Universiteit Gent Faculteit der Wetenschappen Vakgroep Morfologie, Systematiek en Ecologie Academiejaar 1992-1993 Instituut voor Dierkunde Sektie Mariene Biologie The ecology of Pomatoschistus Pallas and Pomatoschistus de Buen (Pisces, Gobiidae) in the shallow coastal waters and estuaries of the Southern Bight of the North Sea nr ï by Olivier Hamerlynck Promotor: Prof. Dr. C. Heip Verhandeling voorgelegd tot het behalen van de graad van Doctor in de Wetenschappen Groep Dierkunde for Iß ID and »3» who created me for 'p p ’ who is the present for p i l» who holds the future Leaders destroy the follower and the followers destroy the leader. Why should you have fate in anyone? Jiddu Krishnamurti fgffl UNIVERSITEITSBIBLIOTHEEK GENT f lllllllllllllllllllllllllllll 000000300915 I Universiteit Gent Faculteit der Wetenschappen Vakgroep Morfologie, Systematiek en Ecologie Academiejaar 1992-1993 Instituut voor Dierkunde Sektie Mariene Biologie The ecology of Pomatoschistus minutus Pallas and Pomatoschistus lozanoi de Buen (Pisces, Gobiidae) in the shallow coastal waters and estuaries of the Southern Bight of the North Sea Y Y by Olivier Hamerlynck Promotor: Prof. Dr. C. Heip Verhandeling voorgelegd tot het behalen van de graad van Doctor in de Wetenschappen Groep Dierkunde for IO 10 and »3» who created me for ] Op who is the present for ] Oil» who holds the future Leaders destroy the follower and the followers destroy the leader. Why should you have fate in anyone? Jiddu Krishnamurti TABLE OF CONTENTS SUMMARY ..........................................................................................................1 SAMENVATTING...............................................................................................5 CHAPTER 1. The success of the Gobiidae: a short review of the recent literature .............................................................9 Introduction ............................................................................................................ 9 Global status of the G obiidae .............................................................................. 9 General biological features .................................................................................. 10 Abundance ...........................................................................................................12 Trophic role ........................................................................................................13 Gobiidae in various types of research ............................................................... 15 References ...........................................................................................................16 CHAPTER 2. The mobile epibenthic fauna of soft bottoms in the Dutch Delta (south-west Netherlands): Spatial structure ..................... 29 A bstract................................................................................................................29 Introduction .......................................................................................................... 30 Materials and m ethods ....................................................................................... 31 Study a re a ........................................................................................................31 Sampling .......................................................................................................... 32 Environmental variables ............................................................................... 33 Multivariate analysis of community structure ...............................................35 Terminology .................................................................................................. 36 Results...................................................................................................................36 Species composition ....................................................................................... 36 Spatial structure .............................................................................................38 Classification .............................................................................................39 Characterisation of the species assemblages ..........................................39 Relation to environmental variables ...........................................................43 Diversity .....................................................................................................47 Discussion .......................................................................................................... 48 Conclusions .......................................................................................................... 51 Acknowledgements .............................................................................................52 CHAPTER 3. The identification of Pomatoschistus minutus (Pallas) and Pomatoschistus lozanoi (de Buen) (Pisces, Gobiidae) ............................53 A bstract................................................................................................................53 Introduction .......................................................................................................... 53 Material and methods .......................................................................................... 54 Results and discussion ....................................................................................... 54 Pomatoschistus minutus..................................................................................55 Pomatoschistus lozanoi..................... 56 Summary .............................................................................................................58 Acknowledgements .............................................................................................59 CHAPTER 4. The parasites of two sympatric gobies Pomatoschistus minutus and Pomatoschistus lozanoi in the Belgian coastal waters ......................... 61 A bstract................................................................................................................61 Introduction .......................................................................................................... 61 Materials and m ethods ....................................................................................... 62 Results.................................................................................................................. 62 Discussion .......................................................................................................... 64 Conclusions .......................................................................................................... 66 Acknowledgements .............................................................................................66 CHAPTER 5. The trophic position of Pomatoschistus lozanoi (Pisces, Gobiidae) in the Southern B ig h t .......................................................67 A bstract............................................................................................................... 67 Introduction ..........................................................................................................67 Materials and m ethods ....................................................................................... 68 Results.................................................................................................................. 69 Discussion ..........................................................................................................73 Acknowledgements .............................................................................................75 CHAPTER 6. Daily ration of juvenile Pomatoschistus lozanoi de Buen (Pisces: Gobiidae). Influence of circadian, circatidal and semilunar rhythms................................................................................................................. 77 A bstract............................................................................................................... 77 Introduction .......................................................................................................... 77 Materials and m ethods ....................................................................................... 79 Study a re a ....................................................................................................... 79 Sampling .......................................................................................................... 80 Calculation of daily ra tio n .............................................................................82 Results.................................................................................................................. 84 Discussion .......................................................................................................... 87 Conclusions ..........................................................................................................91 Acknowledgements .............................................................................................92 CHAPTER 7. Mesacanthion diplechma (Nematoda: Thoracostomopsidae), a link to higher trophic levels? ....................................................................... 93 A bstract................................................................................................................93 Introduction ..........................................................................................................93