Growth performances of juvenile soleSolea soleaunder environmental constraints of embayed nursery areas

Abstract

-Tidal embayments in the Bay of Biscay (France) host nursery grounds where common sole, Solea solea, is the most abundant flatfish species. This study aimed to appraise the way those habitats function as nurseries through juvenile sole's responses in somatic growth and condition (Fulton's K) during their first year of occupancy. Field data, two yearly trawling series, taken monthly, were compared with a 6-month-long mesocosm experiment involving reared fish of the same wild origin. Growth rates were compared with predicted maximum growth according to an experimentally established model in relation to temperature. In the field, 0-group sole total length (TL) averaged 130 mm from September onwards in 1999 and 2000. Mean growth rates were 0.7-0.9 mm day −1 in summer and 0.1 mm day −1 in autumn, when the model predicted 1.4 and 0.9 mm day −1 , respectively. In the mesocosm, the growth rates were 0.9 and 0.4 mm day −1 for the same seasons and for stocking densities (300 fish 1000 m −2 ) about 10 times higher than usually recorded in the field. Wild sole remained in medium condition (K ca. 1 g cm −3 ) during the entire growing season, whereas they attained a higher K after being released into the mesocosm (1.2-1.3 g cm −3 ). During the mesocosm experiment, growth was shown to be primarily temperature-controlled: fish reached 150-160 mm (TL) in November. From this investigation, it can be concluded that sole's responses in condition and growth are altered over the whole growing season on nursery grounds. The situation is exacerbated in autumn when the sum of abiotic constraints increases as the competitive biomass does. This indicates impairment of the nursery functioning which, in the context of fish habitat conservation, emphasises the particular vulnerability of embayments to the addition of any further constraint. Key words:Coastal nursery / Habitat quality / 0-group fish / Growth / Condition factor / Mesocosm experiment / Flatfish / Solea solea Résumé -Croissance des juvéniles de la sole Solea solea sous contraintes environnementales de nourriceries côtières. Les baies du golfe de Gascogne (France) hébergent des habitats où la sole, Solea solea, est le plus abondant des poissons plats. Cette étude vise à évaluer le fonctionnement des habitats pour leur rôle de nourriceries, en analysant la croissance et la condition des juvéniles de sole pendant leur première année. Les données de deux séries, 1999 et 2000, de chalutages mensuels sont comparées à celles acquises lors d'une expérience de 6 mois en mésocosme impliquant l'élevage de poissons originaires de la même nourricerie. La croissance observée est comparée à la croissance potentielle, en utilisant un modèle expérimental décrivant la croissance en fonction de la température. Les soles du groupe d'âge 0 capturées dans la nourricerie atteignent une taille moyenne de 130 mm en septembre. Le taux de croissance est de 0,7-0,9 mm jour −1 en été et 0,1 mm jour −1 en automne, alors que le modèle prédit respectivement 1,4 et 0,9 mm jour −1 . En mésocosme, la cro...

Influence of Hydrocarbons Exposure on Survival, Growth and Condition of Juvenile Flatfish: A Mesocosm Experiment

“…There was no sign of food limitation in both tidal ponds and these mesocosms provide temperature and salinity similar to near shore waters. In addition growth rates of unexposed fish were similar to those reported in situ (Amara et al 2001) or in previous experiments in tidal ponds (Laffargue et al 2007). Since temperature and food are the two most important factors governing fish growth (Fonds 1979) the growth reduction of exposed fish in this study is likely to be related to their exposure to fuel oil and to impaired ability to allocate energy to growth.…”

“…Juvenile sole growth in the control pond followed well known patterns (Laffargue et al 2007), with high growth rate in summer then low values between D63 and D109, characteristic of a growth stop related to both reduction in temperature at the end of the summer growing season for Solea solea (Amara et al 2001) and lower photoperiod action on hormonal levels (Laffargue et al 2007). On the contrary, exposure to fuel-oil for as little as 24 hours had inhibited growth in flatfish juveniles.…”

Validation of age determination methods and growth studies of the sand sole Pegusa lascaris (Soleidae) from the eastern-central Atlantic

“…The average seawater temperature recorded with the CTD off Gran Canaria Island at 5 and 60 m depth was, respectively, 19 and 18.5 ºC in late winter, rising to 24.5 and 21 ºC in summer. This rise in water temperature could introduce changes in the metabolic activity of fish during spring and summer and could be the main factor responsible for opaque ring deposition (Laffargue et al 2007, Matta et al 2010. Félix et al (2011) indicated that temperature is one of the most important factors in growth of the flatfishes since it plays an important role in metabolism regulation.…”

“…La formación de anillos de crecimiento observada en los otolitos sagita examinados en el presente trabajo parece estar íntimamente relacionada con la temperatura del mar (Nash y Geffen 2005, Laffargue et al 2007. Durante el invierno la Figure 5.…”

“…Los registros de temperatura media del agua de mar tomados con CTD en Gran Canaria entre 5 y 60 m de profundidad fueron, respectivamente, 19 y 18.5 ºC a finales de invierno y 24.5 y 21 ºC en verano. Este aumento de la temperatura podría introducir cambios en la actividad metabólica de los peces durante primavera y verano, y causar la formación del anillo opaco (Laffargue et al 2007, Matta et al 2010. Félix et al (2011) indicaron que la temperatura es uno de los factores más importantes en el crecimiento de los peces planos, ya que juega un papel importante en la regulación del metabolismo.…”