variation among Pacific salmon in early marine movements. In some areas, Atlantic salmon of exploitable size are sufficiently abundant that commercial high seas fisheries have developed. Such areas are off west Greenland, where North American and European fish are harvested, and in the Norwegian Sea, north of the Faroe Islands, where mainly European fish are exploited. Atlantic salmon feed on a wide range of large crustaceans, pelagic fish, and squid in the marine environment, supporting the hypothesis that Atlantic salmon are opportunistic feeders. In the ocean the salmon grow relatively quickly and the sea age when they become sexually mature depends on both genetics and on growing conditions. Natural marine mortality of salmon is highest during the first few months at sea and the major mortality factor is probably predation. However, marine mortality of Atlantic salmon has increased in recent years, apparently correlated with a decline in sea surface temperatures. Similar relationships between environmental conditions and the growth and survival of Pacific salmon have been reported. Atlantic salmon life histories most closely mimic stream-type chinook salmon or steelhead trout among the Pacific species. Finally, Atlantic and Pacific salmon return to their home rivers with high precision and possible mechanisms controlling the oceanic homing migration are presented and discussed.

ISSN:0706-652X    

DOI:10.1139/d98-010

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Ocean climate and ocean-linked terrestrial climate affect nearly all phases of Atlantic salmon (Salmosalar) life history. Natural mortality in salmon occurs in two main phases: juvenile stages experience high mortality during freshwater residency and pre-adult salmon experience high mortality in estuarine and ocean environments. Freshwater survivorship is well characterized and tends to be less variable than marine mortality. Sources of marine mortality are poorly known due to a lack of basic knowledge about post-smolt distributions and habits. Coherence patterns among regional and continental stock groups suggest broad scale forcing functions play a more important role in defining recruitment than mortality effects associated with individual rivers. The action of mesoscale regional environment is most prominent during the post-smolt year when survival, maturation, and migration trajectories are being defined. During the early weeks at sea, growth mediated survival defines recruitment patterns. A correlation between sea surface water temperature and survival has been observed for salmon stocks in the northeast Atlantic suggesting temperature either directly affects growth or modifies post-smolt behavior. Age at first maturity is controlled by environmental as well as genetic factors. The abundance of two seawinter spawners in North America is directly scaled to the size of overwintering thermal habitat in the northwest Atlantic, which suggests a link between maturation and environment.

ISSN:0706-652X    

DOI:10.1139/d98-003

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Today, over 94% of all adult Atlantic salmon (Salmo salar) are in the aquaculture niche and wild numbers continue to decline while aquaculture numbers increase. The developmental and evolutionary forces in the aquaculture or "domestic" niche are so unlike those in the wild niche that two distinct biologies are being created from the original Atlantic salmon species. We may now need to recognize a new biological entity -Salmo domesticus- and treat it as an "exotic" when it escapes into the wild. Escapement therefore raises important concerns about ecological and genetic impacts, both within and outside the native range ofSalmo salar. This paper explains why escaped domestic Atlantic salmon have had an impact on wild Atlantic salmon populations and now threaten Pacific salmonids as well. A polarization of views between aquaculturists and environmentalists will not resolve the problems. The three interest groups in fisheries - aquaculture, biodiversity, and capture - must begin to work together if we are to take up the challenge of preserving biodiversity and if aquaculturists, who hold the future of Atlantic salmon in their hands, can be expected to willingly prevent further impacts from their industry.

ISSN:0706-652X    

DOI:10.1139/d98-024

出版商:NRC Research Press    

年代:1998

数据来源: NRC