Posts Tagged 'fisheries'

California shellfish farmers: perceptions of changing ocean conditions and strategies for adaptive capacity

Highlights

  • Shellfish growers were interviewed about their experiences with environmental change.
  • Growers expressed concerns about multiple observed environmental changes.
  • Growers identified seventeen adaptive strategies.
  • Strategies can be categorized as policy/networking, farm management, and science.

Abstract

Coastal communities along the U.S. West Coast experience a myriad of environmental stressors, including exposure to low pH waters exacerbated by ocean acidification (OA). This can result in ecological and social consequences, making necessary the exploration and support for locally relevant strategies to adapt to OA and other environmental changes. The shellfish aquaculture industry along the West Coast is particularly vulnerable to OA, given the negative effects of low pH on shellfish survival and growth. As such, the social-ecological system exemplified by this industry serves as an opportunity to identify and address strategies for local adaptation. Through interviews conducted with West Coast shellfish farm owners and managers (‘growers’), we investigate perceptions of OA and environmental change and identify specific strategies for adaptation. We find that growers are concerned about OA, among many other environmental stressors such as marine pathogens and water temperature. However, growers are often unable to attribute changes in shellfish survival or health to these environmental factors due to a lack of data and the resources and network required to acquire and interpret these data. From these interviews, we identify a list of adaptive strategies growers employ or would like to employ to improve their overall adaptive capacity to multiple stressors (environmental, economic, political), which together, allow farms to weather periods of OA-induced stress more effectively. Very few studies to date have identified specific adaptive strategies derived directly from the communities being impacted. This work therefore fills a gap in the literature on adaptive capacity by amplifying the voices of those on the front lines of climate change and identifying explicit pathways for adaptation.

Continue reading ‘California shellfish farmers: perceptions of changing ocean conditions and strategies for adaptive capacity’

Influence of climate on seawater quality and green mussel production

This study aimed to investigate the relationships between atmospheric parameters, seawater quality and green mussel production which were cultured in pond, estuary and coastal areas. Seawater and mussel samples were collected from mussel farms in the inner Gulf of Thailand from January to December 2019. Climate data were obtained from the Thai Meteorological Department. The correlations between selected atmospheric and seawater parameters were developed using linear and non-linear models. The influence of seawater quality on mussel production was evaluated using principal component analysis and stepwise multiple linear regression. The effects of atmospheric variation on green mussel productivity were simulated. The results showed that high air temperature and rainfall caused an increase in seawater temperature and a decrease in salinity, respectively. It was observed that the most influential factors affecting mussel production were nutrients and dissolved oxygen in ponds, temperature and salinity in estuaries, and nutrients and pH in coastal areas. The simulation indicated that mussel production can deteriorate when air temperature reaches 34°C and rainfall is higher than 200 mm per month. Our results suggest that under climate change events, locations with less riverine influence can provide higher mussel productivity. These results can be used as a guideline for farmers during a climate change event.

Continue reading ‘Influence of climate on seawater quality and green mussel production’

Ocean futures for the world’s largest yellowfin tuna population under the combined effects of ocean warming and acidification

The impacts of climate change are expected to have profound effects on the fisheries of the Pacific Ocean, including its tuna fisheries, the largest globally. This study examined the combined effects of climate change on the yellowfin tuna population using the ecosystem model SEAPODYM. Yellowfin tuna fisheries in the Pacific contribute significantly to the economies and food security of Pacific Island Countries and Territories and Oceania. We use an ensemble of earth climate models to project yellowfin populations under a high greenhouse gas emissions (IPCC RCP8.5) scenario, which includes, the combined effects of a warming ocean, increasing acidification and changing ocean chemistry. Our results suggest that the acidification impact will be smaller in comparison to the ocean warming impact, even in the most extreme ensemble member scenario explored, but will have additional influences on yellowfin tuna population dynamics. An eastward shift in the distribution of yellowfin tuna was observed in the projections in the model ensemble in the absence of explicitly accounting for changes in acidification. The extent of this shift did not substantially differ when the three-acidification induced larval mortality scenarios were included in the ensemble; however, acidification was projected to weaken the magnitude of the increase in abundance in the eastern Pacific. Together with intensive fishing, these potential changes are likely to challenge the global fishing industry as well as the economies and food systems of many small Pacific Island Countries and Territories. The modelling framework applied in this study provides a tool for evaluating such effects and informing policy development.

Continue reading ‘Ocean futures for the world’s largest yellowfin tuna population under the combined effects of ocean warming and acidification’

A framework for assessing harvest strategy choice when considering multiple interacting fisheries and a changing environment: the example of eastern Bering Sea crab stocks

Ecosystem Based Fisheries Management aims to broaden the set of factors included in assessments and management decision making but progress with implementation remains limited. We developed a framework that examines the consequences of temporal changes in temperature and ocean pH on yield and profit of multiple interacting stocks including eastern Bering Sea (EBS) snow, southern Tanner, and red king crab. Our analyses integrate experimental work on the effects of temperature and ocean pH on growth and survival of larval and juvenile crab and monitoring data from surveys, fishery landings, and at-sea observer programs. The impacts of future changes in temperature and ocean pH on early life history have effects that differ markedly among stocks, being most pessimistic for Bristol Bay red king crab and most optimistic for EBS snow crab. Our results highlight that harvest control rules that aim to maximize yield lead to lower profits than those that aim to maximize profit. Similarly, harvest control rules that aim to maximize profit lead to lower yields than those that aim to maximize yield, but differences are less pronounced. Maximizing profits has conservation benefits, especially when the implemented harvest control rule reduces fishing mortality if population biomass is below a threshold level.

Continue reading ‘A framework for assessing harvest strategy choice when considering multiple interacting fisheries and a changing environment: the example of eastern Bering Sea crab stocks’

Fisheries surveys are essential ocean observing programs in a time of global change: a synthesis of oceanographic and ecological data from U.S. West Coast fisheries surveys

As climate change and other anthropogenic impacts on marine ecosystems accelerate in the 21st century, there is an increasing need for sustained ocean time series. A robust and collaborative network of regional monitoring programs can detect early signs of unanticipated changes, provide a more holistic understanding of ecosystem responses, and prompt faster management actions. Fisheries-related surveys that collect fisheries-independent data (hereafter referred to as “fisheries surveys”) are a key pillar of sustainable fisheries management and are ubiquitous in the United States and other countries. From the perspective of ocean observing, fisheries surveys offer three key strengths: (1) they are sustained due to largely consistent funding support from federal and state public sector fisheries agencies, (2) they collect paired physical, chemical, and biological data, and (3) they have large and frequently overlapping spatial footprints that extend into the offshore region. Despite this, information about fisheries survey data collection can remain poorly known to the broader academic and ocean observing communities. During the 2019 CalCOFI Symposium, marking the 70th anniversary of the California Cooperative Oceanic Fisheries Investigations (CalCOFI), representatives from 21 ocean monitoring programs on the North American West Coast came together to share the status of their monitoring programs and examine opportunities to leverage efforts to support regional ecosystem management needs. To increase awareness about collected ocean observing data, we catalog these ongoing ocean time series programs and detail the activities of the nine major federal or state fisheries surveys on the U.S. West Coast. We then present three case studies showing how fisheries survey data contribute to the understanding of emergent ecosystem management challenges: marine heatwaves, ocean acidification, and contaminant spills. Moving forward, increased cross-survey analyses and cooperation can improve regional capacity to address emerging challenges. Fisheries surveys represent a foundational blueprint for ecosystem monitoring. As the international community moves toward a global strategy for ocean observing needs, fisheries survey programs should be included as data contributors.

Continue reading ‘Fisheries surveys are essential ocean observing programs in a time of global change: a synthesis of oceanographic and ecological data from U.S. West Coast fisheries surveys’

Climate vulnerability assessment of key fishery resources in the Northern Humboldt Current System

The Northern Humboldt Current System sustains one of the most productive fisheries in the world. However, climate change is anticipated to negatively affect fish production in this region over the next few decades, and detailed analyses for many fishery resources are unavailable. We implemented a trait-based Climate Vulnerability Assessment based on expert elicitation to estimate the relative vulnerability of 28 fishery resources (benthic, demersal, and pelagic) to the impacts of climate change by 2055; ten exposure factors (e.g., temperature, salinity, pH, chlorophyll) and 13 sensitivity attributes (biological and population-level traits) were used. Nearly 36% of the species assessed had “high” or “very high” vulnerability. Benthic species were ranked the most vulnerable (gastropod and bivalve species). The pelagic group was the second most vulnerable; the Pacific chub mackerel and the yellowfin tuna were amongst the most vulnerable pelagic species. The demersal group had the relatively lowest vulnerability. This study allowed identification of vulnerable fishery resources, research and monitoring priorities, and identification of the key exposure factors and sensitivity attributes which are driving that vulnerability. Our findings can help fishery managers incorporate climate change into harvest level and allocation decisions, and assist stakeholders plan for and adapt to a changing future.

Continue reading ‘Climate vulnerability assessment of key fishery resources in the Northern Humboldt Current System’

The Patagonian fisheries over time: facts and lessons to be learned to face global change

Environmental and anthropic stressors have triggered unprecedented effects on the marine ecosystem. The global increase of marine temperature and acidification caused changes in fish availability and thus catches worldwide. Fostered by a legal framework favoring the investment in extractive capacity, industrial fishing in Atlantic Patagonia grew markedly since the 1960s, leading to the overexploitation of certain stocks. Nowadays, the regulatory system of individual transferable quotas is enforced for hake, but most resources in Patagonia continue being managed under an olympic system lacking planning for sustainability. We analyzed the vulnerability of the Patagonian fisheries to environmental (water temperature and acidification) and human stressors (overexploitation and market forces) in terms of their exposure, sensitivity, and adaptive capacity. Most of the Patagonian fisheries have operated in a scenario of low exposure to climate change. The shellfisheries, however, exhibited the highest sensitivity, as well as the lowest adaptive capacity, to acidification. Regarding the anthropic stressors, both the king crab and shrimp fisheries scored highly sensitive to overexploitation and market forces. Finally, the fisheries targeting the king crab and the Bonaerense demersal fish assemblage evidenced the lowest adaptive capacity against market forces. We propose management options for each case within the context of the Ecosystem Approach to Fisheries.

Continue reading ‘The Patagonian fisheries over time: facts and lessons to be learned to face global change’

Climate change, marine resources and a small Chilean community: making the connections

Climate change is affecting large-scale oceanic processes. How and when these changes will impact those reliant on marine resources is not yet clear. Here we use end-to-end modeling to track the impacts of expected changes through the marine ecosystem on a specific, small community: Cochamó, in the Gulf of Ancud wider area, Chile. This area is important for Chilean fisheries and aquaculture, with Cochamó reliant on both lower and upper trophic level marine resources. We applied the GOTM-ERSEM-BFM coupled hydro-biogeochemical water-column model to gauge lower-trophic level marine ecological community response to bottom-up stressors (climate change, ocean acidification), coupled to an existing Ecopath with Ecosim model for the area, which included top-down stressors (fishing). Social scientists also used participatory modeling (Systems Thinking and Bayesian Belief Networking) to identify key resources for Cochamó residents and to assess the community’s vulnerability to possible changes in key resources. Modeling results suggest that flagellate phytoplankton abundance will increase at the cost of other species (particularly diatoms), resulting in a greater risk of harmful algae blooms. Both climate change and acidification slightly increased primary production in the model. Higher trophic level results indicate that some targeted pelagic resources will decline (while benthic ones may benefit), but that these effects might be mitigated by strong fisheries management efforts. Participatory modeling suggests that Cochamó inhabitants anticipate marine ecosystem changes but are divided about possible adaptation strategies. For climate change impact quantification, detailed experimental studies are recommended based on the dominant threats identified here, with specific local species.

Continue reading ‘Climate change, marine resources and a small Chilean community: making the connections’

Emerging trends in science and news of climate change threats to and adaptation of aquaculture

Highlights

  • Temp & sea level rise threats to aquaculture were the main focus in science & news.
  • Focus on Asia, Europe, & N./C. America accounted for 70% of studies.
  • At least 10 countries linked current impacts on aquaculture to climate change.
  • Global papers cited technology for adaption, while regional papers cited governance.

Abstract

Food production is one of the main contributors to climate change, but is also vulnerable to the resulting stressors, which is well documented for agriculture and fisheries. Attention is now turning to the rapidly growing aquaculture sector and its vulnerability to a changing climate. Here we explore the extent to which climate stressors and aquaculture, and concomitant adaptation strategies, are studied in science and addressed in public media (news) to assess focus and attribution of climate change. We reviewed 555 scientific publications and 228 news media articles on climate stressors, impacts, and adaptation approaches with respect to aquaculture. Results indicate that coverage in the scientific community of climate stressors on aquaculture have not kept pace with growth of production in the sector, especially compared to agriculture and fisheries. Temperature, sea level rise and ocean acidification were most often the focus in science (44%) and news (42%), suggesting some alignment. Combined coverage tended to revolve around Asia, Europe, and North/Central America (70%) and at least 10 countries’ science and news linked current impacts on aquaculture to climate change. The majority of scientific articles addressing adaptation were regional rather than global, and emphasized governance and institutional strategies over technological solutions. In all, this research highlights the comparatively nascent focus of climate change implications for aquaculture, narrow emphasis of stressors, but fairly representative coverage of regions with more aquaculture. Our work highlights the need for more research and public awareness of the social and ecological climate change threats and impacts on, and adaptive strategies for aquaculture.

Continue reading ‘Emerging trends in science and news of climate change threats to and adaptation of aquaculture’

Modelling ocean acidification effects with life stage-specific responses alters spatiotemporal patterns of catch and revenues of American lobster, Homarus americanus

Ocean acidification (OA) affects marine organisms through various physiological and biological processes, yet our understanding of how these translate to large-scale population effects remains limited. Here, we integrated laboratory-based experimental results on the life history and physiological responses to OA of the American lobster, Homarus americanus, into a dynamic bioclimatic envelope model to project future climate change effects on species distribution, abundance, and fisheries catch potential. Ocean acidification effects on juvenile stages had the largest stage-specific impacts on the population, while cumulative effects across life stages significantly exerted the greatest impacts, albeit quite minimal. Reducing fishing pressure leads to overall increases in population abundance while setting minimum size limits also results in more higher-priced market-sized lobsters (> 1 lb), and could help mitigate the negative impacts of OA and concurrent stressors (warming, deoxygenation). However, the magnitude of increased effects of climate change overweighs any moderate population gains made by changes in fishing pressure and size limits, reinforcing that reducing greenhouse gas emissions is most pressing and that climate-adaptive fisheries management is necessary as a secondary role to ensure population resiliency. We suggest possible strategies to mitigate impacts by preserving important population demographics.

Continue reading ‘Modelling ocean acidification effects with life stage-specific responses alters spatiotemporal patterns of catch and revenues of American lobster, Homarus americanus’

A marine-biology-centric definition of ocean connectivity and the law of the sea

The inter-connectedness of marine ecosystems has been repeatedly acknowledged in the relevant literature as well as in policy briefs. Against this backdrop, this article aims at further reflecting on the question of to what extent the law of the sea takes account of or disregards ocean connectivity. In order to address this question, this article starts by providing a brief overview of the notion of ocean connectivity from a marine science perspective, before taking a closer look at the extent to which the law of the sea incorporates the scientific imperative of ocean connectivity in the context of four examples: (i) straits, (ii) climate change and ocean acidification, (iii) salmon and (iv) the ecosystem approach to fisheries. Tying the findings of the different examples together, this study concludes by stressing the need of accommodating ocean connectivity not only in the interpretation and implementation of the existing law (of the sea) but also in its further development.

Continue reading ‘A marine-biology-centric definition of ocean connectivity and the law of the sea’

The Gulf of St. Lawrence biogeochemical model: a modelling tool for fisheries and ocean management

The goal of this paper is to give a detailed description of the coupled physical-biogeochemical model of the Gulf of St. Lawrence that includes dissolved oxygen and carbonate system components, as well as a detailed analysis of the riverine contribution for different nitrogen and carbonate system components. A particular attention was paid to the representation of the microbial loop in order to maintain the appropriate level of the different biogeochemical components within the system over long term simulations. The skill of the model is demonstrated using in situ data, satellite data and estimated fluxes from different studies based on observational data. The model reproduces the main features of the system such as the phytoplankton bloom, hypoxic areas, pH and calcium carbonate saturation states. The model also reproduces well the estimated transport of nitrate from one region to the other. We revisited previous estimates of the riverine nutrient contribution to surface nitrate in the Lower St. Lawrence Estuary using the model. We also explain the mechanisms that lead to high ammonium concentrations, low dissolved oxygen, and undersaturated calcium carbonate conditions on the Magdalen Shallows.

Continue reading ‘The Gulf of St. Lawrence biogeochemical model: a modelling tool for fisheries and ocean management’

Seasonality and life history complexity determine vulnerability of Dungeness crab to multiple climate stressors

Abstract

Scaling climate change impacts from individual responses to population-level vulnerability is a pressing challenge for scientists and society. We assessed vulnerability of the most valuable fished species in the Northwest U.S.—Dungeness crab—to climate stressors using a novel combination of ocean, population, and larval transport models with stage-specific consequences of ocean acidification, hypoxia, and warming. Integration across pelagic and benthic life stages revealed increased population-level vulnerability to each stressor by 2100 under RCP 8.5. Under future conditions, chronic vulnerability to low pH emerged year-round for all life stages, whereas vulnerability to low oxygen continued to be acute, developing seasonally and impacting adults, which are critical to population growth. Our results demonstrate how ontogenetic habitat shifts and seasonal ocean conditions interactively impact population-level vulnerability. Because most valuable U.S. fisheries rely on species with complex life cycles in seasonal seas, chronic and acute perspectives are necessary to assess population-level vulnerability to climate change.

Plain Language Summary

The release of carbon dioxide (CO2) into the atmosphere by human activities is altering ocean conditions including pH, oxygen, and temperature. One way to understand how these changing conditions will affect ecologically, economically, and culturally important marine species is to scale individual responses from laboratory experiments to population-level impacts. In this study, we assessed the vulnerability of Dungeness crab, one of the most valuable fisheries in the NW USA, to stressful conditions based on the predicted habitat exposure and response of each life stage (eggs, larvae, juveniles, and adults). The degree of vulnerability was determined by the seasonality of the ocean conditions in combination with the crab’s complex life cycle. This approach revealed that Dungeness crab life stages and populations will be more vulnerable to low pH, low oxygen, and high temperature in the future (year 2100) under an aggressive CO2 emissions scenario. Based on these results, we recommend that fishery managers incorporate changing conditions into their decision-making to protect vulnerable life stages in areas prone to stressful conditions (e.g., adult crabs in hypoxic areas). Our approach can be adapted for many other economically and ecologically important marine species in order to inform conservation and management strategies.

Continue reading ‘Seasonality and life history complexity determine vulnerability of Dungeness crab to multiple climate stressors’

Capacity building to address ocean change: organizing across communities of place, practice and governance to achieve ocean acidification and hypoxia resilience in Oregon

Fossil fuel combustion and related accumulation of carbon dioxide (CO2) and other greenhouse gases in the atmosphere and oceans have contributed significantly to climate and ocean change. While coastal upwelling is responsible for the incredible diversity and productivity that has fueled iconic West Coast wild fisheries and ecosystems, it also is the source of extremes in OAH impacts, especially during the late summer (e.g., Chan et al. 2019). While upwelled waters of the California Current Ecosystem are typically low in dissolved oxygen (DO), high in dissolved CO2 and thus more acidified, the chemical balance of upwelled waters has notably changed in recent decades. Ocean absorption of atmospheric CO2 and other ocean changes are resulting in upwelled waters lower or more acidified in pH, higher in CO2 and further depressed in dissolved oxygen (DO) (e.g., Chan et al. 2019). As a result, the West Coast of North America is now considered a hotspot of ocean acidification and hypoxia (OAH). Even as ocean conditions are predicted to change further over the coming decades (e.g., Ekstrom et al. 2015; Hodgson et al. 2018), Oregon and the West Coast are experiencing ocean changes today and expecting further trends in shifting ocean food webs (e.g., Marshall et al. 2017; Xiu et al. 2018), loss of fishery productivity (e.g., Lomonico et al. 2021; Haugen et al. 2021), and reduced economic opportunity for ocean-dependent businesses (e.g., Doney et al. 2020; Hoelting and Burkardt 2017). This paper focuses on identifiable actions that human communities are taking in reaction to ocean change to mitigate these increasingly apparent impacts.

Whiskey Creek Shellfish Hatchery, located in Netarts Bay, Oregon, was among the first places in the world to experience direct impacts from ocean acidification (OA) starting in 2006/2007 (Barton et al. 2015). At that time the hatchery was suddenly unable to reliably produce Pacific oyster larvae (Magallana gigas), with production reduced by over 75% (Barton et al. 2015). As a result, oyster seed supply became limited from Alaska to California, threatening the West Coast’s $270 million dollar oyster growing industry (Northern Economics, Inc. 2013). In response, Oregon researchers worked collaboratively with the oyster industry to eventually rule out disease and identify the problem as OA, from hatchery pumping of bay waters during summer upwelling events, bringing increasingly acidified deep ocean waters. Hatchery operations successfully resumed once they developed water quality practices to mitigate deleterious water conditions (Kelly, Cooley, and Klinger 2014; Barton et al. 2015). However, treatment of water quality is now central to business success and is increasingly challenging to manage.

Continue reading ‘Capacity building to address ocean change: organizing across communities of place, practice and governance to achieve ocean acidification and hypoxia resilience in Oregon’

Expanding ocean observation and climate services to build resilience in West African fisheries

The Canary Current is a potential hotspot for climate change impacts on the oceans where 63 million people depend upon marine resources for national economies and livelihoods. Their unique vulnerability highlights the key roles of climate services and capacity building in order to develop effective adaptation measures.

Continue reading ‘Expanding ocean observation and climate services to build resilience in West African fisheries’

Combined effects of ocean warming and acidification on marine fish and shellfish: a molecule to ecosystem perspective

Highlights

  • Climate change would have profound repercussion on fisheries sector
  • Multiple interactive stressors can incapacitate biological functioning.
  • Trophic pyramids and food web architecture studies need to be approached.
  • Combined in situ monitoring and laboratory studies should be prioritized.

Abstract

It is expected that by 2050 human population will exceed nine billion leading to increased pressure on marine ecosystems. Therefore, it is conjectured various levels of ecosystem functioning starting from individual to population-level, species distribution, food webs and trophic interaction dynamics will be severely jeopardized in coming decades. Ocean warming and acidification are two prime threats to marine biota, yet studies about their cumulative effect on marine fish and shellfishes are still in its infancy. This review assesses existing information regarding the interactive effects of global environmental factors like warming and acidification in the perspective of marine capture fisheries and aquaculture industry. As climate change continues, distribution pattern of species is likely to be altered which will impact fisheries and fishing patterns. Our work is an attempt to compile the existing literatures in the biological perspective of the above-mentioned stressors and accentuate a clear outline of knowledge in this subject. We reviewed studies deciphering the biological consequences of warming and acidification on fish and shellfishes in the light of a molecule to ecosystem perspective. Here, for the first time impacts of these two global environmental drivers are discussed in a holistic manner taking into account growth, survival, behavioural response, prey predator dynamics, calcification, biomineralization, reproduction, physiology, thermal tolerance, molecular level responses as well as immune system and disease susceptibility. We suggest urgent focus on more robust, long term, comprehensive and ecologically realistic studies that will significantly contribute to the understanding of organism’s response to climate change for sustainable capture fisheries and aquaculture.

Continue reading ‘Combined effects of ocean warming and acidification on marine fish and shellfish: a molecule to ecosystem perspective’

Climate change effects on North American fish and fisheries to inform adaptation strategies.

Climate change is a global persistent threat to fish and fish habitats throughout North America. Climate-induced modification of environmental regimes, including changes in streamflow, water temperature, salinity, storm surges, and habitat connectivity can change fish physiology, disrupt spawning cues, cause fish extinctions and invasions, and alter fish community structure. Reducing greenhouse emissions remains the primary mechanism to slow the pace of climate change, but local and regional management agencies and stakeholders have developed an arsenal of adaptation strategies to help partially mitigate the effects of climate change on fish. We summarise common stressors posed by climate change in North America, including (1) increased water temperature, (2) changes in precipitation, (3) sea level rise, and (4) ocean acidification, and present potential adaptation strategies that fishery professionals may apply to help vulnerable fish and fisheries cope with a changing climate. Although our adaptation strategies are primarily from North America, they have broader geographic applicability to fish and aquatic biota in other jurisdictions. These strategies provide opportunities for managers to mitigate the effects of climate change on fish and fish habitat while needed global policies to reduce greenhouse gas emissions emerge, which may offer more lasting solutions.

Continue reading ‘Climate change effects on North American fish and fisheries to inform adaptation strategies.’

Effects of ocean acidification on young-of-the-year golden king crab (Lithodes aequispinus) survival and growth

Ocean acidification, a reduction in the pH of the oceans caused by increasing CO2, can have negative physiological effects on marine species. In this study, we examined how CO2-driven acidification affected the growth and survival of juvenile golden king crab (Lithodes aequispinus), an important fishery species in Alaska. Juveniles were reared from larvae in surface ambient pH seawater at the Kodiak Laboratory. Newly molted early benthic instar crabs were randomly assigned to one of three pH treatments: (1) surface ambient pH ~ 8.2, (2) likely in situ ambient pH 7.8, and (3) pH 7.5. Thirty crabs were held in individual cells in each treatment for 127 days and checked daily for molting or death. Molts and dead crabs were photographed under a microscope and measured using image analysis to assess growth and morphology. Mortality was primarily associated with molting in all treatments, differed among all treatments, and was highest at pH 7.5 and lowest at ambient pH. Crabs at pH 7.5 were smaller than crabs at ambient pH at the end of the experiment, both in terms of carapace length and wet mass; had a smaller growth increment after molting; had a longer intermolt period. Carapace morphology was not affected by pH treatment. Decreased growth and increased mortality in laboratory experiments suggest that lower pH could affect golden king crab stocks and fisheries. Future work should examine if larval rearing conditions affect the juvenile response to low pH.

Continue reading ‘Effects of ocean acidification on young-of-the-year golden king crab (Lithodes aequispinus) survival and growth’

Evaluating the impact of climate and demographic variation on future prospects for fish stocks: an application for northern rock sole in Alaska

Climate-enhanced stock assessment models represent potentially vital tools for managing living marine resources under climate change. We present a climate-enhanced stock assessment where environmental variables are integrated within a population dynamics model assessment of biomass, fishing mortality and recruitment that also accounts for process error in demographic parameters. Probability distributions for the impact of the associated environmental factors on recruitment and growth can either be obtained from Bayesian analyses that involve fitting the population dynamics model to the available data or from auxiliary analyses. The results of the assessment form the basis for the calculation of biological and economic target and limit reference points, and projections under alternative harvest strategies. The approach is applied to northern rock sole (Lepidopsetta polyxystra), an important component of the flatfish fisheries in the Eastern Bering Sea. The assessment involves fitting to data on catches, a survey index of abundance, fishery and survey age-compositions and survey weight-at-age, with the relationship between recruitment and cold pool extent and that between growth increment in weight and temperature integrated into the assessment. The projections also allow for an impact of ocean pH on expected recruitment based on auxiliary analyses. Several alternative models are explored to assess the consequences of different ways to model environmental impacts on population demography. The estimates of historical biomass, recruitment and fishing mortality for northern rock sole are not markedly impacted by including climate and environmental factors, but estimates of target and limit reference points are sensitive to whether and how environmental variables are included in stock assessments and projections.

Continue reading ‘Evaluating the impact of climate and demographic variation on future prospects for fish stocks: an application for northern rock sole in Alaska’

Impacts of large-scale aquaculture activities on the seawater carbonate system and air-sea CO2 flux in a subtropical mariculture bay, southern China

In this study, the variations of the seawater carbonate system parameters and air-sea CO2 flux (FCO2) of Shen’ao Bay, a typical subtropical aquaculture bay located in China, were investigated in spring 2016 (March to May). Parameters related to the seawater carbonate system and FCO2 were measured monthly in 3 different aquaculture areas (fish, oyster and seaweed) and in a non-culture area near the bay mouth. The results showed that the seawater carbonate system was markedly influenced by the biological processes of the culture species. Total alkalinity was significantly lower in the oyster area compared with the fish and seaweed areas, mainly because of the calcification process of oysters. Dissolved inorganic carbon (DIC) and CO2 partial pressure ( pCO2) were highest in the fish area, followed by the oyster and non-culture areas, and lowest in the seaweed area. Oysters and fish can have indirect influences on DIC and pCO2by releasing nutrients, which facilitate the growth of seaweed and phytoplankton and therefore promote photosynthetic CO2 fixation. For these reasons, Shen’ao Bay acts as a potential CO2 sink in spring, with an average FCO2 ranging from -1.2 to -4.8 mmol m-2 d-1. CO2 fixation in the seaweed area was the largest contributor to CO2 flux, accounting for ca. 58% of the total CO2 sink capacity of the entire bay. These results suggest that the carbonate system and FCO2 of Shen’ao Bay were significantly affected by large-scale mariculture activities. A higher CO2 sink capacity could be acquired by extending the culture area of seaweed.

Continue reading ‘Impacts of large-scale aquaculture activities on the seawater carbonate system and air-sea CO2 flux in a subtropical mariculture bay, southern China’

  • Reset

Subscribe

OA-ICC Highlights


%d bloggers like this: