Jeffrey A Hutchings

Dalhousie University | Dal · Department of Biology

To reduce the risk of overexploitation and the ensuing conservation and socioeconomic consequences, fisheries management relies on receiving accurate scientific advice from stock assessments. Biomass dynamics models used in stock assessment tend to rely primarily on indices of abundance and commercial landings data. Standard practice for calculatin...

The positive effects of reduced fishing pressure in marine protected areas (MPAs) are now well documented globally. Yet, evidence of MPA benefits from long-term replicated before-after control-impact (BACI) studies and their usefulness in protecting target species are still rare, especially in northern temperate areas. Scientific rigor in the monit...

Providing science-based advice can be challenging. Personal in its reflections, the story that follows asks throughout: What constitutes an appropriate model for the communication of science-based advice that best serves society? The first “front line,” in 1992, involved tenuous hypotheses on the collapse and recovery of Newfoundland's Northern cod...

Climate change is anticipated to have multiple consequences for aquatic ectotherms. Warming temperatures, for example, are predicted to reduce body size in many fish species. Smaller sizes may be caused by physiological constraints associated with respiration, life-history responses to faster growth and concomitant earlier age at maturity, and inte...

Offspring number and size are two of the most variable life-history traits. Among species, much of this variability can be attributed to genetic, developmental, physiological, or structural constraints. Some trait combinations are not possible because of differences associated with a species’ evolutionary history. Substantial variation in propagule...

By affecting age-specific survival and fecundity, human-induced disturbances affect life history. This has potential to affect r max with negative consequences for species viability and persistence. Several types of assessments are used to classify vulnerability to extinction, exploitation, and climate change. When information on r max is unavailab...

Life histories describe how genotypes schedule their reproductive effort throughout life in response to factors that affect their survival and fecundity. Life histories are solutions that selection has produced to solve the problem of how to persist in a given environment. These solutions differ tremendously within and among species. Some organisms...

Predictions about life-history evolution are intellectually bereft without a consideration of trade-offs. Benefits derived from making one life-history ‘decision’ are made at a cost of not realizing potential benefits associated with alternative decisions. These trade-offs are the inevitable product of constraints, often driven by an individual’s d...

When compared to the unexploited environments in which organismal life histories evolved, hunting and fishing impose additional sources of extrinsic mortality often several times greater than natural mortality. This has direct consequences for l x and potentially b x . Efforts to achieve sustainable exploitation, which are often based on the concep...

The sustainable management of fisheries has largely relied on stock assessment models that assume stocks are homogeneous throughout their domain. However, ignoring complex underlying spatial patterns can lead to increased risk of failures in management. Utilizing geostatistical approaches in conjunction with a traditional fishery biomass dynamics m...

The fishery for Northern Atlantic cod (Gadus morhua) off Newfoundland and Labrador, Eastern Canada, presents the most spectacular case of an exploited stock crashed in a few decades by an industrial bottom trawl fishery under a seemingly sophisticated management regime after half a millennium of sustainable fishing. The fishery, which had generated...

Stochastic environments shape life‐history traits and can promote selection for risk‐spreading strategies, such as bet‐hedging. Although the strategy has often been hypothesised to exist for various species, empirical tests providing firm evidence have been rare, mainly due to the challenge in tracking fitness across generations. Here, we take a ‘p...

Declines in wild Atlantic salmon (Salmo salar) abundance throughout the north Atlantic are primarily attributed to decreases in survival at sea. However, comparing trends in marine survival among populations is challenging as data on both migrating smolts and returning adults are sparse and models are difficult to parameterize due to their varied l...

Management of Canada’s fisheries is guided by federal policy that stresses taking a precautionary approach using the best available science. Despite nearly 30 years in the making, the Northern cod rebuilding plan manages to do neither.

As a consequence of climate change and open net-pen salmon farming, wild Atlantic salmon Salmo salar are increasingly likely to encounter elevated temperatures and parasite abundances during their early marine migration. Such stressors can compromise fitness by diminishing liver energy stores and impairing cardiac muscle. To assess whether temperat...

Although temperature is known to drive species dynamics and distributions, our understanding of the extent to which thermal plasticity varies within species is poor. Differences in plasticity can arise through local adaptation to heterogeneous environments, hybridization, and the release of cryptic genetic variation in novel environments. Here, wil...

Infectious diseases are key drivers of wildlife populations and agriculture production, but whether and how climate change will influence disease impacts remains controversial. One of the critical knowledge gaps that prevents resolution of this controversy is a lack of high-quality experimental data, especially in marine systems of significant ecol...

Regime shifts are increasingly prevalent in the ecological literature. However, definitions vary and detection methods are still developing. Here, we employ a novel statistical algorithm based on the Bayesian online change-point detection framework to simultaneously identify shifts in the mean and (or) variance of time series data. We detected mult...

Phenotypic variance is a function of genetic variability, environmental variation, and the ways in which genetic and environmental variation interact, i.e., VG×E. Reaction norms are a means of conceptually, graphically, and mathematically describing this total variance and are a powerful tool for decomposing it into its constituent parts (i.e., nat...

Shifts in size structure have been documented for many commercially exploited marine fish stocks, thought to be attributed to size-selective harvesting practices coupled with changing oceanic conditions. Northwest Atlantic monkfish (Lophius americanus) is a commercially valued species in the United States that is commonly caught as bycatch in Canad...

The status of many Canadian fisheries is poor, a consequence of inadequate implementation of sustainable fishery policy within the context of the Precautionary Approach (PA). A key component of implementation lies with the provision of science advice. Scientists are responsible for advising on options likely to meet policy intent and objectives. He...

Natural populations of ectothermic oviparous vertebrates typically experience thermal variability in their incubation environment. Yet an overwhelming number of laboratory studies incubate animals under constant thermal conditions that cannot capture natural thermal variability. Here, we systematically searched for studies that incubated eggs of ec...

Regime shifts are increasingly prevalent in the ecological literature. However, definitions vary, and many detection methods are subjective. Here, we employ an operationally objective means of identifying regime shifts, using a Bayesian online change-point detection algorithm able to simultaneously identify shifts in the mean and(or) variance of ti...

Genetic and genomic architectures of traits under selection are key factors influencing evolutionary responses. Yet, knowledge of their impacts has been limited by a widespread assumption that most traits are controlled by unlinked polygenic architectures. Recent advances in genome sequencing and eco-evolutionary modelling are unlocking the potenti...

The marine phase of anadromous Atlantic salmon (Salmo salar) is the least known yet one of the most crucial with regards to population persistence. Recently, declines in many salmon populations in eastern Canada have been attributed to changes in the conditions at sea, thus reducing their survival. However, marine survival estimates are difficult t...

Having the longest coastlines in the world and some of the largest freshwater ecosystems, Canada has a rich history of exploitation and stewardship of its marine and freshwater fisheries resources. For thousands of years prior to European settlement, Indigenous peoples across what is now Canada utilized and managed marine and freshwater fisheries t...

A 2012 Expert Panel Report on marine biodiversity by the Royal Society of Canada (RSC) concluded that Canada faced significant challenges in achieving sustainable fisheries, regulating aquaculture, and accounting for climate change. Relative to many countries, progress by Canada in fulfilling international obligations to sustain biodiversity was de...

Genetic and genomic architectures of traits under selection are key factors influencing evolutionary responses. Yet, knowledge of their impacts has been limited by a widespread assumption that most traits are controlled by unlinked polygenic architectures. Recent advances in genome sequencing and eco-evolutionary modelling are unlocking the potenti...

Iteroparity is a bet-hedging strategy where individuals spread the risk of reproductive failure over time. The occurrence of iteroparity (i.e. proportion of repeat spawners in annual returns) varies among Atlantic salmon (Salmo salar) populations, yet information on its ecological importance is limited. We compiled multi-decadal time series on the...

The argument that sufficiently high fishing mortality (selective or not) can effect genetic change in fished populations has gained considerable traction since the late 1970s. The intervening decades have provided compelling experimental and model‐based evidence that fisheries‐induced evolution (FIE) can cause genetic changes in life history, behav...

Advances in genetic and genomic technologies have become widely available and have potential to provide novel insights into fish biology and fisheries science. In the present overview, we explore cases for which genomic analyses have proven instrumental in the rejection of hypotheses that have been well-motivated based on phenotypic and ecological...

Non-anadromous Atlantic salmon (Salmo salar) exhibit a combination of variation in life history, habitat, and species co-existence matched by few vertebrates. Distributed in eastern North America and northern Europe, habitat ranges from hundreds of metres of river to Europe’s largest lakes. As juveniles, those with access to a lake usually migrate...

• Body size determines key ecological and evolutionary processes of organisms. Therefore, organisms undergo extensive shifts in resources, competitors, and predators as they grow in body size. While empirical and theoretical evidence show that these size‐dependent ontogenetic shifts vastly influence the structure and dynamics of populations, theory...

Size-selective harvesting is expected to reduce the average age and weight of commercially exploited fishes. The loss of larger, older fish has been hypothesized to negatively affect metrics of population viability, such as spawning behaviour, recruitment, and adult survival. Most studies to date have focussed on individual stocks. Here, we examine...

Successful resource‐management and conservation outcomes ideally depend on matching the spatial scales of population demography, local adaptation, and threat mitigation. For marine fish with high dispersal capabilities, this remains a fundamental challenge. Based on daily parentage assignments of more than 4,000 offspring, we document fine‐scaled t...

The protracted spawning period of broadcast-spawning marine fishes has potential to generate considerable variability in metrics of individual reproductive output. We undertook a temporally detailed genetic study of larvae produced by Atlantic cod (Gadus morhua) from two spatially proximate populations spawning under controlled semi-natural conditi...

Coexistence in the same habitat of closely related yet genetically different populations is a phenomenon that challenges our understanding of local population structure and adaptation. Identifying the underlying mechanisms for such coexistence can yield new insight into adaptive evolution, diversification, and the potential for organisms to adapt a...

Senescence is the physiological deterioration of adult organisms leading to an age-specific decline in fitness principally associated with an increase in mortality rate (actuarial senescence) and decline in fecundity (reproductive senescence). Senescence is common in natural populations of many taxa; however, there are few examples among fishes, ev...

Chromosomal rearrangements such as inversions can play a crucial role in maintaining polymorphism underlying complex traits and contribute to the process of speciation. In Atlantic cod (Gadus morhua), inversions of several megabases have been identified that dominate genomic differentiation between migratory and nonmigratory ecotypes in the Northea...

The need to better understand how plasticity and evolution affect organismal responses to environmental variability is paramount in the face of global climate change. The potential for using RNA sequencing (RNA-seq) to study complex responses by non-model organisms to the environment is evident in a rapidly growing body of literature. This is parti...

Probability of species recovery is thought to be correlated with specific aspects of organismal life history, such as age at maturity and longevity, and how these affect rates of natural mortality (M) and maximum per capita population growth (rmax). Despite strong theoretical underpinnings, these correlates have been based on predicted rather than...

Decreasing fishmeal availability and increasing prices promote the usage of plant-derived feedstuff as a substitution for fishmeal in commercial salmonid diets. However, little is known about the impact of plant-derived feedstuff on juvenile brown trout (Salmo trutta), a species that exhibits strong phenotypic plasticity with various genetic sub-st...

Life-history traits are generally assumed to be inherited quantitatively. Fishing that targets large, old individuals is expected to decrease age at maturity. In Atlantic salmon ( Salmo salar ), it has recently been discovered that sea age at maturity is under strong control by a single locus with sexually dimorphic expression of heterozygotes, whi...

Population connectivity among adult marine organisms is often attributed to disper- sal during the egg/larval stage. However, post-larval dispersal may also influence connectivity, particularly when juvenile nursery habitats are separated from adult spawning habitats. Here we used age-based population genetics and kinship analysis to explore change...

According to density-dependent habitat selection theory, areas of high density can be indicative of high population productivity and have positive individual fitness consequences. Here, we explore six groundfish populations on the Scotian Shelf, Canada, where a decline in areas of high density beyond a certain threshold is associated with dispropor...

This article compares the law and policy frameworks for protecting marine species at risk in Australia and Canada. The sea of practical challenges is examined, including achieving listing of threatened commercial species; attaining timely and effective recovery planning; and identifying and protecting critical habitats.

Table S1. Age‐specific vital rates for simulated cod populations at representative time periods. Table S2. Age‐specific vital rates for cod life table #2 under different assumptions about adult survival.

Data S1. Age‐specific variance in reproductive success. Figure S1. Patterns of adult survival (individuals age 3+) as a function of age in simulated cod populations. Figure S2. Effects of varying levels of fishing intensity for simulated cod populations. Results are for selective fishing without evolution (i.e., as in Fig. 5, main text, but witho...

Barriers to migration can negatively affect population persistence. To explore how dams can influence the viability of a diadromous fish, we developed an empirically based stochastic model to estimate per capita population growth rate (r) and probability of population decline (Pr(r<0)). Our simulations incorporated life-history parameters common fo...

Much has been written about fishery-induced evolution (FIE) in exploited species, but relatively little attention has been paid to the consequences for one of the most important parameters in evolutionary biology—effective population size (Ne). We use a combination of simulations of Atlantic cod populations experiencing harvest, artificial manipula...

We critique advisory models for the communication of science to government.

We employed common-garden experiments to test for genetic variation in responses of larval life-history traits to temperature between two populations of Atlantic cod (Gadus morhuaL., 1758) that naturally experience contrasting thermal environments during early life due to spatial and temporal differences in spawning. Southern Gulf of St. Lawrence c...

Background: A highly mobile marine fish, Atlantic cod (Gadus morhua), inhabits southern Norwegian coastal habitats that offer limited potential for individual dispersal and migration. Questions: Do coastal populations of cod differ in life history? If so, is the variability spatially persistent and does it vary with time? What factors are responsib...

Population trends play a large role in species risk assessments and conservation planning, and species are often considered threatened if their recent rate of decline meets certain thresholds, regardless how large the population is. But how reliable an indicator of extinction risk is a single estimate of population trend? Given the integral role th...

A basic challenge to successful management and conflict resolution is to correctly identify the spatial scale at which strategies for harvesting are developed. For commercially exploited marine fish, distributional boundaries of many stocks are based on the premise that productivity is similar at spatial scales that represent a small fraction of an...

The ability of populations to adapt to environmental change and the spatial scale at which this adaptation occurs are fundamentally important issues in evolutionary biology, and ones that may benefit greatly from the study of genetic variability in reaction norms, which represent the plasticity of phenotypic traits across an environmental gradient....

The level of phenotypic plasticity displayed within a population (i.e. the slope of the reaction norm) reflects the short-term response of a population to environmental change, while variation in reaction norm slopes among populations reflects spatial variation in these responses. Thus far, studies of thermal reaction norm variation have focused on...

Studies on small and declining populations dominate research in conservation biology. This emphasis reflects two overarching frameworks: the small-population paradigm focuses on correlates of increased extinction probability; the declining-population paradigm directs attention to the causes and consequences of depletion. Neither, however, particula...

The abundance–occupancy relationship is one of the most well-examined relationships in ecology. At the species level, a positive association has been widely documented. However, until recently, research on the nature of this relationship at broad taxonomic and spatial scales has been limited. Here, we perform a comparative analysis of 12 taxonomic...

Alternative reproductive phenotypes represent adaptive life-history responses to local environments. Hybridization with domesticated conspecifics exposed to selection against one of the phenotypes could affect the plasticity and incidence of alternative reproductive phenotypes within wild populations, potentially influencing individual fitness and...

Exploited fish populations frequently exhibit truncated age-structure. To address a basic question in fisheries science and conservation biology—how does age truncation affect population dynamics and productivity?—we explored the effect of age-structure on recruitment dynamics of ten stocks of Atlantic cod (Gadus morhua). Based on six alternative s...

The Silences of the Archives, the Reknown of the Story. The Martin Guerre affair has been told many times since Jean de Coras and Guillaume Lesueur published their stories in 1561. It is in many ways a perfect intrigue with uncanny resemblance, persuasive deception and a surprizing end when the two Martin stood face to face, memory to memory, befor...

Natural environmental change has produced countless opportunities for species to disperse into and persist in habitats where they previously did not exist. Introduction and stocking programmes have facilitated similar sorts of colonization opportunities across considerably greater geographical scales and often in much shorter periods of time. Even...

Many studies have identified the importance of local adaptation in Atlantic salmon (Salmo salar) and the strong genetic differences that exist between allopatric or parapatric resident and anadromous populations. However, as truly sympatric migratory phenotypes of Atlantic salmon have not been studied, it remains unclear whether distinct genotypes...

Figure S1. Relative selectivity of fishing as a function of fish body length.

Data S1. Sensitivity to the magnitude of heritability.