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144 Oceanography vs. behaviour Figure 6.12 Development of critical speed throughout the larval period and effect of temperature. Speed is zero before hatching. When larvae hatch (around 2.5 days here), the development of maximum U crit is deduced from Fisher 57 (solid curve). The effect of a 2ºC increase in water temperature on the pelagic larval duration is computed from O’Connor et al. 37 and ontogeny of swimming speed is re-calculated. In warmer temperatures, the pelagic stage is shorter and swimming abilities develop faster (dashed curve). Exponential decrease of PLD when temperature increases Faster development of swimming abilities after a 2ºC increase etc.). They attributed the wide applicability of this relationship to the universal effect of temperature on metabolism. In all taxa, PLD decreases exponentially with temperature ln(P LD) = β 0 + β 1 ln(T/T c) + β 2(ln(T/T c)) 2 (6.10) where β 0 is a species-specific constant, β 1 and β 2 are constants valid for all species: β 1 = -1.368 and β 2 = -0.283, and T c = 15ºC (Figure 6.13). Dividing by T c is equivalent to subtracting ln(T c) to each observation on a log scale and is a form of centring, to improve the fit. For any species, β 0 can be calculated by substituting the species’ PLD and the water temperature in the environment where PLD was measured in equation (6.10). Once the relationship is calibrated, it allows to predict the variations of PLD in response to changes in temperature. In our model, the effect of a 2ºC increase in water temperature is simulated. 2ºC corresponds to the estimated mean variation expected in most climate change scenarios over the next century (A. Clement and C. Paris, pers. comm.). A 3ºC difference in rearing temperature was found to decrease critical swimming speed of 7 days old Amphiprion melanopus larvae from 17 cm s -1 to 12 cm s -1 , because larvae reared at the lower temperature were smaller and less advanced in ontogeny 262 . However, the same 3ºC difference in the temperature of the water in
Oriented swimming and passive advection 145 Larval Duration (Days) 150 100 50 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! !! 0 0 5 10 15 20 25 30 35 A Larval Duration (Days) 150 100 50 0 0 5 10 15 20 25 30 35 B Temperature (°C) Temperature (°C) Figure 6.13 Decrease of larval duration with increasing temperature; observations for 72 species (A, left) and model (B, right). Thick lines with diamonds in plot A are species identified as outliers in the subsequent analysis. Light lines in plot B are the models for individual species. The dark solid line is the grand mean model with 95% confidence interval (dotted lines). Reproduced with permission from O’Connor et al. 37 . which larvae were set to swim had no significant influence on their critical speed. So, within a few degrees, the only noticeable effect of temperature on swimming is through muscle development and growth. Therefore, in the model, the only effect of temperature is on PLD. For a tropical fish with PLD = 25 d, the relationship predicts a decrease of 3 d. The PLD of a temperate fish decreases more, because of the convexity of the curve, from 27 d to 21.7 d. From the reduced PLD, the development of swimming speed is re-computed with equation (6.9) and, as a consequence, at any given age, U crit of larvae developing in warmer waters is higher than U crit of larvae developing at present-day rate (Figure 6.12). Different view of the energy budget In addition to setting maximum speeds, the time larvae can sustain such speeds also needs to be bounded for swimming strategies to be biologically sensible (section 6.2.1, page 119). Measures of swimming endurance involve setting larvae to swim in flumes of constant speed and timing how long they are able to maintain their position against the current 236 . As noticed before, this technique measures the maximum potential of larvae because it disregards any concern about maintaining growth. Such studies reveal that, even unfed, coral reef 236 and temperate rocky shore 268 fish larvae can swim continuously for several days and cover tenths of kilometres. In the same setting, when larvae are fed, their swimming endurance increases to the point that the experiment must sometimes be stopped before the fish is exhausted 269 . In such cases, the oldest individuals even grow at a rate comparable to control, non-swimming, larvae 270 . Similarly to swimming speed, in this new Extraordinary swimming endurance
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À mon étoile.
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vi Résumé La plupart des organism
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viii Abstract Most demersal marine
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x Table des matières 1.3.3 Simple
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xii Table des matières 6.2.3 Examp
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xiv Liste des figures 4.6 Distribut
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Liste des tableaux 1.1 Potential or
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2 Introduction La survie des larves
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4 Introduction Limitation par le re
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6 Introduction Les courants déterm
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8 Introduction où m est le taux de
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10 Introduction biologique simple.
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12 Introduction Le milieu lui-même
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14 Introduction Figure I.6 Schémat
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16 Introduction obstacles technique
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18 Introduction Figure I.8 Prédict
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20 Introduction I.5 La biologie des
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22 Introduction du fonctionnement d
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24 Introduction L’objectif de cet
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26 Behaviour in models 1.1 Introduc
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28 Behaviour in models Using mean p
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30 Behaviour in models 1.3 Vertical
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32 Behaviour in models . . . bring
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34 Behaviour in models of measured
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36 Behaviour in models Additive dis
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38 Behaviour in models In situ stud
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40 Behaviour in models Operational
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42 Behaviour in models Effects on p
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44 Behaviour in models begins is no
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46 Behaviour in models 1.10 Conclus
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48 Larvae orientation in situ Diver
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50 Larvae orientation in situ . . .
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52 Larvae orientation in situ optio
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54 Larvae orientation in situ if >
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56 Larvae orientation in situ Table
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58 Larvae orientation in situ that
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60 Larvae orientation in situ 2.A A
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62 Behaviour of settling fishes at
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Chapter 4 Biophysical correlates in
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Methods 71 4.2 Methods 4.2.1 Sampli
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Methods 73 Three rotations were com
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Methods 75 test really focuses on w
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Results 77 Figure 4.3 Mean of insta
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Results 79 Figure 4.5 Perspective v
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Results 81 Table 4.1 Abundances of
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Results 83 Figure 4.8 Distribution
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Results 85 Figure 4.10 Concentratio
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Discussion 87 Figure 4.11 Compariso
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Discussion 89 But the most likely e
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Acknowledgements 91 This evidence a
Page 111 and 112: Chapter 5 Ontogenetic vertical “m
Page 113 and 114: The statistical analysis of vertica
Page 119 and 120: Methods 101 80, 55, 30 m (Figure 4.
Page 121 and 122: Methods 103 same station were likel
Page 123 and 124: Results 105 Figure 5.2 Univariate r
Page 125 and 126: Results 107 5.4.3 Ontogenetic shift
Page 127 and 128: Results 109 Figure 5.5 Violin plot
Page 129 and 130: Discussion 111 5.5 Discussion 5.5.1
Page 131 and 132: Discussion 113 expression of differ
Page 133 and 134: Chapter 6 Oceanography vs. behaviou
Page 135 and 136: Introduction 117 a good description
Page 137 and 138: A general modelling framework for l
Page 145 and 146: The balance between feeding and pre
Page 155 and 156: Oriented swimming and passive advec
Page 161: Oriented swimming and passive advec
Page 179 and 180: General discussion 161 such integra
Page 181 and 182: General discussion 163 6.5.2 Why se
Page 183 and 184: General discussion 165 such as the
Page 185 and 186: General discussion 167 energeticall
Page 187: Acknowledgements 169 Therefore: •
Page 190 and 191: 172 Conclusion Un environnement pé
Page 192 and 193: 174 Conclusion global sur la connec
Page 194 and 195: 176 Conclusion l’intérêt est po
Page 196 and 197: 178 Conclusion La différence entre
Page 198 and 199: 180 Conclusion Mieux décrire la di
Page 200 and 201: 182 Conclusion Comme tout comportem
Page 202 and 203: 184 Undescribed Chaetodonthidae Fig
Page 204 and 205: 186 Undescribed Chaetodonthidae Fig
Page 206 and 207: 188 Bibliographie [12] Cushing DH.
Page 208 and 209: 190 Bibliographie [39] Johnson MW.
Page 210 and 211: 192 Bibliographie [71] Paris CB, Co
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194 Bibliographie [99] Lara MR. Mor
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196 Bibliographie [127] Masuda R, S
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198 Bibliographie [157] Holbrook SJ
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200 Bibliographie [187] Bowen B, Ba
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202 Bibliographie [218] Oxenford HA
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204 Bibliographie [246] Wellington
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206 Bibliographie [276] Sargent RC,
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208 Bibliographie [308] Greenberg D
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210 Remerciements solides pour ces
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212 Remerciements tri des larves de
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214 Remerciements Évidemment, tout
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