Dynamics of large sessile seabed fauna, important for structural fisheries habitat and biodiversity of marine ecosystems – and use of these habitats by key finfish species No. 97/205 Project CSIRO Marine Research C. R. Pitcher T. J. Wassenberg G. P. Smith M. Austin S. R. Gordon R. H. Bustamante C. H. Moeseneder Australian Institute of Marine Science M. C. Cappo P. J. Speare P. J. Doherty Queensland Museum J. A. Kennedy J. N. A. Hooper August 2004 DYNAMICS OF LARGE SESSILE SEABED FAUNA, IMPORTANT FOR STRUCTURAL FISHERIES HABITAT AND BIODIVERSITY OF MARINE ECOSYSTEMS – AND USE OF THESE HABITATS BY KEY FINFISH SPECIES C.R. Pitcher¹, T.J. Wassenberg¹, M.C. Cappo², G.P. Smith¹, M. Austin¹, S.R. Gordon¹, R.H. Bustamante¹, C.H. Moeseneder¹, P.J. Speare², J.A. Kennedy³, P.J. Doherty², J.N.A. Hooper³ 1 2 3 PROJECT No. 97/205 ISBN 1 876 996 77 3 ii National Library of Australia Cataloguing-in-Publication entry: Dynamics of large sessile seabed fauna, important for structural fisheries habitat and biodiversity of marine ecosystems — and use of these habitats by key finfish species. ISBN 1 876996 77 3. 1. Fishery management - Australia. 2. Fish habitat improvement - Australia. 3. Marine sciences - Australia. 4. Marine ecology - Australia. 5. Marine fauna. I. Pitcher, C. R. (Clifford Roland). II. CSIRO Marine Research. III. Fisheries Research & Development Corporation (Australia). 333.9560994 This Report should be cited as: Pitcher, C.R., Wassenberg, T.J., Cappo, M.C., Smith, G.P., Austin, M., Gordon, S.R., Bustamante, R.H., Moeseneder, C.H., Speare, P.J., Kennedy, J.A., Doherty, P.J., Hooper, J.N.A. (2004). Dynamics of large sessile seabed fauna, important for structural fisheries habitat and biodiversity of marine ecosystems — and use of these habitats by key finfish species. Final report to Fisheries Research & Development Corporation. CSIRO Marine Research. Pp. 304 Copyright Fisheries Research and Development Corporation and CSIRO Marine Research 2004 This work is copyright. Except as permitted under the Copyright Act 1968 (Cth), no part of this publication may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owners. Neither may information be stored electronically in any form whatsoever without such permission. The Fisheries Research and Development Corporation plans, invests in and manages fisheries research and development throughout Australia. It is a federal statutory authority jointly funded by the Australian Government and the fishing industry. iii Table of Contents Acknowledgements iv 1 Non-technical summary: 1-1 2 Background 2-5 3 Need 3-6 4 Objectives 4-8 5 The initial survey to find suitable study sites 5-9 5.1 Introduction 5-11 5.2 Methods 5-12 5.3 Results 5-23 5.4 Discussion 5-38 5.5 Appendix 5-43 6 Dynamics of tagged megabenthos 6-57 6.1 Introduction 6-59 6.2 Methods 6-60 6.3 Results 6-68 6.4 Discussion 6-97 6.5 Appendices 6-102 7 Modeling the dynamics of sessile megabenthos 7-105 7.1 Introduction 7-108 7.2 Methods 7-109 7.3 Results 7-117 7.4 Discussion 7-129 7.5 Appendices 7-136 8 The ecological usage of epibenthic habitat by key commercial finfish species 8-176 8.1 Introduction 8-179 8.2 Methods 8-181 8.3 Results 8-190 8.4 Discussion 8-212 8.5 Appendices 8-219 9 Acoustic techniques for surveying tropical demersal finfish resources 9-224 9.1 Introduction 9-226 9.2 Desktop approach 9-227 9.3 Field survey approach 9-231 9.4 Discussion 9-265 9.5 Appendix 9-269 10 Benefits 10-271 11 Further development 11-273 12 Planned outcomes 12-277 13 Conclusions 13-279 13.1 Objective 1. Determine the dynamics of megabenthos. 13-279 13.2 Objective 2. Model the dynamics of megabenthos. 13-280 13.3 Objective 3. Document the use of megabenthos by key fish species. 13-282 13.4 Objective 4. Assess methods for surveying fish abundance. 13-283 14 References 14-286 15 Appendices 15-299 15.1 Intellectual Property 15-299 15.2 Staff 15-300 iv Acknowledgements This project was a collaboration between CSIRO Marine Research, the Australian Institute of Marine Science and the Queensland Museum. The project was funded by Fisheries Research and Development Corporation and the research agencies. We are indebted to many people who helped us to obtain a successful conclusion to this project. Don Battersby and Marc Lennard, (Crew of the James Kirby). Paula Tomkin (then of the Queensland Museum) contributed her expertise to the initial epibenthos field survey and Gary Fry (CSIRO) sorted many of the epibenthos samples. Sue Cheers and Anthea Koutsoukos did much of the video analysis. Dr Christie Adams and Steve Cook (Queensland Museum) identified many of the specimens collected. Darren Dennis (CSIRO) was a helped with many of the dives to measure the megabenthos animals. Louise Bell designed the report covers. FRDC’s anonymous reviewers provided helpful comments on the draft report. Toni Cannard co-ordinated and collated the revisions by multiple co-authors, and corrected our typographic, formatting and cross-referencing errors and inconsistencies. 1-1 97/205 Dynamics of large sessile seabed fauna, important for structural fisheries habitat and biodiversity of marine ecosystems — and use of these habitats by key finfish species Principal Investigator: Dr C.R. Pitcher Address: CSIRO Marine Research PO Box 120 Cleveland, Qld 4163 Telephone: 07 3826 7250 Fax: 07 3826 7222 Objectives: 1. To determine the dynamics (recruitment, growth, mortality, and reproduction) of structurally dominant large seabed habitat organisms (ie. megabenthos = sponges, gorgonians, and alcyonarians and corals etc) important for demersal fisheries habitat and biodiversity of the seabed environment, in a tropical region. 2. To model the dynamics of seabed habitat organisms and predict the potential of trawled megabenthos to recover and contribute as fisheries habitat. 3. To document the ecological usage of living epibenthic habitat by key commercial finfish species, in terms of species micro-distribution, shelter requirements, and food chain links. 4. To assess three fishery-independent and “environmentally-friendly” techniques for surveying tropical finfish resource abundance in inter-reefal areas, including fish-traps, remote (baited) video stations and quantitative acoustics. 1 Non-technical summary: OUTCOMES ACHIEVED This project has delivered outputs in relation to each objective that have contributed to a high priority area for research identified previously by the FRDC (i.e. habitat dynamics and processes), and will contribute to a range of outcomes as they are adopted by management, industry and the wider community. The project’s results have contributed to increased understanding of the nature and importance of deeper water habitats, provided fishery-independent tools for monitoring tropical finfish resources that have little or no environmental impact, and will be useful for planning management strategies for sustainable fisheries, planning habitat protection areas, refuges, and marine protected areas, and consideration of the feasibility of habitat restoration activities. The results will be used in a “trawl- scenario-model” that enables managers to examine alternative management strategies that have less impact on habitat, preserve critical habitat in refuges, reduce conflict between commercial extractive activities and conservation needs, and may lead to increased productivity among commercial species. These results and approaches have become increasingly important as fisheries, particularly tropical trawl fisheries, respond to and implement changes to meet the sustainability and ecological assessment requirements of contemporary legislation. For example, the results are now being taken up in developing ecological risk assessments for Commonwealth and Queensland fisheries, and for Environmental Strategic Assessments. The scope and importance of these outcomes will increase as other new and ongoing projects deliver additional information needed for fisheries sustainability evaluations. The ultimate outcomes of these activities are ecologically sustainable fisheries and an objective balance between commercial fishing and national biodiversity conservation goals. 1-2 1: Non technical Summary NEED FOR THE RESEARCH Assemblages of sponges, sea-fans and whips (megabenthos) that provide structural complexity to the seabed are an important component of fisheries habitats, and also contribute to the biodiversity of the marine environment. These assemblages can be impacted by trawling; however, management is now required to achieve ecological sustainability of such fisheries. To evaluate management strategies to achieve these goals, information is needed on the population dynamics of megabenthos and their use by other species, including fish species that may move between trawled areas and habitat. This project focused on these information needs in the Great Barrier Reef region near Townsville. Also needed by fisheries managers are methods for monitoring tropical finfish resources. To assist this need, we have also examined environmentally-friendly, fishery-independent techniques for estimating finfish abundance, including remote (baited) video stations and acoustics. Information on fish-habitat associations is needed to develop habitat proxies for estimating the spatial distribution of deeper water fish stocks. SUMMARY OF RESULTS AND CONCLUSIONS 1.1 Objective 1. Determine the dynamics of megabenthos. The population dynamics parameters (growth, mortality, recruitment, and reproduction) of nine species of structurally dominant