Abstract and Figures

Several studies have documented fish populations changing in response to long-term warming. Over the past decade, sea surface temperatures in the Gulf of Maine increased faster than 99% of the global ocean. The warming, which was related to a northward shift in the Gulf Stream and to changes in the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation, led to reduced recruitment and increased mortality in the region’s Atlantic cod (Gadus morhua) stock. Failure to recognize the impact of warming on cod contributed to overfishing. Recovery of this fishery depends on sound management, but the size of the stock depends on future temperature conditions. The experience in the Gulf of Maine highlights the need to incorporate environmental factors into resource management.
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Climate change is reshaping ecosystems in ways that impact
resources and ecosystem services (1). Fisheries, with their
tight coupling between ecosystem state and economic
productivity, are a prime example of interacting social-
ecological systems. The social and ecological value of a
fishery depends first and foremost on the biomass of fish,
and fishing has often been the dominant driver of the status
of the resource and the economics of the fishing community.
Modern fisheries management is designed to reduce
harvesting levels in response to low stock biomass (and vice
versa), creating a negative feedback that, in theory, will
maintain steady long-term productivity (2).
A failure to detect changes in the environment or to act
appropriately when changes are detected can jeopardize
social-ecological systems (3). As climate change brings
conditions that are increasingly outside the envelope of past
experiences, the risks increase. The Gulf of Maine has
warmed steadily, and the record
warm conditions in 2012
impacted the fishery for
American lobster (4). Here, we
consider how ocean warming
factored into the rapid decline of
the Gulf of Maine cod stock (5).
We used sea surface
temperature data to characterize
temperature trends in the Gulf
of Maine since 1982 and over the
last decade (2004-2013). We
compared the changes in this
region with trends around the
globe and related temperature
variability to an index of Gulf
Stream position and the Pacific
Decadal Oscillation and the
Atlantic Multidecadal Oscillation.
We then examined the impact of
temperature conditions in the
Gulf of Maine on the
recruitment and survival of
Atlantic cod. The resulting
temperature-dependent population
dynamics model was used to
project the rebuilding potential
of this stock under future
temperature scenarios.
From 1982-2013, daily
satellite-derived sea surface
temperature in the Gulf of
Maine rose at a rate of 0.03°C
yr−1 (R2 = 0.12, p < 0.01, n =
11,688; Fig. 1A). This rate is
higher than the global mean rate
of 0.01°C yr−1 and led to gradual
shifts in the distribution and
abundance of fish populations (68). Beginning in 2004, the
warming rate in the Gulf of Maine increased more than
seven-fold to 0.23°C yr−1 (R2 = 0.42, p < 0.01, n = 3,653). This
period began with relatively cold conditions in 2004 and
concluded with the two warmest years in the time series.
The peak temperature in 2012 was part of a large “ocean
heat wave” in the northwest Atlantic that persisted for
nearly 18 months (4).
The recent 10 year warming trend is remarkable, even for
a highly-variable part of the ocean like the northwest
Atlantic. Over this period, substantial warming also
occurred off of western Australia, in the western Pacific, and
in the Barents Sea; and cooling was observed in the eastern
Pacific and Bering Sea (Fig. 1B). The global ocean has a total
area of 3.6 x 108 km2, yet only 3.1 x 105 km2 of the global
ocean had warming rates greater than that in the Gulf of
Maine over this time period. Thus, the Gulf of Maine has
Slow adaptation in the face of rapid
warming leads to collapse of the Gulf of
Maine cod fishery
Andrew J. Pershing,1* Michael A. Alexander,2 Christina M.
Hernandez,1† Lisa A. Kerr,1 Arnault Le Bris,1 Katherine E. Mills,1
Janet A. Nye,3 Nicholas R. Record,4 Hillary A. Scannell,1,5‡ James
D. Scott,2,6 Graham D. Sherwood,1 Andrew C. Thomas5
1Gulf of Maine Research Institute, 350 Commercial Street, Portland, ME 04101, USA. 2NOAA Earth System Research
Laboratory, Boulder, CO 80305, USA. 3School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook,
NY 11794, USA. 4Bigelow Laboratory for Ocean Sciences, 60 Bigelow Drive, East Boothbay, ME 04544, USA. 5School of
Marine Sciences, University of Maine, Orono, ME 04469, USA. 6Cooperative Institute for Research in Environmental
Sciences, University of Colorado, Boulder, CO 80309, USA.
*Corresponding author. E-mail: apershing@gmri.org
†Present address: Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
‡Present address: University of Washington School of Oceanography, Seattle, WA 98105, USA.
Several studies have documented fish populations changing in response to
long-term warming. Over the last decade, sea surface temperatures in the
Gulf of Maine increased faster than 99% of the global ocean. The warming,
which was related to a northward shift in the Gulf Stream and to changes in
the Atlantic Multidecadal and Pacific Decadal Oscillations, led to reduced
recruitment and increased mortality in the region’s Atlantic cod (
) stock. Failure to recognize the impact of warming on cod
contributed to overfishing. Recovery of this fishery depends on sound
management, but the size of the stock depends on future temperature
conditions. The experience in the Gulf of Maine highlights the need to
incorporate environmental factors into resource management.
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/ sciencemag.org/content/early/recent / 29 October 2015 / Page 2 / 10.1126/science.aac9819
warmed faster than 99.9% of the global ocean between 2004
and 2013 (Fig. 1C). Using sea surface temperatures from
1900-2013, the likelihood of any 2° by 2° segment of the
ocean exceeding this 10-year warming rate is less than 0.3%.
Based on this analysis, the Gulf of Maine experienced
decadal warming that few marine ecosystems have
As a first step toward diagnosing the potential drivers of
the recent warming trend, we correlated the quarterly
temperatures in the Gulf of Maine with large-scale climate
indicators (table S1). An index of Gulf Stream position (9)
has the strongest and most consistent relationship with Gulf
of Maine temperatures. The correlations with the Gulf
Stream Index (GSI) are positive and significant in all
quarters, with the strongest correlation occurring in
summer (r = 0.63, p < 0.01, n = 31). The Pacific Decadal
Oscillation (PDO) (10) is negatively correlated with the Gulf
of Maine temperatures during spring (r = 0.50) and
summer (r = 0.67). Summer temperatures are also
positively correlated with the Atlantic Multidecadal
Oscillation (AMO) (11) (r = 0.48, p < 0.01, n = 31).
Building on the strong correlations with summer
temperatures, we developed multiple regression models for
summer Gulf of Maine temperatures using combinations of
the three indices (Table 1). Based on AIC score, the best
model used all three indices, and this model explained 70%
of the variance in Gulf of Maine summer temperature (R2 =
0.70, p < 0.01, AIC = 46.0, n = 31). This model was slightly
better than one using GSI and the AMO (R2 = 0.66, p < 0.01,
AIC = 48.2, n = 31). We refit each model using data from
1982-2003, and then applied the model to the 2004-2012
period. The three-index and the GSI-AMO models had
nearly identical out-of-sample performance, explaining 65%
and 64% of the variance, respectively.
A long-term poleward shift in the Gulf Stream occurred
over the 20th century and has been linked to increasing
greenhouse gasses (12). Previous studies have reported an
association between Gulf Stream position and temperatures
in the northwest Atlantic (7, 13), and an extreme northward
shift in the Gulf Stream was documented during the record
warm year of 2012 (14). Although the Gulf Stream does not
directly enter the Gulf of Maine, northward shifts in the
Gulf Stream are associated with reduced transport of cold
waters southward on the continental shelf (15, 16). The
association between Gulf of Maine temperature and the
PDO suggests an atmospheric component to the recent
trend. A detailed heat-budget calculation for the 2012 event
(17) found that the warming was due to increased heat flux
associated with anomalously warm weather in 2011-2012.
These results suggest that atmospheric teleconnections from
the Pacific, changes in the circulation in the Atlantic Ocean,
and background warming have contributed to the rapid
warming in the Gulf of Maine.
The Gulf of Maine cod stock has been chronically
overfished, prompting progressively stronger management,
including the implementation of a quota-based
management system in 2010. Despite these efforts,
including a 73% cut in quotas in 2013, spawning stock
biomass (SSB) continued to decline (Fig. 2A). The most
recent assessment found that SSB in this stock is now less
than 3,000 mt, only 4% of the spawning stock biomass that
gives the maximum sustainable yield (SSBmsy) (5). This has
prompted severe restrictions on the commercial cod fishery
and the closure of the recreational fishery.
The Gulf of Maine is near the southern limit of cod, and
previous studies have suggested that warming will lead to
lower recruitment, suboptimal growth conditions, and
reduced fishery productivity in the future (1820). Using
population estimates from the recent Gulf of Maine cod
stock assessment (5), we fit a series of stock-recruit models
with and without a temperature effect (table S2). The best
models exhibited negative relationships between age-1
recruitment and summer temperatures (table S3). Gulf of
Maine cod spawn in the winter and spring, so the link with
summer temperatures suggests a decrease in the survival of
late-stage larvae and settling juveniles. Although the
relationship with temperature is statistically robust, the
exact mechanism for this is uncertain but may include
changes in prey availability and/or predator risk. For
example, the abundance of some zooplankton taxa that are
prey for larval cod has declined in the Gulf of Maine cod
habitat (21). Warmer temperatures could cause juvenile cod
to move away from their preferred shallow habitat into
deeper water where risks of predation are higher (22).
We also looked for other signatures of temperature
within the population dynamics of cod. We found a strong
association between the mortality of age-4 fish and fall
temperatures from the current year and the second year of
life (Fig. 2B, R2 = 0.57, p < 0.01, n = 21). Age 4 represents an
energetic bottleneck for cod due to the onset of
reproduction and reduced feeding efficiency as fish
transition from benthic to pelagic prey (23). Elevated
temperatures increase metabolic costs in cod (24),
exacerbating the energetic challenges at this age. The
average weight-at-age of cod in the Gulf of Maine region has
been below the long-term mean since 2002 (25), and these
poorly conditioned fish will have a lower probability of
survival (26).
The age-4 mortality relationship improves significantly
with the addition of temperatures from the second year of
life (table S6). This suggests that a portion of the estimated
age-4 mortality reflects mortality over the juvenile period
that is not explicitly captured in the assessment.
Temperature may directly influence mortality in younger
fish through metabolic processes described above; however,
we hypothesize that predation mortality may also be higher
during warm years. Many important cod predators migrate
into the Gulf of Maine or have feeding behaviors that are
strongly seasonal. During a warm year, spring-like
conditions occur earlier in the year, and fall-like conditions
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occur later. During the 2012 heat wave, the spring warming
occurred 21 days ahead of schedule, and fall cooling was
delayed by a comparable amount (4). This change in
phenology could result in an increase in natural mortality of
44% on its own, without any increase in predator biomass
(see supplementary text).
If fishing pressure had been effectively reduced, the
population should have rebuilt more during the cool years
and then declined less rapidly during the warming period.
Instead, fishing mortality rates consistently exceeded target
levels, even though fishermen did not exceed their quotas.
The quota-setting process that is at the heart of fisheries
management is highly sensitive to the number of fish aging
into the fishery in each year. For Gulf of Maine cod, age
classes 4 and 5 dominate the biomass of the stock and the
catch (5). The temperature-mortality relationship in Fig. 2B
means that during warm years, fewer fish are available for
the fishery. Not accounting for this effect leads to quotas
that are too high. The resulting fishing mortality rate was
thus above the intended levels, contributing to overfishing
even though catches were within prescribed limits.
Socioeconomic pressures further compounded the
overfishing. In order to minimize the impact of the quota
cuts on fishing communities, the New England Fishery
Management Council elected to defer most of the cuts
indicated for 2012 and 2013 until the second half of 2013.
The socioeconomic adjustment coupled with the two
warmest years in the record led to fishing mortality rates
that were far above the levels needed to rebuild this stock.
The impact of temperature on Gulf of Maine cod
recruitment was known at the start of the warming period
(20), and stock-recruitment model fit to data up to 2003 and
incorporating temperature produces recruitment estimates
(Fig. 2A, yellow diamonds) that are similar to the
assessment time series. Ignoring the influence of
temperature produces recruitment estimates that are on
average 100% and up to 360% higher than if temperature is
included (Fig. 2A, gray squares). Based on a simple
population dynamics model that incorporates temperature,
the spawning stock biomass that produces the maximum
sustainable yield (SSBmsy) has been declining steadily since
2002 (Fig. 3) rather than remaining constant as currently
assumed. The failure to consider temperature impacts on
Gulf of Maine cod recruitment created unrealistic
expectations for how large this stock can be and how
quickly it can rebuild.
We estimated the potential for rebuilding the Gulf of
Maine cod stock under three different temperature
scenarios: a “cool” scenario that warms at a rate of 0.02°
yr−1, a “warm” scenario that warms at 0.03° yr−1, the mean
rate from climate model projections, and a “hot” scenario
that follows the 0.07°C yr−1 trend present in the summer
temperature time series. If fishing mortality is completely
eliminated, populations in the cool and warm scenarios
could rebuild to the temperature-dependent SSBmsy in 2025,
slightly longer than the 10 year rebuilding timeline
established by US law, and the hot scenario would reach its
target one year later (Fig. 3). Allowing a small amount of
fishing (F = 0.1) would delay rebuilding by three years in the
cool and warm scenarios and 8 years in the hot. Note that
estimating SSBmsy without temperature produces a
management target that may soon be unachievable. By
2030, a rebuilt fishery could produce more than 5,000 tons
yr−1 under the warm scenario, a catch rate close to the
average for the fishery for the previous decade. Under the
hot scenario, the fishery would be 1,800 tons yr−1small, but
potentially valuable. Thus, how quickly this fishery rebuilds
now depends arguably as much on temperature as it does
on fishing. Future management of Gulf of Maine cod would
benefit from a reevaluation of harvest control rules and
thorough management strategy evaluation of the
application of temperature-dependent reference points and
projections such as these.
As climate change pushes species poleward and reduces
the productivity of some stocks, resource managers will be
increasingly faced with trade-offs between the persistence of
a species or population and the economic value of a fishery.
Navigating decisions in this context requires both accurate
projections of ecosystem state and stronger guidance from
society in the form of new policies. Social-ecological systems
that depend on steady state or are slow to recognize and
adapt to environmental change are unlikely to meet their
ecological and economic goals in a rapidly changing world.
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This work was supported by the NSF’s Coastal SEES Program (OCE-1325484; AP,
MA, CH, AL, KM, JN, HS, JS, and AT), the Lenfest Ocean Program (AP, AL, KM, and
GS), and institutional funds from the Gulf of Maine Research Institute (LK) and the
Bigelow Laboratory for Ocean Sciences (NR). The lead author’s knowledge of fishery
management was greatly enhanced by discussions with Patrick Sullivan, Steve Ca-
drin, Jake Kritzer, and other members of the NEFMC Scientific and Statistical Com-
mittee. Michael Palmer provided helpful comments on earlier drafts of the
manuscript and facilitated access to the recent stock assessment. The manuscript
also benefitted from helpful feedback from Jon Hare and two anonymous reviewers.
The data reported in this paper are tabulated in the supplementary materials and are
available from the referenced technical reports and from the National Climate Data
Materials and Methods
Figs. S1 to S6
Tables S1 to S5
References (2735)
9 July 2015; accepted 23 September 2015
Published online 29 October 2015
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Index, PDO = Pacific Decadal Oscillation Index, AMO = Atlantic Multidecadal Oscillation Index. The final model
uses all three indices. The first set of statistics refer to the models fit to the entire 1982-2013 record. The models
were also fit to the 1982-2003 period then projected on to the 2004-2013 period. The last two columns
summarize the out of sample performance of the models.
Time series 1 Time series 2
2004-2013 Out of Sample
PDO 0.58 0.00 54.41 0.54 0.00
AMO 0.50 0.00 59.78 0.32 0.01
All 0.70 0.00 45.99 0.65 0.00
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Fig. 1.
Sea surface temperature trends from the Gulf of Maine and the global ocean.
) Daily (blue, 15d smoothed)
and annual (black dots) SST anomalies from 1982-2013 with the long-term trend (black dashed line) and trend over the
last decade (2004-2013) (red solid line). (
) Global SST trends (° yr−1) over the period 2004-2013. The Gulf of Maine is
outlined in black. (
) Histogram of global 2004-2013 SST trends with the trend from the Gulf of Maine indicated at the
right extreme of distribution.
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Fig. 2. Relationships between Gulf of Maine cod and temperature. (A) Time series of Gulf of Maine cod spawning
stock biomass (blue), and age-1 recruitment (green) from the 2014 assessment. Cod age-1 recruitment modeled
using adult biomass and summer temperatures (dashed line). The gray squares are recruitment estimated using a
model without a temperature effect fit to data prior to 2004. The yellow diamonds are a temperature-dependent
model fit to this earlier period. (
) Mortality of age-4 cod as a function of temperature (R2 = 0.57, p < 0.01, n = 21). The
temperature is composed of the fall values from the current year and three years prior, weighted using the
coefficients from the linear model.
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Fig. 3. Temperature-dependent rebuilding potential of Gulf of Maine cod. We simulated a population
growing from the 2013 biomass (black curves) without fishing under three temperature scenarios: a cool
scenario (solid line) represented by the 10% lower bound of the CMIP-5 ensemble, a warm scenario (heavy
line) represented by the climate model ensemble mean, and a hot scenario (“+”s) with warming at the 0.07°
yr−1 rate observed in the summer in the Gulf of Maine since 1982. This population is contrasted against an
estimate of the temperature-dependent SSBmsy (blue lines and shading), an estimate of SSBmsy without
accounting for temperature (grey dashed line), and the carrying capacity of the population (green lines and
shading). The yellow circles mark where the rebuilding population reaches the temperature-dependent
SSBmsy, squares denote when a population fished at F = 0.1 would be rebuilt.
... Globally, warming oceans have received increased attention with respect to the occurrence and intensification of HABs as water temperatures reach values that support maximum growth of these species, including A. catenella (Gobler et al., 2017;Seto et al., 2019). The Gulf of Maine is subject to global climate change and is experiencing a dramatic increase in its surface temperature regime and shift in seasonal SST phenology (Pershing et al., 2015;Thomas et al., 2017). Phenological shifts in the physical environment (e.g. ...
... The northeast North American continental shelf, including the Gulf of Maine, is among the most rapidly warming pieces of ocean on the planet (e.g. Forsyth et al., 2015;Pershing et al., 2015;Kavanaugh et al., 2017;Thomas et al., 2017). Associated with this warming is a shift in thermal phenology, with spring arriving earlier, fall later, and summer lasting longer (Thomas et al., 2017). ...
... The systematic reduction in the timing of both thermal habitats (EDTHab and BITHab) over the study period is consistent with climate-linked warming trends for the Gulf of Maine (e.g. Pershing et al., 2015;Thomas et al., 2017;Alexander et al., 2018;Balch et al., 2022). Increased temperatures, especially during summer, drive thermal phenological shifts, including earlier arrival dates of specific temperature thresholds and an average reduction in summer start date by approximately 1 day year -1 (Thomas et al., 2017). ...
Harmful Algal Blooms (HABs) of the toxic dinoflagellate Alexandrium catenella are an annually recurring problem in the Gulf of Maine (GoM), resulting in risks to human health and substantial economic losses due to shellfish harvesting closures. The monitoring approaches in the region are restricted to real-time identification of the HABs events, when they are clearly underway and already causing deleterious effects to the environment. To fully function as an early warning system rather than an immediate response, monitoring strategies need to be focused on environmental conditions preceding A. catenella HABs. However, the current understanding of the preferred habitat for A. catenella in the GoM is still scarce due to the complex interactions between this organism and the environment. My dissertation research contributes to the solution of these problems by determining the preferred thermal habitat for A. catenella, contrasting environmental conditions for two extremes in A. catenella concentration, and exploring the benefits of using high resolution spectral data to characterize the GoM surface waters. This dissertation is focused on the application of current and future remote sensing technology to the measurement and management of GoM HABs. Chapter 1 briefly introduces the problematic of HABs, monitoring efforts and the study species. Chapter 2 characterizes the interannual variability in the thermal habitat and bloom phenology of A. catenella in the Bay of Fundy, identifying the environmental conditions associated with this variability and its responses to climate change. Chapter 3 contrasts the optical and thermal conditions associated with two extremes in A. catenella concentration over multiple years and areas in the GoM and establishes a set of typical water types for each concentration category. Chapter 4 characterizes the spatial and temporal variability of hyperspectral reflectance of surface waters in the GoM and determines the advantage of hyperspectral resolution over multispectral to identify important spatial patterns and regions. Chapter 5 will conclude with a discussion on the implications of these results to monitoring efforts in the GoM, implications of climate change, and discusses future directives to further explore habitat suitability approaches in monitoring efforts.
... The fate of many species across the planet are inexplicably linked with climate change. An ecosystem of particular interest is that of the Gulf of Maine, where the warming rates here are higher than most anywhere else in the oceans (Mills et al. 2013;Pershing et al. 2015). ...
... However, in recent history, the waters in this system have been warming at an alarming rate (Mills et al. 2013;Pershing et al. 2015), due in part by melting Arctic sea ice (Saba et al. 2016). This melting phenomenon is releasing a lot of fresh water into the Arctic Ocean. ...
... Climate change is causing the NGOM ecosystem to warm at an accelerated rate compared with a majority of the world's oceans; with an average-per-year increasing temperature of 0.026˚C (Pershing et al. 2015). Bottom temperature and bottom salinity fluctuate around yearly means as seasons change, but these yearly means for both variables are rising in the face of climate change (Pershing et al. 2015;Saba et al. 2016). ...
Climate change is impacting many marine species distributions, life histories, and behaviors, as well as their associated fisheries and overall production. This is perhaps especially true for the Gulf of Maine (GOM). Here, warming rates are exceeding a vast majority of the world’s oceans. This highly dynamic system supports myriad species, but is both economically recognized and culturally known for its Atlantic sea scallop (Placopecten magellanicus) and American lobster (Homarus americanus) fisheries. This dissertation examines the influence of regional climate change on these species in an effort to predict how these stocks and their fisheries may change in the future. For scallops, this was accomplished by examining and aging shells collected throughout the GOM to determine if spatial and temporal differences in growth patterns could be explained by regional thermal habitats and salinities. For lobster, a five-step process was developed. Firstly, I conducted a simulation study to evaluate the stock assessment model performance under possible changes in lobster molting probability, lobster molt increment size, and size-at-maturity as a result of changes in thermal habitat. Secondly, using two temperature covariates important for early survival and development, a stock-wide, thermally-explicit Beverton-Holt stock-recruit relationship was estimated for the GOM. This relationship served as the basis of a framework to be used by management to test what levels of spawning biomass are necessary in the current year to achieve the desired levels of recruitment in the near future. Thirdly, a delta-generalized linear mixed model was used to predict lobster spatial density throughout the GOM. This spatial density informed a stock-wide abundance index which was used to replace the traditionally used design-based indices in the stock assessment model. Fourthly, a stock forecasting model was developed that could utilize the aforementioned stock-recruit relationship and consequences of ignoring this thermal influence on recruitment estimations were explored. Lastly, a bioclimate envelope model was used to determine relationships of multiple habitat covariates to lobster abundance from trawl survey data before using these relationships to map and forecast lobster habitat in the GOM.
... marine areas in the world (Pershing et al., 2015). Rising temperatures have increased the area's susceptibility to novel and ongoing biological invasions, including that of the Asian shore crab (Hemigrapsus sanguineus). ...
... Quantifying the metabolism of H. sanguineus is especially important given the rapidly changing climate in the Gulf of Maine (Pershing et al., 2015). Climate change is predicted to accelerate the propagation and success of some invasive species and decrease the success of others (Hellmann et al., 2008). ...
... The need to more deeply understand metabolic adaptations associated with limb loss-and other metabolic adaptations-is especially pressing considering the rapid warming in the Gulf of Maine (Pershing et al., 2015). Metabolic injury resilience and other energetic traits may be altered by rising temperatures and elevated metabolic rates associated with climate change (Parry, 1983). ...
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Rapid warming in the Gulf of Maine may influence the success or invasiveness of the Asian shore crab, Hemigrapsus sanguineus. To better predict the effects of climate change on this invasive species, it is necessary to measure its energy dynamics under a range of conditions. However, previous research has only focused on the metabolism of this intertidal species in water. We sampled adult crabs from three different sites and measured their metabolic rates in the air. We show that metabolic rate increases with body mass and the number of missing limbs, but decreases with the number of regenerating limbs, possibly reflecting the timing of energy allocation to limb regeneration. Importantly, metabolic rates measured here in the air are ~4× higher than metabolic rates previously measured for this species in water. Our results provide baseline measurements of aerial metabolic rates across body sizes, which may be affected by climate change. With a better understanding of respiration in H. sanguineus, we can make more informed predictions about the combined effects of climate change and invasive species on the northeast coasts of North America. The Asian shore crab, Hemigrapsus sanguineus, is an invasive species along the northeast coast of North America. Previous work has focused on metabolic rate measurements for this species in water, but not in air. Our study examined the metabolic rate of this invasive species in air as a function of body size, location, and injury.
... In contrast, early or late season killing frost may be less likely in the Southern Interior and Coastal climate divisions because of proximity to the warming Gulf of Maine and North Atlantic. The Gulf of Maine is reported to be one of the fastest-warming regions of the global ocean(Seidov et al., 2021;Fernandez et al., 2020;Pershing et al., 2015). The warming of the Gulf of Maine is most commonly attributed to a weakening of the Atlantic Meridional Overturning Circulation (AMOC) and subsequent changes in the Gulf Stream that increase the flux of warm water into the basin(Seidov et al., 2021, Pershing et al., 2015. ...
... The Gulf of Maine is reported to be one of the fastest-warming regions of the global ocean(Seidov et al., 2021;Fernandez et al., 2020;Pershing et al., 2015). The warming of the Gulf of Maine is most commonly attributed to a weakening of the Atlantic Meridional Overturning Circulation (AMOC) and subsequent changes in the Gulf Stream that increase the flux of warm water into the basin(Seidov et al., 2021, Pershing et al., 2015. However, the Gulf Stream is a wind-driven surface current, and changes in large-scale atmospheric circulation also play a role in the Gulf of Maine(Birkel and Mayewski, 2018;Bricknell et al., 2020).Consistent with the findings of Maine's Climate Future (2020) and Maine Climate Council's Scientific and Technical Subcommittee (2020), the historically wet period of 2005-2014 is evident in this analysis of the growing season. ...
Climate change is a wicked problem with global impacts, one of which being the sustainability of the existing global food system. As temperatures and variability in precipitation are projected to increase, the challenges to agriculture are expected to intensify. This thesis examines the Maine historical climate record over the growing season, in combination with future projections, to assess how conditions have changed and will change with agricultural implications. In this analysis, relevant climatic variables are analyzed, and agriculture-significant measures are derived for Maine’s three climate divisions using four decades of daily and monthly gridded datasets. In addition, this thesis explores climate change risk perceptions of Maine wild blueberry growers and establishes a survey instrument which may be used to measure the risk perceptions of migrant workers in the state and within other regions of the United States, by drawing from and expanding upon the Climate Change Risk Perception Model (CCRPM). In all, this work will help inform climate adaptation and mitigation strategies for safeguarding the productivity, safety, and sustainability of food systems in Maine.
... The environmental shift can selectively affect the habitat suitability of target species (Farrell et al., 2008). Lower habitat suitability of any life-history stage can lead to species-specific "habitat bottleneck" and later can have large consequences for loss of several fish's climatically suitable habitat, for example, Norwegian herring, Maine cod, and Mid-Atlantic Bight winter flounder (Bell et al., 2015;Pershing et al., 2015). ...
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Intense fishing pressure and climate change are major threats to the fish population and coastal fisheries. Larimichthys crocea (large yellow croaker) is a long‐lived fish, which performs seasonal migrations from its spawning and nursery grounds along the coast of the East China Sea (ECS) to overwintering grounds offshore. This study used length‐based analysis and habitat suitability index (HSI) model to evaluate the current life‐history parameters and overwintering habitat suitability of L. crocea, respectively. We compared recent (2019) and historical (1971–1982) life‐history parameters and overwintering HSI to analyze the fishing pressure and climate change effects on the overall population and overwintering phase of L. crocea. The length‐based analysis indicated serious overfishing of L. crocea, characterized by reduced catch, size truncation, constrained distribution, and advanced maturation causing a recruitment bottleneck. The overwintering HSI modeling results indicated that climate change has led to decreased sea surface temperature during L. crocea overwintering phase over the last half‐century, which in turn led to area decrease and an offshore‐oriented shifting of optimal overwintering habitat of L. crocea. The fishing‐caused size truncation may have constrained the migratory ability, and distribution of L. crocea subsequently led to the mismatch of the optimal overwintering habitat against climate change background, namely habitat bottleneck. Hence, while heavy fishing was the major cause of L. crocea collapse, climate‐induced overwintering habitat suitability may have intensified the fishery collapse of L. crocea population. It is important for management to consider both overfishing and climate change issues when developing stock enhancement activities and policy regulations, particularly for migratory long‐lived fish that share a similar life history to L. crocea. Combined with China's current restocking and stock enhancement initiatives, we propose recommendations for the future restocking of L. crocea in China. Length‐based analysis indicated serious overfishing of Larimichthys crocea, characterized by reduced catch, size truncation, constrained distribution, and advanced maturation. The overwintering HSI modeling results indicated that climate change has led to decreased sea surface temperature during L. crocea overwintering phase, which in turn led to area decrease and an offshore‐oriented shifting of optimal overwintering habitat of L. crocea. Hence, heavily fishing was the major cause of L. crocea collapse, while climate‐induced overwintering habitat suitability may have intensified the fishery collapse of L. crocea population
... However, while climate change is having measurable effects on kelp, the dominant effects on kelp projected to 2025 are fishing, through its effects on herbivores and predators (medium confidence) (Steneck et al., 2002). Although fishing affected Atlantic cod in the Barents Sea (H214) and Gulf of Maine (H207) biodiversity hotspots, it was also affected by climate change, but negatively and positively, respectively (Kjesbu et al., 2014;Pershing et al., 2015). ...
The Gulf of Maine (GOM) has seen an increasing number of introduced species, some of which have significantly impacted benthic community structure. In 2017, a number of specimens of the European dorid nudibranch, Doris pseudoargus, were observed on rocky ledges in waters off Cape Ann, Massachusetts. The presence of numerous specimens and egg masses suggested the species had been established before 2017. Additional field observations and literature searches revealed specimens occurring from Nova Scotia to the northern end of the Cape Cod Canal, which poses the question, when and where did the initial introduction take place and how? Genetic analysis confirmed the species as Doris pseudoargus with genomic similarities to specimens from Northern Europe. Until this introduction, the GOM had only one species of sponge feeding nudibranch, Cadlina laevis, which is a trophic specialist on one genus of sponge. Unlike this endemic, stenotrophic feeding dorid, the introduction of another large sized, sponge predator known to feed on diverse sponge species, that occur from the intertidal to at least 25 m in depth has the potential to significantly impact community structure over a wide variety of hard bottom habitats.
Climate change is altering the distribution and abundance of fish species in ways not anticipated by current management policy. We created spatially explicit, dynamic models of marine habitats that can inform stock assessments for 25 commercial species on the US Northeast Shelf. The habitat models integrated substrate and seabed features along with the dynamic properties of the ocean. Changes in climate-mediated habitat can affect the survey results by altering the availability component of catchability. Changes in availability were examined (1980–2014) by combining species distribution models with hindcast ocean models. Three patterns in availability were evident: (1) the availability for most species varied over time with no trend; (2) for a number of estuary-dependent species, availability varied with no trend and then dropped dramatically in 2009 when the federal trawl survey changed vessels; and (3) for a set of mid-depth, non-estuary dependent species, availability showed a continuous decline over time. There were few changes in dynamic habitat as the bottom water temperature did not exhibit a strong trend over the time-period studied, resulting in little climate-attributed changes in catchability. Changes in survey design can also have dramatic impacts on catchability, highlighting the method’s ability to detect both climate driven and survey driven changes in catchability.
Variations in Sea Surface Temperature (SST) are an important driver of marine species abundance in Large Marine Ecosystems (LMEs). Studies concerned with climate change induced SST trends within these LMEs have so far been relying on satellite data and reanalysis products, with the disadvantages of only having short time-periods available and having to rely on the ability of the models to correctly simulate SST-dynamics, respectively. Here, we provide for the first time a long-term trend analysis of SST for 17 LMEs of the Atlantic Ocean over two different time-periods (1957-2020 and 1980-2020) based on in-situ data gathered from three data collections. We sort our results according to warming categories that were established in an earlier study, i.e., “cooling” (below 0°C/dec), “slow” (0-0.07°C/dec), “moderate” (0.07-0.14°C/dec), “fast” (0.14-0.21°C/dec) and “superfast” (above 0.21°C/dec). Our results show a persistent “slow” to “superfast” warming in all considered LMEs. However, the sparse data coverage induces large uncertainties, so that many LMEs cannot uniquely be assigned to one warming category only. We detect no systematic changes in the seasonal SST amplitude of the considered LMEs. We find that the LMEs of the North Atlantic warm faster than those of the South Atlantic and that this difference is increasing with time. Out of the North Atlantic LMEs, the Norwegian Sea, North Sea, Celtic-Biscay Shelf, Gulf of Mexico and the Northeast U.S. Continental Shelf belong exclusively to the superfast warming category for the period 1980-2020.
Over the past several decades, the Gulf of Maine has experienced significant socio‐ecological change. Coastlines have become more densely populated and developed, rapid and dramatic climate change has affected coastal ocean environments, and seal populations have grown as a result of federal protections. Long‐term data sets from marine mammal stranding networks represent a valuable resource for investigating indicator species for coastal ocean health during this period of change. Using data collected from stranded harbor (Phoca vitulina), harp (Pagophilus groenlandicus), and gray (Halichoerus grypus) seals from 2002 to 2017 in Massachusetts, New Hampshire, and Maine, we tested for spatiotemporal correlations between stranding density and human population density, size of and proximity to seal haul‐outs, sea surface temperature, North Atlantic Oscillation, snowfall, and sea ice extent. We found that in the Gulf of Maine proximity to coastal human population centers and large seal haul‐outs are the greatest drivers of reported seal stranding density. Environmental factors played an important role only for harp seals, which do not breed in the study area, although recent shifts in the environmental seascape have the potential to affect all seal species in the Gulf of Maine.
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Climate change became real for many Americans in 2012 when a record heat wave affected much of the United States, and Superstorm Sandy pounded the Northeast. At the same time, a less visible heat wave was occurring over a large portion of the Northwest Atlantic Ocean. Like the heat wave on land, the ocean heat wave affected coastal ecosystems and economies. Marine species responded to warmer temperatures by shifting their geographic distribution and seasonal cycles. Warm-water species moved northward, and some species undertook local migrations earlier in the season, both of which affected fisheries targeting those species. Extreme events are expected to become more common as climate change progresses (Tebaldi et al., 2006; Hansen et al., 2012). The 2012 Northwest Atlantic heat wave provides valuable insights into ways scientific information streams and fishery management frameworks may need to adapt to be effective as ocean temperatures warm and become more variable.
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A mismatch between the scale of fishery management units and biological population structure can potentially result in a misperception of the productivity and sustainable yield of fish stocks. We used simulation modelling as a tool to compare the perception of productivity, stability, and sustain-ability of Atlantic cod (Gadus morhua) off New England from an operating model based on the current US management units to a model that more closely reflects the biological complexity of the resource. Two age-structured models were compared: (i) the management unit model, wherein cod were grouped based on the current spatially defined US management areas (Gulf of Maine and Georges Bank), and (ii) the biological unit model, consisting of three genetically defined population components (northern spring spawning, southern winter/spring spawning, and eastern Georges Bank spring-spawning groups). Overall, the regional productivity and maximum sustainable yield of the biological unit model was lower compared with the management unit model. The biological unit model also provided insights on the distribution of productivity in the region, with southern and northern spawning groups being the dominant contributors to the regional spawning-stock biomass and yield and the eastern Georges Bank spawning group being the minority contributor at low to intermediate levels of fishing mortality. The comparison of models revealed that the perception of Atlantic cod derived from the management unit model was of a resource that is more resilient to fishing mortality and not as susceptible to "collapse" as indicated by the biological unit model. For Atlantic cod, one of the main risks of ignoring population structure appears the potential for overexploitation of segments of the population. Consideration of population structure of cod changed our perception of the magnitude and distribution of productivity in the region, suggesting that expectations of sustainable yield of cod in US waters should be reconsidered.
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The temperature in the coastal ocean off the northeastern U.S. during the first half of 2012 was anomalously warm, and this resulted in major impacts on the marine ecosystem and commercial fisheries. Understanding the spatio-temporal characteristics of the warming and its underlying dynamical processes is important for improving ecosystem management. Here we show that the warming in the first half of 2012 was systematic from the Gulf of Maine to Cape Hatteras. Moreover, the warm anomalies extended through the water column, and the local temperature change of shelf water in the Middle Atlantic Bight was largely balanced by the atmospheric heat flux. The anomalous atmospheric jet stream position induced smaller heat loss from the ocean and caused a much slower cooling rate in late autumn and early winter of 2011-2012. Strong jet stream intraseasonal oscillations in the first half of 2012 systematically increased the warm anomalies over the continental shelf. Despite the importance of advection in prior Northeast U.S. continental shelf inter-annual temperature anomalies, our analyses show that much of the 2012 warming event was attributed to local warming from the atmosphere.
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Organisms are expected to adapt or move in response to climate change, but observed distribution shifts span a wide range of directions and rates. Explanations often emphasize biological distinctions among species, but general mechanisms have been elusive. We tested an alternative hypothesis: that differences in climate velocity—the rate and direction that climate shifts across the landscape—can explain observed species shifts. We compiled a database of coastal surveys around North America from 1968 to 2011, sampling 128 million individuals across 360 marine taxa. Climate velocity explained the magnitude and direction of shifts in latitude and depth much more effectively than did species characteristics. Our results demonstrate that marine species shift at different rates and directions because they closely track the complex mosaic of local climate velocities.
Autocorrelation in fish recruitment and environmental data can complicate statistical inference in correlation analyses. To address this problem, researchers often either adjust hypothesis testing procedures (e.g., adjust degrees of freedom) to account for autocorrelation or remove the autocorrelation using prewhitening or first-differencing before analysis. However, the effectiveness of methods that adjust hypothesis testing procedures has not yet been fully explored quantitatively. We therefore compared several adjustment methods via Monte Carlo simulation and found that a modified version of these methods kept Type I error rates near a. In contrast, methods that remove autocorrelation control Type I error rates well but may in some circumstances increase Type II error rates (probability of failing to detect some environmental effect) and hence reduce statistical power, in comparison with adjusting the test procedure. Specifically our Monte Carlo simulations show that prewhitening and especially first-differencing decrease power in the common situations where low-frequency (slowly changing) processes are important sources of covariation in fish recruitment or in environmental variables. Conversely, removing autocorrelation can increase power when low-frequency processes account for only some of the covariation. We therefore recommend that researchers carefully consider the importance of different time scales of variability when analyzing autocorrelated data.
Conference Paper
Future CO(2)-induced climate change scenarios from Global Circulation Models (GCMs) indicate increasing air temperatures, with the greatest warming in the Arctic and Subarctic, Changes to the wind fields and precipitation patterns are also suggested. These will lead to changes in the hydrographic properties of the ocean, as well as the vertical stratification and circulation patterns. Of particular note is the expected increase in ocean temperature. Based upon the observed responses of cod to temperature variability, the expected responses of cod stocks throughout the North Atlantic to the future temperature scenarios are reviewed and discussed here. Stocks in the Celtic and Irish Seas are expected to disappear under predicted temperature changes by the year 2100, while those in the southern North Sea and Georges Bank will decline. Cod will likely spread northwards along the coasts of Greenland and Labrador, occupy larger areas of the Barents Sea, and may even extend onto some of the continental shelves of the Arctic Ocean. In addition, spawning sites will be established further north than currently. It is likely that spring migrations will occur earlier, and fall returns will be later. There is the distinct possibility that, where seasonal sea ice disappears altogether, cod will cease their migration. Individual growth rates for many of the cod stocks will increase, leading to in overall increase in the total production of Atlantic cod in the North Atlantic. These responses of cod to future climate changes are highly uncertain, however, as they will also depend on the changes to climate and oceanographic variables besides temperature, such as plankton production, the prey and predator fields, and industrial fishing. (c) 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.
Warming of the oceans and consequent loss of dissolved oxygen (O2) will alter marine ecosystems, but a mechanistic framework to predict the impact of multiple stressors on viable habitat is lacking. Here, we integrate physiological, climatic, and biogeographic data to calibrate and then map a key metabolic index-the ratio of O2 supply to resting metabolic O2 demand-across geographic ranges of several marine ectotherms. These species differ in thermal and hypoxic tolerances, but their contemporary distributions are all bounded at the equatorward edge by a minimum metabolic index of ~2 to 5, indicative of a critical energetic requirement for organismal activity. The combined effects of warming and O2 loss this century are projected to reduce the upper ocean's metabolic index by ~20% globally and by ~50% in northern high-latitude regions, forcing poleward and vertical contraction of metabolically viable habitats and species ranges. Copyright © 2015, American Association for the Advancement of Science.
Climate change alters the functions of ecological systems. As a result, the provision of ecosystem services and the well-being of people that rely on these services are being modified. Climate models portend continued warming and more frequent extreme weather events across the US. Such weather-related disturbances will place a premium on the ecosystem services that people rely on. We discuss some of the observed and anticipated impacts of climate change on ecosystem service provision and livelihoods in the US. We also highlight promising adaptive measures. The challenge will be choosing which adaptive strategies to implement, given limited resources and time. We suggest using dynamic balance sheets or accounts of natural capital and natural assets to prioritize and evaluate national and regional adaptation strategies that involve ecosystem services.