Stocking density and sex influence individual growth of Senegalese sole (Solea senegalensis)

Abstract

Growth is usually inversely correlated with stocking density of fish in culture. Senegalese sole aquaculture is affected by a high size variability and thus, this work tried to investigate the relationship of growth with density of two populations of 96 individually tagged Senegalese sole (318.7± 7.9 g; mean± standard error of the mean). Fish were reared at low (LD) and high (HD) density (60% and 180% of bottom coverage respectively) for 195 days. After 134 days (period 1), density conditions were exchanged between groups. Mean weight, standard length, maximum width and centroid size were calculated for each of the 11 census days of the experiment. White muscle biopsies were taken in 7 of the census days in order to assess the RNA/DNA ratio, as a biochemical indicator of growth. Stocking density had an important effect on growth, as fish reared under HD showed poor or no growth during a 'lag phase' on the first 61 days of the experiment, leading to a significantly lower specific growth rate (0.23 ± 0.014) for period 1 compared with LD fish (0.34 ± 0.016). Fitting of linear mixed-effects (LME) models for the first 134 days of experiment showed a significant effect of density and sex on all the assessed biometric parameters. These results could be attributed mainly to the first 61 days of the experiment, as no differences were observed between days 61 and 134 in all the measurements, except for standard length, that showed to be lower for HD fish throughout the whole period. Fish reared under high density tended to grow slower than fish held at low density, while females showed faster growth than males, particularly in HD. Nevertheless, due to high size variability, no significant differences could be found in the mean values of weight or standard length after 134 days (467.2± 21.6 g and 28.7± 4.2 cm; 502.6 ± 22.5 g and 29.7± 4.5 cm for HD and LD fish respectively). Size variability could be an indicator of the onset of hierarchies, being stronger and with more females as dominant individuals than males in HD. After exchanging densities, and up to day 195, a similar lagging effect could be observed in LD fish exposed to high density, suggesting that a sudden change in density, more than density itself, could be the responsible for a detrimental effect on growth. RNA/DNA ratios, were significantly lower for HD fish between days 20 and 61.

Effect of some rearing systems on growth and development of the Egyptian sole (Solea aegyptiaca Chabanaud, 1927) larvae.

“…The growth rate for larvae has been increased gradually with increasing temperature until 20 °C then decreased. These results agreed with most studies on biological development and temperature in Senegal sole as many authors have used a constant temperature of 20 ºC (Martinez et al, 1999;Parra and Yufera, 1999;Ribeiro et al, 1999;Yufera et al, 1999;Canavate et al, 2006;Sanchez et al, 2010;Salas-Leiton et al, 2011, 2012. The Senegal sole (Solea senegalensis) is a flatfish adapted to temperate waters of around 20-21 ºC (Drake et al, 1984).…”

Influence of stocking density on growth, metabolism and stress of thick- lipped grey mullet (Chelon labrosus) juveniles

“…Moreover, growth rate is probably one of the most well studied physiological parameters related to aquaculture, although other variables related to stress and endocrine systems have been studied in different species of interest for aquaculture, as in S. aurata (Caruso et al, 2005;Montero et al, 1999), S. senegalensis (Ambrosio et al, 2008;Salas-Leiton et al, 2008;Sánchez et al, 2010), D. labrax (Lupatsch et al, 2010) or Salmo salar (Hosfeld et al, 2009). Aquaculture activity requires the optimization of stocking densities along the life cycle of the species of interest in order to avoid the activation of the stress system and the consequent economic losses (Barton, 2002).…”

Gender‐dependent effects of water quality and conspecific density on the feeding rate of fish – factors behind sexual growth dimorphism

“…Because the sexes are often subject to different selective pressures regarding the tradeoff between growth and reproduction, the consequences of changes in resource abundance associated with changes in population density should be different for males and females (LeBlanc et al 2001). Accordingly, differential effects of population density variations on the growth of males and females have been reported for many taxa including fish (Isaac 2005, Sánchez et al 2010), but also minor effects of density on dimorphism have been reported (Garel et al 2006). In our experiments, perch females and males showed similar response to fish density variations.…”

“…The female–male growth differences in the study lakes were tested with analysis of variance for repeated measurements. This method can be used in growth studies including several back‐calculated and temporally autocorrelated measurements from the same individuals (Horppila and Nyberg 1999, Sánchez et al 2010). Additionally, the female–male difference in the average annual length increment was calculated for each lake for age group 1–6 and plotted against the water colour of the lakes.…”