Climate change is affecting marine and coastal ecosystems in the United States, including commercial, recreational, and subsistence fisheries and aquaculture. Climate change, in addition to other regional pressures, is having and will continue to have effects on all aspects of fisheries, including fish production, essential fish habitats, and fishing-dependent communities. Fisheries managers are tasked with applying scientific and conservation principles in order to sustainably exploit fish stocks while minimizing negative effects on fish habitats, often despite uncertainty. Climate change and ocean acidification will add an additional layer of complexity in balancing the extraction and conservation of fish stocks. The extent to which these changes occur and how quickly they become manifest depends on the mitigation of greenhouse gas emissions, as well as the vulnerability of and level of preparedness in natural and human systems.
Fisheries managers and scientists will need to prepare for and respond to the unavoidable effects of past, current, and projected CO2 emissions, in addition to limiting the compounding effects of non-climatic stressors with respect to changes in abundance and productivity, distribution and recruitment, and habitat conversion or loss. Traditional fisheries management tools, such as allowable catch, size restrictions, seasonal closures, gear restrictions, marine protected areas, essential fish habitat protection, and protection of spawning aggregations, may not be sufficient to sustain fisheries in the face of the combined effects of climatic and non-climatic stressors, which will affect both fish stock populations and the economies of fisheries-dependent communities.
Managers will need to continuously evaluate responses of fish populations to changing environmental conditions, test adaptation options and their outcomes, and share information regarding successful adaptation strategies with other fisheries managers. This report provides a summary of climatic and non-climatic effects on and management challenges for fisheries, and examples of climate-informed fisheries activities.
Climate change is manifesting in a variety of ways around the planet, including increasing air and sea temperatures, variable precipitation patterns, increasing storm frequency and intensity, changes in ocean circulation and oscillation events, rising sea levels, and ocean acidification. These changes have major implications for marine food webs and the viability of commercially and recreationally important species, inter- and intra-species interactions, reproductive and developmental abilities of flora and fauna, and fundamental processes such as respiration, photosynthesis, and nitrogen fixation. Climate impacts, in addition to non-climatic stressors, such as overfishing, pollution, and habitat degradation, may have independent, synergistic, additive, or antagonistic effects with one another. These interlinked issues threaten fish species, critical nursery and breeding habitats (e.g., estuaries, coral reefs, mangroves, seagrass beds), and the sustainability and management of fisheries as a whole. For example, shellfish culture operations on the east and west coasts of the United States are likely to suffer declines in productivity and increases in mortality rates due to waters that are increasingly hypoxic and acidic (expected pH declines of 0.3 to 0.4 units by the end of the 21st century).
For commercial fisheries, some major fish stocks such as Atlantic cod will migrate northward and to deeper depths due to warming oceans and changing ocean circulation patterns. Smaller-scale traditional and recreational fisheries will also be greatly affected by climatic changes. Traditional, subsistence, and recreational fishermen tend to fish closer to home and may be less able or willing to travel greater distances to reach shifting stocks, although they may exhibit flexibility by shifting to new fish species and shifting fishing locations.
In the Pacific Northwest, where tribal communities are highly dependent on salmon and shellfish for cultural and subsistence purposes, continued declines in populations will greatly impact their traditions and lifestyle. Additionally, increasing frequency of storms and sea level rise may cause damage to fishing infrastructure (e.g., fishing boats, piers, ports) and present challenges to the operations of smaller-scale fishing operations. Finally, aquaculture operators are likely to experience declines in shellfish production and higher rates of mortality due to increasing ocean acidification and hypoxia.
Climate change may also have positive effects on fisheries; for example, decreased primary productivity rates and species range shifts may disrupt the ecosystem in one area but allow for new fishing opportunities in another. However, whether these changes will be permanent or temporary is difficult to predict, and any new species fishing opportunities, as well as the response of fishermen to these changes, will need to be evaluated carefully. In Maine, for instance, warmer temperatures during a particularly warm summer in 2012 led to earlier shoreward migrations of lobster and an extended lobster fishing season. However, the high availability of lobster also caused declines in price and negative economic consequences for the lobster fishermen. Fisheries management must address both possibilities in order to decrease climate vulnerability and increase climate resilience.
“Best Bets” for Advancing Long-term Climate-informed Fisheries Management
- Advance monitoring efforts of climate-driven impacts on species, habitat, and fishing communities. Documenting environmental and climatic change is key to natural resources management. As these changes manifest in ocean systems, monitoring cascading effects on species abundance, composition, and presence and/or absence will be increasingly important to track relationships between environmental pressures, fishing effort, and socioeconomics.
- Enhance habitat connectivity and areas under protection. Protecting ecological connectivity and increasing the amount and/or improving the management of protected areas will be increasingly important to support climate-driven range shifts and vulnerable habitats. This includes removing physical barriers to connectivity, creating ecologically connected networks of protected areas, and protecting space to allow critical habitats such as mangroves and marshes to migrate landward.
- Reduce non-climate stressors. The cumulative effects of non-climate stressors reduce the overall resilience of species, habitats, and communities to climate change. Limiting or eliminating stressors, such as pollution, destructive fishing practices, and non-native and invasive species, will reduce vulnerability.
- Create flexible multi-species permitting, licensing, and management plans. As species’ ranges shifts due to warming temperatures, enabling flexibility in terms of when, where, what, and how much is harvested will become increasingly important to sustain fishing livelihoods. These concerns need to be balanced with the sustainability of fish populations overall.
- Adjust quotas to help sustain stocks (e.g., reduce fishing pressure on vulnerable stocks). Evaluating the climatic and non-climatic factors that contribute to the vulnerability of fish stocks may help managers adjust harvest allocations. Climate change will require managers to move beyond using the maximum sustainable yield of target species for allocating quotas and instead consider ecosystem-based approaches to reducing vulnerability.
- Temporarily close fisheries, if necessary. Given the uncertainty of climate change and the risks associated with extreme events that may collapse entire fisheries, managers can adjust status quo policies by supporting rapid response measures to reduce stress on vulnerable stocks, including temporary closures.
- Evaluate potential and establish procedures for new commercial and recreational fisheries (e.g., establishment of catch limits, new permitting procedures). As species migrate to more climatically suitable habitat, managers will need to prepare for the closure of existing fisheries as well as the emergence of new fisheries. This may require full-scale changes in fishing gear for different species, limiting allocations while emerging stocks establish themselves, and restrictions on recreational fishing calendars.
- Create international cooperative fisheries agreements. Climate change will not be confined by political or social boundaries. Establishing climate-informed cooperative agreements between countries will create shared fisheries management goals and objectives to help achieve long-term viability.
- Develop resistant and resilient seed/broodstock for shellfish and finfish hatcheries. Some species and habitats may be at risk of complete destruction from climate change impacts. Developing resistant and resilient strains of seed and broodstock can determine if and how different species such as coral will be viable under future conditions.
- Diversify fisheries and/or livelihoods. In some areas, climate-induced effects on fisheries may threaten entire communities’ livelihoods. Diversifying either the fish stocks targeted and/or the sector in which fishermen operate (e.g., ecotourism) may be prudent but may require capital investments (e.g., funding, training).
- Promote fishing opportunities for non-native and invasive species. The direct removal of problematic non-native and invasive species may help alleviate stress on species and habitats. Lionfish that have invaded Atlantic and Caribbean waters are voracious predators of commercially important species such as snapper and grouper. Lionfish are now promoted as a viable food source and are available at restaurants and supermarkets.
- Restore degraded freshwater habitat. Managers need to examine the land-sea connection to understand how changes in terrestrial, freshwater, and marine systems affect fisheries.