Skip to content

Case Studies

Blue Tree with bird icon

American Lobster and Blue Crab: Changing Water Temperatures, Changing Populations

As historical fisheries decline due to changing water temperature, new opportunities could arise.

Temperature Influence on Ecosystems

Climate-induced changes in water temperature drive changes in ecosystem organization and structure, including species presence, distribution, and abundance.1 For example, warming temperatures on the coast of New York State (Figure 1) are driving coldwater species like the American lobster northward and deeper, while warmwater species like the blue crab are increasingly inhabiting the region. This change has ramifications for fishing industries, communities, cultures, and economies that rely on these resources.2

Declines in American Lobster

The American lobster has historically been an important ecological, economic, and cultural resource for New York State. During the 1990s, it was the state’s most valuable commercial marine fishery.3 However, in the fall of 1999, a massive mortality event occurred that resulted in a near-total collapse of the southernmost American lobster population (the Southern New England stock) and the once prosperous fishery (Figure 2). The population has yet to recover and continues to see failure in lobsters moving from young to reproducing adults.3,4 This is believed to be a result of warming waters (Figure 1) that create an inhospitable habitat for the American lobster.5

Highlights

  • American lobster require temperatures below 68°F (20°C). With rising water temperatures, lobster numbers already declining.
  • Blue crabs are a warmwater species historically less prevalent in New York State waters, but their numbers are increasing with rising water temperatures.
  • Regular monitoring and updated regulations will help ensure a smooth transition in fisheries and other ecosystem interactions as American lobsters and blue crabs continue to migrate.
Lobster sitting on a pile of rocks.
The population of the American lobster is declining in New York State, possibly as a result of warming water temperatures. Photo by Ian Manning, licensed under CC BY 4.0.

The American lobster’s maximum thermal limit is 68°F (20°C)—temperatures above this threshold are lethal.4,5 New York State’s bottom waters are now routinely above 68°F (20°C),5,6 making the environment uninhabitable for the lobster.

Four line plots, each with a time series of dots connected by straight line segments, a solid line showing a linear trend, and a dashed curve with a segment of solid blue line along it. The vertical axis on each plot shows temperature in degrees Celsius, and the horizontal axis shows year spanning from 1980 to 2020. The four panels represent values for winter, spring, summer, and autumn.
FIGURE 1. Seasonal mean sea surface temperature (SST) along the Atlantic coast off New York State. The solid black lines show an increase in water temperature across all seasons from 1990 to 2020. Warming trends could be an indication of conditions not suitable for lobster and enhanced thermal habitat for blue crab. Figure from Gruenburg et al. (2021).5
A screenshot of a black screen divided into two columns. The right column has a map of the east coast of the United States, with small red numbered circles. Below the map is a matching red circular icon with the text 'State of New York landings', followed by a date range and descriptive paragraph. The right column has a histogram and a curve, with two vertical axes. The horizontal axis shows years from 1950 to 2020. The right vertical axis corresponds with a curve and shows millions of pounds, from 0 to 10. The left vertical axis shows millions of dollars ranging from 0 to 35 and corresponds with the histogram.
FIGURE 2. State of New York lobster landings from 1950 to 2019 that highlights the rise and collapse of the lobster fishery from the 1990s to the 2000s. Figure from Harrington et al. (2022).4

Increases in Blue Crab

Blue crab play an important role in the dynamics of the ecosystem and support both commercial and recreational fishing industries.

Blue crab under water on a rock.
Blue crab populations are increasing on Long Island possibly due to warming water temperatures. Photo by Jarek Tuszyński, licensed under CC BY-SA 3.0.

Since the 1990s, blue crab have been increasing in abundance on Long Island.7 New York State is the northern extent for blue crab range historically, and winter mortality has kept populations in check. But warming water temperatures could be increasing habitat suitability and blue crab survival, as well as a northward expansion of its range, resulting in increased distribution and abundance in the Long Island area.3 The most recent (2021) survey of blue crab conducted by the New York State Department of Environmental Conservation demonstrated a substantial increase in abundance over the course of the five-year history of the survey, and even within the past year.

The increasing blue crab population on Long Island has economic implications as a potential growing industry that will require new management and regulations. Recreational and commercial fishing for blue crab will be conducted differently if the species becomes a fishery focus.

Evidence shows that warming waters due to climate change play a role in the increased blue crab population on Long Island. The National Oceanic and Atmospheric Administration and New York State Department of Environmental Conservation collect air temperature data, which serve as a proxy for water temperatures. These data show that winter water temperatures were 3.6°F (2°C) above average in 2021, making 2021 the third-warmest year on record for New York State’s coastal region.8 Both warmer winters and warmer and longer growing seasons (Figure 1) could support increases in blue crab populations (Figure 3).

Three map panels showing the coast of Long Island, titled 'Blue Crab CPUE.' A legend at the bottom is titled 'BioData2016 Blue_crab' and shows 8 circles of ranging sizes and associated values correlating to the size of blue crab catch. The top map panel is labeled '2014' and shows many small blue circles along the shoreline. The second map panel is labeled '2015' and also shows small blue circles along the shoreline, however the panel is less densely covered in circles than the first panel. The third panel is labeled '2016' and shows a mixture of small and large blue dots. This panel is less densely covered in dots than the first two panels.
FIGURE 3. Increases in blue crab population in the Long Island area, measured as blue crab catch per unit effort (CPUE). Changes in the size of the blue dots show the increases in blue crab population from 2014-2016. Understanding changes in blue crab populations over time, including in response to warming waters, will help New York State create a blue crab management plan as part of the state’s 2017–2027 New York Ocean Action Plan. Figure from Cerrato et al. (2019).7

Other ecological interactions will also affect the future of blue crab in the state. For example, blue crab preys on other important species such as winter flounder and hard clams. Blue crab could also compete with other species, such as lady crab, for resources. These considerations will be important for future scenario or management planning.3

Opportunities and Adaptation

As one species or fishery declines, another can rise to fill its economic niche. This may be the case with lobster and blue crab in New York State. As waters warm and the blue crab population expands, blue crab could potentially fill a commercial fisheries gap left by lobster. However, this shift requires forecasting, forethought, communication, and collaboration, as well as responsive and adaptive management frameworks informed by research in the physical, natural, and social sciences; monitoring and modeling; and a holistic, ecosystem-based co-management approach.9–11

For More Information

References

1. Kleisner, K. M., Fogarty, M. J., McGee, S., Hare, J. A., Moret, S., Perretti, C. T., & Saba, V. S. (2017). Marine species distribution shifts on the U.S. Northeast Continental Shelf under continued ocean warming. Progress in Oceanography, 153, 24–36. https://doi.org/10.1016/j.pocean.2017.04.001

2. Colburn, L. L., Jepson, M., Weng, C., Seara, T., Weiss, J., & Hare, J. A. (2016). Indicators of climate change and social vulnerability in fishing dependent communities along the Eastern and Gulf Coasts of the United States. Marine Policy, 74, 323–333. https://doi.org/10.1016/j.marpol.2016.04.030

3. New York State Department of Environmental Conservation & New York State Department of State. (2017). New York ocean action plan 2017–2027. https://dos.ny.gov/system/files/documents/2020/08/ny_ocean_action_plan.pdf

4. Harrington, A., Rheuban, J., & Bastidas, C. (2022, July 21). A fishery in a sea of change. ArcGIS StoryMaps. Retrieved October 13, 2023, from https://storymaps.arcgis.com/stories/f50bd80b84d349048e9d814769dc29cd

5. Gruenburg, L. K., Nye, J., Thorne, L., Beltz, B., Menz, T., Chen, B., Heywood, E., Stepanuk, J., Warren, J., & Flagg, C. (2021). New York Bight indicator report 2021. New York State Department of Environmental Conservation and State University of New York Stony Brook. https://www.dec.ny.gov/docs/fish_marine_pdf/dmrsomasindicatorsii.pdf

6. Nye, J. (2022, March 29). [Personal communication].

7. Cerrato, R. M., Frisk, M. G., Nye, J. A., McCartin, K., Mitch, M., Molina, A., Olin, J. A., & Zacharias, J. P. (2019). Blue crab abundance, life history and climate change on Long Island (NYSDEC MOU AM08702). Stony Brook University.

8. Scott, C. R. (2021). Great South Bay beam trawl survey report. New York State Department of Environmental Conservation.

9. Busch, D. S., Griffis, R., Link, J., Abrams, K., Baker, J., Brainard, R. E., Ford, M., Hare, J. A., Himes-Cornell, A., Hollowed, A., Mantua, N. J., McClatchie, S., McClure, M., Nelson, M. W., Osgood, K., Peterson, J. O., Rust, M., Saba, V., Sigler, M. F., … Merrick, R. (2016). Climate science strategy of the US National Marine Fisheries Service. Marine Policy, 74, 58–67. https://doi.org/10.1016/j.marpol.2016.09.001

10. Gaines, S. D., Costello, C., Owashi, B., Mangin, T., Bone, J., Molinos, J. G., Burden, M., Dennis, H., Halpern, B. S., Kappel, C. V., Kleisner, K. M., & Ovando, D. (2018). Improved fisheries management could offset many negative effects of climate change. Science Advances, 4(8), eaao1378. https://doi.org/10.1126/sciadv.aao1378

11. Kleisner, K. M., Ojea, E., Battista, W., Burden, M., Cunningham, E., Fujita, R., Karr, K., Amorós, S., Mason, J., Rader, D., Rovegno, N., & Thomas-Smyth, A. (2021). Identifying policy approaches to build social–ecological resilience in marine fisheries with differing capacities and contexts. ICES Journal of Marine Science, fsab080. https://doi.org/10.1093/icesjms/fsab080

Case Studies