Science Advisory Report 2020/034

Biophysical and Ecological Overview of the Fundian Channel – Browns Bank Area of Interest (AOI)

Summary

Physical Features of the Fundian Channel – Browns Bank Area of Interest (AOI)

• The Fundian Channel – Browns Bank is an offshore AOI of approximately 7,200 km2 composed of two geographically separate components. The western component of the AOI is centered on Georges Basin and the larger eastern component includes portions of Browns Bank, Fundian Channel^{Footnote 1} , and the continental slope.
• The AOI is primarily located within Northwest Atlantic Fisheries Organization (NAFO) Division 4X. Several existing fisheries closures overlap with the AOI, including the Northeast Channel Coral Conservation Area (NECCCA); nearly 50% of Lobster Fishing Area (LFA) 40, which is currently closed to lobster fishing; and portions of the Browns Bank groundfish spawning seasonal closure.
• The bathymetry of the AOI varies from approximately 50 m on Browns Bank to 370 m in Georges Basin, with depths up to 2,200 m, extending from the eastern section of the AOI to the continental slope.
• The Fundian Channel is similar to other shelf-crossing troughs that have been eroded by past glacial ice streams. The Channel is more energetic compared to other shelf-crossing troughs in the region.
• Seabed classification divides the AOI into four main areas: Outer Gulf of Maine Shelf Basin and Channel; Scotian Slope West – Fan; Outer Scotian Shelf – Saddle; and Outer Scotian Shelf – Bank.

Significant Fish and Invertebrate Species

• There has been an overall change in zooplankton abundance and community composition on the Western Scotian Shelf in recent years, including within the AOI.
• Changes in the copepod community could lead to shifts in the distribution of other pelagic zoo- and ichthyoplankton, marine mammals, pelagic fishes, and other species that depend on large copepods as prey.
• The relatively high diversity of benthic invertebrates found within the AOI corresponds to the variety and complexity of habitats associated with the Fundian Channel, Georges Basin, southern Browns Bank, the continental slope, and deeper waters.
• Two prominent deep-water corals in the AOI are the Alcyonacea species Primnoa resedaeformis and Paragorgia arborea. Some of the densest aggregations of these two taxa on the Scotian Slope are found in the NECCCA within the AOI that was established specifically to protect them.
• Significant sponge concentrations have been identified on Southern Browns Bank, partially overlapping the AOI. The Russian Hat Sponge (Vazella pourtalesi) is known to inhabit the Fundian Channel, but in non-significant concentrations based on kernel density estimates.
• Sea pens (Pennatulacea) are concentrated in deep basins and along the continental slope, with a high probability of occurrence along the slope and in deep, offshore waters. Sea pens have been observed throughout the AOI, though additional studies are needed to determine their full distribution.
• Biogenic habitat-forming species, such as corals, sponges, and sea pens, provide important habitat and refuge from predation, as well as feeding and nursery grounds for a variety of fishes and invertebrates.
• Offshore American Lobster (Homarus americanus) populations, in particular within LFA 40, have been shown to have a higher proportion of large, ovigerous female lobsters than observed inshore. Abundances of lobster recorded in the vicinity of the AOI during the Summer Research Vessel (RV) Survey is consistently amongst the highest on the Scotian Shelf.
• The Summer RV Survey has documented 71 fish species within the AOI between 1970 and 2017. The top 20 most abundant species, including Haddock (Melanogrammus aeglefinus), Atlantic Cod (Gadus morhua), Silver Hake (Merluccius bilinearis), Yellowtail Flounder (Pleuronectes ferruginea), and Pollock (Pollachius virens), comprised nearly 80% of all observations.
• The 4X Atlantic Cod (Endangered – The Committee on the Status of Endangered Wildlife in Canada (COSEWIC)) stock has been in the Critical Zone since 2011, and biomass has remained low since this time, with very low recruitment. The AOI includes representative habitat for Atlantic Cod including a portion of the persistent top quintile habitat identified in the Browns Bank portion of the AOI over the past four decades.  
• On the Scotian Shelf, White Hake (Urophycis tenuis; Threatened – COSEWIC) show the highest abundances in the Bay of Fundy and along the deep waters along the shelf break. Adult and juvenile White Hake are commonly found on fine substrates, such as mud at the bottom of basins on the Scotian Shelf. The deeper portions of Georges Basin encompassed by the AOI boundaries are identified as a persistent top quintile habitat for White Hake on the Scotian Shelf.
• On the Scotian Shelf, Browns Bank represents persistent top quintile habitat for Atlantic Wolffish (Anarhichas lupus; Special Concern – The Species at Risk Act (SARA)).
• Atlantic Halibut (Hippoglossus hippoglossus) in Canadian waters are experiencing a period of high recruitment and population growth. The AOI includes one of two distinct areas of persistent juvenile Atlantic Halibut abundance within the Scotian Shelf Bioregion. These regions of high juvenile abundance are consistently observed irrespective of the overall stock abundance, suggesting they are persistent and resilient. 
• Cusk (Brosme brosme; Endangered – COSEWIC) are considered to have been in the Cautious Zone since 2011. The Fundian Channel, including a large portion of the AOI, has among the highest probabilities of Cusk presence based on habitat suitability models.
• Thorny Skate (Amblyraja radiata; Special Concern – COSEWIC) are considered a single Designatable Unit in Canadian waters and have undergone severe population declines over the southern part of their historic distribution. This decline has continued in the southern portion of their range despite a reduction in fishing mortality. Georges Basin has been shown to be persistent top quintile habitat for Thorny Skate in the vicinity of the AOI.
• Winter Skate (Leucoraja ocellata) in Canada are found in three main concentrations, including the Western Scotian Shelf/Bay of Fundy. Browns Bank, including part of the AOI, and the Bay of Fundy are the only areas of persistent top quintile habitat for Winter Skate on the Western Scotian Shelf.
• A diversity of large pelagic fishes, including tunas, billfishes, and sharks are seasonally present and may forage within the AOI.
• Distinct oceanographic processes, including upwelling at the mouth of the Fundian Channel, internal waves generated within the Channel, and local gyres, in conjunction with dynamic features associated with the Gulf stream, concentrate plankton and forage species such as squid and Atlantic Herring (Clupea harengus), attracting large pelagic fishes to the AOI and continental slope.

Marine Mammals

• At least 22 species of cetaceans are known to occur in the waters of Atlantic Canada. Many of these species have been observed off the southwestern coast of Nova Scotia; however, no comprehensive systematic surveys on the occurrence or distribution of cetaceans in the AOI have been conducted, and the abundance of cetaceans has not been estimated for this area.
• The continental shelf edge has been identified as an important foraging area for Blue Whale (Balaenoptera musculus; Endangered – SARA), including a portion of the AOI.
• Sowerby’s Beaked Whale (Mesoplodon bidens; Special Concern – COSEWIC) and Northern Bottlenose Whale (Hyperoodon ampullatus; Endangered – SARA) are distributed along the Scotian Shelf slope near the Fundian Channel, and in submarine canyons on the eastern Scotian Shelf. These species are present within the AOI and their presence is supported by recent acoustic and visual detections.

Marine Birds

• The abundance and diversity of marine birds in the vicinity of the AOI is reflective of an abundant and varied prey base. The AOI has supported top decile (i.e., top 10th percentile) concentrations of most marine bird functional guilds at various annual and decadal timescales based on bird observer data from the 1960s onward.
• The avifaunal community includes species that access prey on the near-surface, such as storm-petrels, phalaropes, gulls, terns, skuas, and jaegers; plunge divers, such as Northern Gannet (Morus bassanus); shallow divers, such as shearwaters; and deep divers such as auks that can reach nearly 200 m in depth.

Species at Risk

• A variety of marine fish, mammals, turtles, and birds that have been observed in the AOI are assessed as at risk by COSEWIC and/or listed under SARA and the International Union for the Conservation of Nature (IUCN).

Knowledge Gaps

• Data documenting the full distribution of corals and sponges within the AOI, knowledge of the infaunal community composition, and population genetic information for most fish and invertebrate populations is not currently available. While this information could assist boundary delimitation and zoning within a potential MPA, its absence does not preclude the development of conservation priorities.
• The Summer RV Survey provided the majority of the groundfish and benthic invertebrate diversity information used in this ecological overview. Therefore, seasonal migrations, variations in abundance, and changes in groundfish and invertebrate community composition within the AOI remain largely unknown.
• Observations of faunal composition in deep water slope habitat are limited to adjacent strata in the Summer RV Survey. There have been no Summer RV Survey sets conducted deeper than 400 m within the AOI.
• Many species occur in the summer months and are presumed to be feeding based on the productivity and oceanographic features of the AOI; however, no direct observations of feeding in association with the features of the AOI have been recorded.

Climate Change Considerations

• There is some uncertainty about how key biological and physical attributes of the AOI have been responding, or will respond to, changing climate conditions.  
• Specifically, we acknowledge the uncertainty regarding the impacts of:
• the observed shift in zooplankton communities within and in the vicinity of the AOI on productivity and distribution of predators, and overall use of the area by pelagic species;
• ocean acidification and warming on corals and sponges, which are noted as conservation priorities;
• climate change and associated warming temperatures on the distribution, biomass, and resilience of groundfish and invertebrate communities within the AOI; and
• changing fish and invertebrate community composition associated with the increased prevalence of warm-water species and loss of habitat for some colder adapted species on the Scotian Shelf, especially in the Western Scotian Shelf.

Conservation Priorities

• Potential conservation priorities for the Fundian Channel – Browns Bank AOI were identified prior to the Canadian Science Advisory Secretariat (CSAS) review by the Oceans Management Program. These conservation priorities were assessed through this CSAS Science Peer-Review process and were either recommended to be retained, modified, or rejected based on the strength of available scientific evidence. Features were assessed against the Ecologically and Biologically Significant Area (EBSA) criteria of aggregation, uniqueness, and fitness consequences, or the species-based vulnerability, conservation status, and Ecologically Significant Species criteria.
• The following features were supported as conservation priorities by the majority of participants, based on the information that was available for review:

Habitat

• Diverse representation of habitat types, including basin, bank, deep water slope and channel habitats, and their associated fish and invertebrate communities
• Persistent habitat for juvenile Atlantic Halibut
• Concentrations of large mature female lobster
• Suitable habitat for Sowerby’s Beaked Whale and Northern Bottlenose Whale

Biodiversity

• Deep-water corals
• Significant concentrations of sponges  
• Representative habitat for Atlantic Cod, Atlantic Wolffish, Winter Skate, Thorny Skate, and White Hake
• Highly suitable habitat for Cusk

Productivity

• The collection of oceanographic features, such as internal waves, areas of upwelling, and occasional presence of Gulf current and warm-core rings, at the mouth of the Fundian Channel that make it a highly productive area that is associated with the presence of large pelagic fishes, sea turtles, and cetaceans   
• A Blue Whale foraging area
• Foraging ground for most functional guilds of marine birds, including Leach’s Storm Petrel (Oceanodroma leucorhoa)

This Science Advisory Report is from the Regional Peer Review Process of the Biophysical and Ecological Overview of the Fundian Channel – Browns Bank Area of Interest held November 27–29, 2018, with follow up meetings on December 19th, 2018, and February 26, 2019. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2020/034 (PDF, 3,238 KB)

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