C S A S S C C S Canadian Science Advisory Secretariat Secrétariat canadien de consultation scientifique Research Document 2006/041 Document de recherche 2006/041 Not to be cited without Ne pas citer sans permission of the authors * autorisation des auteurs * Assessment of Status and Recovery Évaluation de la situation et du Potential for Striped bass (Morone potentiel de rétablissement du bar saxatilis) in the Southern Gulf of St. rayé (Morone saxatilis) dans le sud du Lawrence golfe du Saint-Laurent S.G. Douglas, G. Chaput and D. Caissie Department of Fisheries and Oceans Oceans and Science Branch, Gulf Region P.O. Box 5030 Moncton, New Brunswick E1C 9B6 * This series documents the scientific basis for the * La présente série documente les bases evaluation of fisheries resources in Canada. As scientifiques des évaluations des ressources such, it addresses the issues of the day in the halieutiques du Canada. Elle traite des time frames required and the documents it problèmes courants selon les échéanciers contains are not intended as definitive statements dictés. Les documents qu’elle contient ne on the subjects addressed but rather as progress doivent pas être considérés comme des énoncés reports on ongoing investigations. définitifs sur les sujets traités, mais plutôt comme des rapports d’étape sur les études en cours. Research documents are produced in the official Les documents de recherche sont publiés dans language in which they are provided to the la langue officielle utilisée dans le manuscrit Secretariat. envoyé au Secrétariat. This document is available on the Internet at: Ce document est disponible sur l’Internet à: http://www.dfo-mpo.gc.ca/csas/ ISSN 1499-3848 (Printed / Imprimé) © Her Majesty the Queen in Right of Canada, 2006 © Sa majesté la Reine, Chef du Canada, 2006 ii TABLE OF CONTENTS ABSTRACT................................................................................................................................... v RÉSUMÉ...................................................................................................................................... vi RATIONALE..................................................................................................................................1 LIFE HISTORY .............................................................................................................................1 FISHERIES MANAGEMENT ........................................................................................................3 1 – INDICATORS OF STATUS.....................................................................................................3 PRIMARY INDICATORS OF STATUS................................................................................................3 1. Spawner abundance – Mark and recapture estimates......................................................3 2. Spawner abundance – CPUE-commercial gaspereau fishery ..........................................3 Sources of Uncertainty......................................................................................................4 3. Young-of-the-year abundance as index of spawning success..........................................4 Fall YOY Index ..................................................................................................................4 Summer Beach Seining Index...........................................................................................5 SECONDARY INDICATORS OF STATUS...........................................................................................6 1. Size structure ....................................................................................................................6 2. Sex ratio............................................................................................................................6 3. Age structure.....................................................................................................................6 4. Mortality estimates ............................................................................................................6 Adult (age 3 and older) mortality .......................................................................................6 Natural mortality factors ....................................................................................................7 Winter conditions...........................................................................................................8 Summer conditions........................................................................................................9 Early life stage survival..................................................................................................9 Parasites disease..........................................................................................................9 5. Area of occupancy (Fig. 1.16).........................................................................................10 RECOVERY................................................................................................................................10 ISSUE .......................................................................................................................................10 SMALL DISTRIBUTION ................................................................................................................10 FLUCTUATION IN MATURE INDIVIDUALS.......................................................................................11 RECOVERY DEFINITION .............................................................................................................11 RECOVERY OBJECTIVES FOR SOUTHERN GULF STRIPED BASS ....................................................12 Perceptions of historical abundance ...................................................................................13 Estimates of the spawning stock.........................................................................................13 Relative age distribution of spawners .................................................................................13 Sex ratios on the spawning ground.....................................................................................13 iii Recovery objectives............................................................................................................14 COMPLIANCE RULES..................................................................................................................14 Recovery attributes of abundance ......................................................................................15 Spawner abundance .......................................................................................................15 Index of spawner abundance ..........................................................................................16 Index of spawning success .............................................................................................16 TIME FRAME FOR RECOVERY .....................................................................................................16 RESIDENCE AND CRITICAL HABITAT ............................................................................................17 2 - HUMAN – INDUCED MORTALITY........................................................................................19 MAJOR POTENTIAL SOURCES OF MORTALITY / HARM...................................................................19 Directed fishing – high.........................................................................................................19 Bycatch in gaspereau fisheries – moderate........................................................................20 Bycatch in rainbow smelt fisheries – high ...........................................................................21 Bycatch in American eel fisheries – moderate ....................................................................21 Bycatch in coastal fisheries – uncertain..............................................................................22 Bycatch in Aboriginal fisheries – high .................................................................................22 Habitat alterations under permit - low .................................................................................22 Power generating stations - uncertain.................................................................................22 Industrial and municipal waste water - uncertain ................................................................23 Scientific research - low ......................................................................................................23 CONCLUSION ............................................................................................................................24 3 - MITIGATION AND ALTERNATIVES .....................................................................................24 CONCLUSION ............................................................................................................................25 ACKNOWLEDGEMENTS ...........................................................................................................25 LITERATURE CITED..................................................................................................................26 iv ABSTRACT The COSEWIC’s recommended “Threatened” listing for striped bass in the southern Gulf required that DFO’s Section 73 permitting framework be applied to determine if incidental harm would jeopardize survival