University of Cape Town

Town The copyright of this thesis rests with the University of Cape Town. No quotation from it or information derivedCape from it is to be published without full acknowledgement of theof source. The thesis is to be used for private study or non-commercial research purposes only. University SOME FACTORS INFLUENCING THE TRANSPORT OF CHOKKA SQUID (LOLIGO REYNAUDII D’ORBIGNY, 1839) PARALARVAE OFF THE EASTERN CAPE, SOUTH AFRICA RODRIGO SILVESTRE MARTINS Town Cape of Submitted in fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the Faculty of Science, Department of Zoology UniversityUNIVERSITY OF CAPE TOWN November 2009 Supervisors: DR MICHAEL J. ROBERTS, Marine and Coastal Management, DEAT DR ÉRICA A. G. VIDAL, Universidade Federal do Paraná, Brazil DR COLEEN L. MOLONEY, Zoology Departments and Marine Research Institute, UCT This thesis is dedicated to my mother, Maria Silvestre Martins, my father, Francisco Martins Filho (in loving memory), my brother, Daniel SilvestreTown Martins, my sister Gabriela Silvestre Martins and my nephews Lucas and Luísa, whose infinite love and support have been essential for my growth in my career and character. Cape of University i “SQUID ARE CONSPICUOUS1” Town Loligo reynaudii d’Orbigny, 1839 paralarva (~ natural size). Cape of University 1Roberts, M. J., Rodhouse, P., O’Dor, R. K. and Sakurai, Y. 1998. A global perspective of environmental research on squid. ICES CM 1998/M: 27, 20p. ii Table of Contents Declaration....................................................................................................................6 Declaration....................................................................................................................6 Acknowledgments ........................................................................................................7 Abstract.........................................................................................................................7 Chapter 1 — Introduction and aims ..........................................................................1 1.1. The reproductive habitat of chokka squid......................................................1 1.2. Characteristics of early loliginid paralarvae..................................................4 1.3 The Westward Transport Hypothesis..............................................................6 1.4. Aims and hypotheses.........................................................................................6 1.5. Structure of the thesis.......................................................................................8 Chapter 2 — Design and manufacture of a temperature-controlled, open, rearing system for chokka squid (Loligo reynaudii d’Orbigny, 1839) paralarvae ............10 Abstract.......................................................................................................................10 2.1 Introduction................................................................................................Town ..........10 2.1.1. Tank design system and operation.................................................................12 2.1.2. Temperature-control system ..........................................................................14 Heat exchanger ....................................................................................................14 PLC control and temperature control software...................................................14 2.1.3. Water quality, current velocity and illuminationCape................................ ...........15 Monitoring ...........................................................................................................15 Performance and water quality ................................of ................................................16 Water quality............................................................................................................16 Long term stability...................................................................................................17 2.2. Discussion ............................................................................................................17 2.3. Conclusions..........................................................................................................19 2.4 Future work..........................................................................................................20 Chapter 3 — Effects of temperature on yolk utilization in chokka squid (Loligo reynaudii d’Orbigny,University 1839) paralarvae ....................................................................25 Abstract.......................................................................................................................25 3.1. Introduction.........................................................................................................25 3.2 Methods.................................................................................................................27 3.2.2. Egg collection and incubation........................................................................29 3.2.3. Experimental design.......................................................................................29 3.2.4. Mantle length, wet- and dry- body weights, yolk weights and survival........30 3.2.5. Yolk utilization and growth rates...................................................................31 3.2.6. Energetics.......................................................................................................32 3.3 Results ...................................................................................................................32 3.3.1. Water quality..................................................................................................32 3.3.2. Comparison of ML, WW, DW and YW between temperatures....................33 3.3.3. Predicted and estimated survival times of paralarvae....................................34 3.3.4. Comparing results ..........................................................................................34 3.4. Discussion ............................................................................................................35 iii 3.4.1. Yolk utilization and dispersal ........................................................................35 3.4.2. Predicted vs. experimental survival rates.......................................................36 3.4.3. Yolk consumption on the mid-shelf vs. inshore spawning grounds ..............36 3.4.4. Implications for the WTH and recruitment....................................................37 Chapter 4 — Effects of yolk utilization on the specific gravity of chokka squid (Loligo reynaudii d’Orbigny, 1839) paralarvae: implications for dispersal and vertical distribution ...................................................................................................47 Abstract........................................................................................................................47 4.1 Introduction.....................................................................................................47 4.2. Material and Methods ........................................................................................50 4.2.1. Egg collection, incubation, rearing procedures and experimental design .....50 4.2.2. Measurement of settling rates and seawater specific gravity.........................51 4.2.3. Body measurements, yolk weights, moisture content, survival, yolk utilization and growth rates......................................................................................51 4.2.4. Paralarval specific gravity estimation............................................................52 4.2.5. Effect of paralarval specific gravity on dispersal ..........................................54 4.2.6. Effect of paralarval specific gravity on vertical distribution .........................57 4.3. Results ..................................................................................................................57 4.4. Discussion ........................................................................................................59 Town Chapter 5 — Modelling transport of chokka squid (Loligo reynaudii d’Orbigny, 1839) paralarvae off South Africa: reviewing, testing and extending the ‘Westward Transport Hypothesis’...........................................................................76 Abstract.......................................................................................................................76 5.1. Introduction................................................................Cape................................ .........76 5.2. Material and Methods ........................................................................................78 5.2.1. Hydrodynamic model................................of .....................................................78 5.2.2. Individual-based model..................................................................................79 5.2.3. Transport scenarios ........................................................................................80 5.2.4. Assumptions...................................................................................................81 5.2.5. Modelled transport success and retention......................................................81 5.3. Results ..................................................................................................................82 5.3.1.

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