Posts Tagged 'fisheries'

The influence of ocean acidification on the economic vitality of shellfish hatcheries in the Pacific Northwest: A meta-analysis

Ocean acidification is the chemical process that results in the decrease of ocean pH levels. This decrease is caused by the diffusion of atmospheric carbon dioxide into Earth’s oceans. In other words, Earth’s oceans act as a carbon sink for atmospheric carbon. Prior to the industrial revolution in 1760, the ocean regulated the amount of carbon in earth’s atmosphere in a manner that did not threaten marine ecosystems. However, due to the increased combustion of fossil fuels due to rapid industrialization, urbanization, and population growth, oceans have begun to take up excessive amounts of carbon dioxide, resulting in an alteration of oceanic chemistry. The accumulation of hydrogen ions in ocean water due to the chemical reaction between carbonate carbon dioxide, and water have increased the acidity of the ocean. This has created a corrosive environment for shell-forming organisms that rely on carbonate for their exoskeletons. Many of these organisms, especially those in the Mollusca phylum, are commercially valuable. Ocean acidification has already begun its impact on the shellfish industry in the Pacific Northwest. However, if a business-as-usual scenario of carbon combustion prevails over use of alternative energy sources and mandatory terrestrial pollutant controls, the impact on shellfish aquaculture firms will only intensify and threaten the industry and its associated jobs and revenue. Local, state and federal authorities and agencies have begun to take steps to mitigate the effects of ocean acidification. Mitigation strategies are analyzed on their basis to effectively diminish the physiological and economic impact of ocean acidification on shellfish aquaculture operations. The question remains if these strategies will be able to successfully inhibit the ongoing process of ocean acidification, or simply just delay the impacts.

Continue reading ‘The influence of ocean acidification on the economic vitality of shellfish hatcheries in the Pacific Northwest: A meta-analysis’

Impacts of climate change on fish and shellfish in the coastal and marine environments of Caribbean Small Island Developing States (SIDS)

The commercially important fish and shellfish of Caribbean SIDS have been considered in four groups based on environment and following the typical division of fishery groups used in this region.

There is a dearth of research and long-term datasets on the impacts of climate change on Caribbean marine environments and the important fishery resources. Most research to date has been outside of the Caribbean and has examined the impacts of one or two stressors in short-term ex situ experiments which are unlikely to accurately reflect the true complexity of long-term in situ impacts of climate change in the region. There is a need to consider the combined effects of climate change stressors (direct and indirect) on both individuals and ecosystems, together with the synergistic effects of other chronic anthropogenic stressors in the region.

We consider the reef-associated shallow shelf group to be the most vulnerable of the four fishery groups given: 1) the already apparent negative climate change impacts on their critical habitats; 2) the overexploited state of most reef-associated fishery stocks; 3) the already degraded state of their nearshore habitats as a result of other anthropogenic activities; and 4) their biphasic life history, requiring the ability to settle in specific benthic nursery habitat from a pelagic early life stage.

We consider the most resilient group, over the short-term, to be the oceanic pelagic species that generally show fewer negative responses to the climate change stressors given that they: 1) are highly mobile with generally good acid-base regulation; 2) have an entirely pelagic lifecycle; 3) have less vulnerable reproductive strategies (i.e. they have extended spawning seasons and over broad areas); and 4) are generally exposed to fewer or less severe anthropogenic stressors.

This summary is provided with the following important caveat: “Any attempt to report on what has already happened to fish and shellfish resources in the Caribbean, based on direct evidence, will be strongly biased by the fact that there is a lack of monitoring and directed research examining fish and shellfish species-level impacts of climate change in this region. As such, any conclusions drawn from direct evidence alone will likely misrepresent the true nature and extent of the climate change impacts on the coastal and marine fish and shellfish resources within the Caribbean to date.”

Continue reading ‘Impacts of climate change on fish and shellfish in the coastal and marine environments of Caribbean Small Island Developing States (SIDS)’

Identifying potential consequences of natural perturbations and management decisions on a coastal fishery social-ecological system using qualitative loop analysis

Managing for sustainable development and resource extraction requires an understanding of the feedbacks between ecosystems and humans. These feedbacks are part of complex social-ecological systems (SES), in which resources, actors, and governance systems interact to produce outcomes across these component parts. Qualitative modeling approaches offer ways to assess complex SES dynamics. Loop analysis in particular is useful for examining and identifying potential outcomes from external perturbations and management interventions in data poor systems when very little is known about functional relationships and parameter values. Using a case study of multispecies, multifleet coastal small-scale fisheries, we demonstrate the application of loop analysis to provide predictions regarding SES responses to perturbations and management actions. Specifically, we examine the potential ecological and socioeconomic consequences to coastal fisheries of different governance interventions (e.g., territorial user rights, fisheries closures, market-based incentives, ecotourism subsidies) and environmental changes. Our results indicate that complex feedbacks among biophysical and socioeconomic components can result in counterintuitive and unexpected outcomes. For example, creating new jobs through ecotourism or subsidies might have mixed effects on members of fishing cooperatives vs. nonmembers, highlighting equity issues. Market-based interventions, such as ecolabels, are expected to have overall positive economic effects, assuming a direct effect of ecolabels on market-prices, and a lack of negative biological impacts under most model structures. Our results highlight that integrating ecological and social variables in a unique unit of management can reveal important potential trade-offs between desirable ecological and social outcomes, highlight which user groups might be more vulnerable to external shocks, and identify which interventions should be further tested to identify potential win-win outcomes across the triple-bottom line of the sustainable development paradigm.

Continue reading ‘Identifying potential consequences of natural perturbations and management decisions on a coastal fishery social-ecological system using qualitative loop analysis’

Climate change, zooplankton and fisheries

We summarize responses to and mechanisms by which zooplankton cope with climate change. Effects of ocean warming include altered phenology, body size reduction, decline of tropical zooplankton biomass, functional group shifts in Polar Regions, and poleward expansion of zooplankton distributions. Thermal specialists (zooplankton from tropical and Polar Regions) may already perform near their limits and will be more vulnerable to warming. Evolutionary adaptation may mitigate, but not always fully offset the adverse effects of warming; thus, dispersal may play a prevalent role in the future distribution of species. While direct negative effects of ocean acidification is largely confined to calcifying organisms, early life stages of noncalcifying species (e.g., copepods, fish larvae) are susceptible to sublethal effects, particularly in combination with increasing temperature. Evidence is emerging for a large adaptation potential to hypercapnia in zooplankton. Hypoxia negatively affects physiology and life history traits. Despite zooplankton physiological and behavioral adaptations to hypoxia, shoaling of hypoxic waters likely increases predation mortality. Combined effects of warming, hypercapnia and hypoxia are poorly characterized or understood, but will likely depress performance and narrow the thermal performance curve. Climate change could result in different kinds of mismatches between zooplankton and fish larvae, i.e., (i) temporal, (ii) spatial, (iii) bioenergetic, and (iv) evolutionary mistmatches that individually or in combination, would result in altered larval fish growth and survival. Linkages between climate, zooplankton and fisheries are explored using the Baltic Sea as a case study.

Continue reading ‘Climate change, zooplankton and fisheries’

Future harvest of living resources in the Arctic Ocean north of the Nordic and Barents Seas: A review of possibilities and constraints

Global warming drives changes in oceanographic conditions in the Arctic Ocean and the adjacent continental slopes. This may result in favourable conditions for increased biological production in waters at the northern continental shelves. However, production in the central Arctic Ocean will continue to be limited by the amount of light and by vertical stratification reducing nutrient availability. Upwelling conditions due to topography and inflowing warm and nutrient rich Atlantic Water may result in high production in areas along the shelf breaks. This may particularly influence distribution and abundance of sea mammals, as can be seen from analysis of historical records of hunting. The species composition and biomass of plankton, fish and shellfish may be influenced by acidification due to increased carbon dioxide uptake in the water, thereby reducing the survival of some species. Northwards shift in the distribution of commercial species of fish and shellfish is observed in the Barents Sea, especially in the summer period, and is related to increased inflow of Atlantic Water and reduced ice cover. This implies a northward extension of boreal species and potential displacement of lipid-rich Arctic zooplankton, altering the distribution of organisms that depend on such prey. However, euphausiid stocks expanding northward into the Arctic Ocean may be a valuable food resource as they may benefit from increases in Arctic phytoplankton production and rising water temperatures. Even though no scenario modelling or other prediction analyses have been made, both scientific ecosystem surveys in the northern areas, as well as the fisheries show indications of a recent northern expansion of mackerel (Scomber scombrus), cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and capelin (Mallotus villosus). These stocks are found as far north as the shelf-break north of Svalbard. Greenland halibut (Reinhardtius hippoglossoides), redfish (Sebastes spp.) and shrimp (Pandalus borealis) are also present in the slope waters between the Barents Sea and the Arctic Ocean. It is assumed that cod and haddock have reached their northernmost limit, whereas capelin and redfish have potential to expand their distribution further into the Arctic Ocean. Common minke whales (Balaenoptera acutorostrata) and harp seals (Pagophilus groenlandicus) may also be able to expand their distribution into the Arctic Ocean. The abundance and distribution of other species may change as well – to what degree is unknown.

Continue reading ‘Future harvest of living resources in the Arctic Ocean north of the Nordic and Barents Seas: A review of possibilities and constraints’

Risks of ocean acidification in the California Current food web and fisheries: ecosystem model projections

The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we describe the effects of ocean acidification on an upwelling system that already experiences inherently low pH conditions, the California Current. We used an end-to-end ecosystem model (Atlantis), forced by downscaled global climate models and informed by a meta-analysis of the pH sensitivities of local taxa, to investigate the direct and indirect effects of future pH on biomass and fisheries revenues. Our model projects a 0.2-unit drop in pH during the summer upwelling season from 2013 to 2063, which results in wide-ranging magnitudes of effects across guilds and functional groups. The most dramatic direct effects of future pH may be expected on epibenthic invertebrates (crabs, shrimps, benthic grazers, benthic detritivores, bivalves), and strong indirect effects expected on some demersal fish, sharks, and epibenthic invertebrates (Dungeness crab) because they consume species known to be sensitive to changing pH. The model’s pelagic community, including marine mammals and seabirds, was much less influenced by future pH. Some functional groups were less affected to changing pH in the model than might be expected from experimental studies in the empirical literature due to high population productivity (e.g., copepods, pteropods). Model results suggest strong effects of reduced pH on nearshore state-managed invertebrate fisheries, but modest effects on the groundfish fishery because individual groundfish species exhibited diverse responses to changing pH. Our results provide a set of projections that generally support and build upon previous findings and set the stage for hypotheses to guide future modeling and experimental analysis on the effects of OA on marine ecosystems and fisheries.

Continue reading ‘Risks of ocean acidification in the California Current food web and fisheries: ecosystem model projections’

Climate change impacts on tropical and temperate fisheries, aquaculture, and seafood security and implications – A review

Fish is an important source of animal protein for billions of people and in some tropical countries like Bangladesh, the Pacific islands, and the Maldives, fish provides more than 60% of animal protein supply. Climate change [the rise in temperatures (T°C), ocean acidification (OA), sea-level rise (SLR) and extreme events (EE)] is an additional threat and risk to world fisheries, aquaculture, and seafood security, in addition, to existing threats posed by other stressors. The T°C will have both the negative and positive effects on fisheries and aquaculture, of which, the temperate areas/countries will benefit, while the tropical regions/countries will be losers due to shifting in fish species from the tropical areas to the temperate areas to escape the warmer water. The T°C would cause coral bleaching and mortalities and may enhance seafood contamination (by algal toxins and metals). The OA would adversely affect many organisms that use calcium carbonate for their skeletons and would cause a decrease in abundance of commercially exploited seafood organisms (shellfish and finfish). SLR would cause salinisation of freshwater fisheries and aquaculture facilities and would damage or destroy many coastal ecosystems including mangroves and salt marshes, which are essential habitat for wild fish stocks. Climate change is projected to increase the frequency and intensity of EE. Besides, EE would destroy seagrass and seaweed beds and mangroves (which are important nursery areas for fishes). The economic loss and impacts on fisheries, aquaculture and seafood security due to T°C, OA, SLR, EE could be substantial in both tropical and temperate areas/countries. This review reveals that fisheries in the least developed tropical countries/regions such as Bangladesh, the Maldives, the Pacific islands, and parts of Africa would be most vulnerable due to lack or limited resources, capacity and capabilities to adapt to climate change and high dependency on fish, fisheries, fishing and aquaculture as a source of food, animal protein, revenues, and livelihoods To achieve sustainability in fisheries and aquaculture in line with the new global sustainable development goals (2016-2030), it will be essential to identify appropriate adaptation and mitigation measures. Such measures may include promotion of climate-smart fisheries and climate-smart aquaculture, and conservation of seagrass and seaweed beds, salt marshes, and mangroves. Community awareness and education on climate change, an introduction of climate change courses in schools, colleges, and universities and incorporation of climate change risks in all the current and future development projects/plans would be vital to minimise threats and risks of climate change on fisheries, aquaculture, and seafood security.

Continue reading ‘Climate change impacts on tropical and temperate fisheries, aquaculture, and seafood security and implications – A review’

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Ocean acidification in the IPCC AR5 WG II

OUP book