Content uploaded by Neala W Kendall
Author content
All content in this area was uploaded by Neala W Kendall on Jun 06, 2018
Content may be subject to copyright.
A preview of the PDF is not available
Diadromy and the life history of sockeye salmon: Nature nurture and the hand of man
Figures
Figures - uploaded by Neala W Kendall
Author content
All figure content in this area was uploaded by Neala W Kendall
Content may be subject to copyright.
... For example, individuals spawned in the same year but migrating to sea after one or two years of freshwater residence will enter the ocean in different years, and thus experience different environmental conditions at sea. They will also differ in size during the stressful ocean entry phase, and may spend different lengths of time at sea prior to maturation and return [22]. Climate, life history and productivity are therefore interdependent, and accounting for these relationships is necessary to interpret past variability and predict future responses to environmental change in species such as salmon that display complex life histories [23]. ...
... The river systems that drain to Bristol Bay in southwest Alaska comprise the world's largest sockeye salmon producing region (Fig 2). Intensive commercial fishing with gillnets has occurred for over 100 years in five districts located near river mouths within the bay [22]. Each river drains one or more large lakes where sockeye salmon generally rear for one or two years before migrating to the Bering Sea and Gulf of Alaska [30]. ...
... environmental) and internal (i.e. density dependent) processes [21,22,29]. ...
Detecting the biological impacts of climate change is a current focus of ecological research and has important applications in conservation and resource management. Owing to a lack of suitable control systems, measuring correlations between time series of biological attributes and hypothesized environmental covariates is a common method for detecting such impacts. These correlative approaches are particularly common in studies of exploited fish species because rich biological time-series data are often available. However, the utility of species-environment relationships for identifying or predicting biological responses to climate change has been questioned because strong correlations often deteriorate as new data are collected. Specifically stating and critically evaluating the mechanistic relationship(s) linking an environmental driver to a biological response may help to address this problem. Using nearly 60 years of data on sockeye salmon from the Kvichak River, Alaska we tested a mechanistic hypothesis linking water temperatures experienced during freshwater rearing to population productivity by modeling a series of intermediate, deterministic relationships and evaluating temporal trends in biological and environmental time-series. We found that warming waters during freshwater rearing have profoundly altered patterns of growth and life history in this population complex yet there has been no significant correlation between water temperature and metrics of productivity commonly used in fisheries management. These findings demonstrate that pairing correlative approaches with careful consideration of the mechanistic links between populations and their environments can help to both avoid spurious correlations and identify biologically important, but not statistically significant relationships, and ultimately producing more robust conclusions about the biological impacts of climate change.
... General trends in the literature suggest fish that migrate earlier to the spawning grounds demonstrate higher LRS compared to those that arrive later ( Morbey & Ydenberg, 2003;Quinn et al., 2009Quinn et al., , 2016. Our review of the literature continues to support this finding across species, where males and females that returned earlier to the spawning grounds generally had positive LRS effects compared to those that arrived later. ...
Lifetime reproductive success (LRS), the number of offspring produced over an organism’s lifetime, is a fundamental component of Darwinian fitness. For taxa such as salmonids with multiple species of conservation concern, understanding the factors affecting LRS is critical for development and implementation of successful conservation management practices. Here, we reviewed the published literature to synthesize factors affecting LRS in salmonids including significant effects of hatchery rearing, life history and phenotypic variation, and behavioral and spawning interactions. Additionally, we found that LRS is affected by competitive behavior on the spawning grounds, genetic compatibility, local adaptation, and hybridization. Our review of existing literature revealed limitations of LRS studies and we emphasize the following areas that warrant further attention in future research: 1) expanding the range of studies assessing LRS across different life history strategies, specifically accounting for distinct reproductive and migratory phenotypes, 2) broadening the variety of species represented in salmonid fitness studies, 3) constructing multigenerational pedigrees to track long‐term fitness effects, 4) conducting LRS studies that investigate the effects of aquatic stressors, such as anthropogenic effects, pathogens, environmental factors in both freshwater and marine environments, and assessing overall body condition, and 5) utilizing appropriate statistical approaches to determine the factors that explain the greatest variation in fitness and providing information regarding biological significance, power limitations, and potential sources of error in salmonid parentage studies. Overall, this review emphasizes that studies of LRS have profoundly advanced scientific understanding of salmonid fitness, but substantial challenges need to be overcome to assist with long‐term recovery of these keystone species in aquatic ecosystems.
... Sockeye salmon (Oncorhynchus nerka) demonstrate a well-documented diversity of life-history traits both within and among populations (Groot and Margolis 1991, Hilborn et al. 2003, Quinn et al. 2009). This diversity acts as a buffer against variable environmental conditions to stabilize the dynamics of the aggregate population Schindler 2008, Schindler et al. 2010). ...
Opportunities for growth and survival of aquatic organisms are spatially and temporally variable as habitat conditions across watersheds respond to interacting climatic, geomorphic, and hydrologic conditions. As conservation efforts often focus on identifying and protecting critical habitats, it is important to understand how this spatial and temporal variation in habitat quality affects the production dynamics of populations. Here, we use microchemical records preserved in otoliths to reconstruct juvenile habitat-use by sockeye salmon that survived to spawn in a single population on the Alaska Peninsula. Successful individuals demonstrated a diverse array of juvenile behavioral strategies both within and among years. Importantly, the dominant juvenile behavioral strategy used by successful individuals changed among years, suggesting shifts in the relative benefits of different rearing habitats. The growth benefits of remaining in a more productive rearing lake were greatest in warm years indicating environmental influence on relative habitat quality. However, we found no strong relationship between the amount of growth accumulated in the productive rearing lake and overall population productivity across years. These results highlight the dynamic nature of habitat conditions and the beneficial effect of maintaining connectivity between diverse habitats for population productivity. When short-term studies are used to demonstrate the relative values of different habitats to species of conservation concern, there is a distinct risk of under-valuing habitats that may be critically important under alternative environmental conditions. In particular, land-use decisions that reduce the range of habitat options available to species may erode a population's ability to withstand environmental change over the long term.
... There have been clear shifts in the age composition of sockeye salmon returning to Bristol Bay since brood year 1963 ( Fig. 1), yet the average age (freshwater + ocean) has not changed (Supplementary Table 1). Rivers across the region differ in these freshwater and ocean age compositions, probably reflecting differences in spawning and rearing conditions encountered in different watersheds 31 . Nonetheless, most river systems have seen increases in the proportions of 1.x (younger migration to the ocean) and x.3 (longer residency in the ocean; Fig. 1). ...
The life-histories of exploited fish species, such as Pacific salmon, are vulnerable to a wide variety of anthropogenic stressors including climate change, selective exploitation and competition with hatchery releases for finite foraging resources. However, these stressors may generate unexpected changes in life-histories due to developmental linkages when species complete their migratory life cycle in different habitats. We used multivariate time-series models to quantify changes in the prevalence of different life-history strategies of sockeye salmon from Bristol Bay, Alaska, over the past half-century—specifically, how they partition their lives between freshwater habitats and the ocean. Climate warming has decreased the time spent by salmon in their natal freshwater habitat, as climate-enhanced growth opportunities have enabled earlier migration to the ocean. Migration from freshwater at a younger age, and increasing competition from wild and hatchery-released salmon, have tended to delay maturation toward the salmon spending an additional year feeding in the ocean. Models evaluating the effects of size-selective fishing on these patterns had only small support. These stressors combine to reduce the size-at-age of fish vulnerable to commercial fisheries and have increasingly favoured a single-age class, potentially affecting the age class complexity that stabilizes this highly reliable resource.
... This in turn implies that either some of the genes affecting the threshold(s) are linked to sex-determining genes, or they exhibit sexdependent expression patterns. Thresholds also vary among populations resulting in population-specific norms of reaction between condition and the decision to migrate or remain freshwater (Quinn et al., 2009). Populations with a lower incidence of anadromy would also have lower mean threshold values than populations with a higher incidence. ...
While many brown trout (Salmo trutta) populations spend their entire life cycle in freshwater, especially as river-lake migrants or river residents, others show facultative anadromy. That is, some trout migrate to sea while other individuals of the same population remain within their natal river. Sea trout can give rise to resident offspring and vice versa, although there is a strong tendency to track the parental life history. Anadromy delivers better feeding and thus larger size, which results in higher fecundity in females, enhanced mate choice, and other reproductive benefits. River residence, more prevalent in males as anadromy conveys fewer benefits, can give higher survival and avoids the energy expenditure required by anadromy. Overall, the costs and benefits of anadromy versus residency, measured in terms of survival and reproduction, are finely balanced and small changes to the cost-benefit equation can lead to evolutionary changes in life history. The decision to be anadromous or resident is a quantitative threshold trait, controlled by multiple genes and environmental factors. The dichotomous nature of the trait is postulated to be the result of the environmentally influenced physiological condition (e.g. energy status) relative to a genetically determined threshold. Anadromy ensues when an individual’s condition fails to meet the threshold level, which varies between sexes and among individuals and populations. Environmental factors and genetic architecture may also directly influence life history, e.g., by altering gene expression. A strong genetic influence on the anadromy decision means that facultative anadromy can be altered by natural selection driven by changes such as differential exploitation, stocking with farm-reared brown trout, partial barriers to migration, and changes in climate, and freshwater and marine productivity, together with parasite, pathogen and predator abundance resulting in reduced marine survival and growth. Further studies of the factors determining life history choice, together with multiple population estimates of heritability and differential reproductive success (fitness), are required to understand fully the impact of natural and anthropogenic environmental changes on sea trout dynamics.
... Similarly, data on coho salmon (Shapovalov and Taft 1954) and kokanee (Lorz and Northcote 579 1965) also showed that males arrived prior to females on average. This seems to be a general 580 pattern (Morbey 2000, Quinn et al. 2009), likely evolved to maximize the reproductive success 581 of males. This is paradoxical because the females select, prepare, and guard the nest site so it 582 might seem that males should arrive after females. ...
In several groups of anadromous fishes, but especially the salmonids, some populations migrate from the ocean to fresh water many months prior to spawning. This "premature migration" reduces growth opportunities at sea, compels them to occupy much less productive freshwater habitats, and exposes them to extremes of flow and temperature, disease, and predation. We first review migration in salmonids and find great variation in timing patterns among and within species, relative to the timing of reproduction. Premature migration is widely distributed among species but not in all populations, and we propose two hypotheses to explain it. First, the fish may be making "the best of a bad situation" by entering early because access to suitable breeding sites is constrained seasonally by flow or temperature regimes, so they sacrifice growing opportunities at sea. Alternatively or additionally, some populations may be "balancing risks and benefits" as they trade off the benefits of growth at sea against the risk of mortality there. In this model, the reduced risk of mortality at sea must be balanced against the risk of mortality in freshwater habitats from thermal stress, disease, and predators. Premature migration may be favored where temperatures and flows are moderate or where lakes provide safety from predators and reduce energetic expenditure. Consistent with this hypothesis, early return is characteristic of larger, older salmonids (that would benefit less from additional time at sea to grow than would smaller fish). Finally, we consider the vulnerability of premature migrants to climate change and selective fisheries. Migration timing is an important part of the portfolio of phenotypic diversity that conveys resilience to species, population complexes, and the fisheries that depend on them. The premature migrants are often especially valued in fisheries and also often of particular conservation concern, and the phenomenon merits further research.
... The sockeye salmon (Oncorhynchus nerka) is a large teleost fish widely distributed in coastal water throughout the North Pacific Ocean. It is an anadromous species utilizing both freshwater and marine habitats, for spawning-larval development and growthmaturation, respectively (Quinn et al. 2009). Growth during the early marine phase is critical to recruitment because of sizeselective juvenile mortality (Koenings et al. 1993;McKinnell et al. 2001;Farley et al. 2007;Welch et al. 2011). ...
Monitoring habitat utilization and early marine growth of sockeye salmon juveniles (Oncorhynchus nerka) in fjords of the Pacific Northwest is currently hampered by difficulties in estimating residence times, limiting scientific advances in certain aspects of this species' fisheries management and conservation. Combining otolith microchemistry and conventional daily ring counts, we were able to obtain the date of first entry and the residence time of sockeye juveniles in Rivers Inlet, British Columbia. This operationally inexpensive method builds upon variable microelement concentrations in fresh-and saltwater environments: barium (Ba) and strontium (Sr) concentrations within the sockeye otoliths differed between the freshwater and seawater growth zones; Ba concentrations in the freshwater growth zone were significantly higher than those in the seawater growth zone, while Sr concentrations in the former were significantly lower than in the latter. The concentrations of these elements within otoliths were determined quantitatively at high spatial resolution using in situ laser ablation inductively coupled with a plasma mass spectrometer (ICPMS) providing a record of the ambient environmental conditions experienced by individual fish. Exploratory analysis of a 3-year data set showed that the mean residence time of sockeye juveniles in Rivers Inlet varied between 3 and 6 weeks between years.
Migratory fish species have been particularly impacted by changes to the hydrologic and climatic cues to which migration and spawning behaviours have been adapted across generations. While conservation and recovery programs increasingly implement flow management actions to promote successful migration and spawning, uncertainty regarding how spawning migration phenology responds to changing environmental conditions can limit the ability to effectively target such recovery actions. Here, we use a Bayesian hierarchical modelling framework to analyse spawning migration phenology of individually tagged June suckers ( Chasmistes liorus ) – a federally threatened, long‐lived, iteroparous, adfluvial species endemic to Utah Lake (Utah, USA) and its tributaries. We then examine how annual hydrologic and thermal conditions relate to different components of annual migration phenology, including peak migration date, in‐stream residence time, and among‐individual variation in migration timing. Peak migration date occurred earlier in years with warmer spring air temperatures (a proxy for water temperatures), though this effect interacted with peak runoff timing. Both residence time and among‐individual variation in migration timing were greater in years with larger spring discharge and later peak flows. Residence time was also longer in warmer years. These results highlight how natural and anthropogenic changes to river flow and thermal regimes are likely to impact June sucker migration timing and duration, and our approach can be applied to other migratory species to identify the external drivers of the different components of migration phenology.
Understanding the relative contributions of the environment to commercial fisheries and aquaculture systems is an area of intense importance as it quantifies the dependence these human dominated systems have on healthy and productive ecosystems. Measures of sustainability are required that include environmental support, use of nonrenewable resources, and labor & services. This work draws on primary and secondary data used in an emergy analysis approach to assess environmental support and sustainability of a wild catch sockeye salmon fishery in Bristol Bay, Alaska and Atlantic salmon aquaculture in Norway. The analyses ended at the processing gate for both production systems. Environmental support of the sockeye fishery amounted to 69% of total inputs for landed fish and 37% for processed fish, while the environmental support for farm raised Atlantic salmon was 60% and 42% for landed and processed fish respectively. Labor and services contributed 53% of total inputs for processed sockeye and 44% for Atlantic salmon. The emergy indices for the wild caught sockeye and farmed Atlantic salmon systems were relatively high having emergy yield ratios for landed fish of 3.2 (wild caught sockeye) and 2.3 (farmed Atlantic salmon). After processing emergy yields of both systems were 1.6 (sockeye) and 1.7 (Atlantic salmon). Environmental loading ratios for the sockeye fishery were 0.45 and 1.69 for landed salmon and processed fish respectively, while for Atlantic salmon they were 0.76 and 1.40 for harvested and processed fish respectively. Emergy sustainability indexes (ESI) for both production systems were much higher than other aquaculture systems. Landed sockeye salmon had an ESI of 7.2, while that of farmed raised Atlantic salmon was 3.0, somewhat lower, but still a relatively sustainable source of high-quality protein.
Due to the mediating role of body size in determining fitness, the ‘bigger is better’ hypothesis still pervades evolutionary ecology despite evidence that natural selection on phenotypic traits varies in time and space. For Pacific salmon (genus Oncorhynchus), most individual studies quantify selection across a narrow range of sizes and ages; therefore, uncertainties remain concerning how selection on size may differ among diverse life‐histories. Here, we quantify the direction and magnitude of natural selection on body size among age‐classes of multiple marine cohorts of O. nerka (sockeye salmon). Across four cohorts of seaward migrants, we calculated standardized selection differentials by comparing observed size distributions of out‐migrating juvenile salmon to back‐calculated smolt length from the scales of surviving, returning adults. Results reveal the magnitude of selection on size was very strong (> 90th percentile compared to a database of 3,759 linear selection differentials) and consistent among years. However, the direction of selection on size consistently varied among age‐classes. Selection was positive for fish migrating to sea after two years in freshwater (age 2) and in their first year of life (age 0), but negative for fish migrating after 1 year in freshwater (age 1). The absolute magnitude of selection was negatively correlated to mean ocean‐entry timing, which may underpin negative selection favoring small age‐1 fish, given associations between size and timing of seaward migration. Collectively, these results indicate that ‘bigger is not always better’ in terms of survival and emphasize trade‐offs that may exist between fitness components for organisms with similarly diverse migratory life‐histories.
Pink salmon is found from 40° to 70°N; but successful reproduction occurs over a much more restricted area, from about 47° to 60°N. The time window of spawning opportunities is censored both at the southern and the northern boundaries, and reaches its widest expansion in south east Alaska extending from 54° to 58°N, more or less in the central part of the occupied area. Duration of peak spawning time for a single population seemingly does not vary with latitude, but the number of spawning populations increases from the northern and the southern limits toward the centre of distribution. Recent intensive studies of straying of pink salmon from enhanced stocks in Prince William Sound into wild stocks and vice versa have given estimates of high straying rates (J. Seeb personal communication). But movement of tagged fish into other streams than the one of origin does not automatically indicate successful spawning. The existence of more than 2000 pink salmon streams in south east Alaska, each with a characteristic time of spawning in spite of straying, indicate that there exists barriers, which prevent or reduce successful interpopulation spawning.
In the breeding system of Pacific salmon, females compete for oviposition territories, and males compete to fertilize eggs. The natural selection in females and sexual selection in males likely has been responsible for their elaborate breeding morphologies and the dimorphism between the sexes. We quantified direct-selection intensities during breeding on mature coho salmon (Oncorhynchus kisutch), measured for seven phenotypic characters, including three secondary sexual characters. Wild and sea-ranched hatchery coho were used to enhance the range of phenotypes over which selection could be examined. The fish were allowed to breed in experimental arenas where we could quantify components of breeding success as well as estimate overall breeding success. We found that without competition, natural selection acts only on female body size for increased egg production; there is no detectable selection on males for the phenotypic distribution we used. Under competition, the opportunity for selection increased sixfold among females. Natural selection favored female body size and caudal-peduncle (tail) depth. Increased body size meant increased egg production and access to nesting territories. The caudal peduncle, used in burst swimming and nest digging, influenced both successful egg deposition and nest survival. Increasing density increased competition among females, though it did not significantly intensify natural selection on their characters. In males, competition increased the opportunity for selection 52-fold, which was nine times greater than for females. Sexual selection favored male body size and hooked snout length, both characters directly influencing male access to spawning opportunities. Selection on male body size was also affected significantly by breeding density. The ability of large males to control access to spawning females decreased at higher densities reflecting an increase in the operational sex ratio. Further, the relative success of small males, which could sneak access to spawning females, appeared to increase as that of intermediate-sized males decreased. Such disruptive selection may be responsible for the evolution of alternative reproductive tactics in salmon.
We studied breeding competition among wild female coho salmon (Oncorhynchus kisutch) and quantified natural selection acting on two important female characters: body size and kype size (a secondary sexual character used for fighting). We found that body size contributed to adult female fitness in three ways, through 1) an increased initial biomass of egg production, 2) the ability to acquire a high-quality territory for egg development, and 3) success in nest defense. These factors together resulted in as much as a 23-fold fitness advantage to the largest females in the population. The initial investment into egg production accounted for 50-60% of the measured intensity of natural selection on female body size. The effective investment into egg production (after female competition for territories) accounted for 40-50% of natural selection on female body size. Therefore, success in breeding competition is about as important as egg production in the current evolution of female body size. This is contrary to the expectation based on most fisheries literature. The size of a female's kype was also important to female reproductive success, although its contribution could not be separated from that of body size in our study. The strong natural selection that we have found for female competitive ability is presumably the basis for the evolution of female parental care in salmonids.
Although the Pacific Ocean and associated islands contain the most diverse assemblage of the genus Anguilla of the 15 species), the biology of several species is little known. The best studied species are those of Australasia (A. australis, A. reinhardtii, and A. dieffenbachii), and hence much of the comparative biology described in this chapter comes from these species. Because many of the features of the biology of the eels of the South Pacific are generally similar to those of the better-known northern hemisphere species (A. anguilla, A. japonica, and A. rostrata), emphasis is given to describing features that are different or unique.
