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When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given e.g. AUTHOR (year of submission) "Full thesis title", University of Southampton, name of the University School or Department, PhD Thesis, pagination http://eprints.soton.ac.uk University of Southampton Faculty of Engineering, Science and Mathematics National Oceanography Centre, Southampton School of Ocean and Earth Sciences The Response of a Protandrous Species to Exploitation, and the Implications for Management: a Case Study with Patellid Limpets. William J F Le Quesne Thesis for the degree of Doctor of Philosophy July 2005 Graduate School of the National Oceanography Centre, Southampton This PhD dissertation by William J F Le Quesne has been produced under the supervision of the following persons: Supervisors: Prof. John G. Shepherd Prof Stephen Hawkins Chair of Advisory Panel: Dr Lawrence E. Hawkins Member of Advisory Panel: Dr John A. Williams University of Southampton ABSTRACT Faculty of Engineering, Science and Mathematics School of Ocean and Earth Science National Oceanography Centre, Southampton Doctor of Philosophy The response of a protandrous species to exploitation, and the implications for management: a case study with patellid limpets by William J F Le Quesne July 2005 A zygote production model for the patellid limpet Patella vulgata has been developed to examine the e®ect of exploitation on the reproductive output of a protandrous (male to female sequential) hermaphrodite. Patellid limpets are broadcast spawners which can have speci¯c implications for the e®ect of exploitation on reproductive output, due to sperm limitation. The combined zygote production model was made of three component sub-models; a population fecundity model, a gamete dispersal model, and a fertilisation model. The model makes explicit account of sperm limitation, and is based upon data collected through ¯eld and laboratory investigations conducted as part of this thesis. The model was used to examine the relationship between egg and zygote production, and spawning stock biomass (SSB) and ¯shery yield for a range of P. vulgata populations across a wave exposure gradient. The e®ect of di®erent management strategies, minimum landing size or marine protected areas, on the relationship between reproductive output and yield was also examined. Protandry lead to a decoupling between SSB and zygote production as the populations were ex- posed to the simulated ¯shery. There was a ¯ve-fold variation in zygote production per unit area across a wave exposure gradient. Comparison of di®erent management strategies indicates that the ¯shery yield could vary by up to three-fold depending on the management strategy used, whilst still protecting the same level of population reproductive output. The genetic population structure of the Azorean Patella candei population was also examined to determine the scale of larval dispersal to allow the management recommendations of the zygote production model to be examined in a wider ecological context. Due to evidence of a recent population bottleneck in the Azorean P. candei population no ¯rm conclusions could be drawn from this study as to the scale of larval dispersal. Declaration of Authorship I, William Le Quesne, declare that the thesis entitled `The e®ect of protandry on the e®ect of exploitation: a case study with patellid limpets' and the work presented in it are my own. I con¯rm that: ² this work was done wholly or mainly while in candidature for a research degree at this University; ² where I have consulted the published work of others, this is always clearly attributed; ² where I have quoted from the work of others, the source is always given. With the exception of such quotations, this thesis is entirely my own work; ² I have acknowledged all main sources of help; ² where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself. Signed: ............................................................................... Date: .................................................................................. Acknowledgements I am gratefully indebted to my supervisors, Steve Hawkins, who has enlightened my understanding of the nature of ecological processes and relationships, and John Shepherd, who has shown me how these processes and relationships can be repre- sented mathematically. I am also grateful to many co-workers in Plymouth and the Azores who have as- sisted with ¯eld and laboratory work, especially Jo Preston, Trevor Worsley, Joao Goncalves, Alan Hodgson, Norberto Serpa and HIM; without their assistance this work would not have been possible. The molecular genetic part of this work was done in conjunction with the EUMAR project and the Marine Biological Associa- tion, Plymouth. This work was inspired by my family in countless ways, and I am hugely thankful to my wife and daughter for their continual support and encouragement. Contents List of ¯gures vi List of tables vii 1 Introduction 1 1.1 Fisheries Management and Population Biology of Exploited Species . 3 1.2 Protandry, Sex Allocation and Population Biology . 5 1.2.1 Sequential hermaphroditism and ¯shery exploitation . 6 1.3 Protandry and Population Fecundity . 10 1.3.1 Fecundity-length relationships . 10 1.3.2 Population structure . 12 1.4 Fertilisation Kinetics . 15 1.5 Egg Production, Sperm Limitation and Larval Production . 16 1.6 The Spatial Scale of Populations . 19 1.6.1 Stock identi¯cation and ¯sheries management . 20 1.6.2 Larval dispersal and marine protected areas (MPAs) . 23 1.7 Patellid Limpet Biology, Ecology, and Fisheries . 26 1.8 Aims and Objectives . 28 2 Direct observation of protandry in Patella vulgata 31 2.1 Introduction . 31 2.2 Method . 33 2.3 Results and Discussion . 35 3 Spawning and Gamete Dispersal 37 3.1 Introduction . 37 i 3.2 Methods . 40 3.3 Results . 41 3.4 Discussion . 42 3.5 Surf Zone and Very Nearshore Oceanography: Modelling Gamete Dis- persal . 44 3.5.1 Surf zone hydrodynamics . 44 3.5.2 Modelling gamete dispersal . 49 4 Fertilisation Kinetics 54 4.1 Introduction . 54 4.1.1 Aims . 56 4.2 Materials and Methods . 56 4.2.1 Preparation of sperm stock suspensions . 57 4.2.2 Preparation of egg stock suspensions . 57 4.2.3 Experiment 1: sperm concentration . 57 4.2.4 Experiment 2: gamete contact time . 58 4.2.5 Experiment 3: sperm age . 59 4.2.6 Experiment 4: egg age . 59 4.3 Results . 60 4.3.1 Sperm concentration . 60 4.3.2 Gamete contact time . 61 4.3.3 Gamete age . 62 4.4 Fitting the VCCW Model . 64 4.5 Discussion . 66 4.5.1 Sperm concentration . 67 4.5.2 Gamete contact time . 67 4.5.3 Gamete age . 68 4.5.4 Applying the modi¯ed VCCW model . 69 5 Protandry, Population Fecundity and Spawning Stock Biomass 72 5.1 Introduction . 72 5.1.1 Limpet size-fecundity relationships . 72 5.1.2 Aims . 73 5.2 Methods . 74 ii 5.2.1 Population structure . 74 5.2.2 Fecundity . 75 5.3 Results . 79 5.4 Discussion . 92 5.4.1 What is the e®ect of protandry on the relationship between gametic output, SSB and yield? . 92 5.4.2 Is SSB a good proxy for population egg production for protan- drous hermaphrodites? . 96 5.4.3 Are yield and fecundity best managed by MPAs or MLS? . 97 5.4.4 What is the e®ect of wave exposure and how should habitat variability be accounted for in management decisions? . 99 6 Larval Production Modelling 103 6.1 Introduction . 103 6.1.1 Aims . 104 6.2 Zygote Production Model . 105 6.3 Model Runs . 108 6.3.1 Sensitivity analysis . 108 6.3.2 Simulation runs . 111 6.4 Model Predictions . 111 6.5 Discussion . 117 6.5.1 Is sperm limiting to zygote production? . 117 6.5.2 Does sperm limitation a®ect the relationship between zygote production, SSB and ¯shery yield? . 122 6.5.3 Are SSB and egg production good proxies for population zy- gote production? . 123 6.5.4 In order to conserve zygote production whilst maximising yield, is the population best managed by MLS or MPAs? . 126 7 Population Genetic Di®erentiation of P. candei in the Azores Archipelago: Management Implications for Stock Identi¯cation and Marine Re- serve Placement 128 7.1 Introduction . 128 7.1.1 Aims and Approach . 131 iii 7.2 Methods . 132 7.2.1 Sample collection . 132 7.2.2 Sample analysis . 133 7.2.3 Data analysis . 134 7.3 Results . 137 7.3.1 Haplotype diversity . 137 7.3.2 Diversity and population structure . 137 7.4 Discussion . 151 7.4.1 Population structure . 151 7.4.2 Population history . 155 8 General Discussion and Conclusions 158 8.1 The E®ect of Protandry on the Relationship Between Egg and Zygote Production, and SSB and Yield. 159 8.2 Does Sperm Limitation Matter? . 161 8.3 Management Implications of the Zygote Production Model, and the Importance of MPAs. 163 8.4 Limitations and Further Work . 166 8.5 Concluding Remarks . 168 Appendices . on supplementary cd iv List of Figures 2.1 Sex ratio of P. vulgata from Lynmouth beach . 34 2.2 P.