The egg quality of two common dentex captive broodstocks were monitored for two consecutive years during their natural spawning season. Volume of spawned eggs, volume of buoyant eggs, fertilization rate, egg weight, hatching rate and mortality of larvae were recorded.

According to the volume of spawned eggs, the ratio of buoyant eggs spawned, the number of spawning days and the fertilization rate pointed to an improvement from Year 1 to Year 2. But data on hatching rate and larval mortality lead to the opposite conclusion.info:eu-repo/semantics/acceptedVersio

Estévez, A.

Giménez Papiol, G.

Aquaculture

English

IRTA Pubpro

                       This  document  is  a  postprint  version  of  an  article  published in Aquaculture ©  Elsevier after peer review. To access the final edited and published work seehttps://doi.org/10.1016/j.aquaculture.2018.11.015  Document downloaded from:         Egg quality variability in common dentex (Dentex dentex, L.): comparison of different quality 1 indexes 2 Giménez Papiol, G.*; Estévez, A. 3 IRTA Centre of Sant Carles de la Ràpita, Tarragona, Spain 4  5 Correspondence 6 Gemma Giménez Papiol, International Marine Centre IMC, Loc. Sa Mardini 09170, Torregrande 7 (OR) Italy. 8 Email: g.gimenez@fondazioneimc.it  9   10 Abstract 11 The egg quality of two common dentex captive broodstocks were monitored for two consecutive 12 years during their natural spawning season. Volume of spawned eggs, volume of buoyant eggs, 13 fertilization rate, egg weight, hatching rate and mortality of larvae were recorded. 14 According to the volume of spawned eggs, the ratio of buoyant eggs spawned, the number of 15 spawning days and the fertilization rate pointed to an improvement from Year 1 to Year 2. But data 16 on hatching rate and larval mortality lead to the opposite conclusion. 17  18 Keywords 19 Common dentex, Dentex dentex, egg quality, spawning quality  20 Introduction 21 Common dentex (Dentex dentex L.) was one of the species identified as suitable for Mediterranean 22 aquaculture diversification, mainly after a market crisis occurred in the early 2000’s (Abellán & 23 Basurco 1996, Basurco & Lovatelli 2003). 24 Common dentex is a Sparidae finfish, gonochoristic, with a bisexual period during its juvenile stage. 25 It reaches sexual maturity and sexual differentiation at 1 year old (Jug-Dujakovic, Dulcic & Katavic 26 1995; Pavlidis, Loir, Fostier, Mölsa & Scott 2000). In wild populations, the sex ratio is 1:1 (Ramos 27 & Bayle, 1991; Morales-Nin & Moranta, 1997) and, during Spring, its natural reproductive season 28 (Glamuzina, Jug-Dujakovic & Katavic 1989), pelagic eggs are spawned daily at nightfall or at dawn 29 (Abellán, 2000). In captive populations, hormones have been successfully used for the maturation of 30 gonads (Greenwood, Scott, Vermeirssen, Mylonas & Pavlidis 2001), but the most used and successful 31 method is the photothermal induction (Abellán, 2000; Rueda & Martínez, 2001); i.e. a gradual 32 increase of daylength and temperature, mimicking the shift from Winter to Spring in the wild. 33 Broodstocks are kept in groups of various females and males, which makes difficult to control and 34 assess their reproductive performance because the proportion and timing of spawning females are 35 highly unpredictable (Pavlidis, Loir, Fostier, Mölsa & Scott 2000; Grau, Morales-Nin, Quetglas, 36 Riera, Massuti & Pastor 2001; Loir, Le Glac, Somarakis & Pavlidis 2001), leading to high variability 37 in the number and quality of spawns among farms and stocks (Bodington, 2000).  38 The three basic quality criteria used for finfish species with pelagic eggs are buoyancy of the eggs, 39 fertilization rate, and hatching rate. Good quality eggs are buoyant, while unfertilized and / or 40 damaged eggs sink (Moretti, Pedini, Cittolin & Guidastri 1999). Fertilization rate identifies the 41 amount of fertilized eggs from the total buoyant eggs, which include highly hydrated, non-fertilized 42 mature oocytes (Fabra, Raldúa, Power, Deen & Cerdá 2005). Finally, it requires 24-48h to determine 43 the hatching rate in common dentex, depending on the incubation temperature; this criterion identifies 44 the amount of fertilized eggs that can complete the embryonic development and hatch successfully 45 (Manning & Crim, 1998; Nissling, Larsson, Vallin & Frohlund 1998; Nocilado et al., 2000; 46 Morehead, Hart, Dunstan, Brown & Pankhurst 2001; Salze, Tocher, Roy & Robertson 2005). These 47 criteria do not provide information on the quality of the yolk reserves, which determines the fitness 48 and eventual survival of common dentex larvae in the early stages (first feeding period). Some authors 49 have suggested the use of additional data on larval performance for the assessment of spawning 50 quality in finfish species (Carrillo, Zanuy, Oyen, Cerdá, Navas & Ramos 2000). 51 In the present work, the spawning quality of two common dentex captive broodstocks, photothermally 52 induced, has been monitored for two consecutive years during their natural spawning season. Criteria 53 based on buoyancy, fertilization rate, hatching rate and larval performance have been compared. 54 Materials and methods 55 Common dentex juveniles were fished in the Western Mediterranean Sea and acclimated to captivity. 56 They were kept at natural temperature and photoperiod until sexual maturation, 4 years after the 57 capture. Afterwards, they were kept at natural temperature and photoperiod, and fed with a 58 commercial feed for gilthead sea bream (Skretting, Norway). One month before their natural 59 spawning season, which is usually between March and June, 9 females and 13 males of D. dentex 60 were identified, separated into two groups with a ratio 1:1.4 (Giménez, Estévez, Lahnsteiner, Zecevic, 61 Bell, Henderson, Piñera & Sánchez-Prado 2006) and reared in 4000 L circular tanks connected to a 62 recirculation unit with controlled temperature and photoperiod (Carbó, Estévez & Furones 2002). 63 Females in broodstock 1 had an average weigh of 1449g, males had an average weigh of 1146g. 64 Females in broodstock 2 had an average weigh of 1561g, males had an average weigh of 1482g. 65 Once reared in the 4000 L circular tanks, feed regimes changed and photothermal induction started. 66 On year 1 they were fed ad libitum with a semi-moist pellet with the following composition: fresh 67 minced fish (Boops boops; 41%), fish meal (Skretting, Spain; 41%), fish oil concentrate (TG0525, 68 Croda, UK; 15%), and vitamin premix (Skretting, Spain; 2%). On year 2 they were fed ad libitum 69 with a commercial dry diet for broodstock (Vitalis Repro©, Skretting, Spain) with the following 70 composition: fish meal (65%), wheat gluten (11%), fish oil (11%), bean meal (8%) and wheat (4%). 71 Photoperiod was increased 0.5 h of light per week from 12hL:12hD (hours of Light : hours of 72 Darkness) to 14hL:10hD. Temperature was increased 1°C per week from 14°C to 18°C. During the 73 spawning season, photoperiod was kept at 14hL:10hD and temperature was left to naturally rise up 74 to 20°C. 75 Eggs were collected every morning from a cylindroconical tank covered with a 500 μm net and 76 immersed in a 100 L holding tank, located under the outflow of each 4000 L tank, and connected to 77 the same recirculation system. The volume of buoyant and non-buoyant eggs was measured with a 78 measuring cylinder. A sample of buoyant and fertilized eggs was plated onto a 96-well cell culture 79 plate (EIA plate), one egg per well containing UV-filtered seawater. Plates were incubated in the 80 darkness in a refrigerated incubator at 19ºC, and monitored daily in order to record the hatching rate 81 and larval survival. Subsamples of at least 50 floating eggs were used to obtain wet weight (WW), 82 dry weight (DW) and water percentage (W%): about 20-30 mg eggs were counted and weighed to 83 the nearest 0.1 mg (wet weight, WW); then they were kept at 100°C for 24h and re-weighed (DW). 84 The estimation of water percentage (W%) was based on WW and DW data. 85 Data for WW, DW, W%, fertilization of buoyant eggs (%), hatching rate (%), larval mortality at 3 86 dph (%) and larval mortality at 5 dph (%) were statistically analysed by a Tukey’s test (P < 0.05) 87 using a StatgraphicsPlus 4.1 program (StatPoint Inc., Virginia, USA), in order to compare the results 88 obtained from each broodstock between the two monitored spawning seasons. 89 Results and Discussion 90 Variability of egg quality within the same spawning season has been already described for common 91 dentex captive broodstocks (Giménez, Estévez, Lahnsteiner, Zecevic, Bell, Henderson, Piñera & 92 Sánchez-Prado 2006). In the present work, variability between broodstocks kept under the same 93 management conditions, and among years, is also evidenced.  94 Both broodstocks spawned for longer, and an overall larger amount of eggs, from year 1 to year 2 95 (Table 1). The ratio of buoyant eggs increased from Year 1 to Year 2 in Broodstock 1, which also 96 spawned eggs with higher WW and DW. Broodstock 2 showed no differences in the ratio of buoyant 97 eggs, and the WW and DW of the spawned eggs decreased from Year 1 to Year 2 (Table 1). In both 98 broodstocks and years, the W% remained around 90 – 91%, and the fertilization rate of buoyant eggs 99 was close to 100% in all the monitored batches. 100 The average hatching rate decreased in both broodstocks (Table 2), as well as the minimum hatching 101 rate obtained by a batch. The number of batches with lower hatching rates, i.e. between 50 and 80% 102 or below 50%, increased from Year 1 to Year 2 in both broodstocks. Regarding larval performance 103 under starvation, as an indirect measure of the quality of the yolk reserves, it was worse from Year 1 104 to Year 2 for both broodstocks. The average mortality at 3 days post-hatch (dph) and at 5 dph 105 increased, the number of batches showing higher mortalities at these ages also increased, and the 106 lowest age of last survival of a batch decreased dramatically (i.e. minimal age of surviving starved 107 larva). 108 Considering these results, the different quality indexes lead to opposite conclusions. Based on the 109 total egg production, ratio of buoyant eggs and number of spawning days, there is an improvement 110 from Year 1 to Year 2 in both broodstocks. But this improvement did not correspond to the hatching 111 rate and the data obtained with larval performance such as mortality at 3 and 5 dph, and age of last 112 surviving larva; in this case, it can be concluded that the spawning quality decreased from Year 1 to 113 Year 2 in both broodstocks. 114 The actual age of each fish is unknown since they were captured from the wild, but all were from the 115 same geographical origin and kept captive for the same time period. Their weight average, the sex 116 ratio in the broodstock, their nutritional background and the management was equal for both 117 broodstocks. The differences between Year 1 and Year 2 could be due to the change in the food 118 regime, the age of the fish, but we hypothesize that the main reason would be the overall confinement. 119 Fish kept captive, despite the improvements in diet formulation, animal wellbeing and management 120 are reared under artificial conditions that can impair their physiological cycles and eventually, in the 121 case of broodstocks, lead to lower quality of spawnings.  122 Conclusions 123 Criteria used for assessing the spawning quality can lead to different conclusions. All criteria should 124 be used in order to obtain a reliable assessment, including criteria based on larval performance.  125 Acknowledgements 126 Funding by the Ministry of Science and Education (INIA fellowship) and the Spanish Ministries of 127 Agriculture Fisheries and Food (Jacumar) and Science and Education (INIA project ACU02-006). 128 Thanks are also due to J. Canoura, N. Gras and O. Bellot (IRTA) for their help during common dentex 129 rearing season. 130 References 131 Abellán, E. (2000) Culture of common dentex (Dentex dentex L.) present knowledge, problems and 132 perspectives. Cahiers Options Méditerranéennes, 47: 157 – 168. 133 Abellán, E. & Basurco, B. (1996) Marine finfish species diversification: current situation and 134 prospects in Mediterranean aquaculture. Cahiers Options Méditerranéennes, 24: 9 – 139. 135 Basurco, B. & Lovatelli, A. (2003) The aquaculture situation in the Mediterranean Sea. Predictions 136 for the future. International Conference on the Sustainable Development of the Mediterranean and 137 Black Sea Environment, Thessaloniki, Greece, 29th May – 1st June, 2003. 138 Bodington, Ph. (2000) Enterprise experiences in the culture of new sparids. Cahiers Options 139 Méditerranéennes, 47: 135 – 139. 140 Carbó, R.; Estévez, A. & Furones, M.D. (2002) Intelligent and multifunctional recirculation system. 141 Its application in research at CA – IRTA. EAS Special Publication, 32: 171 – 172. 142 Carrillo, M., Zanuy, S., Oyen, F., Cerdá, J., Navas, J.M. & Ramos, J., 2000. Some criteria of the 143 quality of the progeny as indicators of physiological broodstock fitness. In: Chioccioli, E. (ed.), 144 Recent Advances in Mediterranean Aquaculture Finfish Species Diversification. Cahiers Options 145 Mediterranées, 47. p. 61-74. 146 Fabra, M.; Raldúa, D.; Power, D.M.; Deen, P.M.T. & Cerdá, J. (2005) Marine fish egg hydration is 147 aquaporin-mediated. Science, 307: 545. 148 Giménez, G.; Estévez, A.; Lahnsteiner, F.; Zecevic, B.; Bell J. G.; Henderson, R. J.; Piñera, J. A. & 149 Sánchez-Prado, J. A. (2006) Egg quality criteria in common dentex (Dentex dentex). Aquaculture, 150 260: 232 – 243. 151 Glamuzina, B.; Jug-Dujakovic, J. & Katavic, I. (1989) Preliminary studies on reproduction and larval 152 rearing of common dentex, Dentex dentex (Linnaeus, 1758). Aquaculture, 77: 75 – 84. 153 Grau, A.; Morales-Nin, B.; Quetglas, A.; Riera, F.; Massuti, E. & Pastor, E. (2001) El modelo 154 reproductivo del dentón Dentex dentex (L): bisexualidad juvenil y gonocorismo tardío. Actas del XII 155 Congreso Nacional de Acuicultura. Memoria ICCM, 4: 555 – 560. 156 Greenwood, L.N.; Scott, A.P.; Vermeirssen, E.L.M.; Mylonas, C.C. & Pavlidis, M. (2001) Plasma 157 steroid in mature common dentex (Dentex dentex) stimulated with gonadotropin-releasing hormone 158 agonist. General and Comparative Endocrinology, 123: 1 – 12. 159 Jug-Dujakovic, J.; Dulcic, J. & Katavic, I. (1995) Embryonic and yolk-sac larval development of the 160 sparid Dentex (Dentex) dentex (Linnaeus, 1758). 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(1999) Manual on Hatchery Production of 172 Seabass and Gilthead Seabream. Food and Agriculture Organization of the United Nations, Vol. 1. 173 Nissling, A.; Larsson, R.; Vallin, L. & Frohlund, K. (1998) Assessment of egg and larval viability in 174 cod, Gadus morhua: methods and results from an experimental study. Fisheries Research, 38: 169 – 175 186. 176 Pavlidis, M.; Loir, M.; Fostier, A.; Mölsa, H. & Scott, A. (2000) Recent advances in reproductional 177 aspects of Dentex dentex. Cahiers Options Méditerranéennes, 47: 169 – 170. 178 Ramos, A.A. & Bayle, J. (1991) Estatuto del Dentex dentex (Linnaeus, 1758) en el Mediterráneo. In: 179 Boudouresque, C.F.; Avon, M. & Gravez, V. (Eds.) Les Espèces Marines à Proteger en Méditerranée, 180 pages 237 – 244. 181 Rueda, F.M. & Martínez, F.J. (2001) A review on the biology and potential aquaculture of Dentex 182 dentex. Reviews in Fish Biology and Fisheries, 11: 57 – 70. 183 Salze, G.; Tocher, D.R.; Roy, W.J. & Robertson, D.A. (2005) Egg quality determinants in cod (Gadus 184 morhua L.): egg performance and lipids in eggs from farmed and wild broodstock. Aquaculture 185 Research, 36: 1488 – 1499. 186  187   188 Tables 189 Table 1. Quality data based on production of floating eggs, spawning days and egg weight. 190 Superscripts denote significant differences (P < 0.05, Tukey’s test). 191 Table 2. Quality data based on the hatching rate and the performance of hatched larvae. *: 192 prehatching. 193  194   195 Table 1. Quality data based on production of floating eggs, spawning days and egg weight. Superscripts denote significant differences (P < 0.05, 196 Tukey’s test). 197  198  Broodstock 1 Broodstock 2  Year 1 Year 2 Year 1 Year 2 Total buoyant eggs (mL) 3,520 14,150 4,140 8,925 Total spawned eggs (mL) 5,410 18,535 7,260 15,235 Ratio buoyant : sinking eggs 1.9 3.2 1.3 1.4 Total buoyant eggs (estimated number) 11.7 x 106 47.3 x 106 13.8 x 106 29.8 x 106 Total spawned eggs (estimated number) 18.1 x 106 62.0 x 106 24.3 x 106 51.0 x 106 Number of spawning days 27 58 32 61 Wet weight (g per egg; average ± SD) 511.6 ± 70.3 530.2 ± 65.5 543.9 ± 62.3a 508.0 ± 32.8b Dry weight (g per egg; average ± SD) 44.2 ± 2.9b 47.9 ± 5.5a 48.2 ± 4.4a 44.4 ± 2.4b Water percentage (%; average ± SD) 91.2 ± 0.9 90.8 ± 1.7 91.0 ± 1.1 91.2 ± 0.9  199  200  201   202 Table 2. Quality data based on the hatching rate and the performance of hatched larvae. *: prehatching. Superscripts denote significant differences (P 203 < 0.05, Tukey’s test). 204  205  Broodstock 1 Broodstock 2  Year 1 Year 2 Year 1 Year 2 Hatching rate (%, average ± SD) 92.6 ± 9.2 78.5 ± 17.7 85.3 ± 18.2 65.7 ± 32.0 Maximum hatching rate (%) 100 100 100 100 Minimum hatching rate (%) 57.3 2.1 24.2 0 Number of batches with hatching rate > 80% 27 31 22 31 Number of batches with hatching rate > 50% 0 22 8 14 Number of batches with hatching rate < 50% 0 5 2 16 Mortality at 3 dph (%, average ± SD) 21.2 ± 15.9b 70.0 ± 27.3a  19.0 ± 15.0b 72.9 ± 31.8a Number of batches with mortality at 3 dph < 50% 25 14 31 12 Number of batches with mortality at 3 dph < 80% 2 16 1 13 Number of batches with mortality at 3 dph > 80% 0 28 0 36 Mortality at 5 dph (%, average ± SD) 29.6 ± 20.8b 74.3 ± 24.3a 26.0 ± 17.6b 78.2 ± 27.0a Number of batches with mortality at 5 dph < 50% 23 7 29 11 Number of batches with mortality at 5 dph < 80% 3 19 3 10 Number of batches with mortality at 5 dph > 80% 1 32 0 40 Maximal age of surviving starved larvae 12 12 13 10 Minimal age of surviving starved larvae 9 1 8 -1*  206  207 

Egg quality variability in common dentex (Dentex dentex, L.): Comparison of different quality indexes

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Egg quality variability in common dentex (Dentex dentex, L.): Comparison of different quality indexes

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