Projects
The goal of our NCLIM research is to develop an integrated modeling framework to inform marine resource decision-making under projected climate change in the Northeast U.S. This framework will integrate: 1) global climate models, 2) regional oceanographic models, 3) ecosystem and population models, and 4) human dimensions models. We will demonstrate the utility of this integrated modeling framework to inform fisheries decision challenges for species that have demonstrated shifts in distribution and changes in productivity (Atlantic cod and black sea bass). Our proposed integrative modeling initiative aims to improve our understanding of the changing ocean and tackle the challenge of building climate resilience in the fisheries of the Northeast U.S. Ocean health, food security, community persistence, and our seafood economy all depend on finding a path forward that mitigates risks and maximizes opportunities.
Atlantic cod in U.S. waters are managed as two distinct stocks. Recently, however, an interdisciplinary review revealed that the current stock boundaries do not align with the spatial structure of biological cod populations. In principle, resolving this discrepancy could facilitate both fishery and conservation objectives. Therefore, to inform the management decision making process we are using simulation testing to evaluate the performance of several alternative spatial management scenarios.
For this project we are developing a Management Strategy Evaluation (MSE) framework that reflects the recently understood biological population structure of cod. Specifically, we simultaneously model five biological populations, each with distinct and realistic population dynamics (e.g. spawning region, spawning season, recruitment dynamics, growth rates). As a part of this, we will model climate impacts on population dynamics, such as recruitment or natural mortality, when appropriate.
Over the last 30 years, the Gulf of Maine’s waters have warmed at a rate more than three times the global average. The impact of warming on marine resources in this region is apparent through shifts in species distribution and productivity changes in economically and culturally important stocks. These diverse and interacting influences are reshaping the ecosystem of Maine’s coastal waters in ways that are impacting key resources and will affect all sectors of Maine’s Blue Economy, including wild fisheries, aquaculture, and tourism. Coastal communities in Maine have strong social and cultural ties to marine fisheries and many will be highly vulnerable to projected changes in fishery resources.
We needed information on the state of the ecosystem to improve our ability to make informed decisions in the face of climate change and to support a holistic, ecosystem-based approach to managing marine resources in the coastal waters of Maine.
Integrated ecosystem assessments (IEAs) provide an overview of the status, trends, and possible future conditions of key components of the ecosystem. IEAs facilitate the translation of ocean data to information and knowledge and have the potential to support ocean resource decision-making, business planning, and community adaptation efforts in the face of a rapidly changing ocean. A core feature of IEAs is the tracking of ecosystem indicators that enable characterization of ecosystem change relative to some baseline or target level. Long-term ecosystem and resource monitoring datasets (e.g., bottom trawl surveys) are essential for characterizing the relationships between the ocean environment, important marine resources, and the communities they support. These assessments are typically developed at the regional scale (e.g., State of the Ecosystem: New England, NEFSC 2020) and designed to provide a system-wide context for resource managers and stakeholders supporting an ecosystem approach to marine resource management. However, the IEA approach is scalable and can be implemented at finer geographic scales or scoped to focus on a specific ecosystem service (e.g., fisheries). Developing a focused assessment of status and trends in Maine’s coastal waters has the potential to build a greater awareness of how ecosystem variability and change influence marine resources and fisheries and to support ecosystem-based fishery management and climate adaptation planning efforts.
The goal of our research is to develop fisheries management procedures that consider climate-driven changes and evaluate whether they result in more adaptive, successful management of groundfish species given forecasted climate change in the NESLME.
We are applying Management Strategy Evaluation (MSE) to address our research objectives. At the center of our MSE approach are a series of operating models that incorporate mechanistic relationships between life history processes and temperature to simulate population dynamics of Georges Bank groundfish stocks. These models are simulated under alternative temperature scenarios that capture future projected climate change in the NESLME. We then simulate sampling these stocks through the fishery and through scientific surveys.
The simulated data is used to assess the stocks using standard stock assessment models, and models that allow for non-stationarity or incorporate temperature information directly into process equations. Additionally, we are developing and testing biological reference points and alternative methods of advice setting that captures non-stationarity in aspects of productivity and directly integrates temperature.
We are combining economic metrics with biomass-related and yield metrics derived from the MSE to provide a comprehensive view of the economic and ecological risks and returns of alternative fisheries management strategies. We will develop an interactive web application for synthesizing the results of the MSE and use this as a tool to communicate with stakeholders.
Atlantic bluefin tuna are assessed and managed as two separate stocks — east and west components separated by the 45°W Meridian. Close to 30 countries fish for Atlantic bluefin tuna in the eastern stock, but only three (United States, Canada, Japan) receive the majority of the western bluefin tuna quota.
The United States fills most of its commercial quota in the Gulf of Maine from June to October. Most of these landings come from small vessels catching fish within 150 miles of shore using harpoons and rod and reel.
However, between 2004 and 2008, the commercial fishery in the Gulf of Maine all but disappeared. Landings fell to historic lows, and while it was unclear why the fishery declined so quickly, several hypotheses emerged. Some posited that the historically low landings were due to a dramatic decline in the western Atlantic population, and others suggested the reason for the decline was due to a population shift to more northern waters as a result of poor foraging conditions in the Gulf of Maine.
These competing scenarios have very different outcomes for the management of the stock and the fate of the fisheries that pursue them. If the declines were the result of a distribution shift, it may indicate the status of the stock is still doing well and can sustain current fishing levels. If the lack of landings in the Gulf of Maine results from fewer fish in the population, then management measures may be needed to reduce fishing pressure and allow the stock to rebuild.
This project seeks to evaluate larger scale environmental drivers that may influence Atlantic bluefin tuna catch rates and incorporate new indices and indicators into the western Atlantic stock assessment that may account for the changes in landings and help to better manage the species.
A harvest control rule is a prescribed management action developed in response to stock status assessments. The New England Fishery Management Council (NEFMC) manages groundfish stocks through the Northeast multispecies groundfish fishery management plan (FMP). That plan defines the harvest control rule used to determine the Acceptable Biological Catch (ABC) for each groundfish stock. Because the harvest control rules result from stock assessments, it’s crucial that these assessments are accurate, but updated retrospective stock estimates have generated a level of uncertainty in the assessment process that have put the current harvest control rule, implemented in 2010 through Amendment 16, into question.
Additionally, the current harvest control rules in place, as well as any alternatives, have not been simulation tested. This, combined with policy and management applications since 2010 suggest that the current harvest control rules should be reevaluated to determine if they are still consistent with best practices.
In response to the issues emerging about current harvest control rules, the NEFMC has initiated a groundfish harvest control rule review so that fisheries management can be sure they are prescribing the actions that are best for their respective fisheries and stocks.
We used a management strategy evaluation (MSE) model framework to simulation test a range of alternative harvest control rule performances within the groundfish fishery. Through an MSE approach, we used simulation modeling to test the performance of alternative fisheries management procedures by developing models of the entire fishery resource system — including the fish, fishery, stock assessment, and management process. This will help us to identify possible outcomes and tradeoffs of current and alternative harvest control rules before we actually implement them on the water. MSE is a powerful tool for developing management strategies for fishery resources that are robust to uncertainties about the fish-fishery-management system.
Apex predators like tunas, sharks, and marlins are some of the most charismatic species in the ocean. They can grow to impressive sizes, travel thousands of miles on annual migrations, and are sought after by commercial and recreational fishermen. As apex predators, they also serve to balance and stabilize marine food webs. Migrations tend to follow favorable water masses that aggregate prey in sufficient quantities to support metabolic demands. Often, abundant prey sources like Atlantic herring, mackerel, and menhaden are themselves the target of commercial fisheries.
Identifying what these top predators eat is important if their primary prey is also the target of commercial fisheries, as fisheries managers need to make sure enough of the forage resource is left in the water to support ecosystem needs. Examining important prey items also helps us understand marine food webs and how animals might respond to changes in ocean conditions. Understanding foraging ecology can also help us interpret changes in the distribution of top predators and explain changes in catch per unit effort indices, one of the metrics fisheries scientists use to evaluate the status of the stocks.
For this project, we are evaluating the foraging ecology of marlins and two species of tuna to check for the presence of chub mackerel — an abundant, small pelagic species located along the East Coast. To quantify the stomach contents of these species, we collect stomachs from recreational and commercial fishermen who land these fish. Specimens come from offshore waters between the Hudson and Wilmington Canyons. The marlin and tunas are identified to the species level, and their stomachs are removed. In the lab, we dissect the stomachs and organize the contents. Any species with recognizable morphological characteristics are identified to the lowest taxonomic group. If no visual characteristics remain due to advanced digestion, we remove otoliths and beaks from any teleosts and cephalopods, respectively, as we can use these structures to identify prey samples down to the species level. If no otoliths or squid beaks remain intact, small aliquots of tissue are saved and sent off for genetic barcoding. This is a powerful technique that can identify prey species without physical features. In many highly migratory species, digestion takes place very rapidly and genetic barcoding is becoming the most effective way to identify prey that at times is nothing more than a pile of unrecognizable tissue.
The Atlantic bluefin tuna is a large, highly migratory species distributed throughout the north Atlantic basin. Countries throughout Europe, the Mediterranean, North Africa, and the West Atlantic pursue this fish for commercial and recreational purposes. Bluefin travel throughout the north Atlantic, and such mobility can make them more difficult to study than more sedentary animals, making their life history more complicated to fully understand.
Although studied for decades, long-term programs that collect important biological data to improve information on life history have been largely unsuccessful. Key aspects of life history, for example, age structure, growth, spawning, longevity, and migration still require considerable scientific exploration in order to better manage their population. These efforts are needed on an annual basis, to account for the changes brought about by the environment, fishing pressure, and their respective interactions.
Originally managed as a single Atlantic wide stock, Atlantic bluefin tuna management changed beginning in the 1970s when stocks were split between tuna populations east and west of management division (45°W meridian) under the assumption that the two stocks had separate spawning grounds and did not mix. If these stocks do mix, it’s important to know the mixing rate so we can make sure landings from the west stock came from the west Atlantic population. If unable to account for this mixing, stock statuses face the risk of artificial inflation or deflation.
Our project sets up long-term biological sample collections to fill in life history gaps, including age structure and stock mixing. We do this by using different tissues that can show us how long the fish lived, how fast it grew, and where it traveled. By working with commercial and recreational fishermen, and commercial dealers, we have established a large sampling network stretching from Maine to North Carolina.
Muscle samples and sagittal otoliths we collect can tell us about a fish’s energetic status, stock composition, population abundance, and age structure. Information that greatly supports foraging ecology research. We extract sagittal otoliths from the head of each fish, and use information from those tissues to estimate the age of the fish and its natal origin. Like a tree, otoliths grow at different rates and accrete material faster and slower during winter and summer periods. By cutting these otoliths in half and looking at them under a microscope, you can count the rings and add them up to estimate the age of a fish. At the center of each otolith is the birthmark, material fish generate when on their spawning grounds. Isolating, analyzing, and comparing this birthmark material to chemical signatures in known spawning grounds allows us to determine where these fish originated.
Because of the rapid pace of warming in Maine waters, we need to better understand what that means for our state’s marine resources now, and into the future. The goal of this study is to synthesize data collected through the Maine-New Hampshire Inshore Trawl Survey, and place it in the context of other surveys in the region, like the Northeast Fisheries Science Center Multispecies Bottom Trawl Survey and the Massachusetts Inshore Trawl Survey. Piecing together the temperature and salinity data from these different surveys will help us understand how climate change and other drivers are impacting key fish and invertebrate communities in coastal Maine.