With climate change, the oceans are becoming more acid and that is a threat to the dungeness crab, according to a study by the US National Oceanic and Atmospheric Administration.
The study says ocean acidification expected to accompany climate change may slow development and reduce survival of the larval stages of Dungeness crab.
The dungeness crab is a key component of the Northwest marine ecosystem and vital to fishery revenue from Oregon to Alaska.
The research by NOAA Fisheries’ Northwest Fisheries Science Center in Seattle indicates that the declining pH anticipated in Puget Sound could jeopardize populations of Dungeness crab and put the fishery at risk. The study was recently published in the journal Marine Biology.
Ocean acidification occurs as the ocean absorbs carbon dioxide from the combustion of fossil fuels. Average ocean surface pH is expected to drop to about 7.8 off the West Coast by 2050, and could drop further during coastal upwelling periods.
Survival of Dungeness crab larvae, called zoeae, declined at the lower pH levels expected with ocean acidification. (Jason Miller)
Dungeness crab is the highest revenue fishery in Washington and Oregon, and the second most valuable in California, although the fishery was recently closed in some areas because of a harmful algal bloom. The Dungeness crab harvest in 2014 was worth more than $80 million in Washington, $48 million in Oregon and nearly $67 million in California
“I have great faith in the resiliency of nature, but I am concerned,” said Jason Miller, lead author of the research, which was part of his dissertation. “Crab larvae in our research were three times more likely to die when exposed to a pH that can already be found in Puget Sound, our own back yard, today.”
Scientists collected eggs from Dungeness crabs in Puget Sound and placed them in tanks at the NWFSC’s Montlake Research Laboratory. The tanks held seawater with a range of pH levels reflecting current conditions as well as the lower pH occasionally encountered in Puget Sound when deep water wells up near the surface. Larvae also went into tanks with the even lower-pH conditions expected with ocean acidification.
“The question was whether the lower pH we can expect to see in Puget Sound interferes with development of the next generation of Dungeness crab,” said Paul McElhany, a NOAA Fisheries research scientist and senior author of the paper. “Clearly the answer is yes. Now the question is, how does that play out in terms of affecting their life cycle and populations overall?”
Larvae hatched at the same rate regardless of pH, but those at lower pH took longer to hatch and progressed through their larval stages more slowly. Scientists suggested that the lower pH may reduce the metabolic rate of embryos. That could extend their vulnerable larval period, or could jeopardize the timing of their development in relation to key food sources, researchers suggested.
Larval survival also dropped by more than half at lower pH. At pH 8.0, roughly equivalent to seawater today, 58 percent of the crab larvae – called zoeae – survived for 45 days. At pH 7.5, which sometimes occurs in Puget Sound now, survival was 14 percent. At pH 7.1, which is expected to roughly approximate the pH of water upwelling on the West Coast with ocean acidification, zoeae survival remained low at 21 percent.
“Areas of greatest vulnerability will likely be where deep waters, naturally low in pH, meet acidified surface waters,” such as areas of coastal upwelling along the West Coast and in estuary environments such Hood Canal, the new study predicts.
That’s one of the predictions from a new study from the University of British Columbia, looking at the future of the fishery on the coast.
The study concentrates on the First Nations fishery and warns that aboriginal people could face a catastrophic decline in the harvest of traditional species, especially salmon and herring roe on kelp over the next thirty years, a decline that will also have an equally devastating effect on commercial and recreational fishing.
The main cause of the decline is climate change and the warming of the coastal waters. The study projected “modest to severe declines in catch potential” for all current commercial fisheries along the coast.
The study says that for the First Nations the between $28 million to $36 million in revenue they got from fishing between 2001 and 2010 could fall by up to 90 per cent depending on how the climate changes.
A chart from the UBC study shows possible decline in fish species under different climate scenarios. (PLOS1)
One scenario calls for a decline of up to 40 per cent in chinook and pink salmon.
If there is any good news, if you can call it that, the decline will be not as bad in northern coastal waters as it will be the warmer waters near the Lower Mainland and southern Vancouver Island. The range of some species, including salmon, herring, halibut and possibly oolichan will move to farther north along the BC Coast and into Alaskan waters.
That means in time the warming waters will also encourage an increase in other species, including sardines and some clams.
The changing oceans mean that “an increase in the relative abundance of warmer-water species was projected to lead to new or increased opportunities for commercial harvests by 2050.”
The study is urging the First Nations and other stakeholders in the British Columbia fishery to start long term planning immediately to anticipate changes in the coming decades.
The team of scientists led by Lauren Weatherdon, a graduate student at UBC, noted that while previous studies have looked at the impact of climate change on large-scale commercial fisheries, “few efforts have been made to quantitatively project impacts on small-scale subsistence and commercial fisheries that are economically, socially and culturally important to many coastal communities.”
The study was conducted in cooperation with the BC First Nations Fisheries Council and looked its seven coastal administrative regions “forming a sample of groups with diverse marine resources, geographical locations, territorial sizes, and treaty statuses.”
Within those regions 16 First Nations participated in the study, some under their treaty councils, including the Council of the Haida Nation, the Tsimshian Nations Treaty Society (including the Gitga’at at Hartley Bay and the Kitselas and Kitsumkalum near Terrace) and the Maa-nulth First Nations. The Heiltsuk First Nation at Bella Bella participated as an independent group.
The FNFC’s administrative regions intersect with five distinct ecological regions: the North Coast, comprising the Hecate Strait and Dixon Entrance; Haida Gwaii, which includes the waters surrounding the islands; the Central Coast, including Queen Charlotte Sound, Queen Charlotte Strait, and the southern tip of Hecate Strait; the Strait of Georgia; and the west coast of Vancouver Island (WCVI) .
The study says First Nations are likely to be exposed to different climate-related impacts on fisheries due to the differing ecological and biogeographical characteristics of these regions and to differing traditional and commercial harvests.
The study used a “dynamic bioclimate envelope” computer model to look at the changes to the distribution and relative abundances of the BC coastal species under two climate change scenarios, a high greenhouse gas model where society can’t curb emissions and a low greenhouse gas emission scenarios, depending on how society is able to curb the increase.
The study looked at ocean properties—including sea surface temperature, sea bottom temperature, salinity, oxygen concentration, surface action, and net primary production—using data from the US National Ocean and Atmospheric Administrations’ climate-related earth system model.
Climate change will mean that current species on the BC coast will “shift polewards.”
The study showed that by 2050, there could be declines in 87 of the 98 species in the study.
Greater losses in what the study calls “species richness” is likely to occur towards the southern coast of British Columbia, falling primarily between 48°N and 51°N. But, overall, species richness along coastal BC will continue—only with different species.
Most significantly the study projects a decline in the overall salmon catch from 17.1 per cent to 29.2 per cent, depending on the region and climate.
All aspects of the herring fishery, including roe herring, spawn-on-kelp, and the food and bait fishery could decline between 28.1 per cent and 49.2 per cent depending on the region.
The future of the oolichan is the most uncertain. One of the models studied projected a further 37.1 per cent decline in the oolichan, while other models called for for a decline between 5 per cent and 6.8 per cent. That will depend on how well, the oolichan already threatened in most regions of British Columbia are able to adapt to warmer waters or find a way to move their range northward.
The study says white sturgeon and Pacific sardines were projected to increase in abundance under both climate change scenarios, while manila clams were projected to increase in abundance by 14.5 per cent in one of the models. The eight remaining species showed little change.
The study suggests that the southern territories (Tsawwassen, Tla’amin, and Maa-nulth First Nations) will likely see a reduction in catch potential between -15.2 per cent and -27.8 per cent depending on how the climate changes.
On the north coast. The Haida and Tsimshian First Nations and those situated along the central or north-eastern coasts of Vancouver Island (Heiltsuk and ‘Namgis First Nations) would likely see smaller reductions in relative catch for each territory, with estimates falling between -3.2 per cent and -8.2 per cent.
The study shows that for the First Nations along the North and Central Coasts of British Columbia (Gitga’at and Haida, and Heiltsuk and ‘Namgis) there will be neutral or positive shifts in catch potential for white sturgeon, kelp greenling, and two species of perch under both scenarios.
While varying regionally, both scenarios also suggested either a slight cumulative decline or negligible change in catch potential for clams, rockfish, lingcod, and sculpins across the North and Central Coast.
One potential problem the study suggests is that fishers in southern British Columbia may, in the future, try to move north to follow the harvest, leading to potential conflicts. The cost of travel, may, however, discourage that.
One of the recommendations from the study is that First Nations revive the traditional clam gardens.
Traditional clam beds serve as an ideal example of a method that could be applied to offset climatic impacts through internalized mechanisms, using local cultivation to generate increased productivity by enhancing native habitat rather than redirecting extraction efforts towards other regions or species. Clam gardens constructed in a manner akin to those situated near ancient settlements of the Northern Coast Salish and Laich-kwil-tach First Nations have been found to generate higher clam densities, biomass, and growth rates than non-walled beaches . These benefits were observed for Pacific littleneck clams and butter clams , two clams that are of cultural, economic, and ecological importance to the region Reinstating clam beds in First Nations’ territorial lands has been suggested as a means of simultaneously achieving local conservation and cultural objectives and may thereby provide a politically and ecologically viable option for mitigating climate-related impacts.
The most important recommendation is that the First Nations and other stakeholders start cooperating immediately to offset how the changing climate with affect the fishery:
Management of salmon and herring stocks has been highly contentious due to the myriad of stakeholders who depend upon them, which include First Nations, recreational fisheries, and commercial fisheries….
Aside from fulfilling societal needs, salmon serve as key ecological components of the Pacific Northwest Coast, functioning as the mechanisms by which nutrients are transferred from the ocean to freshwater and terrestrial ecosystems
It says the projections show that a “redistribution of fishing effort” will not “fully offset declines in salmon and herring”
attaining a state of collaboration between First Nations, DFO, and other sectors has the potential to yield beneficial ecological and political results, if implemented correctly. Parallels exist between First Nations’ traditional fisheries management approaches and “modern” approaches (e.g., spatial management, mariculture, selective fishing, fishing closures), with differences arising primarily due to diverging worldviews.
It recommends local application of First Nations’ traditional management strategies to “provide opportunities to collaboratively engage in adaptive ecosystem-based management and to coordinate efforts to attain conservation objectives.”
They give an example of how the Nisga’a Nation have ensured their equal partnership in management by employing traditional fish wheel technology to monitor and assess stocks and by leveraging traditional ecosystem-based management practices that could be applied to plan long-term objectives and management approaches.
It concludes by saying that joint-management will not only work to reduce the impact of climate change but also head off potential conflict.
Through such joint-management regimes, traditional fisheries management strategies could be applied to advance localized research directives and to reduce impacts on stocks under unprecedented environmental change. Moreover, the risk of conflict over declining resources underlines the need to establish common and equitable ground to ensure successful joint management of fisheries, and to leverage collective expertise.
Chart from the study showing which fish species will move north up the coast as the climate changes. (PLOS1)
