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 hatch success (3–6 °C), mechanistic-based models of spawning habitat, and correlations with prerecruit time series. With the exception of single-year El Niño events (1998, 2003), the recent 3-year heatwave (2014–2016) and return to similar conditions in 2019 were potentially the most negative impacts on spawning habitat for Pacific cod in the available time series (1994–2019). Continued warming will likely reduce the duration and spatial extent of Pacific cod spawning in the Gulf of Alaska.
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
and saffron cod,
Eleginus gracilis
) and two North Pacific gadids (walleye pollock,
Gadus chalcogrammus
and Pacific cod,
Gadus macrocephalus
) over a 6-week growth period across five temperatures (0, 5, 9, 16 and 20 °C). Arctic cod demonstrated a cold-water, stenothermic response in that there was relatively high growth at 0 °C (0.73 % day
−1
), near-maximal growth at 5 °C (1.35 % day
−1
) and negative impacts on activity, growth and survival at 16 °C. In contrast, saffron cod demonstrated a warmer-water, eurythermic response, and temperature had a positive effect on growth and condition beyond 16 °C. However, despite these distinct thermal responses, walleye pollock and Pacific cod grew 2–3 times faster than Arctic gadids across a relatively broad temperature range above 5 °C. These results, coupled with possible northward expansion by both Pacific cod and walleye pollock, suggest Arctic cod are highly vulnerable to continued climate change in the Arctic, especially in coastal areas of the Beaufort and Chukchi Seas where temperatures already exceed 14 °C in the summer growth period.
Abstract
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 saida) and walleye pollock (Gadus chalcogrammus). Fertilized egg batches (n = 11 Arctic cod; n = 6 walleye pollock) were collected in the late winter/early spring from laboratory broodstock held under simulated seasonal environmental conditions. Image and lipid analyses indicated that Arctic cod eggs and larvae were ∼25–35% larger than walleye pollock and had nearly 3–6× more energetic reserves. Two batches of eggs from each species were incubated in replicated containers (n = 3/batch/temperature) at −0.4, 1.2, 2.5, 3.8, 5.0, 9.0, and 12.0°C for Arctic cod and −0.8, 0.3, 2.2, 4.5, 9.0, and 12.0°C for walleye pollock. Both species had very similar low thermal tolerance, but Arctic cod were much more sensitive to higher thermal stress in terms of hatch success and size-at-hatch. For example, Arctic cod hatch success declined precipitously at temperatures above 3.5°C yet remained above 50% in walleye pollock at 9°C. Arctic cod also had significantly longer development times, such that embryos could survive for ∼4 months at temperatures <0°C from the time of spawning to first-feeding. Collectively, these results indicate Arctic cod have a much smaller thermal window for survival, but can survive for longer periods in the absence of food than walleye pollock at cold temperatures. These temperature-dependent rates will be useful in the development of population forecasts and biophysical transport models for these species in the northern Bering, Chukchi, and Beaufort seas.
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 experiment, Pacific cod embryos and larvae were reared at one of six combinations of three temperatures (3, 6, 10 °C) and two CO
2
levels (ambient: ~ 360 μatm; high: ~ 1560 μatm) in a factorial design. Both embryonic and larval mortality were highest at the warmest temperature. Embryonic daily mortality rates were lower under elevated CO
2
and there was no effect of CO
2
level on larval daily mortality rates. Growth rates of young larvae (0 to 11 days post-hatch) were faster at warmer temperatures and at high CO
2
levels, but growth during the 11–28 days post-hatch interval increased by temperature alone. The condition of larvae decreased with age, but less markedly under high CO
2
levels. However, at 6 °C, fish incubated in ambient CO
2
remained in higher condition than fish in the high CO
2
treatment throughout the experiment. Overall, temperature had the greater influence on Pacific cod early life stages across each measurement endpoint, while CO
2
effects were more modest and inconsistent. Subtle developmental differences in larval Pacific cod could be magnified later in life and important in the context of recruitment. These results show the complexity of stage- and trait-specific responses to and value of investigating the combined effects of co-occurring climatic stressors.
A multistate listeriosis outbreak associated with cantaloupe consumption was reported in the United States in September, 2011. The outbreak investigation recorded a total of 146 invasive illnesses, ...30 deaths and one miscarriage. Subtyping of the outbreak associated clinical, food and environmental isolates revealed two serotypes (1/2a and 1/2b) and four pulsed-field gel electrophoresis two-enzyme pattern combinations I, II, III, and IV, including one rarely seen before this outbreak. A DNA-microarray, Listeria GeneChip®, developed by FDA from 24 Listeria monocytogenes genome sequences, was used to further characterize a representative sample of the outbreak isolates. The microarray data (in the form of present or absent calls of specific DNA sequences) separated the isolates into two distinct groups as per their serotypes. The gene content of the outbreak-associated isolates was distinct from that of the previously-reported outbreak strains belonging to the same serotypes. Although the 1/2b outbreak associated isolates are closely related to each other, the 1/2a isolates could be further divided into two distinct genomic groups, one represented by pattern combination I strains and the other represented by highly similar pattern combinations III and IV strains. Gene content analysis of these groups revealed unique genomic sequences associated with these two 1/2a genovars. This work underscores the utility of multiple approaches, such as serotyping, PFGE and DNA microarray analysis to characterize the composition of complex polyclonal listeriosis outbreaks.
Listeria monocytogenes is an increasing food safety concern throughout the produce supply chain as it has been linked to produce associated outbreaks and recalls. To our knowledge, this is the first ...systematic literature review to investigate Listeria species and L. monocytogenes prevalence, persistence, and diversity at each stage along the supply chain. This review identified 64 articles of 4863 candidate articles obtained from four Boolean search queries in six databases. Included studies examined naturally detected/isolated Listeria species and L. monocytogenes in fresh produce-related environments, and/or from past fresh produce associated outbreaks or from produce directly. Listeria species and L. monocytogenes were detected in each stage of the fresh produce supply chain. The greatest prevalence of Listeria species was observed in natural environments and outdoor production, with prevalence generally decreasing with each progression of the supply chain (e.g., packinghouse to distribution to retail). L. monocytogenes prevalence ranged from 61.1% to not detected (0.00%) across the entire supply chain for included studies. Listeria persistence and diversity were also investigated more in natural, production, and processing environments, compared to other supply chain environments (e.g., retail). Data gaps were identified for future produce safety research, for example, in the transportation and distribution center environment.
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 changing climate. We use Bayesian regression models to compare fish population processes under historical climate norms and emerging anthropogenic extremes. To define anthropogenic extremes we use the Fraction of Attributable Risk (FAR), which estimates the proportion of risk for extreme ocean temperatures that can be attributed to human influence. We illustrate our approach with estimates of recruitment (production of young fish, a key determinant of sustainability) for two exploited fishes (Pacific cod Gadus macrocephalus and walleye pollock G. chalcogrammus) in a rapidly warming ecosystem, the Gulf of Alaska. We show that recruitment distributions for both species have shifted towards zero during anthropogenic climate extremes. Predictions based on the projected incidence of anthropogenic temperature extremes indicate that expected recruitment, and therefore fisheries sustainability, is markedly lower in the current climate than during recent decades. Using FAR to analyze changing population processes may help fisheries managers and stakeholders to recognize situations when historical sustainability expectations should be reevaluated.
Abstract 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 Alaska Pacific cod ( Gadus macrocephalus ) larval, juvenile, and adult abundances declined dramatically following MHW events in 2014–2016 and 2019. To evaluate coastal nursery function during MHWs, we compared diet composition, recent growth, size, condition, and abundance of age-0 juveniles throughout their first summer before, during, and between MHWs. Diet shifted to larger prey during MHWs, particularly mysids, but diet did not appear to influence growth. We observed faster growth rates during MHWs, yet even when accounting for growth, we could not explain the higher body sizes observed in August during MHWs. Together with lower abundance and the near absence of small fish in the nursery by August during MHWs, these patterns highlight potential for size-selection and a reduced ability of nursery habitats to buffer against environmental variability during MHWs, with only a small number of large “super survivors” persisting through the summer.
Abstract 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 pollock at two larval stages across a range of temperature and food conditions in the laboratory. Results indicated early and late-stage Arctic cod larvae have a competitive growth and survival advantage over walleye pollock at low temperatures. However, these advantages are lost under warmer, food-productive conditions where walleye pollock larvae survived and experienced accelerated growth rates. Growth models developed from this study emphasize the need to account for both species- and stage-specific differences in the thermal response of closely related marine fish larvae. More broadly, these new vital rate data provide a mechanistic framework to forecast spatial-temporal shifts of gadids at the Arctic-boreal interface resulting from climatic warming and altered productivity regimes.
Following the success of the first mission, the High-Resolution Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1) on 2018 May 29 from the White Sands Missile Range, NM, USA. On this ...occasion, 329 s of 17.2 nm data of target active region AR 12712 were captured with a cadence of 4 s, and a plate scale of 0 129 pixel−1. Using data captured by Hi-C 2.1 and co-aligned observations from SDO/AIA 17.1 nm, we investigate the widths of 49 coronal strands. We search for evidence of substructure within the strands that is not detected by AIA, and further consider whether these strands are fully resolved by Hi-C 2.1. With the aid of multi-scale Gaussian normalization, strands from a region of low emission that can only be visualized against the contrast of the darker, underlying moss are studied. A comparison is made between these low-emission strands and those from regions of higher emission within the target active region. It is found that Hi-C 2.1 can resolve individual strands as small as 202 km, though the more typical strand widths seen are 513 km. For coronal strands within the region of low emission, the most likely width is significantly narrower than the high-emission strands at 388 km. This places the low-emission coronal strands beneath the resolving capabilities of SDO/AIA, highlighting the need for a permanent solar observatory with the resolving power of Hi-C.
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