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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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/ / 29 October 2015 / Page 1 / 10.1126/science.aac9819
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:
†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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/ / 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
/ / 29 October 2015 / Page 3 / 10.1126/science.aac9819
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.
1. E. J. Nelson, P. Kareiva, M. Ruckelshaus, K. Arkema, G. Geller, E. Girvetz, D.
Goodrich, V. Matzek, M. Pinsky, W. Reid, M. Saunders, D. Semmens, H. Tallis,
Climate change’s impact on key ecosystem services and the human well-being
they support in the US. Front. Ecol. Environ.
, 483493 (2013).
2. R. Mahon, P. McConney, R. N. Roy, Governing fisheries as complex adaptive
systems. Mar. Policy
, 104112 (2008). doi:10.1016/j.marpol.2007.04.011
3. C. S. Holling, Understanding the complexity of economic, ecological, and social
systems. Ecosystems
, 390405 (2001). doi:10.1007/s10021-001-0101-5
4. K. E. Mills, A. Pershing, C. Brown, Y. Chen, F.-S. Chiang, D. Holland, S. Lehuta, J.
Nye, J. Sun, A. Thomas, R. Wahle, Fisheries management in a changing climate:
Lessons from the 2012 ocean heat wave. Oceanography
, 191195 (2013).
5. M. C. Palmer, 2014 Assessment Update Report of the Gulf of Maine Atlantic Cod
Stock (U.S. Department of Commerce, 2014).
6. J. A. Nye, J. S. Link, J. A. Hare, W. J. Overholtz, Changing spatial distribution of fish
stocks in relation to climate and population size on the Northeast United States
continental shelf. Mar. Ecol. Prog. Ser.
, 111129 (2009).
7. J. A. Nye, T. M. Joyce, Y.-O. Kwon, J. S. Link, Silver hake tracks changes in
Northwest Atlantic circulation. Nat. Commun.
, 412 (2011). Medline
8. M. L. Pinsky, B. Worm, M. J. Fogarty, J. L. Sarmiento, S. A. Levin, Marine taxa track
local climate velocities. Science
, 12391242 (2013). Medline
9. T. J. Joyce, C. Deser, M. A. Spall, The relation between decadal variability of
Subtropical Mode Water and the North Atlantic Oscillation. J. Clim.
, 2550
/ / 29 October 2015 / Page 4 / 10.1126/science.aac9819
2569 (2000). doi:10.1175/1520-0442(2000)013<2550:TRBDVO>2.0.CO;2
10. N. J. Mantua, S. R. Hare, The Pacific Decadal Oscillation. J. Oceanogr.
, 3544
(2002). doi:10.1023/A:1015820616384
11. R. A. Kerr, A North Atlantic climate pacemaker for the centuries. Science
19841985 (2000). Medline doi:10.1126/science.288.5473.1984
12. L. Wu, W. Cai, L. Zhang, H. Nakamura, A. Timmermann, T. Joyce, M. J. McPhaden,
M. Alexander, B. Qiu, M. Visbeck, P. Chang, B. Giese, Enhanced warming over the
global subtropical western boundary currents. Nat. Clim. Change
, 161166
(2012). doi:10.1038/nclimate1353
13. D. G. Mountain, J. Kane, Major changes in the Georges Bank ecosystem, 1980s to
the 1990s. Mar. Ecol. Prog. Ser.
, 8191 (2010). doi:10.3354/meps08323
14. G. G. Gawarkiewicz, R. E. Todd, A. J. Plueddemann, M. Andres, J. P. Manning.
Direct interaction between the Gulf Stream and the shelfbreak south of New
England. Sci. Rep.
, 553 (2012). doi:10.1038/srep00553
15. T. Rossby, R. L. Benway, Slow variations in mean path of the Gulf Stream east of
Cape Hatteras. Geophys. Res. Lett.
, 117120 (2000).
16. A. J. Pershing, C. H. Greene, C. Hannah, D. Sameoto, E. Head, D. G. Mountain, J.
W. Jossie, M. C. Benfield, P. C. Reid, T. G. Durbin, Oceanographic responses to
climate in the Northwest Atlantic. Oceanography
, 7682 (2001).
17. K. Chen, G. G. Gawarkiewicz, S. J. Lentz, J. M. Bane, Diagnosing the warming of
the Northeastern U.S. Coastal Ocean in 2012: A linkage between the atmospheric
jet stream variability and ocean response. J. Geophys. Res.
, 218227 (2014).
18. B. Planque, T. Frédou, Temperature and the recruitment of Atlantic cod (Gadus
morhua). Can. J. Fish. Aquat. Sci.
, 20692077 (1999). doi:10.1139/f99-114
19. K. F. Drinkwater, The response of Atlantic cod (Gadus morhua) to future climate
change. ICES J. Mar. Sci.
, 13271337 (2005).
20. M. Fogarty, L. Incze, K. Hayhoe, D. Mountain, J. Manning, Potential climate
change impacts on Atlantic cod (Gadus morhua) off the Northeastern United
States. Mitig. Adapt. Strategies Glob. Change
, 453466 (2008).
21. K. D. Friedland, J. Kane, J. A. Hare, R. G. Lough, P. S. Fratantoni, M. J. Fogarty, J.
A. Nye, Thermal habitat constraints on zooplankton species associated with
Atlantic cod (Gadus morhua) on the US Northeast Continental Shelf. Prog.
, 113 (2013). doi:10.1016/j.pocean.2013.05.011
22. J. E. Linehan, R. S. Gregory, D. C. Schneider, Predation risk of age-0 cod (Gadus)
relative to depth and substrate in coastal waters. J. Exp. Biol. Ecol.
, 2544
(2001). doi:10.1016/S0022-0981(01)00287-8
23. G. D. Sherwood, R. M. Rideout, S. B. Fudge, G. A. Rose, Influence of diet on
growth, condition and reproductive capacity in Newfoundland and Labrador cod
(Gadus morhua): Insights from stable carbon isotopes (δ13C). Deep Sea Res. II
, 27942809 (2007). doi:10.1016/j.dsr2.2007.08.007
24. C. Deutsch, A. Ferrel, B. Seibel, H.-O. Pörtner, R. B. Huey, Climate change
tightens a metabolic constraint on marine habitats. Science
, 11321135
(2015). Medline doi:10.1126/science.aaa1605
25. Northeast Fisheries Science Center, 55th Northeast Regional Stock Assessment
Workshop (55th SAW) Assessment Report (U.S. Department of Commerce,
26. J. D. Dutil, Y. Lambert, Natural mortality from poor condition in Atlantic cod
(Gadus morhua). Can. J. Fish. Aquat. Sci.
, 826836 (2000). doi:10.1139/f00-
27. R. W. Reynolds, T. M. Smith, C. Liu, D. B. Chelton, K. S. Casey, M. G. Schlax, Daily
high-resolution-blended analyses for sea surface temperature. J. Clim.
54735496 (2007). doi:10.1175/2007JCLI1824.1
28. B. J. Pyper, R. M. Peterman, Comparison of methods to account for
autocorrelation in correlation analyses of fish data. Can. J. Fish. Aquat. Sci.
21272140 (1998). doi:10.1139/f98-104
29. J. W. Hurrell, Decadal trends in the North Atlantic Oscillation: Regional
temperatures and precipitation. Science
, 676679 (1995). Medline
30. E. P. Ames, Atlantic cod stock structure in the Gulf of Maine. Fisheries
, 1028
(2004). doi:10.1577/1548-8446(2004)29[10:ACSSIT]2.0.CO;2
31. A. I. Kovach, T. S. Breton, D. L. Berlinsky, L. Maceda, I. Wirgin, Fine-scale spatial
and temporal genetic structure of Atlantic cod off the Atlantic coast of the USA.
Mar. Ecol. Prog. Ser.
, 177195 (2010). doi:10.3354/meps08612
32. L. A. Kerr, S. X. Cadrin, A. I. Kovach, Consequences of a mismatch between
biological and management units on our perception of Atlantic cod off New
England. ICES J. Mar. Sci.
, 13661381 (2014). doi:10.1093/icesjms/fsu113
33. S. M. L. Tallack, Regional growth estimates of Atlantic cod, Gadus morhua:
Applications of the maximum likelihood GROTAG model to tagging data in the
Gulf of Maine (USA/Canada) region. Fi sh. Res.
, 137150 (2009).
34. K. E. Taylor, R. J. Stouffer, G. A. Meehl, An Overview of CMIP5 and the experiment
design. Bull. Am. Meterol. Soc.
, 485498 (2012). doi:10.1175/BAMS-D-11-
35. K. E. Alexander, W. B. Leavenworth, J. Cournane, A. B. Cooper, S. Claesson, S.
Brennan, G. Smith, L. Rains, K. Magness, R. Dunn, T. K. Law, R. Gee, W. Jeffrey
Bolster, A. A. Rosenberg, Gulf of Maine cod in 1861: Historical analysis of fishery
logbooks, with ecosystem implications. Fish Fish.
, 428449 (2009).
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
/ / 29 October 2015 / Page 5 / 10.1126/science.aac9819
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
/ / 29 October 2015 / Page 6 / 10.1126/science.aac9819
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.
/ / 29 October 2015 / Page 7 / 10.1126/science.aac9819
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.
/ / 29 October 2015 / Page 8 / 10.1126/science.aac9819
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.
... The impacts of ephemeral warming events linked to Gulf Stream intrusions (sensu Brickman et al. 2018, Gawarkiewicz et al. 2012 and overall warming associated with climate change (i.e., Brickman et al. 2016) remain unresolved, but could have a strong impact on species distribution (e.g., Pinsky et al. 2013, Stanley et al. 2018, Zisserson and Cook 2017 and, in particular, survival of sensitive life history stages of several vertebrate and invertebrate species. For example, sustained warming in the Gulf of Maine and short-term incursions of warm slope water onto the Scotian Shelf have been linked to decreased survival and local population declines of juvenile Cod (Pershing et al. 2015) and Snow Crab (Chionoecetes opilio) (Zisserson and Cook 2017), respectively. Continued warming of the bioregion is expected and has been simulated using a regional ocean model . ...
... Connectivity with other deep-water corals could potentially allow immigration rescue in the AOI, but this will require further study of deep-water coral larval dispersal and genetic analysis. Pershing et al. (2015) note that sea surface temperatures in the Gulf of Maine have warmed faster than 99% of the global ocean. This warming is related to a northward shift in the Gulf Stream and shifts in the Atlantic Multidecadal Oscillation that have led to reduced recruitment and increased mortality in Atlantic Cod in this region. ...
... Brander (2018) suggests that climate change is not a primary cause of the continued decline of Cod in the Gulf of Maine, instead attributing fishing pressure(s) as the primary determinant, noting that Cod stocks have increased in the North Sea, which has undergone a similar climate shift to the Gulf of Maine. Pershing et al. (2015) model that rebuilding the Cod stock in the Gulf of Maine under different temperature scenarios could be achievable by 2025 in the absence of any fishing mortality; however, including even small amounts of fishing mortality delays rebuilding the stock by at least three to eight years. Zwanenburg (2000) shows that since the 1970s, the average individual weight of commercial demersal fish has decreased by 41% on the WSS and 51% on the ESS. ...
... Observed impacts of climate change include the expansion, contraction or shift of species ranges (e.g., Nye et al. 2009;Poloczanska et al. 2013;Orio et al. 2019), shifting phenology (e.g., Parmesan and Yohe 2003;Dufour et al. 2010;Poloczanska et al. 2013;Langan et al. 2021), and changes in depth distributions (e.g., Dulvy et al. 2008), changes in metabolism (Pörtner and Knust 2007), species composition and abundance (e.g., Hastings et al. 2020;Pershing et al. 2021;Gordó-Vilaseca et al. 2023), species interactions (e.g., Grady et al. 2019), and trophic transfer efficiency (Barneche et al. 2021;Eddy et al. 2021), all of which affect ecosystem structure, functions, and services to human well-being (Bindoff et al. 2019;Pershing et al. 2021). Moreover, climate change can undermine the effectiveness of fisheries management and marine conservation efforts (e.g., Pershing et al. 2015;; Wilson et al. 2020;Lotze 2021). However, integra-tion of climate change adaptation, mitigation, and resilience into marine conservation planning and management is limited both in Canada and elsewhere (Bryndum-Buchholz et al. 2022;O'Regan et al. 2021). ...
... Although all of Canada's oceans will be affected by climate change (Bryndum-Buchholz et al. 2020), the Northwest Atlantic in particular is considered a climate change hotspot, with average rates of projected warming two times higher than the global average (Pershing et al. 2015;Saba et al. 2016). This is largely due to the high sensitivity of the area to changes in the strength and position of the Labrador Current System and the Gulf Stream, which strongly influence oceanographic conditions (Richaud et al. 2016;Gonçalves Neto et al. 2021) and ecological communities (Lotze et al. 2022). ...
... The projected changes in the Gulf of Maine are in line with recent observations in the region (Pershing et al. 2021), which may give insight into near-future changes further north in the Canadian Maritimes. Recently, the Gulf of Maine has seen one of the fastest rises in temperatures compared with the global mean, negatively impacting populations of commercially important species such as Atlantic cod and American lobster (Pershing et al. 2015(Pershing et al. , 2021. On the other hand, an influx of warm-adapted species from the south has led to a restructuring of the food web (Friedland et al. 2019(Friedland et al. , 2021, and similar northward shifts of species are projected for the Scotian Shelf (Shackell et al. 2014). ...
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Climate change is altering marine ecosystems across the globe and is projected to do so for centuries to come. Marine conservation agencies can use short- and long-term projections of species-specific or ecosystem-level climate responses to inform marine conservation planning. Yet, integration of climate change adaptation, mitigation, and resilience into marine conservation planning is limited. We analysed future trajectories of climate change impacts on total consumer biomass and six key physical and biogeochemical drivers across the Northwest Atlantic Ocean to evaluate the consequences for Marine Protected Areas (MPAs) and Other Effective area-based Conservation Measures (OECMs) in Atlantic Canada. We identified climate change hotspots and refugia, where the environmental drivers are projected to change most or remain close to their current state, respectively, by mid- and end-century. We used standardized outputs from the Fisheries and Marine Ecosystem Model Intercomparison Project and the 6th Coupled Model Intercomparison Project. Our analysis revealed that, currently, no existing marine conservation areas in Atlantic Canada overlap with identified climate refugia. Most (75%) established MPAs and more than one-third (39%) of the established OECMs lie within cumulative climate hotspots. Our results provide important long-term context for adaptation and future-proofing spatial marine conservation planning in Canada and the Northwest Atlantic region.
... A major challenge for stock recovery is that management has control over fishing pressure (at best), but no control over global drivers, such as climatic change or economic dynamics external to the fishery. While previous research has investigated how climatic and ecosystem changes affect cod sustainability [41,48,52] we still have a very limited understanding of how economic dynamics in the global cod market can affect local fisheries. The impact of telecouplings on fisheries is likely to be dependent on the management structure of the fisheries in question. ...
... Emerging non-negligible changes in demographic responses to rising climate variability nevertheless may influence the efficacy of fisheries management. Although historical climate conditions promoted the productivity of fish stocks in the northeast Atlantic Ocean, some stocks in this region and elsewhere in the Northern Hemisphere already are experiencing adverse effects of changing climates (Free et al., 2019;Pershing et al., 2015). Because many biological responses to climate-driven changes in surface temperature and other ocean properties are often nonlinear, we would expect continued shifts in how climate influences marine resource populations and management (Britten et al., 2016). ...
Large-scale commercial harvesting and climate-induced fluctuations in ocean properties shape the dynamics of marine populations as interdependent drivers at varied timescales. Persistent selective removals of larger, older members of a population can distort its demographic structure, eroding resilience to fluctuations in habitat conditions and thus amplifying volatility in transient dynamics. Many historically depleted marine fish stocks have begun showing signs of recovery in recent decades following the implementation of stricter management measures. But these interventions coincide with accelerated changes in the oceans triggered by increasingly warmer, more variable climates. Applying multilevel models to annual estimates of demographic metrics of 38 stocks comprising 11 species across seven northeast Atlantic ecoregions, this study explores how time-varying local and regional climates contributed to the transient dynamics of recovering populations exposed to variable fishing pressures moderated by management actions. Analyses reveal that progressive reductions in fishing pressure and shifting climate conditions discontinuously shaped rebuilding patterns of the stocks through restorations of maternal demographic structure (reversing age truncation) and reproductive capacity. As the survival rate and demographic structure of reproductive fish improved, transient growth became less sensitive to variability in recruitment and juvenile survival and more to that in adult survival. As the biomass of reproductive fish rose, recruitment success also became increasingly regulated by density-dependent processes involving higher numbers of older fish. When reductions in fishing pressure were insufficient or delayed, however, stocks became further depleted, with more eroded demographic structures. Although warmer local climates in spawning seasons promoted recruitment success in some ecoregions, changing climates in recent decades began adversely affecting reproductive performances overall, amplifying sensitivities to recruitment variability. These shared patterns underscore the value of demographic transients in developing robust strategies for managing marine resources. Such strategies could form the foundation for effective applications of adaptive measures resilient to future environmental change.
... The GOM is an oceanographically complex system influenced by the warm Gulf Stream, the cold Labrador Current, and framed by diverse watersheds, coastlines, and bathymetry (Maine Climate Council Science and Technical Subcommittee, 2020 ). The need to reflect on our past and better understand the future of this complicated system is sharpened by (1) the rapid rises in sea surface temperature (SST) that have already occurred since the 1980s and (2) the ecosystem level shifts that are projected to occur by 2050 (Pershing et al., 2015 ). Rising SST trends in the last 40 years have been attributed to anthropogenic forces, shifts in the positioning of currents, and broader atmospheric events (Gonçalves Neto et al., 2021 ). ...
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The Maine Department of Marine Resources (MEDMR) is a state agency tasked with developing , conserving , researching , and promoting commercial and recreational marine fisheries across Maine's vast coastline. Close collaborations with industry members in each of the 30 or more fisheries that support Maine's coastal economy are central to MEDMR's efforts to address this suite of tasks. Here we reflect on recent decades of MEDMR's work and demonstrate how MEDMR fisheries research programmes are preparing for an uncertain future through the lens of three broadly applicable climate-driven challenges: (1) a rapidly changing marine ecosystem; (2) recommendations driven by state and federal climate initiatives; and (3) the need to share institutional knowledge with a new generation of marine resource scientists. We do this by highlighting our scientific and co-management approach to coastal Maine fisheries that ha v e prospered, declined, or followed a unique trend over the last 25 + years. We use these examples to illustrate our lessons learned when studying a diverse array of fisheries, highlight the importance of collaborations with academia and the commercial fishing industry, and share our recommendations to marine resource scientists for addressing the climate-driven challenges that motivated this work.
... McMahan 2017), as well as fishery-independent surveys (Miller et al. 2016), report an increasing abundance of Black Sea Bass in Maine, a region in which they were once rare (Collette and Klein-McPhee 2002). These changes may be in response to the rapid warming of the Gulf of Maine (Pershing et al. 2015) by either migratory response (Nye et al. 2009) or an increase in reproductive productivity (McBride et al. 2018). Additionally, studies have shown that the northerly distribution trends of Black Sea Bass are associated with increasing temperatures of the northwest Atlantic (Bell et al. 2015;Kleisner et al. 2016;Miller et al. 2016). ...
Objective A recent expansion of the northern stock of Black Sea Bass Centropristis striata into the northern Gulf of Maine raises questions about this species’ movement and population dynamics in this region. Determining the origin of these fish is essential, as dramatic changes in migration patterns or current population boundaries could have profound effects on stock assessment estimates and subsequent management regulations. Methods In this study, we measured otolith core concentrations of stable isotopes (δ ¹⁸ O, δ ¹³ C) and trace element:calcium ratios (Mg:Ca, Mn:Ca, Cu:Ca, Zn:Ca, Ba:Ca, Sr:Ca) to assess the natal origin of Black Sea Bass that were caught off the coast of Maine. Spawning condition adults from southern New England (SNE) and the mid‐Atlantic Bight (MAB) were used to characterize the chemical fingerprint of these known spawning regions. Result Unique chemical fingerprints were identified for fish from SNE and the MAB, with high reclassification success using random forest analysis (16% error rate). The classification of Black Sea Bass of unknown origin that were caught in Maine waters indicated that 85% of the samples matched to SNE and 13% to the MAB, whereas one sample remained unclassified. Conclusion Results from this study support the current management population separation of the northern stock of Black Sea Bass between SNE and the MAB and lends additional information to the understanding of this species’ movement into the northern Gulf of Maine. As fish stocks around the world continue to shift into new regions due to climate change, knowledge of their natal origin will be critical to long‐term sustainable management of this species.
Hybrid zones are important windows into the evolutionary dynamics of populations, revealing how processes like introgression and adaptation structure population genomic variation. Importantly, they are useful for understanding speciation and how species respond to their environments. Here, we investigate two closely related sea star species, Asterias rubens and A. forbesi, distributed along rocky European and North American coastlines of the North Atlantic, and use genome-wide molecular markers to infer the distribution of genomic variation within and between species in this group. Using genomic data and environmental niche modelling, we document hybridization occurring between northern New England and the southern Canadian Maritimes. We investigate the factors that maintain this hybrid zone, as well as the environmental variables that putatively drive selection within and between species. We find that the two species differ in their environmental niche breadth; Asterias forbesi displays a relatively narrow environmental niche while conversely, A. rubens has a wider niche breadth. Species distribution models accurately predict hybrids to occur within environmental niche overlap, thereby suggesting environmental selection plays an important role in the maintenance of the hybrid zone. Our results imply that the distribution of genomic variation in North Atlantic sea stars is influenced by the environment, which will be crucial to consider as the climate changes.
The future of American lobster (Homarus americanus; H. Milne Edwards, 1837) habitat has been extensively studied in the Gulf of Maine and Georges Bank regions, but studies quantifying spatiotemporal changes to suitable habitat in Southern New England (SNE) regions remain sparse. The American lobster stock assessment for SNE is conducted separately from the northern stock because of negligible migration and recruitment sharing between them. This fact, coupled with the assumption of spatial nonstationarity between the two stocks when it comes to environmental preferences, suggests that analyses of suitable habitat must be conducted for each stock region independently. This study employs the use of a previously developed habitat suitability index model for American lobster to map historical and forecasted habitat in both the Gulf of Maine and SNE stock regions so that comparisons between long-term forecasts can be accurately made. The suitability indices generated in this study support the hypothesis of environmental nonstationarity between the stocks, with lobster in SNE preferring significantly different environments than their northern counterparts. In the coming decades, the Gulf of Maine lobster fishery may see changes in lobster migration timing as spring suitability decreases and fall suitability rises, whereas the SNE fishery will most likely see the continued use of northern waters by lobsters as more southern waters become less suitable. The rate of change in SNE remains smaller than in the Gulf of Maine owing to the lesser rate of warming observed.
Climate change is profoundly affecting the physical environment and biota of the Northeast U.S. Continental Shelf ecosystem. To understand adaptations to climate change, in particular warming temperatures, we used bottom trawl survey data to describe the size of individual fish and macroinvertebrates. Using species distribution models to estimate abundance and biomass, we determined body size in weight for all modeled species. We demonstrate a tendency for increased abundance and biomass and a concomitant decline in body size over time. An analysis of length frequency data supports this assertion. There was no trend in the combined anthropogenic removals from the ecosystem, i.e. catches, suggesting a limited role of fisheries in influencing these changes. The changes in the fish and macroinvertebrate communities are consistent with the hypothesis of a tropicalization of this ecosystem, where the ecosystem experiences a change in diversity, abundance, biomass, and the size of individuals consistent with lower latitudes. The changes in how productivity is expressed in the ecosystem factors into how human populations relate to it; in a practical sense, change in body size will likely influence the strategies and efficiencies of harvest procedures and the industries built to support them.
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We present the development and evaluation of MOM6-COBALT-NWA12 version 1.0, a 1/12° model of ocean dynamics and biogeochemistry in the Northwest Atlantic Ocean. This model is built using the new regional capabilities in the MOM6 ocean model and is coupled with the COBALT biogeochemical model and SIS2 sea ice model. Our goal was to develop a model to provide information to support living marine resource applications across management time horizons from seasons to decades. To do this, we struck a balance between a broad, coastwide domain to simulate basin-scale variability and capture cross-boundary issues expected under climate change, high enough spatial resolution accurately simulate features like the Gulf Stream separation and advection of water masses through finer-scale coastal features, and the computational economy required to run the long simulations of multiple ensemble members that are needed to quantify prediction uncertainties and produce actionable information. We assess whether MOM6-COBALT-NWA12 is capable of supporting the intended applications by evaluating the model with three categories of metrics: basin-wide indicators of the model's performance, indicators of coastal ecosystem variability and the regional ocean features that drive it, and model run times and computational efficiency. Overall, both the basin-wide and regional ecosystem-relevant indicators are simulated well by the model. Where notable model biases and errors are present in both types of indicators, they are mainly consistent with the challenges of accurately simulating the Gulf Stream separation, path, and variability: for example, the coastal ocean and shelf north of Cape Hatteras is too warm and salty and has minor biogeochemical biases. During model development, we identified a few model parameters that exerted a notable influence on the model solution, including the horizontal viscosity, mixed layer restratification, and tidal self-attraction and loading, which we discuss briefly. The computational performance of the model is adequate to support running numerous long simulations, even with the inclusion of coupled biogeochemistry with 40 additional tracers. Overall, these results show that this first version of a regional MOM6 model for the Northwest Atlantic Ocean is capable of efficiently and accurately simulating historical basin-wide and regional mean conditions and variability, laying the groundwork for future studies to analyze this variability in detail, develop and improve parameterizations and model components to better capture local ocean features, and develop predictions and projections of future conditions to support living marine resource applications across time scales.
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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.