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Publications (100)
We examine estimates of dispersal in a broad range of marine species through an analysis of published values, and evaluate how well these values represent global patterns through a comparison with correlates of dispersal. Our analysis indicates a historical focus in dispersal studies on low-dispersal/low-latitude species, and we hypothesize that th...
The success of marine protected areas (MPAs) as fisheries management tools in tropical latitudes has generated interest in their applicability and potential elsewhere. Here we suggest that dispersal and gene flow in marine fish populations (a primary biological consideration for marine reserve design) increases with latitude. For example, north tem...
As Arctic ice recedes, future oil spills pose increasing risk to keystone species and the ecosystems they support. We show that Polar cod (Boreogadus saida), an energy-rich forage fish for marine mammals, seabirds, and other fish, are highly sensitive to developmental impacts of crude oil. Transient oil exposures ≥300 μg/L during mid-organogenesis...
Pacific cod (Gadus macrocephalus) stocks in the Gulf of Alaska experienced steep, unexpected declines following an unprecedented 3-year marine heatwave (i.e., “warm blob”) from 2014 to 2016. We contend that stock reproductive potential was reduced during this period, evidenced by a combination of new laboratory data demonstrating narrow thermal hat...
The rapid decline in Pacific cod (Gadus macrocephalus, Gadidae) biomass following multiple Gulf of Alaska marine heatwaves (2014-2016 and 2019) may be one of the most dramatic documented changes in a sustainably managed marine fishery. As such, fisheries managers are exploring new recruitment paradigms for Pacific cod under novel environmental cond...
Marine heatwaves (MHWs) are often associated with physiological changes throughout biological communities but can also result in biomass declines that correspond with shifts in phenology. We examined the response of larval Pacific cod (Gadus macrocephalus) to MHWs in the Gulf of Alaska across seven years to evaluate the effects of MHWs on hatch phe...
Marine Heatwaves (MHWs) can directly influence survival of marine fishes, particularly for early life stages, including age-0 juveniles during their residence in coastal nursery habitats. However, the ability of nurseries to support high fish densities, optimize foraging and growth, and protect against predators may be altered during MHWs. Gulf of...
The eastern North Pacific is simultaneously experiencing ocean warming (OW) and ocean acidification (OA), which may negatively affect fish early life stages. Pacific cod (Gadus macrocephalus) is an economically and ecologically important species with demonstrated sensitivity to OW and OA, but their combined impacts are unknown. Through a ~ 9-week e...
Warming temperatures in the Gulf of Alaska have been linked to recruitment failure in Pacific cod (Gadus macrocephalus), but the mechanisms and timing of mortality events for juveniles are unclear. To date, limited research has focused on overwintering success, and the knowledge of juvenile ecology and physiology is based entirely on summer observa...
Warming climates are creating unprecedented environmental conditions, such as more frequent and intense marine heatwaves (MHWs), that directly impact phenology and growth of fish and other marine organisms. Understanding individual phenological and growth responses to temperature is critical to predict species and population responses to climate ch...
Arctic cod (Boreogadus saida) is the most abundant forage fish in the Arctic Ocean. Here we review Arctic cod habitats, distribution, ecology, and physiology to assess how climate change and other anthropogenic stressors are affecting this key species. This review identifies vulnerabilities for different life stages across the entire distribution r...
Warming temperatures elicit shifts in habitat use and geographic distributions of fishes, with uneven effects across life stages. Spawners and embryos often have narrower thermal tolerances than other life stages, and are thus particularly sensitive to warming. Here, we examine the spatiotemporal variability of thermal spawning habitat for Pacific...
Juvenile Atlantic cod Gadus morhua in coastal Newfoundland, Canada, settle in nearshore habitats in 3-6 pulsed events each year, from mid-summer to early winter, creating a broad size range of age-0 fish within each year-class, with potentially different survival trajectories entering their first winter. We hypothesized that early-arriving pulses,...
Climate change will drive sea ice loss, resulting in increased light availability across polar marine ecosystems, but the consequences of these changes are largely unknown. We quantify how future conditions for sea ice and snow, storm-driven waves, clouds, ozone, and chlorophyll will affect the seasonal absorption and reflection of light in Arctic...
Many fish species have moved poleward with ocean warming, and species distribution shifts can occur because of adult fish movement, or juveniles can recruit to new areas. In the Bering Sea, recent studies document a dramatic northward shift in the distribution of Gadus macrocephalus (Pacific cod in English and tikhookeanskaya treska in Russian) dur...
Warming temperatures elicit shifts in habitat use and geographic distributions of fishes, with uneven effects across life stages. Spawners and embryos are particularly sensitive to environmental conditions, with direct impacts of temperature on spawning habitat, as well as indirect connections between their population dynamics and fisheries effort,...
In the Arctic, winter warming and loss of sea ice pose largely unknown risks to keystone species and the marine ecosystem that they support. Young-of-the-year juvenile polar cod, Boreogadus saida, are an energy-rich forage fish that accumulate high levels of lipid in the summer but retain a relatively small body size during the winter. To address w...
The Arctic is undergoing dramatic environmental change with decreasing sea-ice extent and increasing summer temperatures. The late summers of 2017 and 2019 on the eastern Chukchi Sea were anomalously warm, nearly 4°C warmer than the previous 30-year average. Increased ocean temperatures can affect the energetics of North Pacific fish by increasing...
The Arctic is undergoing dramatic environmental change with decreasing sea-ice extent and increasing summer temperatures. The late summers of 2017 and 2019 on the eastern Chukchi Sea were anomalously warm, nearly 4 °C warmer than the previous 30-year average. Increased ocean temperatures can affect the energetics of North Pacific fish by increasing...
Climate change makes fish stocks more vulnerable to recruitment failure, and early detection of these events is important for an effective management response. Here, we evaluate the value of larval and juvenile surveys, and a thermal spawning habitat index, for predicting recruitment in two economically important gadids, walleye pollock (Gadus chal...
In subarctic Newfoundland, age-0 juvenile Atlantic cod (Gadus morhua) settle into coastal habitats in several summer and fall pulses, yielding a broad length-frequency distribution prior to their first winter. The first winter is often associated with physiological and metabolic stress and has been considered a critical survival period determining...
High-latitude climate warming is expected to have wide-ranging effects on habitats, ecosystems, and the fish species that occupy them. Not all fish species will be able to adapt to increasing temperatures. We investigated oxygen isotope fractionation in fish otoliths and its relationship to environmental temperature and thermal histories of individ...
Over the past two decades, numerous ecosystem surveys and process studies have emerged to monitor and assess the large marine ecosystems of Alaska. Several regional collaborative integrated ecosystem research projects (IERPs) were conducted to gain understanding of fish population fluctuations in relation to the surrounding environment. The Gulf of...
Sustainability—maintaining catches within the historical range of socially and ecologically acceptable values—is key to fisheries success. Climate change may rapidly threaten sustainability, and recognizing these instances is important for effective climate adaptation. Here, we present one approach for evaluating changing sustainability under a cha...
The Pacific cod (Gadus macrocephalus) fishery recently collapsed in the Gulf of Alaska after a series of marine heatwaves that began in 2014. To gauge the likelihood of population recovery following these extreme warming events, we investigate potential thermal stress on age-0 cohorts through a comprehensive analysis of juvenile cod abundance, cond...
Climate change will alter ecosystems and impose hardships on marine resource users as fish assemblages redistribute to habitats that meet their physiological requirements. Marine gadids represent some of the most ecologically and socio-economically important species in the North Atlantic, but face an uncertain future in the wake of rising ocean tem...
Quantifying the spatial and temporal footprint of multiple environmental stressors on marine fisheries is imperative to understanding the effects of changing ocean conditions on living marine resources. Pacific Cod (Gadus macrocephalus), an important marine species in the Gulf of Alaska ecosystem, has declined dramatically in recent years, likely i...
Climate change, along with environmental pollution, can act synergistically on an organism to amplify adverse effects of exposure. The Arctic is undergoing profound climatic change and an increase in human activity, resulting in a heightened risk of accidental oil spills. Embryos and larvae of polar cod (Boreogadus saida), a key Arctic forage fish...
Polar cod (Boreogadus saida) and saffron cod (Eleginus gracilis) are the most abundant and ecologically important forage fishes in the Pacific Arctic marine ecosystem, yet little is known about their spawning locations or the habitats occupied by their early life stages (ELS). We developed a biophysical transport model coupled to a Pan-Arctic hydro...
In subarctic Newfoundland, age-0 Atlantic cod (Gadus morhua) settle into coastal habitats in several summer–autumn pulses, resulting in broad length-frequency distributions before winter. Low winter temperatures and potential decreases in food availability pose challenges for young-of-year fish. To examine how size variation affects overwintering s...
Some of the longest and most comprehensive marine ecosystem monitoring programs were established in the Gulf of Alaska following the environmental disaster of the Exxon Valdez oil spill over 30 years ago. These monitoring programs have been successful in assessing recovery from oil spill impacts, and their continuation decades later has now provide...
The match-mismatch hypothesis predicts that variability in spring primary production will increase starvation risk for marine fish populations. However, it is often unclear whether the synergic effects of temperature, phytoplankton phenology and metabolic demands of fish support these prediction within and across regions. In this study, we combine...
Climate change in Arctic and sub-Arctic seas is leading to rapid changes in the dispersal potential of marine organisms. In Alaskan waters, loss of sea ice and salinity changes associated with warming may have a strong effect on the distribution and survival of eggs and larvae of key fish species at the Pacific–Arctic interface, such as polar cod (...
Characterizing the condition of fish in dynamic seasonal environments requires an understanding of their energy allocation strategies. Both polar cod (Boreogadus saida) and saffron cod (Eleginus gracilis) are important mid-trophic fish in Alaska Arctic waters, and changes in their lipid allocation could have important implications for their overwin...
The Gulf of Alaska experienced extreme temperatures during 2014-2019, including the four warmest years ever observed. The goal of this study is to evaluate the ecological consequences of that warming event, across multiple trophic levels and taxa. We tested for evidence that observed sea surface temperature (SST) anomalies were outside the envelope...
The Gulf of Alaska experienced extreme temperatures during 2014-2019, including the four warmest years ever observed. The goal of this study is to evaluate the ecological consequences of that warming event, across multiple trophic levels and taxa. We tested for evidence that observed sea surface temperature (SST) anomalies were outside the envelope...
In the Arctic, changing environmental conditions and increasing anthropogenic activity poses largely unknown risks to keystone species and the marine ecosystem they support. This includes Arctic cod, Boreogadus saida, a lipid-rich forage fish. To address the effect of overwinter temperatures on their energetics and survival, we ran overwintering la...
We present the results of a study of the connectivity between Pacific cod spawning and nursery areas, and settlement of Pacific cod in the Gulf of Alaska. This work was conducted to address the hypothesis that spatial and temporal patterns of recruitment are related to variability in connectivity between spawning and nursery areas. To examine this...
Changes in Arctic fish assemblages resulting from climate change will likely be determined by the differential thermal response of key species during their early life history. In this study, we incubated multiple batches of eggs and larvae of two ecologically important gadids co-occurring at the Pacific–Arctic interface, Arctic cod (Boreogadus said...
Arctic cod (Boreogadus saida) is an ecologically significant species that is uniquely adapted to occupy ice edges, but warming and loss of sea ice are hypothesized to favour more facultative gadids, such as walleye pollock (Gadus chalcogrammus). To test this hypothesis, we experimentally measured the growth and survival of Arctic cod and walleye po...
The Arctic marine environment is rapidly changing with rising sea surface temperatures, declining sea ice habitat and projected increases in boreal species invasions. The success of resident Arctic fish will depend on both their thermal tolerance and their ability to cope with changing trophic interactions. Larval fish energetic condition is closel...
Multiple aspects of climate change are expected to co-occur such that ocean acidification will take place in conjunction with warming and a range of trophic changes. Previous studies have demonstrated that nutritional condition plays a significant role in the responses of invertebrates to ocean acidification, but similar studies have yet to be cond...
ABSTRACT: Climate change impacts on Arctic fish communities will largely be determined by temperature-dependent vital metabolic rates of resident and invading species. In this study, we experimentally measured total lipids and lipid class storage in the liver and muscle of two juvenile Arctic gadids (Arctic cod, Boreogadus saida and saffron cod, El...
Forecasting climate-driven ecosystem impacts in the Arctic is currently limited by the availability of biological data on key species. In this study, we carried out a series of temperature-dependent growth experiments on juvenile Arctic cod (Boreogadus saida), an important forage fish species at the Atlantic- and Pacific-Arctic interface. Multi-wee...
Accurate forecasting of the environmental impacts of climate change on food webs in the Arctic is limited by our understanding of the physiological response of marine fish to changes in temperature and food availability. Both Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus) co-occur in the North Bering Sea and Chukchi Sea but...
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...
Coastal seine surveys contain some of the only direct measures of age-0 abundance for Atlantic cod (Gadus morhua) and Pacific cod (Gadus macrocephalus), yet their utility in forecasting future year-class strength has not been evaluated among regions. We analyzed coastal time series from the Gulf of Alaska, Newfoundland, and Norway to test the hypot...
Climate models indicate the Arctic will undergo dramatic environmental change with forecasted increases in temperature and river runoff. Saffron cod (Eleginus gracilis) is abundant in nearshore waters and appears in the diet of many Arctic sea birds and marine mammals, however, little is known about its early ecology and consequently how they might...
p id="p-2">Age-0 juveniles may be the earliest, reliable indicators of recruitment into commercial marine fisheries, but independent
fisheries assessments are usually conducted on older life stages in adult habitats. We used an 8 year juvenile gadid survey
along the coast of Kodiak, Alaska to examine annual abundance, growth and mortality in age-0...
The thermal sensitivity of Arctic fish species is poorly understood, yet such data are a critical component of forecasting and understanding ecosystem impacts of climate change. In this study, we experimentally measured temperature-dependent growth and routine swim activity in the juvenile stage of two Arctic gadids (Arctic cod, Boreogadus saida an...
The naturally occurring taurine concentrations of rotifers (Brachionus sp.) may not be sufficient to meet the nutritional demands of several species of marine fish larvae. In this study, we evaluated the use of liposomes for taurine-enrichment of rotifers and compared them with standard methods in which taurine was dissolved in the rotifer enrichme...
We addressed the hypothesis that larval flatfish have behavioral control over the timing and habitat in which they settle. Annual and seasonal settlement patterns of northern rock sole Lepidopsetta polyxystra were characterized across varying depths and sediments in 2 nursery areas around Kodiak, Alaska, USA. These data were compared to experimenta...
Northern rock sole (Lepidopsetta polyxystra) is a commercially important fish in the North Pacific and a focal species in understanding larval transport to nursery grounds in the Bering Sea. However, the temperature-dependent vital rates and settlement dynamics for this species have not been described in detail. We reared northern rock sole larvae...
Naturally-occurring taurine concentrations in rotifers may not meet the nutritional requirements for species of cultured marine fish during the larval stages. Traditional methods for the enrichment of rotifers by immersion in a nutrient solution may be inefficient and may promote the growth of pathogenic bacteria. Microparticles, spe- cifically wax...
Tubes of the ampharetid polychaete Sabellides sibirica are a prominent yet spatially variable habitat feature in shallow-water flatfish nurseries around Kodiak, Alaska, USA. Juvenile flatfish associate with the edges of worm tube regions but seldom use the dense 'turf-like' worm beds that sometimes form on the bottom in the late summer. The present...
Northern rock sole (Lepidopsetta polyxystra) is a commercially important flatfish species whose settlement dynamics are poorly understood. Recently collected field data from known nursery sites show that newly settled juveniles are initially settling in the shallowest region of juvenile nursery areas (< 3 m in depth) where substrates are too coarse...
During early development, oviparous fish species must use finite lipid and fatty acid (FA) reserves for both catabolism and structural components. In cold environments, developing fish have the additional constraint of maintaining membrane fluidity for metabolic efficiency (homeoviscous adaptation), resulting in further demand on lower melting poin...
Most marine fish larvae are thought to be gape-limited predators, and the presence of suitably sized prey at the appropriate time in the foraging environment is a key factor for their growth and survival. Two experiments were carried out: in experiment 1, we investigated feeding of Atlantic cod (Gadus morhua L., 1758) larvae from 5 to 35 days post...
The matchmismatch hypothesis (MMH) predicts that marine fish larvae will have their highest rate of growth and survival when they overlap with their prey. However, Pacific cod (Gadus macrocephalus) and other gadids continue to thrive in the Bering Sea despite delayed prey production resulting from warming and loss of sea ice. In this study, we exam...
Northern rock sole (Lepidopsetta polyxystra) is a commercially important f latf ish in Alaska and was recently classified as a distinct species from southern rock sole (L. bilineata). Taxonomic and vital rate data for northern rock sole are still not fully described, notably at early egg and larval stages. In this study, we provide new taxonomic de...
Global declines of eelgrass (Zostera marina) have major ramifications for the juvenile fishes for which this plant can provide nursery habitat. However, it is less clear how rapidly fishes can recover when habitat loss is reversed, either through natural growth or through habitat enhancement efforts. We investigated the consequences of natural expa...
Pacific cod (Gadus macrocephalus) is an important component of fisheries and food webs in the North Pacific Ocean and Bering Sea. However, vital rates of early life stages of this species have yet to be described in detail. We determined the thermal sensitivity of growth rates of embryos, preflexion and postflexion larvae, and postsettlement juveni...
The 'shallow water refuge hypothesis' (SWRH) holds that predation upon juvenile fish and crustaceans is reduced in shallow water because larger predatory fish increase in abundance with depth. We tested predictions of this hypothesis in 2 Kodiak Island flatfish nurseries, Pillar Creek Cove and Holiday Beach, using baited camera, tethering and video...
Changing environmental conditions in the North Pacific are altering the lipid/fatty acid (FA) composition of zooplankton assemblages, but the consequences to resident fish larvae are unknown. In the laboratory, we reared Pacific cod Gadus macrocephalus larvae over 4 wk on prey enriched with varying levels of 2 essential FAs (docosahexaenoic acid, D...
The lipid/fatty acid composition of marine fish eggs and larvae is linked with buoyancy regulation, but our understanding
of such processes is largely restricted to species with pelagic eggs. In this study, we examined developmental changes in
the lipid/fatty acids of eggs and embryos of Pacific cod (Gadus macrocephalus), a species that spawns deme...
The role of behavior, especially vertical migration, is recognized as a critical component of realistic models of larval fish dispersion. Unfortunately, our understanding of these behaviors lags well behind our ability to construct three-dimensional flow-field models. Previous field studies of vertical behavior of larval Pacific cod (Gadus macrocep...
Habitat use of age-0 and age-1 juvenile Pacific cod (Gadus macrocephalus) was examined in coastal regions in Kodiak Alaska over daily, seasonal and annual scales. Catch data indicated highly variable recruitment to nursery areas, but a strong separation of distribution by depth among age groups. Age-0 cod were most abundant in the shallows (b3 m) w...
Phase transitions between alternate stable states in marine ecosystems lead to disruptive changes in ecosystem services, especially fisheries productivity. We used trawl survey data spanning phase transitions in the North Pacific (Gulf of Alaska) and the North Atlantic (Scotian Shelf) to test for increases in ecosystem variability that might provid...
We examined the spatial dynamics of Atlantic cod, Gadus morhua, through its life history on the northeast and southeast coasts of Newfoundland in order to delineate dispersal and critical habitat requirements as potential determinants of appropriate spatial scales for management. Hydroacoustic surveys across the northeast Newfoundland shelf in 1990...
Cannibalism in Atlantic cod Gadus morhua is widespread under both field and culture conditions, but no studies have been conducted on the behavioural ontogeny of cannibalism in this species. We carried out an experiment to investigate the onset and ontogenetic changes in cannibalistic behaviour of Atlantic cod during early developmental stages. Cod...
Juvenile fishes are sometimes difficult to survey because they occur in a variety of structurally complex habitats that are not readily sampled with traditional trawl or seine gear. Laboratory experiments and field sampling were conducted to determine whether a baited-camera system could be used effectively to survey age-0 gadids. Pacific cod (Gadu...
The recent study by Svedäng et al. (2007; Mar Ecol Prog Ser 345:1-12) purports to have revealed explicit evidence of natal homing in Atlantic cod Cadus morhua, based on extensive archival tagging; the study, however, ignored the 'natal' component of dispersal (i.e. the ichthyoplanktonic phase). The authors observed non-random directional movements...
Pacific cod are commercially and ecologically important in the North Pacific, currently ranking 2nd in tonnage and value landed in the Alaskan groundfish fishery. To date, few studies have focused on the habitat requirements of Pacific cod, and as a result, our understanding of their ecology has largely been borrowed from better-studied gadid speci...
Our understanding of the habitat requirement and spatial dynamics of juvenile Atlantic cod (Gadus morhua) is almost entirely based on daytime studies. Diel spatial patterns of age-0 juvenile cod over sand and eelgrass habitat were examined using a combination of infrared videography in the laboratory and repeated net-sampling in the field. Both lab...
Changes in habitat use with increasing conspecific density are well-documented, but such patterns are likely to be dynamic over the lifespan of the organism and responsive to changes in the environment. In the laboratory, we examined how habitat selection was mediated by ontogeny (6, 8 and 12 mo) and temperature (4 and 9 degrees C) in 2 juvenile, m...
The recent study by Svedang et al. (2003; Mar Ecol Prog Ser 345:1-12) purports to have revealed explicit evidence of natal homing in Atlantic cod Gadus morhua, based on extensive archival tagging; the study, however, ignored the 'natal' component of dispersal (i.e. the ichthyoplanktonic phase). The authors observed non-random directional movements...
Taxonomic comparisons of the early life history stages of Gadus species were conducted from new and published data on morphological descriptions of eggs and yolk-sac larvae. Findings suggestass="Abstract">Taxonomic comparisons of the early life history stages of Gadus species were conducted from new and published data on morphological descriptions...
Predators and prey often co-exist at high densities within the same habitat, yet the behavioural and spatial dynamics underlying this co-existence are not well known. To better understand small-scale, predator–prey co-occurrence, the spatial patterns and behaviour of age 0 juvenile cod Gadus morhua 75–88 mm SL and two of their known predators, age...
Growth, survival and condition of redfish larvae Sebastes spp., reared in the laboratory (0, 500 1500 and 4500 prey l-1) were highest in the 1500 prey l-1 treatment. Significantly lower larval growth and survival in the 4500 prey l-1 treatment corresponded with lower prey bite: orient ratios in later weeks, suggesting that larvae were unable to for...
A new technique using a single camera and shadows to determine 3-D spatial positions of fishes in the laboratory is described. The apparatus consisted of a large aquarium (2·0 × 1·5 × 0·4 m), a wide-angle camera mounted above and two light sources to cast shadows to either side of the fish. Using image analysis and vector mathematics, aquarium obje...
Fish behaviour can change to accommodate a variable environment, but changes in behaviour have not been considered in the context of density-dependent habitat use. In Bonavista Bay, Newfoundland, we measured how fish density movement and schooling behaviour changed with habitat in 2 gadids, Atlantic cod Gadus morhua and Greenland cod Gadus ogac, us...
In Bonavista Bay, Newfoundland, we monitored patterns of settlement and distribution of 2 species of gadids, Atlantic cod Gadus morhua and Greenland cod G. ogac, following a large-scale alteration of nearshore eelgrass Zostera marina habitat. Comparisons between control and experimental sites, based on bi-weekly sampling from 1995 to 2001, indicate...
Eelgrass Zostera marina provides refuge to numerous fish species but is vulnerable to fragmentation through natural and anthropogenic disturbance. In Bonavista Bay, Newfoundland, eelgrass patch size was altered to measure changes in predation risk in Age-0 juvenile cod, Gadus morhua. Artificial eelgrass mats of 5 sizes (0.32, 1.1, 5.5, 11 and 22 m2...
