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The Gully a Scientific Review of Its Environment and Ecosystem

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The Gully a Scientific Review of Its Environment and Ecosystem Fisheries Pêches ~ and Oceans et Océan s Canadian Stock Assessment Secretariat Secrétariat canadien pour l'évaluation des stocks Research Document 98/83 Document de recherche 98/8 3 Not to be cited without Ne pas citer sans permission of the authors ' autorisation des auteurs ' The Gully : A Scientific Review of its Environment and Ecosyste m W. Glen Harrison' and Derek G. Fenton2 (Editors ) Fisheries and Oceans Canada 'Ocean Sciences Division ZOceans Act Coordination Office Bedford Institute of Oceanography Box 1006, Dartmouth, NS B2Y 4A2 ' This series documents the scientific basis for ' La présente série documente les bases the evaluation of fisheries resources in Canada . scientifiques des évaluations des ressources As such, it addresses the issues of the day in halieutiques du Canada . Elle traite des the time frames required and the documents it problèmes courants selon les échéanciers contains are not intended as definitive dictés. Les documents qu'elle contient ne statements on the subjects addressed but doivent pas être considérés comme des rather as progress reports on ongoing énoncés définitifs sur les sujets traités, mais investigations . plutôt comme des rapports d'étape sur les études en cours . Research documents are produced in the Les documents de recherche sont publiés dans official language in which they are provided to la langue officielle utilisée dans le manuscrit the Secretariat . envoyé au secrétariat . ISSN 1480-4883 Ottawa, 199 8 Canad' Abstract The Gully, a large submarine canyon east of Sable Island on the eastern Scotian Shelf, is a feature which has been described as a unique ecological site and valued component of Atlantic Canadian coastal waters. Its suspected uniqueness and biological significance has attracted the attention of a wide range of government agencies, researchers, ocean resource industries and conservationists . The Department of Fisheries and Oceans (DFO) has as one of its mandates the identification of sensitive marine areas and the development of a strategy for their conservation ; the Gully is one such area which DFO has been asked to evaluate . As a first step in developing a Conservation Strategy for the Gully, DFO coordinated a thorough scientific review of the region to establish the state of knowledge of its environment and ecosystem and to place that information in the context of the greater Scotian Shelf system. Thirty-two scientific experts from DFO, other federal natural resources departments, universities and other NGOs contributed to the Gully Science Review which describes what is presently known about the regions geology, oceanography, benthos, fish, seabirds and mammals. In addition to summarizing what is known about the region's environment and ecosystem, the review also identifies information gaps and outlines future research needs . Résumé Le Gully, un important canyon sous-marin de l'Île de Sable, dans la partie est du plateau néo-écossais, est une entité qui a été décrite comme un site écologique unique et un élément important des eaux côtières du Canada atlantique . Les caractères uniques et l'importance biologique qu'on lui attribue ont attiré l'attention d'une large gamme d'organismes gouvernementaux, de chercheurs, d'industries océaniques et de conservationistes . Le Ministère des Pêches et des Océans (MPO) a notamment pour mandat d'identifier les zones marines vulnérables et d'élaborer une stratégie pour leur conservation. Le Gully est l'une de ces zones pour lesquelles il a été demandé au MPO de procéder à une évaluation. À titre de première étape de l'élaboration d'une stratégie de conservation pour le Gully, le MPO a coordonné un examen scientifique détaillée de la région afin de définir l'état des connaissances en ce qui a trait à l'environnement et à l'écosystème de cette zone et de les situer dans le contexte du système global du plateau néo-écossais. Au total, 32 scientifiques du MPO, d'autres ministères fédéraux des ressources naturelles, d'universités et d'ONG ont participé à l'examen scientifique qui cerne nos connaissances actuelles de la géologie, de l'océanographie, du benthos, des poissons, des oiseaux de mer et des mammifères de cette région . En plus de résumer les connaissances sur l'environnement et l'écosystème, l'examen précise les lacunes en matière d'information et résume les besoins en recherche . TABLE OF CONTENTS SUMMARY ....................................................................................................... ............... ii Acknowledgements ................................................................ .-....................... ................... x 1 .0 Geographical Setting and Conservation Efforts .................................. ................... 1 2.0 The Science Review ............................................................................... ...... ............... 6 3.0 Surficial, Bedrock Geology, and Morphology .................................... ..................... 8 4.0 Hydrography ......................................................................................... ...... .............15 5.0 Acoustic Ambient Noise ........................................................................ ................... 19 6.0 Oceanography ....................................................................................... ................... 20 6.1 Physical Oceanography ............................................................ ...... ................... 20 6.2 Chemical Oceanography .......................................................... ...... ................... 58 6.3 Biological Oceanography - Plankton ................................................................ 71 6.4 Submarine Canyons : Deposition Centres for Detrital Organi c Matter? .............................................................................................. ................. 105 6.5 Benthos ..............................................................................................................107 6.5.1 The Sedimentary Interface Fauna ......................................................... 107 6.5.2 Deep Sea Corals .......................................................................................113 7.0 Fish and Fisheries ................................................................................................... 121 7.1 Finfish and Selected Invertebrates .................................................................121 7.2 Invertebrate Fisheries ...................................................................................... 171 8.0 Pelagic Seabirds ......................................................................................................180 9.0 Marine Mammals ...................................................................................................186 10.0 Ecosystem Classification ...................................................................................... 222 10.1 A System Planning Approach to Marine Classification an d Boundary Considerations ............................................................................. 222 10.2 Submarine Landscapes ......................................................... ......................... 237 11.0 Knowledge Gaps, Recommendations and Future Researc h Requirements ........................................................................... ............................. 248 12.0 The Gully Ecosystem - An Integrated View ................... ........ ........................... 252 13.0 Appendices ............................................................................................................. 255 13.1 Fish and Fisheries : Mackerel ........................................................................ 255 13.2 Fish and Fisheries : Large Pelagics Fisheries .................. ............................. 258 i SUMMARY Background Ocean Sciences Division, Maritimes Region, of the Department of Fisheries and Oceans (DFO) was asked in the summer of 1997 to initiate and lead a thorough scientific review of the Gully, a large submarine canyon on the eastern edge of the Scotian Shelf, in order to characterize its environment and ecosystem(s) in the context of the Scotian Shelf system as a whole . The Review Team*, consisting of some 32 government (DFO, DOE, NRCan), university (Dalhousie) and other NGO (WWF, NS Museum, Ecology Action Centre) researchers, were asked to produce a document summarizing the current state of knowledge of the Gully with respect to its geology, hydrography, oceanography, fisheries, seabirds and mammals. The individual reports produced for the Review document are organized by discipline and (1) describe the sources of available scientific information on the Gully region, (2) provide an interpretation of the data with regard to general as well as unique or special features and (3) identify information/data gaps where they exist. What follows are some of the major highlights of the Gully Science Review . Geosciences & Hydrograph y Description : This section describes the Gully's origin, bathymetric morphology, bedrock and surficial geology, sediment transport and mineral potential . The data are derived from the Geological Survey of Canada inventory and are characterized as limited and patchy. Interpretation of the history of the gully and geological processes are largely based on seismic reflection surveys . The Gully is characterized as a large shelf-edge canyon on the eastern Scotian Shelf unique among canyons of the Eastern Canadian margin because of its great depth, steep
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