finding 9.2 : key-message-9-2

Marine fisheries and fishing communities are at high risk from climate-driven changes in the distribution, timing, and productivity of fishery-related species (likely, high confidence). Ocean warming, acidification, and deoxygenation are projected to increase these changes in fishery-related species, reduce catches in some areas, and challenge effective management of marine fisheries and protected species (warming: very likely, very high confidence; acidification and deoxygenation: likely, high confidence). Fisheries management that incorporates climate knowledge can help reduce impacts, promote resilience, and increase the value of marine resources in the face of changing ocean conditions.

This finding is from chapter 9 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

The goal when building the writing team for the Oceans and Marine Resources chapter was to assemble a group of scientists who have experience across the range of marine ecosystems (such as coral reefs and temperate fisheries) that are important to the United States and with expertise on the main drivers of ocean ecosystem change (temperature, deoxygenation, and acidification). We also sought geographic balance and wanted a team that included early-career and senior scientists. 

We provided two main opportunities for stakeholders to provide guidance for our chapter. This included a town hall meeting at the annual meeting of the Association for the Sciences of Limnology and Oceanography and a broadly advertised webinar hosted by the National Oceanic and Atmospheric Administration. Participants included academic and government scientists, as well as members of the fisheries and coastal resource management communities. We also set up a website to collect feedback from people who were not able to participate in the town hall or the webinar.

An important consideration in our chapter was what topics we would cover and at what depth. We also worked closely with the authors of Chapter 8: Coastal Effects to decide which processes and ecosystems to include in which chapter. This led to their decision to focus on the climate-related physical changes coming from the ocean, especially sea level rise, while our chapter focused on marine resources, including intertidal ecosystems such as salt marshes. We also decided that an important goal of our chapter was to make the case that changing ocean conditions have a broad impact on the people of the United States. This led to an emphasis on ecosystem services, notably fisheries and tourism, which are easier to quantify in terms of economic impacts.

Description of evidence base:

Most evidence of the impacts of climate variability on U.S. living marine resources comes from numerous studies examining the response of these species to variability in ocean temperature. There is strong evidence that fluctuations in ocean temperature, either directly or indirectly via impacts to food web structure, are associated with changes in the distribution,4c1d952b-234b-4f64-8757-d94e3565b067,128194f0-1295-4321-a7bf-a8dee1fc2247,8b09bbe8-9f42-412e-a4d6-ef4889f56556,71910705-6b0b-4f61-8249-5a2d444ad5fb productivity,8c3c048d-74b7-4c5e-b071-381d74036bfe,222c74a9-f62a-4667-a747-2468ad0d26b9,fb1f46cd-8b70-4a44-923a-66df61ffa0be,6d463f21-0ac9-48a2-a86b-41a4b46d8a95,d3fff127-e459-4fe9-a2c7-c2b25bbd1bc0,d5fcbe41-4775-4aae-a2ba-8d3962d40e4c,5408c6b9-945d-4b0e-b474-d22765970ead and timing of key life-history events, such as the spawning1dfd2171-2be3-40b2-a8e2-c0df84ec462a,4c1d952b-234b-4f64-8757-d94e3565b067,c4ef0bdb-c461-423c-a881-b67bd7eb40b3,18e57808-1999-4c24-911d-abce180ac68b of fish and invertebrates in U.S. waters. These temperature-driven changes in the dynamics of living marine resources in turn affect commercial fisheries catch quantity,128194f0-1295-4321-a7bf-a8dee1fc2247 composition,2e04e4ff-6097-4e89-9235-fe7856aeb350 and fisher behavior.1dfd2171-2be3-40b2-a8e2-c0df84ec462a,2331d02c-7dc2-4a6f-8244-4806c2360f53,59740c2a-5744-488b-b86c-c3d732342bf0,f147452b-e846-4fdd-aad9-3110322e071c Beyond temperature, there is robust evidence from experimental studies demonstrating the impacts of oxygen and pH variability on the productivity of marine fish and invertebrates.d721e218-0d4a-47ef-81a1-a148a38bca7c,e1b785b3-0123-4378-973f-d19db994e26f,c7532591-a7aa-4110-ad34-60c178c9a0fe However, studies linking changes in oxygen or pH to variations in fisheries and aquaculture dynamics in the field are few and are mainly regional and/or specific to localized deoxygenation or acidification events.7bfdcd59-36f2-4ac1-a120-11460933f947,bacbf706-64ce-4d4c-95e5-04bc1651fe96,f01c17c0-20ad-4e1a-a8ab-fd3be97b0021

These observational and experimental studies have provided the foundation for the development of models projecting future impacts of changing climate and ocean conditions on fisheries. Global and regional applications of such models provide strong evidence that changes in future ocean warming will alter fisheries catches in U.S. waters.fda5d878-d7b2-48d9-a2c4-bb0721262ce5,d055c0df-2c85-4ee1-a3c6-8e6c79e425bd,a354ff5e-743d-4588-a0a8-411d21820076,9a6b5247-ea62-4f66-a840-0f1d00712573,d3a26c81-d72d-4c3d-a9f0-d7c4c10096ab,41f0be78-707a-4169-8838-2446d6587a79 The projected decrease in catch potential in the tropics and the projected increase in high-latitude regions under both RCP4.5 and RCP8.5 scenarios are robust to model structural uncertaintya354ff5e-743d-4588-a0a8-411d21820076 and are consistent across modeling approaches.d055c0df-2c85-4ee1-a3c6-8e6c79e425bd,a354ff5e-743d-4588-a0a8-411d21820076,d3a26c81-d72d-4c3d-a9f0-d7c4c10096ab,41f0be78-707a-4169-8838-2446d6587a79 In addition, there is moderate evidence from regional ecosystem and single-species models of reduced future catch in specific U.S. regions from future ocean acidification.79fffe59-14cc-48e9-b6e2-0e70906f6d28,867d1e64-e364-496c-9e0c-1593182bb40d,2716b10a-54e8-4ba6-affc-90fd49f9e006,f12c40d3-4265-4e90-b852-026deec041fd,021a1471-ddc7-435a-bc2d-6e2a3d2214d4

Fisheries management in the United States has become increasingly effective at setting sustainable harvest levels, and the number of U.S. fisheries that are overfished or subjected to overfishing has declined in most regions.fe404309-3247-4e64-a401-c4916db3fd2a Science-informed management in general has been shown to be effective in improving ecosystem status901dd046-6f95-42d3-932a-7bb1071c02ac and has been projected to greatly improve the benefits from marine resources.1ca5d69a-758a-4d01-bdd9-fbb8537a8ae1 Climate change presents new challenges to management systems, as some species move across management boundaries and away from traditional fishing grounds and as productivity patterns shift. Management approaches that do not consider climate-driven ecosystem changes can lead to overfishing when the environment shifts rapidly.fb1f46cd-8b70-4a44-923a-66df61ffa0be,04e39e1a-6d28-4afb-ad64-c12a26b9f809 Some measures have been proposed to make the fisheries management system more climate ready.ad9cbd45-a115-4a2a-9e9f-9ed17a171a8b,372d0974-9c5c-4501-be26-0a787ba59ec3,a2a10440-9cb1-45a4-9911-ffc878ceb6bb In many cases, these management strategies will include measures to allow for greater flexibility for harvesters to adapt to changing distributions and quantities of target species. Some preliminary evidence suggests that the use of climate-informed harvest rules can improve fishery sustainability in a variable environment,be93bd33-d4a5-4814-a005-6e368b6cda3c but at present, few fisheries management decisions integrate climate-related environmental information.4d9029dc-72c4-458a-a0a6-5071d8e99893 The North Pacific Fishery Management Council is currently examining a strategic, multispecies, climate-enhanced model that informs managers how climate change and variation are expected to impact key stocks.2c6edbef-f715-4eb8-a64f-1b35a40b8e7f

New information and remaining uncertainties:

While shifts in the productivity and distribution of living marine resources and ecosystem structure are expected to change catch potential and catch composition in U.S. regions, many uncertainties exist. Projections of catch potential have largely been performed using dynamical bioclimatic envelope models (e.g., Cheung et al.).a354ff5e-743d-4588-a0a8-411d21820076 In these models, the spatial population dynamics of fish stocks are forced by temperature (with additional net primary productivity effects on carrying capacity and pH and oxygen effects on growth) and do not include the potential for major changes in species interactions, as has previously occurred with warming events (e.g., Vergés et al.)e4313895-fb80-4d31-906c-2fadb9da71de and food web structure (e.g., Fay et al.).f12c40d3-4265-4e90-b852-026deec041fd Furthermore, recent studies indicate that zooplankton and export production may serve as better indicators of carrying capacity for fisheries than net primary productivity.41f0be78-707a-4169-8838-2446d6587a79,0dc39e20-44c8-4b80-b2ff-84a7e8b81f19 Net primary productivity trends will likely be amplified by higher trophic levels, such as zooplankton and ultimately fish; thus, trends in catch potential projected from primary productivity alone may underestimate future changes.41f0be78-707a-4169-8838-2446d6587a79 These models also do not consider the potential for evolutionary adaptation of marine species. Uncertainties in projections are particularly high for primary productivity, oxygen, and pH, especially at regional and coastal scales,9feddc00-479e-4381-ab30-063c92f6a203,c3f1af37-f5af-4fc9-8e57-f6ded71bc265,ae24a90b-1ca0-4709-9598-c5aff0a21903 but these uncertainties are not typically incorporated into projected catch trends. In terms of the economic impacts on consumers, there is also uncertainty about how potential decreases in the catch of some species will impact net revenues, as lower quantities will be compensated in some cases by increased prices paid by consumers (e.g., Seung and Ianelli).e0d49ed8-a074-4530-95c2-47678dcc4b50 Fish prices are expected to increase very modestly over the next decade, yet there are great uncertainties in longer-term prices based on uncertainty about climate, economic growth, and the effectiveness of management in fisheries around the world.7981b9f8-de54-45d9-9669-ed94dfa87bf8

In addition, climate change is only one of many stressors affecting fish dynamics. Future fish distribution, abundance, and productivity will depend on the interaction between these stressors, including fishing and climate-related stressors. Conceptually and empirically, it is clear that fishers are responding to a wide diversity of factors and may not narrowly follow shifting fish populations.2331d02c-7dc2-4a6f-8244-4806c2360f53,c5e975db-8650-45a8-a24c-87f22abdb150,2b9a04a8-b3f6-422e-87ef-20c79cbc99c0 The development of management measures that respond rapidly to dramatic shifts in environmental factors that impact recruitment, productivity, and distribution will also reduce the potential impacts of climate change by avoiding overfishing in times of environmental stress.

Assessment of confidence based on evidence:

There is high confidence that climate change-driven alterations in the distribution, timing, and productivity of fishery-related species will likely lead to increased risk to the Nation’s valuable marine fisheries and fishing communities. There is very high confidence that future ocean warming will very likely increase these changes in fishery-related species, reduce catches in some areas, and challenge effective management of marine resources. There is high confidence that ocean acidification and deoxygenation will likely reduce catches in some areas, which will challenge effective management of marine fisheries and protected species.

This finding was derived from scenario rcp_8_5

References :

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