Does Plant Morphology Influence Fish Fauna Associated with Seagrass Meadows?
Total Page:16
File Type:pdf, Size:1020Kb
Edith Cowan University Research Online Theses : Honours Theses 2002 Does plant morphology influence fish fauna associated with seagrass meadows? Michael C. Burt Edith Cowan University Follow this and additional works at: https://ro.ecu.edu.au/theses_hons Part of the Marine Biology Commons Recommended Citation Burt, M. C. (2002). Does plant morphology influence fish fauna associated with seagrass meadows?. https://ro.ecu.edu.au/theses_hons/568 This Thesis is posted at Research Online. https://ro.ecu.edu.au/theses_hons/568 Edith Cowan University Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorize you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: Copyright owners are entitled to take legal action against persons who infringe their copyright. A reproduction of material that is protected by copyright may be a copyright infringement. Where the reproduction of such material is done without attribution of authorship, with false attribution of authorship or the authorship is treated in a derogatory manner, this may be a breach of the author’s moral rights contained in Part IX of the Copyright Act 1968 (Cth). Courts have the power to impose a wide range of civil and criminal sanctions for infringement of copyright, infringement of moral rights and other offences under the Copyright Act 1968 (Cth). Higher penalties may apply, and higher damages may be awarded, for offences and infringements involving the conversion of material into digital or electronic form. DOES PLANT MORPHOLOGY INFLUENCE FISH FAUNA ASSOCIATED WITH SEAGRASS MEADOWS? by Michael C. BURT This thesis is submitted for the award of Bachelor of Science (Environmental Management) with Honours at the School ofNatural Sciences, Edith Cowan University, Joondalup, Western Australia. DATE OF SUBMISSION: 22"" November 2002 Supervisor: Dr Glenn HYNDES, Edith Cowan University USE OF THESIS The Use of Thesis statement is not included in this version of the thesis. DECLARATION I certify that this thesis does not, to the best of my knowledge and belief, incorporate without acknowledgement any material previously submitted for a degree or diploma in any institution of higher education; contain any material previously published or written by another person except where due reference is made in the text; or contain any defamatory material. J Signature: Date: ;A ;)._I {I I ?-- 00 L I I I I ABSTRACT Three distinct seagrass habitats were sampled to determine whether fish assemblages differed between meadows comprising of different seagrass species with different morphological characteristics and whether plant morphology influences species assemblages. Three scagrass habitats consisting of Posidonia sinuosa, Posidonia coriacea and meadows of a mixture of P. coriacea and Heterozostera tasmanica in the Success Bank region, off the coast of Fremantle, Western Australia were selected. For each habitat, sampling was carried out using a lm wide beam trawl over a distance of 50m at six replicated locations, on three occasions between June and September 2002. Seagrass samples were collected at each location. On each sampling, occasion a 0.025m2 quadrat was used to collect data on leaf area index (LAI), seagrass density and biomass, leaf width and length, and epiphytic algal biomass. MDS ordinations and ANOSIM showed that P. sinuosa habitats contain a significantly different composition of fish species to P. coriacea habitats (with or without H. tasmanica). Species composition was similar in P. coriacea on its own or mixed with H. tasmanica. SIMPER showed that the; differences between P. sinuosa and the P. coriacea habitats reflected the gr~ater abundances of Stigmatopora argus, Siphonognathus radiatus and Scobinichthys granulatus, whereas Stigmatopora nigra was restricted to the P. coriacea habitats only. ANOVA demonstrated that total densities and biomass of fish and species richness were greatest in P. simwsa, while little difference occurred for those variables between the twn P. coriacea habitats. ANOVA indicated that densities of S. argus and Siphamia cephalotes did not differ between habitats, while densities of S. radiatus and S. nigra differed between P. sinuosa and the P. coriacea habitats. Densities of S. granulatus differed only between P. simwsa and P. coriat:ea with H. tasmanica. Seagrass leaf density, leaf area index (LAI), leaf width, dty seagr(lsS biomass and dry epiphytic biomass differed significantly among the three habitats, where as leaf length did not differ between these habitats. Regression analysis indicated that leaf II area index influenced species richn~ss, fish abundance and biomass, while leaf width influenced the abundance of S. argus and S. radiatus, and leaf density influenced the abundances of S. nigra and S. granulatus. BIOENV revealed that leaf width, leaf density and LAI influenced the fish composition in the seagrass meadows. Specific plant features appear to influence the fish assemblages associated with these habitats. Plant morphology also separated size-Classes of an abundant seagrass species supporting the "nursery habitat" theory. Artificial seagrass and live animals were used in laboratory experiments to evaluate habitat preference of the most abundant seagrass-associated fish species in the absence of predators and food, and to determine whether juvenile and/or adult-sized fish exhibit a preference for a particular seagrass morphology, corresponding to those of P. sinuosa, P. coriacea and H. tasmanica. Habitat preference experiments were conducted separately for each size class in three experimental aquaria containing artificial seagrass to simulate three different scagrass habitats. Each aquarium contained two different s:eagrass habitats and ten fish of the same size class. Habitat preference observations were made at hourly intervals over a 10-hour period. Three replicates were conducted for each experiment. The laboratory experiments showed that both juvenile and adult-sized S. argus had a strong preference towards the narrow leaves of P. coriacea and particularly H. tasmanica. However, the preference was morz: pronounced for the juvenile fish. Thus, seagrass morphology, specifically leaf width, appears to play a significant role in the habitat selection of S. argus. However, the ability to avoid predation is equally dependant on their body shape, size and ability to mimic their surroundings. The findings described i.n this study have shown that plant morphology appears to play a significant role in influencing fish faunal assemblages associated with seagrass meadows. The results of this study have clear implications for the environmental management of coastal marine ecosystems, highlighting the need to conserve seagrass meadows of different plant morphology to maintain the biodiversity of the fish assemblages in those regions. Ill ACKNOWLEDGMENTS Although my name is on the cover of this thesis, it's contents would not have been possible without the generous help and support from a number of people. Firstly, I would like to thank my supervisor, Dr Glenn Hyndes, for his vast expert knowledge, supervision, guidance and stress management throughout the project. To my vast anny of volunteers: Catherine Collier, K<lren Crawley, Daniclla Hanf, Rebekah Kenna, Jason How, Alan Kendrick, Brad Stirling and Peter Quintana, tOr their help with field sampling. Without you guys, the project would not have hewn possible. Thanks to my fellow Honours students: Olivier Oldfield, Ruth Rogan, Kirsty Suffel, Simone Vellekoop and all the staff and students at the School ofNatural Sciences for all their advice and comments throughout the project. And last, but definitely not least, thanks to my parents, David and Lyn and brother, Aaron for their support and encouragement throughout the year. Everybody's time, effort and patience were very much appreciated. Cheers. IV TABLE OF CONTENTS DECLARATION ..................................................................................... 1 ABSTRACT ............................................................................................ 11 ACKNOWLEDGMENTS .................................................................... IV TABLE OF CONTENTS ....................................................................... V LIST OF FIGURES ........................................................................... VIII LIST OF TABLES ............................................................................. XIII LIST OF T'ABLES ............................................................................. XIII LIST OF PLATES ............................................................................ XVII LIST OF PLATES ............................................................................ XVII CHAPTER 1: INTRODUCTION .......................................................... 1 1.1 THE INFLUENCE OF HABITAT PREFERENCE ON FAUNAL DISTRIBUTION ..................................................................................... ! 1.2 SEAGRASS MEADOWS PRODUCE COMPLEX ECOSYSTEMS.2 1.3 THE FAUNAL ASSEMBLAGES OF SEAGRASS MEADOWS ....... 2 1.4 THE INFLUENCE OF SEAGRASS COMPLEXITY ON FISH ASSEMBLA.GES ..................................................................................... J 1.5 WESTERN AUSTRALIA'S SEAGRASS MEADOWS ...................... S 1.6 AIMS AND OBJECTIVES OF PROJECT .........................................