Biofouling‐induced increases in labor costs are among the most impactful factors determining the technoeconomic feasibility and profitability of aquaculture operations. Understanding how different cultivation methods and environmental conditions influence the severity of biofouling is crucial to support informed decision‐making by farmers and minimize the economic impacts of biofouling in the aquaculture industry. This study used a factorial design to compare the extent and type of biofouling across three common cultivation methods (floating bags, floating cages, and bottom‐culture) in exposed and sheltered locations that differ in temperature, salinity, turbidity, and wave energy. The ratio of fouling weight to oyster wet weight for oysters grown in floating bags was significantly higher than for oysters grown in floating cages, which were in turn significantly more fouled than bottom‐planted oysters. Oysters cultivated in the exposed location had a significantly higher fouling ratio than oysters cultivated in the sheltered location. However, this pattern was driven by the stark difference in fouling by location for the floating bags, indicating that differences in temperature and wave exposure between sites would have the greatest impact on fouling severity for oysters grown in floating bags. Common fouling organisms included solitary and colonial tunicates, filamentous algae, and hard fouling (mussels, oyster spat, and barnacles). The significant differences observed in the composition and severity of oyster biofouling by gear type and growing site underscore the importance of considering fouling potential when evaluating the profitability of a farming strategy and the need for further development of region‐ and gear‐specific biofouling mitigation strategies.

Triploid oysters have become a crucial tool for aquaculture because of their rapid growth rates and reduced reproduction compared to diploids. While extensively adopted in temperate regions along the U.S. East Coast, limited research has evaluated triploid oyster performance in the colder waters of the Northwest Atlantic where the growing season is shorter. This study investigated the growth performance, morphology, and physiology of cultured triploid and diploid Crassostrea virginica in their northern range. Environmental conditions as well as oyster shell and tissue growth were monitored over a 17-month period at two farm sites in Maine. Triploids averaged 22 % greater for shell height and 53 % greater for tissue mass compared to diploids. The effects of ploidy and environmental factors (temperature, chlorophyll-a, and particulate organic matter) on shell growth were examined using generalized additive models. Triploids exhibited a significant growth advantage in temperatures above 17 degrees C and at higher food concentrations with minimal advantage outside these conditions. In a laboratory experiment, tissue loss and oxygen consumption rates were examined over a ten-week period along with cell size measurements. Although triploids had larger cell sizes, standardized oxygen consumption rates during starvation did not differ significantly between ploidies, suggesting similar maintenance needs after contributions to feeding, growth, and reproduction are removed. Diploids, however, experienced faster tissue loss during starvation, indicating potential energetic disadvantages. These findings highlight the culture potential of triploid C. virginica in their northern range, provide insight into optimal environmental conditions for triploid advantage, and contribute to refining mechanistic triploid oyster growth models.

In temperate regions experiencing rapid ocean warming, kelp forests are being replaced by chemically rich turf algae. However, the extent to which these turf algae alter the surrounding chemical environment or affect the rebound potential of kelp forests (through chemically mediated interactions) remains unknown. Here, we used underwater visual surveys, comprehensive chemical profiling, and laboratory experiments to reveal that turf algae release bioactive compounds into the water that fundamentally alter the reef “chemical landscape” and directly suppress kelp recruitment. Therefore, our study reveals that chemical ecology is critical in shaping modern kelp forest ecosystems and their resilience. Further, it demonstrates that reversing climate-driven state shifts will require not only curbing global carbon emissions but also implementing targeted local interventions that break harmful ecological feedback loops and foster recovery.

Scallop aquaculture is a rapidly expanding global shellfish industry with high market value and consumer demand. However, growth in the aquaculture industry for the Atlantic sea scallop (Placopecten magellanicus) in North America has been uneven. Uncertainty in grow-out dynamics across the potential product portfolio make it difficult to establish robust business plans and bioeconomic benchmarks. Most Atlantic sea scallop aquaculture growth studies have focused on a whole scallop market, with a harvest target at a shell height of similar to 90 mm. Meanwhile, growth studies exceeding 100 mm, where scallops would enter the established adductor muscle market, are far less common because they require a product cycle of greater than three years under well- characterized conditions. In this study, shell height measurements were collected every three months using two husbandry methods, ear-hanging and lantern net suspended culture, over a four-year product cycle. Adductor muscle weight was tracked for the final year of grow-out, when an adductor muscle product would be economically feasible to sell. At the conclusion of the study, measurements for both husbandry methods exceeded 115 mm shell height and 37 g adductor muscle weight. While shell height differences between ear-hanging and lantern net cultures were relatively small (1.19-4.22 %) depending on temperature, the exponential relationship between shell height and adductor muscle weight resulted in a 10.9 % increase for ear-hanging over lantern net scallops harvested in August at approximately three years old (i.e., > 90 mm). Adductor muscle weight differences between grow-out techniques indicate that ear-hanging could provide a more profitable option for aquaculture growers looking to improve production capacity, particularly if the risks of a longer production cycle can be mitigated.

Global scallop production has rapidly transitioned from a wild-capture fishery to an aquaculture industry over the past several decades. However, aquaculture of the Atlantic sea scallop (Placopecten magellanicus) in the Gulf of Maine has remained limited by the high labor burden and costs within the United States and Canada, particularly when using traditional lantern net culture. As a result, specialized ear-hanging equipment designed to automate husbandry processes is increasingly being employed in scallop aquaculture to reduce labor, despite the higher initial investment. Here, we used a techno-economic model to compare the cost of production, net present value, modified internal rate of return, lease size requirements, and labor-bounded maximum annual production of automated ear-hanging and traditional lantern net culture, production cycle duration, and market products. While ear-hanging entailed higher initial capital expenditures, it was notably more cost effective compared to lantern net culture; the advantages were compounded at larger production scales, longer production cycle durations, and when targeting an adductor muscle market. Labor efficiencies in ear-hanging related to a total annual production capacity of almost double that for lantern net culture and a lease acreage reduction of 40 % at comparable annual production. We recommend that growers looking to scale scallop production (>100,000 annual production) consider automated ear-hanging targeting an adductor muscle product. Meanwhile small-scale growers (<100,000 annual production) would likely need to adjust assumptions for a profitable business model. To assist growers in this decision-making process, we have included a scenario-testing application to adjust assumptions to fit their specific business requirements.

Oyster aquaculture holds tremendous potential to diversify coastal economies and increase resilience to climate change, but expansion can conflict with other marine resource users. These conflicts are difficult to characterize quantitatively. Here, we developed an analytical framework using difficulty scores to analyze the difficulty of obtaining an oyster aquaculture lease through publicly available application decisions in Maine, USA. We applied this quantitative framework to a case study examining the potential of using existing fishery infrastructure as a means of diversifying working waterfronts. Specifically, repurposing tidal impoundments historically used to store American lobsters (lobster pounds) for oyster aquaculture has been proposed as an actionable method of overcoming obstacles to aquaculture development in Maine. While the environmental suitability of lobster pounds for oyster aquaculture has been established, there has been minimal exploration of potential regulatory or socioeconomic benefits. We assessed the relative difficulty of obtaining a lease for an aquaculture site within a lobster pound compared to a traditional open-water site. Our analysis demonstrated that the enclosed and privately-owned nature of a lobster pound eliminated many issues that commonly arise during oyster farm site selection, including conflict with riparian landowners, impeded navigation, and interference with commercial fishing or other existing water uses. These results provide the first empirical evidence that repurposing vacant waterfront infrastructure like lobster pounds can minimize social, institutional, financial, and logistical barriers to marine aquaculture development.

The installation and operation of floating offshore wind power is an integral component of societal transition to renewable energy generation where fixed bottom offshore wind is not possible. However, it will cause unique ecosystem changes. To disentangle the effects of offshore wind installations from the concurrent effects of climate change and the fishing practices on commercially significant resources, we must develop detailed characterizations of the resources before development occurs. In the Gulf of Maine, American lobster is the most commercially and culturally important fishery. At the time of writing, this is the largest fishery by value in North America. Our understanding of baseline localized parameters (such as catch per trap at the spatial scale of individual turbines) should be informed by relationships to environmental, biological, and survey-specific functional drivers of catch. A more mechanistic understanding of catch will allow for strategic adjustments to Post-Deployment fishery responses and ultimately, the development of research- and commercial-scale floating offshore wind development. Here, we used survey data from the New England Aqua Ventus Pre-Construction Commercial Trapping Survey to develop Generalized Additive Models describing seasonal catch per trap for legal and sublegal lobsters. We found fall catch to be nearly twice that of spring. Bottom temperature dynamics could be used to predict catch, and the Fall survey was associated with a warmer temperature regime. By using analytical tools that incorporate environmental heterogeneity, we developed monitoring methods from pre-construction baseline data that will be applicable over the post-construction operating period of an offshore wind farm.

Hypoxia in coastal waters is a pressing ecological problem caused by continued eutrophication and climatic change that has widespread consequences for metazoan life and biogeochemical cycles. Numerous studies have investigated the controls on seasonal hypoxia formation and persistence in many of the world’s large estuaries and coastal hypoxic zones, but far fewer studies have examined the controls on short-term oxygen variability that leads to diel-cycling hypoxia in shallow-water environments. We utilized a unique, comprehensive (181 stations) record of dissolved oxygen concentrations collected at shallow water sites (primarily < 2 m) at high frequency (15 min) throughout the estuarine complex of the Chesapeake Bay and its tributaries to quantify how internal and external variables co-varied with dissolved oxygen. We used a combination of time-series analysis, harmonic analysis, and machine learning (e.g., classification and regression trees (CART)) approaches to identify spatial patterns in major controls on oxygen variability and the duration of moderate hypoxia. We found that key controls on oxygen variability varied substantially over space. For example, photosynthetically active radiation (PAR) was a strong predictor of oxygen dynamics in the majority of mesohaline waters. In more fetch-exposed stations, wind strongly controlled hypoxic duration, but in eutrophic, inshore locations, chlorophyll a, or turbidity were often better predictors. Specifically, diel oxygen variability was muted in upstream regions characterized by high turbidity. The duration of low oxygen conditions, which we defined conservatively as less than 4.8 mg O2 L−1 (156 µM), was strongly controlled by temperature, and simple projections of regional warming and CART-derived oxygen thresholds suggest that the Bay could experience a 10

Climate change is anticipated to alter the phenology of phytoplankton blooms in the ocean, making their recent dynamics of interest to inform models of future ocean states. We characterized temperature change in the North Atlantic using metrics that track the patterns of sea surface water temperature (SST) defined by quantiles. To complement these thermal indicators, we estimated a thermal phenology index in the form of the date of the spring transition, taken as the date that temperature achieved the long-term mean at a specific location. We then used ocean color data (1998–2022) and characterized spring bloom phenology using change point methods to derive bloom initiation, duration, magnitude, and intensity. The North Atlantic has warmed over recent decades, averaging a rate of increase of 0.27°C decade−1, yet throughout most of the basin, spring transition timing has remained constant, with the exception of small areas with either delayed or advanced transitions. There were no clear trends in bloom start or duration in the North Atlantic, indicating that spring bloom phenology was independent of climate-driven temperature change. Bloom magnitude and intensity trended downward in some North Atlantic continental shelf seas, indicating that increased temperatures may have had negative effects on overall bloom productivity. However, exclusive of the areas where the bloom parameters were trending, there was a decrease in magnitude and intensity with warmer winter temperatures, suggesting that the inter-annual variability of these parameters may be affected by thermal conditions at the onset of the bloom. While temperature has increased in the North Atlantic, vernal light availability has remained unchanged, which may explain why spring bloom phenology has remained resistant to climate change. Consequently, it seems plausible that future climate change may have limited effects on spring bloom phenology, but could have substantial effects on overall phytoplankton production.

The Northeast US Continental Shelf (NES) is a highly productive marine ecosystem that has experienced wide swings in phytoplankton chlorophyll concentration (CHL). To better understand this variability, we examined changes in CHL over the period 1998-2022, while also considering three indicators of the potential supply of nutrient source waters including cross-shelf advection via deep channels, transport from beyond the shelf edge via Gulf Stream warm core rings (WCR), and input from river and estuarine discharge. Traditionally, deep channel advection of water across the NES was assumed to be derived from Labrador Slope Water (LSW) and Warm Slope Water (WSW). These designations do not fully capture the range of water types contributing to cross-shelf advection. The contribution of LSW and WSW was reciprocal over time, with the presence of WSW at an increased level in recent years. There has been an increase in the number of WCRs off the NES represented by indices of ring occupancy. Precipitation increased over the study period as well, generally over the NES region and in particular in the Mid-Atlantic Bight drainage. We see evidence of the effect of increased precipitation on the NES proper through a change in the area of the ocean surface having 555 nm reflectance with sr-1 > 0.004. Using a canonical analysis, CHL correlated positively with the proportion of LSW and negatively with WSW. These correlations suggest there are aspects of the nutrient content associated with these water masses that are key to phytoplankton growth. WCR frequency negatively correlated with CHL, which was expected since the nutrient loadings of WCRs tends to be low. Finally, CHL negatively correlated with precipitation rate, which suggests terrestrial origin nutrient inputs to the NES are minor. We suggest that in order to understand future CHL dynamics in the NES, careful consideration of advective sources of nutrients in the Northwest Atlantic is necessary.

Post-harvest mortality in the American lobster (Homarus americanus) fishery can result in a significant loss in revenue for the largest single species fishery in North America. At least 2% of American lobster landed in Maine, USA die before they reach consumers. The landed value of the Maine lobster fishery was $730 million USD in 2021. Yet, the industry loses roughly 952 metric tons annually due to post-harvest mortality each year. The lobster supply chain is a network of harvesters, dealers, and distributors that facilitates the transport of live product domestically and internationally. The majority of product loss comes in the form of delayed mortality as a result of stressors within the supply chain. Because of the high volume of lobster transported through the supply chain and its many links, a standard protocol is needed to quickly diagnose whether a high-value live lobster will survive the trip to the consumer. Based on empirical observations, we developed a reflex action mortality predictor (RAMP) model to reliably predict subsequent mortality, days after exposure to the supply chain. A suite of physical characteristics, injuries, and discrete reflex actions of 975 lobsters that were monitored at two standard lobster dealer facilities were recorded to build logistic RAMP models. Results suggest that body size along with four specific reflex actions and five types of injury are significant predictors of mortality five days later. The reflex actions were eye motion, pereiopod motion, 3rd maxilliped retraction, and 2nd maxilliped motion. The five injuries were missing chelae, damaged chela, damaged antenna, damaged carapace, and damaged uropod. The RAMP model can be an important tool in identifying supply chain stressors that impact lobster quality and inform efforts to improve the efficiency and resiliency of the industry. The highly predictive, non-invasive, quick, and cost-effective nature of this method has potential to become a versatile tool for both industry and scientific applications.

The American lobster, Homarus americanus, supports the most valuable single-species fishery in North America; however to-date, a reliable and robust method to determine age does not exist, and thus some of the more traditional catch-at-age stock assessment methods cannot be used to determine status. In lieu of this, the Atlantic States Marine Fisheries Commission's American Lobster Stock Assessment Model uses a probabilistic growth transition matrix to determine how lobsters of different sizes will grow and recruit into the fishery. Developing and updating the growth transition matrix to reflect current growth dynamics requires estimates of molt increment and interval. Tagging studies are an inexpensive method to collect this type of information, but relying on fishing industry reported recapture data and buy-in can be challenging, resulting in varied return rates and uncertainty in measurement accuracy. Here, we report on a subset of recaptured lobsters released in the Gulf of Maine and Georges Bank regions between 2015 and 2020, where in addition to recapture locations, harvesters were encouraged to submit images of recaptured lobsters alongside a standard lobster gauge as a scale to estimate carapace length. Some fishermen were able to provide both direct measurements and images. Images were analyzed in ImageJ to estimate individual lobster carapace length (CL); and each image was assigned a quality score. For all groups, image-derived lengths were correlated with measured observations, regardless of the overall image quality, with only a slight underestimation at the maximum end of CL. This image-based method for length estimation provides high-quality length predictions regardless of image quality and can significantly increase the likelihood of harvesters contributing data with broad potential to engage commercial fisherman in collaborative science. Using this method we were able to expand the dataset of length records from this project by 251 or 33 %, providing additional data at a rate similar to tagging an additional 6000 lobsters.

As global temperatures continue to rise, accurate predicted species distribution models will be important for forecasting the movement of range-shifting species. These predictions rely on measurements of organismal thermal tolerance, which can be measured using classical threshold concepts such as Arrhenius break temperatures and critical thermal temperatures, or through ecologically relevant measurements such as the temperature at which reproduction and growth occur. Many species, including invasive species, exhibit thermal plasticity, so these thresholds may change based on ambient temperature, life stage, and measurement techniques. Here, we review thermal thresholds for 15 invertebrate species invasive to the Gulf of Maine. The high degree of variability within a species and between applied conceptual frameworks suggests that modeling the future distribution of these species in all ecosystems, but especially in the rapidly warming northwest Atlantic and Gulf of Maine, will be challenging. While each of these measurement techniques is valid, we suggest contextualization and integration of threshold measurements for accurate modeling.

Some species are so linked to specific environments that their habitat association almost becomes a species-defining character and is used by managers and policymakers to direct their conservation. The American lobster Homarus americanus is among the most valuable fisheries species in North America and among the best studied benthic marine invertebrates in the world. Its populations and habitats have been studied and detailed in publications for over 35 yr. This lobster species was known to dwell in shelters, and their populations had historically been concentrated in shelter-providing boulder habitat. Our study revisited 20 long-term monitored sites at 10 m depth along more than 320 km of the Gulf of Maine. Surprisingly, we recorded fundamental changes in lobster abundance, habitat use, and distribution. Specifically, lobster population densities declined overall and occupancy in boulder habitats declined 60%, while densities on featureless ledge and sediment habitats increased 633 and 280%, respectively, from 2000 to 2019. Lobster rock shelter occupancy declined in recent years, but average body size increased, due in part to declines in smaller size classes. These demographic changes may result from both reduced recruitment and intraspecific competition resulting from the lower population densities. Habitat changes at our monitored sites included declines in kelp abundance, increases in diminutive algal turfs, and nearly 3 degrees C warming of benthic water temperature in July (1995-2021), some of which may have contributed indirectly to those shifts. While these changes in shallow water habitat and demography have implications for the lobster fishery and stock assessments, it also illustrates previously undescribed behavioral plasticity.

The planktonic copepod Calanus finmarchicus is a fundamental prey resource for the critically endangered North Atlantic right whale Eubalaena glacialis . Incorporation of prey information into E. gla cialis decision support tools could improve management. Zooplankton time series are usually analyzed with respect to abundance, but predators such as E. glacialis forage based on whether prey aggregations exceed energetic thresholds. In order to better understand the distribution and dynamics of the high-abundance end of C. finmarchicus on the northeastern US continental shelf, where E. glacialis feed, we modeled the environmental conditions associated with C. finmarchicus densities that exceed nominal feeding thresholds. Threshold values were chosen based on a review of E. glacialis feeding behavior throughout the domain. Following model selection procedures, we used a random forest model with bathymetry, bottom temperature, bottom salinity, day of year, sea surface temperature, sea surface temperature gradient, bathymetric slope, time-integrated chlorophyll, current velocity gradient, and wind covariates. Model performance was highest with thresholds that matched reported E. glacialis feeding thresholds equivalent to 10000 copepods m -2 . The high-density aggregations of C. finmarchicus had some different covariate responses compared to previous statistical abundance models, such as a warmer temperature range at both the surface and at depth, as well as a much higher degree of spatial variability. The output data layers of the model are designed to link with E. glacialis models used in US governmental decision support tools. Including this type of foraging information in decision support tools is a step forward in managing this critically endangered species.

Predicting the impact of marine ecosystem warming on the timing and magnitude of phytoplankton production is challenging. For example, warming can advance the progression of stratification thereby changing the availability of nutrients to surface phytoplankton, or influence the surface mixed layer depth, thus affecting light availability. Here, we use a time series of sea surface temperature (SST) and chlorophyll remote sensing products to characterize the response of the phytoplankton community to increased temperature in the Northeast US Shelf Ecosystem. The rate of change in SST was higher in the summer than in winter in all ecoregions resulting in little change in the timing and magnitude of the spring thermal transition compared to a significant change in the autumn transition. Along with little phenological shift in spring thermal conditions, there was also no evidence of a change in spring bloom timing and duration. However, we observed a change in autumn bloom timing in the Georges Bank ecoregion, where bloom initiation has shifted from late September to late October between 1998 and 2020-on average 33 d later. Bloom duration in this ecoregion also shortened from similar to 7.5 to 5 weeks. The shortened autumn bloom may be caused by later overturn in stratification known to initiate autumn blooms in the region, whereas the timing of light limitation at the end of the bloom remains unchanged. These changes in bloom timing and duration appear to be related to the change in autumn thermal conditions and the significant shift in autumn thermal transition. These results suggest that the spring bloom phenology in this temperate continental shelf ecosystem may be more resilient to thermal climate change effects than blooms occurring in other times of the year.

As the world develops sources of renewable energy, there is an intensifying interest in offshore wind energy production. The Northeast U.S. Continental Shelf (NES) ecosystem has favorable wind dynamics, with active development of wind energy. In this study, we present species distribution models that consider both occupancy and biomass responses for a broad spectrum of fish and macroinvertebrate taxa (n = 177). Building upon prior analyses, habitat was differentiated into overall and core habitats based on statistical distributions of habitat scores. Overall habitat was used to show each species' regional distribution based on fishery-independent survey captures between 1976 and 2019, whereas core habitat represented where the focus of the species' abundance was located as a subset of overall habitat. Wind energy developments may modify the water column in ways that impact lower-trophic-level productivity; therefore, added attention was given to the response of forage species. Over 20% of species showed preferential use of putative and potential wind development areas, including a disproportionate number of forage taxa. Principal usage varied by season, with forage species like Atlantic Menhaden Brevoortia tyrannus and Atlantic Mackerel Scomber scombrus preferentially using the lease areas in spring and Round Herring Etrumeus teres and longfin inshore squid Doryteuthis pealeii using lease areas in autumn. For species with relatively low usage of the lease areas, there was a tendency for the usage related to overall habitat to be lower than usage for core habitat; in contrast, for species with high usage of the lease areas, that usage was higher for overall habitat than for core habitat. The area of habitat tended to have positive trends across species, with these positive trends being disproportionately higher among forage taxa. These results frame the importance of wind lease areas for species in the NES, particularly forage taxa that fulfill many important ecological functions.