Gulf of Maine is a semi-enclosed sea that extends from MA to New Brunswick and Nova Scotia to the Northeast.

The waters of GOM are bound by Georges Bank to the south and the Scotian Shelf to the east.

The darker region in this figure shows the watershed serving Gulf of Maine, which total to around 70,000 sq miles of land area in the US and Canada

Teleconnection - A causal relationship between climate conditions over some distance

The image here shows the underlying topography of the Northeast Shelf, where areas in purple are depressions and whitish regions are raised seabeds. Shallow sloping regions are shown in green, and steeper slopes in red and orange.

The southern and western portions of the Gulf are characterized by more gently sloping topography covered by thick sediments and glacial deposits.

The northern and eastern portions are characterized by exposed Paleozoic rocks dating to 250 mya. The topography in this region is composed of series of irregular channels and ridges.

In this figure, Georges Bank is clearly visible as a raised landmass extending to the continental slope. Georges Bank is unique as being a shallow and well-mixed offshore region, allowing for high primary production and a reputation as one of the historically most productive fisheries in the world.

Regional currents are major influencers of ocean temperatures in the NW Atlantic, and the two biggest players in Gulf of Maine and Georges Bank are the Labrador Current and Gulf Stream.

The Labrador Current is composed of deep, nutrient-rich waters that flow southwards and into Gulf of Maine through the Northeast Channel (point it out). The percentage of Labrador Slope Water entering into Gulf of Maine is mediated by the northern position of the Gulf Stream. A more northerly Gulf Stream (called the "North Wall") is associated with warmer water temperatures in the region.

Shelf waters moving into GOM through the Northeast Channel result in a counter-clockwise flow in the Gulf and a clockwise pattern on Georges Bank.

The influence of Labrador Shelf Water in Gulf of Maine is also influenced by the NAO. When the NAO is in a positive state, the transport of Labrador Shelf Water is relatively low and less enters into GOM.

Ice-free winters and high fish abundance supports breeding, migrating or staging, and non-breeding populations of birds across the Gulf.

It's not surprising to know that all of these components to the ecosystem are linked in some direct or indirect way. The real question then becomes, from the perspective of managing the system, how can we make use of this information?

Tackling that question requires managing from a holistic perspective, which manifests as what is known as ecosystem-based fisheries management.

Magnuson-Stevens, Endangered Species Act, National Environmental Protection Act...

• Feeding guilds assigned based on NEFSC food habits data base

  • Food habits change with age and size, so guilds assigned based on most common size class

• Simplified from existing guild structures^1,2

Because we focus on ecosystem context, we've aggregated species in most of our indicators up to the level of feeding guild, shown here.

These feeding guilds were derived from NEFSC food habits data and existing guilds identified in the literature

Many social-ecological systems in New England are reliant on lobster, as in Gulf of Maine, or scallop, for Georges Bank. As these species are considered moderately to highly at risk due to climate change, the communities dependent on them could be a heightened risk as well.

Maine and South coast of MA have high reliance

This reliance becomes apparent if we look at the breakdown of catch volume and prices by feeding guild.

In these figures, the catch price is shown in blue and the catch volume is shown in green, and total revenue change from the long term is shown by the black line. It's not perfect, but it's relatively clear that the benthivore feeding guild is driving revenue in Gulf of Maine and benthos in Georges Bank.

Along with strong reliance on a few species in New England, we've also seen a decline in catch of managed species since the mid 1980s.

While commercial fisheries have high specialization of catch, there's a positive long-term trend for recreational catch diversity in the recreational sector.

Updated Marine Recreational Information Program data shows that there's been an upswing in harvest since the mid-90s, although the trend overall is negative

An increase in diversity of recreational catch will likely benefit communities that are reliant upon recreational fisheries by increasing their resilience to ecosystem changes.

The maps here show density estimates of the widely distributed harbor porpoise in the spring and fall months, as estimated by the Atlantic Marine Assessment Program for Protected Species.

The red line in the time series plot shows the potential biological removal. Above this line removals from the population will prevent the stock from reaching a stable population size.

2016 and 2017 estimates for bycatch are among the lowest values in the series, suggest that management actions have been effective in reducing harbor porpoise bycatch.

Fisheries interactions are the largest contributor to NARW mortality, with more than half of the mortality events in 2018-2019 attributed to vessel strikes or entanglement

Changing ecosystem conditions may contribute to increased interactions between NARW and fisheries.

Changes in fishery management to address the issue of fishery interactions with protected species could have large implications for the fixed gear sector, and particularly for pot gear fisheries like lobster.

Unusual mortality event in gray and harbor seals may be caused by phocine distemper virus

SST Figure on left shows estimated time series of SST extending back to to 1850s. *7 out of 10 of the hottest years have been in the past decade

GSI The figure on the right shows that deviation from the mean latitude of the north wall of the gulf stream, showing anomalously high value for the past 5 years

Regional currents are major influencers of ocean temperatures in the NW Atlantic

The Gulf Stream is a reliable indicator of bottom water temps

An offshoot of the gulf stream is the warm slope water, which makes its way into gulf of maine through the northeast channel

These changes have implications for fish populations in the region that are already at the southern extent of their ranges, like Atlantic cod. Suitable habitat for these species is predicted to contract as waters continue to warm.

• Gulf of Maine summer SSTs were the highest on record in 2018 (~3°C > long-term mean)

Making use of the NEFSC bottom trawl data which extends back to the 1960s, we can quantify how species distributions on the shelf have changed through time by estimating the yearly centroids of their distributions.

The predominant pattern across species is a shift northwards and into deeper waters. These shifts are due to a number of factors, including fishing pressures and climate changes

A clear example of this occurring is the American lobster, whose populations have become more productive in Gulf of Maine compared to the northern Mid-Atlantic due to favorable climate conditions.

• Driven by warmer temperatures and increased bacterial remineralization and nutrient recycling
• Increasing primary production likely due to higher productivity of smaller phytoplankton

To assess the size structure of copepods in the region, we use the small-large index.

• A measure of relative size composition of the dominant copepod taxa
• A lower value means higher abundance of large copepods (Calanus)
• Primary production may play a role in copepod size dynamics*

Looking at condition in aggregate across all managed stocks, we can see a clear decline in condition between 2000-2010

Recent improvement within past decade

Interestingly, the drop-off in condition around 2000 resembles a shift in zooplankton size-structure on the shelf, and this is a topic for future research

While management action has had a postive impact on harbor porpoise mortality, there are multiple signals indicating challenges to meeting management goals.

Management objectives are being met for 20 species at the single species level, but 9 stocks are below biomass thresholds.