Posts Tagged 'fisheries'

Seaweeds (Ulva, Gracilaria) significantly increase the growth rates of North Atlantic oysters, scallops, and clams grown in an aquaculture setting

Published 17 February 2026 Science Leave a Comment
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Highlights

  • Seaweeds significantly increased the growth rates of oysters by 20–70%, of clams by 60–70%, and of scallops by 130–140%.
  • Seaweeds caused significant increases in pH, DO, and the saturation state of calcium carbonate (Ω).
  • Seaweeds caused a significant increase in the concentrations of suspended chlorophyll a.
  • Co-culture of seaweeds with bivalves accelerates the growth rate of bivalves by increasing pH, DO, Ω, and food availability.

Abstract

While bivalve populations are threatened by climate change stressors including ocean acidification and hypoxia, the photosynthetic activity of seaweeds can raise the pH and dissolved oxygen (DO) of seawater, combatting these stressors. Here, three commercially important North Atlantic bivalves (Eastern oysters, Crassostrea virginica; hard clams, Mercenaria mercenaria; bay scallops, Argopecten irradians) were grown in the presence and absence of two common seaweeds (Ulva sp. and Gracilaria sp.) in replicated 300 L outdoor aquaculture tables with flow-through seawater. Environmental conditions including pH, DO, and chlorophyll a were continuously monitored and levels of dissolved inorganic carbon and the complete carbonate chemistry of seawater were quantified. The presence of seaweeds significantly increased shell- and tissue-based growth rates of oysters by 20–70%, of clams by 60–70%, and of scallops by 130–140% (p < 0.05) with both seaweeds being similarly effective. Both seaweed species caused significant increases in pH, DO, and the saturation state of calcium carbonate (Ω) during the day (p < 0.05) whereas differences at night were muted with night-time Ωaragonite levels being at or below saturation in all treatments. In some experiments, the presence of seaweeds caused a significant increase in the concentrations of suspended chlorophyll a, suggesting that seaweeds increased the total amount and diversity of food available to bivalves. Collectively, this study demonstrates that the co-culture of seaweeds with bivalves in a land-based aquaculture setting can significantly accelerate the growth rate of bivalves by increasing pH, DO, Ω, and food availability.

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Triple threat: ocean acidification, warming, and hyposalinity synergistically weaken shell integrity in a Mediterranean calcifying mollusk

Published 30 January 2026 Science Closed
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Highlights

  • OA, OW, and hyposalinity drive skeletal and mineralogical responses in a Mediterranean clam.
  • Combined stress makes shells less dense, more porous, and more fracture-prone.
  • Microstructural changes reveal early calcification impairments under triple stress.
  • Triple-stressor synergy compromises shell integrity and threatens fishery species resilience.

Abstract

Anthropogenic climate change is rapidly altering marine environments primarily through ocean warming, acidification, and hyposalinity, posing significant challenges for marine calcifying organisms. This study investigated the short-term effects of these stressors on the Mediterranean bivalve Chamelea gallina, a key fishery species in the Adriatic Sea, by integrating skeletal, mechanical, and mineralogical responses. Adult clams of commercial size were exposed for 21 days to eight experimental treatments manipulating two levels of temperature (18 °C vs. 22 °C), pH (8.0 vs. 7.9), and salinity (35 vs. 32), chosen to reproduce near-future climate projections and the freshwater-driven variability typical of the Adriatic Sea. Despite the short exposure duration, the combined exposure to low pH, high temperature, and reduced salinity weakens the shell of Chamelea gallina at multiple levels, compromising shell integrity, by making shells less dense, more porous, more fragile, and more susceptible to fracture, and increasing mortality. Microstructural analysis revealed smaller aragonite crystallites and lower calcium content, indicative of early impairments in the calcification process. The study highlights the occurrence of synergistic effects among stressors and reveals the vulnerability of Chamelea gallina to near-future ocean conditions, with potential cascading consequences for ecosystem functioning and fishery sustainability, given the species’ key ecological role and commercial relevance in the Adriatic Sea.

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How oysters are impacted by environmental conditions and farming practices

Published 29 January 2026 Web sites and blogs Closed
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The Rhode Island aquaculture industry is more robust than ever. The value of aquaculture products was $8,795,493 in 2024 and 89 active aquaculture farms covered 392.5 acres, according to a report by the Rhode Island Coastal Resources Management Council.

Eastern oysters account for approximately 99% of the state’s aquaculture production, the report noted. Jacqueline Rosa, who is pursuing her master’s degree in oceanography from GSO, spent 18 months conducting field work on how water quality and farming practices impact these mollusks.

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Jacqueline Rosa (center) uses a water quality sensor to measure key parameters, including temperature, salinity, and pH during weekly sampling at Wickford Oyster Company in 2024. Rosa is accompanied by oyster farmers John McKillop (left) and Kevin Tuttle. (Photo courtesy of Gage Whilden)

To examine the environmental conditions, Rosa deployed two sensors at Wickford Oyster Company’s 4-acre farm in May 2024, one at the surface of the water and one at the bottom of the water column.

Rosa revisited the farm each week to collect water samples from the surface and the bottom. She brought the samples to the Ocean Carbon Laboratory at the Graduate School of Oceanography for analysis.

“I tested the samples for pH, salinity, alkalinity, and dissolved inorganic carbon,” said Rosa, who is from Newtown, Connecticut. “These carbonate chemistry parameters help us understand trends in ocean acidification and how changing conditions may impact calcifying organisms. Shifts in carbonate chemistry can influence shell formation, growth rates, and survival, particularly during early-life stages, making these measurements critical for understanding potential stressors for farmed oysters.”

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Ocean acidification effects on growth, survival and physiological immunity of farmed Larimichthys crocea

Published 29 January 2026 Science Closed
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Ocean acidification has become a significant global ecological issue, particularly in coastal regions with intensive aquaculture. Fish farming is a crucial component of global food security, yet research on the impact of acidification on the aquaculture performance of economically important teleosts remains limited. In this study, we reared the fast-growing large yellow croaker (Larimichthys crocea) for 30 days under three different pH conditions: severe acidification (LA, pH 7.4), moderate acidification (MA, pH 7.8), and control (HA, pH 8.1). We comprehensively evaluated growth performance, survival rate, tissue structure, antioxidant enzyme activity, and innate immunity. The results showed that the LA group exhibited suppressed growth (significantly lower than the MA group, p < 0.05), elevated cortisol and T4 levels (p < 0.05), and trends of reduced antioxidant enzyme and innate immune enzyme activities, along with organ-specific pathological changes (vacuolation, structural loosening) in gills, liver, kidneys, and intestines, though most indices showed no significant difference from the HA group. Notably, the MA group showed optimal growth performance, stable physiological and immune responses. In conclusion, while acidification did not markedly affect the survival rate of L. crocea, severe acidification (pH 7.4) induces stress responses and tissue damage. These findings suggest that L. crocea exhibits a certain degree of tolerance to the acidification conditions tested, as several physiological parameters were not significantly affected. However, when considering the overall set of observations, including histological alterations across multiple tissues and changes in plasma and tissue parameters, long-term exposure to severe acidification (pH 7.4) appears to induce tissue damage and stress-related physiological disturbances, indicating potential health risks. This study provides empirical evidence regarding the potential risk posed by projected ocean acidification on L. crocea aquaculture and supports the development of climate change adaptation strategies for coastal mariculture.

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Transgenerational effects of extreme weather on Manila clam resilience: implications for aquaculture sustainability

Published 27 January 2026 Science Closed
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Highlights

  • SAE+MHW synergistically impaired clams during reproduction.
  • Progeny exhibited lasting developmental delays and high mortality.
  • Long-term physiological dysfunction persisted into later life stages.
  • Compound extremes threaten bivalve aquaculture resilience.

Abstract

Extreme environmental events, including sea acidity extremes (SAE) and marine heatwaves (MHW), pose increasing threats to coastal aquaculture species. This study examined the individual and combined effects of SAE and MHW on Manila clams (Ruditapes philippinarum) and their transgenerational impacts. Adults exposed to SAE+MHW showed reduced survival, decreased condition index, lower clearance rate (CR) and assimilation efficiency (AE), elevated ammonia excretion (ER), and negative scope for growth, indicating disrupted energy budgets. Reproductive output and gonadal development were also compromised. Offspring from stressed parents exhibited lower larval survival, stunted shell growth, reduced metamorphic success, smaller settlement size, reduced juvenile (6-month-old) survival rate and disrupted energy homeostasis, revealing persistent transgenerational impacts on development and energy homeostasis. These findings suggest that parental exposure to synergistic SAE+MHW alters energy allocation and may involve epigenetic mechanisms, ultimately impairing offspring fitness. Overall, our study demonstrates that compound extreme events can severely affect metabolic resilience and cross-generational performance in Manila clams, highlighting the need for multigenerational assessments, selective breeding, and aquaculture strategies to enhance climate resilience.

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Explainable machine learning models for coastal pH forecasting at aquaculture-relevant thresholds in Eastern Canada

Published 19 January 2026 Science Closed
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Highlights

  • Benchmark of ML models for coastal pHSWS forecasting.
  • Models trained on rare high-frequency data from Eastern Canada.
  • XGBoost balances sensitivity and precision at pHSWS < 7.75
  • SHAP shows Julian day dominance as composite environmental driver.
  • Promising low-cost framework for aquaculture acidification early warning.

Abstract

Ocean acidification poses a growing threat to marine ecosystems and aquaculture productivity, particularly in under-monitored coastal regions such as Eastern Canada. Existing pH prediction frameworks typically rely on multi-year records combining extensive carbonate chemistry, physical, and biological parameters. While these models can achieve high accuracy, their data requirements make them costly, complex, and challenging to implement for local, site-specific acidification forecasting in aquaculture contexts. To address this limitation, this study benchmarks several machine learning models for coastal pHSWS prediction using only three routinely measured environmental variables (temperature, salinity, sea level), from which we derived moving-average descriptors, local gradients, and two temporal indicators, resulting in a compact set of 11 input features. Six different models and a multivariate linear regression baseline were trained on one of the most complete and extended high-frequency datasets available (BSSS2018) and evaluated across four independent datasets: one from the same site but six months earlier (BSSS2017), and three from nearby bays in northeastern New Brunswick collected between 2017 and 2019. Among all tested models, XGBoost emerged as the most reliable and interpretable, achieving the best trade-off between sensitivity and precision at the operational acidification threshold (pHSWS < 7.75). Its performance remained acceptable within-site but declined across bays due to environmental and seasonal discrepancies, underscoring the importance of training data representativeness. SHAP-based explainability confirmed that Julian day was the dominant predictor, integrating the composite effects of seasonal environmental variability. Overall, this study demonstrates that using only low-cost, routinely measured features provides a promising foundation for short-term coastal pH forecasting, particularly for aquaculture monitoring needs. Despite limited inter-bay generalization, the proposed framework shows that interpretable machine learning models can deliver actionable early-warning insights under realistic data constraints. It constitutes one of the first data-driven benchmarks explicitly tested at aquaculture-relevant thresholds, highlighting a scalable and transparent approach toward operational acidification forecasting.

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Ocean acidification and anthropogenic carbon in the Eastern Mediterranean Sea and the effects of acidification on marine organisms

Published 15 January 2026 Science Closed
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Ocean acidification (OA), driven by rising atmospheric carbon dioxide (CO2) levels, is a critical issue affecting our oceans. The Eastern Mediterranean Sea (EMS) remains poorly understood in terms of the carbonate system and the impact of OA, despite its key role in Levantine Intermediate Water (LIW) formation and its peculiar characteristics in buffering capacity and ongoing OA. This study provides the first comprehensive spatial and temporal assessment of carbonate system in the North-Eastern Levantine Basin, in EMS, providing essential reference data for Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), and Anthropogenic Carbon (CANT). The mean TA of the measurements was 2622.11 μmol/kg, with higher surface values in summer, reflected also in the surface salinity (S) maximum caused by strong evaporation. A clear vertical gradient was observed, with TA decreasing with depth. Hot and dry meteorological conditions contribute to increased S and TA, resulting in seasonal and vertical variations in the water column. The mean DIC of the measurements was 2291.23 μmol/kg. In contrast to the observations for TA, surface DIC values were higher in winter than in summer. The higher DIC values in winter are attributed to thermodynamic equilibrium and vertical mixing in the surface waters. This study has also investigates the presence of CANT, has infiltrated deep layers, with a mean concentration of 52.07 μmol/kg, decreasing significantly throughout the water column. These findings confirms the ongoing influence of human activities on intermediate and deep layers in EMS. To reconstruct past carbonate system dynamics, the relationships of TA and DIC were determined with salinity (S) and temperature (T) data. Long-term data from METU-IMS Erdemli Time Series (ETS) stations, collected monthly for a decade, provided valuable findings into seasonal patterns and temporal shifts in TA, DIC, and pH. The coastal station displayed clear trends in the carbonate system over time, reflecting its sensitivity to local environmental changes. In contrast, the offshore station exhibited minimal variability, indicating greater stability against seasonal and long-term fluctuations. These results highlight the heightened vulnerability of coastal waters to carbonate system changes, while offshore waters remain more stable. Understanding carbonate chemistry and acidification levels is crucial for assessing impacts on marine life. In addition to the characterization of carbonate chemistry, this study also explores OA’s biological impacts on two key organisms of the Mediterranean ecosystem: phytoplankton and mussels. Firstly, effects of elevated CO₂ on phytoplankton, an essential primary producer in aquatic food webs and global biogeochemical cycles are explored. Specifically, the study explores the impacts on phytoplankton physiology, focusing on growth rates, respiration, and photopigment content in selected species from the coccolithophores, dinoflagellates, and diatoms groups. While growth rates and respiration remained relatively stable under reduced pH conditions, photopigment content was significantly influenced by changes in seawater pH, highlighting the importance of considering environmental influences on photopigment composition. The study further investigated the effects of acidification on calcifying organisms through a global program aimed at understanding the long-term effects of acidification on key seafood species and exploring adaptation strategies with a collaborative approach. This study focused on the long-term (6 months long experiment) physiological impacts of OA on marine calcifiers, specifically Mediterranean mussel, Mytilus galloprovincialis, an abundant species and one of the most consumed non-fish marine species in Türkiye. Results indicate that OA poses a substantial threat to mussel health and survival. Reduced pH levels negatively impacted survival rates, while other physiological parameters like clearance rate, condition index, respiration, and the distribution of a radionuclide, 210Po, did not significantly change. However, lipid content and immune response were affected. Oxygen consumption decreased over time, especially at lower pH. This study underscores the potential risks of OA to the fitness of the commercially important mussel species, indicating that future OA may impact both this key seafood species and its associated ecosystems. The established baseline data are crucial for future monitoring and provide valuable insights into the vulnerability of marine organisms and ecosystems to ongoing OA. By integrating chemical, biological, and ecological perspectives, this dissertation offers a comprehensive assessment of OA in EMS. It establishes baseline data for carbonate system variables, revealing distinct spatial and temporal variations influenced by S, T, and mixing processes. By linking changes in carbonate chemistry to physiological responses in primary producers and a commercially vital shellfish species, this study highlights the ecological and economic impacts of OA in EMS. The findings emphasize the need for continued research and mitigation efforts to protect marine ecosystems and commercially important species. This integrated approach provides valuable insights into the vulnerability of marine organisms and ecosystems to ongoing OA, underscoring the significance of this research for the Mediterranean Sea.

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Developing indicators of risk to environmental variability based on species dependency in U.S. fishing communities in the Northeast and Southeast Regions

Published 13 January 2026 Science Closed
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Fishing communities worldwide have or are likely to experience social, economic, and cultural impacts from environmental variability. Changes in marine fisheries will require adaptation by fishing communities and fisheries managers alike. Here, Community Environmental Variability Risk Indicators (CEVRI) were developed to assess risk to environmental change for fishing communities in the U.S. Northeast and Southeast Regions based on spatial and temporal trends between 2000 and 2022. To accomplish this, we analyzed commercial landings value as it relates to species level Climate Vulnerability Assessment (CVA) scores for species considered commercially, recreationally, and ecologically important. The CVA considers the vulnerability of species to 12 sensitivity and 12 exposure factors relating to important environmental factors within the regional context. Here, we used three sensitivity factors: Stock Size/Status, Ocean Acidification, and Temperature, as well as Total Sensitivity and Total Vulnerability. Community level scores were used to analyze intra and inter region variation, and to understand trends in community risk as revenue dependence on different species changes through time. In general, communities in the Gulf of America/Florida Keys sub-region presented lower risk to the factors analyzed than the South Atlantic sub-region and the Northeast. Ocean Acidification was the sensitivity factor with the highest levels of risk for communities. The findings of this study have important applications to inform decision-making and to help communicate environmental variability associated risks to broader audiences, thus further developing the ability of stakeholders to understand and assess cumulative impacts and complex trade-offs affecting the sustainability of marine ecosystems and resources.

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Effect of experimental seawater acidification on the prooxidant-antioxidant system of the Pacific oyster Magallana gigas (Thunberg, 1793) under normoxic and hypoxic conditions

Published 8 January 2026 Science Closed
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Highlights

  • Lipid peroxidation in oyster gills was enhanced during exposure to acidification + hypoxia.
  • SOD and GPx activities changed in gills and hepatopancreas, while CAT activity unchanged in both.
  • Water acidification does not promote DNA strand breaks in hemocytes of M. gigas.
  • Acidification + hypoxia more severe damaging than acidification under normoxia.

Abstract

Bivalve mollusks, particularly the Pacific oyster (Magallana gigas), are both environmentally and commercially significant species that live in coastal waters and may be affected by global climate change factors including hypoxia and acidification. In this study, we investigated the impact of acidification in combination with normoxia and hypoxia on oxidative stress markers in the gills and hepatopancreas of M. gigas oysters. Oysters were collected from a shellfish farm and subjected to acidified conditions (pH 7.3 ± 0.05) in combination with either normoxic (8.0 ± 0.3 mg/L O2) or hypoxic (2.0 ± 0.3 mg/L O2) conditions for an 8-day period. Changes of DNA damage levels, reactive oxygen species (ROS) production in hemocytes, as well as antioxidant enzyme activities (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx)) and lipid peroxidation in the gills and hepatopancreas were evaluated. Additionally, the mortality rate in experimental groups was monitored throughout the experiment. Our results showed that lipid peroxidation in gills was enhanced during prolonged acidification in combination with hypoxia (6–8 days). We observed rapid and consistent changes in SOD and GPx activity in gills and hepatopancreas. CAT activity remained stable in both tissues. The results of the study indicate that acidification was shown to induce oxidative stress in oysters. Combination of acidic environment to hypoxia had a more severe effect on oysters compared to acidification under normal oxygen conditions, leading to their death after 8 days of exposure.

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Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management

Published 7 January 2026 Science Closed
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Highlights

  • We spatially couple a scallop bioenergetic model to a regional oceanographic model.
  • Our model reproduces observed growth patterns using temperature, food, and pCO2.
  • Mid-century warming enhances scallop growth except in the south.
  • By 2100, scallops grow faster but reach smaller sizes under warming and acidification.
  • This tool can inform adaptive fisheries management under climate change.

Abstract

Climate-ready fisheries management requires reliable predictions of species responses to changing conditions across large-scale environmental gradients. Bioenergetic frameworks, such as Dynamic Energy Budget (DEB) models, relate physiological processes to environmental conditions, enabling predictions of organismal growth under projected climate change conditions. Here, we provide the first large-scale coupling of a DEB model to downscaled regional oceanographic simulations to resolve spatiotemporal changes and reveal how climate stressors emerge at relevant biogeographic, economic, and oceanographic scales. We calibrated our DEB model for the Atlantic sea scallop (Placopecten magellanicus) with forcing from a realistic oceanographic and biogeochemical model for the Northeast U.S. continental shelf to predict the effects of ocean acidification (OA) and warming on individual growth historically and over the next century. Our model reproduced observed historical patterns in scallop age at harvest size and maximum size. At mid-century (2035–2050), scallop growth was projected to increase in most areas except the southern Mid-Atlantic, and OA effects were limited to the deep Gulf of Maine. By the end of the century (2080–2095) under a high emissions scenario, scallops were predicted to grow faster but attain smaller maximum sizes. Our results highlight that warming stress is more acute than previously accounted for, particularly in the southern Mid-Atlantic. While warming stress emerges in the south first, OA stress emerges before warming in the north. Together, these emerging stressors compress the spatial range for optimal growth. Altogether, our findings demonstrate the utility of the spatially coupled DEB model as a tool to inform adaptive fisheries management.

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Navigating uncertainty: an assessment of climate change risks to the marine and coastal environment of Sri Lanka

Published 7 January 2026 Science Closed
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Sri Lanka is highly vulnerable to the impacts of marine climate change due to the low coastal profile, which is densely populated with many rural areas dedicated to fishing and aquaculture. Motivated by this, this study aimed to compile and analyse the available evidence and identify steps to improve climate adaptation by undertaking an assessment of marine climate change risks for Sri Lanka. The stepwise approach consisted of a comprehensive literature review and synthesis of risks, followed by appraisal, validation and scoring by expert stakeholders. Here we present a summary of key findings regarding marine climate variables (temperature, sea-level rise, ocean circulation, salinity, ocean acidification, dissolved oxygen, storminess, precipitation and wind), and risks to marine biodiversity and ecosystem services. The most important biodiversity risks identified include decreasing plankton productivity; threats to sea turtles; changes in fish communities; increasing threats to coral reefs; changes to mangrove and seagrass habitats; shoreline erosion; and increasing risk of bio-invasions. Key risks to ecosystem services include declining fisheries; damage and disruption to critical infrastructure and services; threats to tourism; and loss of protective coastal habitats. We also identified important knowledge gaps and uncertainties involving lack of climate data and evidence of impacts. Finally, we provide recommendations regarding marine monitoring and research, and options to strengthen climate policies and climate adaptation in Sri Lanka.

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From sea to shore: the impact of ocean acidification on child health

Published 5 January 2026 Science Closed
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Since the Industrial Revolution, ocean water acidity has risen by 26% due to anthropogenic emissions—a process known as ocean acidification—posing a risk for marine life and the communities depending on it. This paper examines the consequences of ocean acidification for child health, using data from coastal regions in 36 low- and middle-income countries from 1972 to 2018, encompassing 41% of the world’s coastal population. Leveraging short-term exogenous shifts in ocean acidity near human settlements for identification, we find that prenatal exposure to higher water acidity significantly raises the risk of death in the first months of life and impacts early childhood development. We show evidence consistent with these effects being associated with maternal malnutrition, as increased acidity reduces catches for small-scale fisheries, increasing seafood prices and reducing consumption of crucial nutrients. Our findings indicate limited adaptation to these impacts. We estimate that, absent intervention, ocean acidification could contribute to as many as 77 million neonatal deaths in this region by 2100—a consequence that should not be ignored in the projected cost of climate change.

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Acidification and plastic pollution threaten Bangladesh’s blue economy

Published 2 January 2026 Media coverage Closed
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The Bay of Bengal has long been the engine of Bangladesh’s blue economy—a vast, resource-rich frontier that sustains millions of people and generates vital export earnings.

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Bangladesh’s total marine fish harvest fell to 628,622 tonnes in FY 2023–24, the lowest in nine years (Department of Fisheries – Annual Report 2024). Deep-sea trawler catches declined by 21% year-on-year (FAO), while catch per artisanal boat has dropped nearly 70% over the past two decades—from 13 tonnes in 2000 to barely 4 tonnes in 2020 (World Bank Fisheries and Aquaculture Review).

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Overfishing and IUU (Illegal, Unreported, and Unregulated) fishing are well-known problems. But two largely untold reasons lie behind this steady deterioration: acidification and plastic pollution—silent yet powerful forces that destabilise the marine ecosystem.

Acidification: An invisible enemy beneath the waves

The ocean has long served as Earth’s greatest climate regulator, absorbing nearly one-third of all carbon dioxide (CO₂) emitted by human activities (IPCC, 2023). While this process helps slow global warming on land, it comes at a devastating cost beneath the surface.

When CO₂ dissolves in seawater, it forms carbonic acid, lowering the ocean’s pH and disrupting marine chemistry.

In the early 1980s, Bay of Bengal surface waters averaged a pH of 8.3 (Indian Ocean Research Consortium). Today, coastal and estuarine zones measure between 7.9 and 8.0, with some readings as low as 7.73 (UNEP South Asia Marine Assessment). This 0.2–0.3 drop in pH represents nearly a 30% increase in ocean acidity over five decades (NOAA; IPCC).

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Yemen fisheries and climate change

Published 31 December 2025 Newsletters and reports Closed
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Yemen’s extensive coastline, encompassing the southern Red Sea, Gulf of Aden, and northwest Arabian Sea, is home to rich marine biodiversity and historically productive fisheries, crucial for the nation’s economy, food security, and livelihoods (Figure 1). However, the intersection of global climate change and a prolonged internal conflict has significantly disrupted marine ecosystems and fisheries management, exacerbating already critical challenges.

This report addresses these pressing issues through two interconnected analyses. The first examines recent climate-driven changes in marine ecosystem health indicators, providing insights into seasonal variability, long-term trends, and impacts from extreme climate events such as Cyclone Tej in 2023. The second analysis investigates the status of Yemen’s fisheries, highlighting historical trends, the impacts of conflict, and gaps in current monitoring and management practices.

Leveraging innovative methodologies, satellite remote sensing, computer vision, and collaborative in situ data collection, the report aims to present a cohesive framework for revitalizing Yemen’s marine research and fisheries management. Ultimately, the findings underscore the urgency of implementing targeted, adaptive, and evidence-based policies to sustain Yemen’s coastal ecosystems and the livelihoods dependent upon them.

The report is structured as follows: Section 1 presents analysis of seasonal variability, climate shocks and extreme events along with longer-term temporal trends on temperature, oceanic biomass and productivity, salinity and ocean acidification in Yemen’s coastal waters; Section 2 presents analysis of the fisheries sector, notably identifying the existing data gaps and the absence of reliable monitoring as a result of the ongoing unrest; based on these analyses, Section 3 proposes a framework for the creation of a dynamic fisheries monitoring and management model; and Section 4 concludes with policy recommendations.

While this study does not include formal projections, observed decadal trends across Yemen’s marine regions allow for indicative interpretation of the likely direction of change in key ecosystem indicators. The table below summarizes historical trajectories (2004 – 2024) of these variables, which may inform expectations of future biological productivity if current drivers persist.

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Aquaculture of seaweeds (Saccharina latissima, Ulva spp., Gracilaria spp.) significantly improves the growth of co-cultivated bivalves in mesotrophic, but not eutrophic, estuaries

Published 29 December 2025 Science Closed
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The co-cultivation of seaweeds with bivalve shellfish is a potential strategy for protecting bivalve crops against anthropogenic coastal acidification and hypoxia. We co-cultivated seaweeds and bivalves using a succession of seaweed species according to season (winter, Saccharina latissima → spring, Ulva spp. → summer, Gracilaria spp.) together with eastern oysters (Crassostrea virginica) and blue mussels (Mytilus edulis). Bivalves and seaweeds were deployed in two estuaries that contrasted in trophic state, one mesotrophic and one eutrophic. In all five experiments in the mesotrophic system, cocultivation with seaweeds significantly increased weight- and/or shell-based growth of bivalves (p < 0.05). Growth rate increases for C. virginica were modest, with weight-based growth improving by 17–21% and shell-based growth improving by 3–27% with seaweed co-culture of all macroalgal species. For M. edulis, the effect was large; co-culture with S. latissima caused 47% and 114% increases in shell- and weight-based growth rates, respectively. In the four experiments in the eutrophic estuary, co-culture with seaweeds did not significantly improve bivalve growth. Seaweed cultivation significantly improved water quality metrics (increased pH and dissolved oxygen (DO); p < 0.05 in all cases) in and around the seaweed sites at both locations, although increases in pH and DO were modest, and even in control treatments, there were no prolonged periods of harmful pH or DO levels. An abundance of macroalgal detritus may have bolstered the diets of co-cultivated bivalves in the mesotrophic estuary, a hypothesis supported by lower chlorophyll a concentration, and therefore lower planktonic food levels, at that site. Given that seaweeds display species-specific allelopathic effects against phytoplankton, it is also possible that the presence of seaweeds altered the phytoplankton community to the benefit of the bivalves. Regardless, the findings here demonstrate that co-cultivation with seaweeds can accelerate the growth of bivalves.

Continue reading ‘Aquaculture of seaweeds (Saccharina latissima, Ulva spp., Gracilaria spp.) significantly improves the growth of co-cultivated bivalves in mesotrophic, but not eutrophic, estuaries’

A global meta-analysis reveals consistently negative effects of ocean acidification on marine cultured bivalves: implications for future bivalve aquaculture

Published 16 December 2025 Science Closed
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The exponential rise in atmospheric CO₂ driven by human activities is accelerating climate change and causing ocean acidification (OA). While the effects of elevated CO₂ on a wide range of marine species have been well documented, the implications of OA for bivalve aquaculture have received comparatively little attention. Using a multi-level meta-analytical approach, we evaluated the impacts of two elevated pCO₂ levels—classified as high and extreme—on cultured bivalves, based on 266 observations from 24 species across tropical and temperate regions. Overall, both elevated pCO₂ levels negatively affected bivalves, reducing survival, growth, feeding rates, development, and calcification. Larvae were generally more vulnerable than juveniles and adults. Our analyses further indicated that temperate bivalves were more sensitive to OA than tropical and subtropical counterparts. Among taxa, clams were the most vulnerable under high CO₂ emission scenarios, whereas scallops were the most sensitive under extreme pCO₂ levels. We also discuss potential mitigation strategies for the bivalve aquaculture industry. With advancements in local and regional monitoring, coupled with targeted measures such as buffering sites, selective breeding, and integrated multi-trophic aquaculture, the adverse effects of OA on bivalve farming could be mitigated.

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Saving oysters from ocean acidification with seaweed

Published 3 December 2025 Web sites and blogs Closed
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Oyster farms are one of the most environmentally sustainable farms in the world. As filter-feeders, oysters and other bivalve mollusks like clams, mussels, and scallops, require no additional feed or fertilizers. They simply eat plankton from their surroundings, leaving cleaner shallows for the rest of the ecosystem to enjoy.

However, the late 2000’s brought a concerning trend of oyster farm mortality events. One culprit is higher levels of carbon dioxide absorbed into our waters, which creates a more acidic environment. As climate change progresses, the oceans grow more acidic and less hospitable for shellfish.

“It affects many ocean organisms, but especially animals that build shells and skeletons,” says graduate student Leah Wessler. “It’s a big barrier for aquaculture and wild fisheries.”

Wessler is in the MSc program Applied Animal Biology studying how ocean acidification affects shellfish farms and how we can mitigate or even reverse the damage. From coral reefs in the Caribbean to beluga whales in Alaska, Wessler has worked in marine conservation and research around the world. She was drawn back home to the Pacific North West by a growing sense of optimism and momentum in the shellfish aquaculture sector.

“Here’s an avenue of farming that’s sustainable, produces high-quality protein, and is already quite common in many areas of the world,” Wessler says.

Continue reading ‘Saving oysters from ocean acidification with seaweed’

Acidification-mediated perturbations of developmental pathways and life-stage transitions in Artemia salina

Published 27 November 2025 Science Closed
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Projected increases in atmospheric carbon dioxide are anticipated to induce a 0.3–0.5 unit decline in oceanic pH by the year 2100, posing a significant threat to marine ecosystems. This study investigated the sub lethal effects of simulated ocean acidification on the ontogenetic success of Artemia salina, a key trophic link in aquaculture systems. A controlled, in vitro experiment employing a Completely Randomized Design (CRD) was conducted, maintaining constant temperature, salinity, and dissolved oxygen. Embryonic development and larval survival were assessed across a gradient of pH levels, representing projected future ocean acidification scenarios. Preliminary data indicate a negative correlation between decreasing pH and both hatching success and larval survivorship. Further investigations are warranted to elucidate the long-term ecological consequences of ocean acidification on Artemia salina populations and their role in aquaculture.

Continue reading ‘Acidification-mediated perturbations of developmental pathways and life-stage transitions in Artemia salina’

Perceptions of oyster farmers on adopting environmental monitoring technologies to mitigate ocean acidification: a case study in Bahía San Quintín, México

Published 19 November 2025 Science Closed
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Coastal ecosystems face multiple stressors, and their responses are magnified by global stressors associated with climate change, such as warming and ocean acidification (OA). Oyster farming are vulnerable to the effects of these stressors. Environmental monitoring technologies have been proposed as an adaptive strategy to OA. This study examined the perceptions of the oyster farmers in Bahía San Quintín, Mexico, toward this strategy. Through surveys and workshops, we identified the main challenges oyster farmers face in their industry, their level of awareness about OA, and their openness to adopting new technologies. Most respondents (66 %) did not recognize OA, which suggests that they had a low perception of its risks and its potential consequences for their activities. The most frequent problems were environmental issues (48 %), such as extreme temperature events, biofouling, and predation, followed by limited technical and financial resources (34 %). Recognizing the negative effect that high temperatures have on their activity, especially during El Niño Southern Oscillation (ENSO) events, is a positive outcome, as it allows them to adopt strategies to cope with OA. The main barriers to adopt new technologies were related to management issues (56 %), including a lack of economic resources. We recommend that interactions between oyster producers, academia, and governmental actors must be strengthened to promote environmental monitoring, thus improving their adaptive capacity and reducing potential impacts of stressors on their industry, such as climate change and OA. This study case is a valuable reference for other oyster farming communities in similar environmental and socio-economic contexts.

Continue reading ‘Perceptions of oyster farmers on adopting environmental monitoring technologies to mitigate ocean acidification: a case study in Bahía San Quintín, México’

Mothers know best: maternal signaling boosts larval resilience under ocean acidification conditions

Published 12 November 2025 Science Closed
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Highlights

  • Environmental priming effectively rescued larval phenotype under OA conditions.
  • Egg ‘omics were investigated to elucidate mechanism of priming across generations.
  • Clam egg lipidomes were largely unperturbed by maternal low-pH exposure.
  • Differentially expressed genes were identified in eggs of low-pH primed clams.

Abstract

Bivalve aquaculture is a growing sector worldwide, producing sustainable animal protein to meet growing demand from consumers. Yet, the industry remains vulnerable to environmental changes that can impact their product across life stages, especially at the larval stage. Parental priming, or the exposure of broodstock to adverse environmental conditions as they undergo gametogenesis, holds promise as a method to increase resilience in bivalve offspring. We exposed Manila clam (Ruditapes philippinarum) broodstock to low pH conditions (pH 7.4 for 78 days during gametogenesis). Larvae were produced from primed (low pH) and unprimed (ambient pH) broodstock and exposed to ambient or low pH conditions in a full factorial design. Larval phenotype in response to low pH was partially rescued by broodstock priming: larvae from low pH-exposed broodstock had better survival and growth than larvae from broodstock held under ambient conditions. Clam egg lipidomic and transcriptomic analyses were performed to determine the physiological differences associated with broodstock environmental conditions. Egg lipid abundance profiles were not significantly different between parental treatments. The egg transcriptome revealed 48 differentially expressed transcripts associated with parental environmental conditions. These genes are involved in important processes for early larval physiology, including metabolism, cell cycle, and transcriptional regulation. Broodstock clams were minimally impacted by their exposure to low pH for 78 days, however we show here that subtle maternal signals may contribute to the vastly improved larval performance observed under low pH conditions.

Continue reading ‘Mothers know best: maternal signaling boosts larval resilience under ocean acidification conditions’

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