Growth heterogeneity in rearing sea bass (Dicentrarchus labrax): test of hypothesis with an iterative energetic model

Abstract

This study aimed at modeling the relative importance of food intake on growth heterogeneity among cultured sea bass (Dicentrarchus labrax). First, we designed an individual growth model comprising five compartments (Energy intake, Losses, Net Energy, Recovered Energy and Maintenance). This model was calibrated with a first experiment carried out in eight tanks; A total of 130 juveniles (11 g) per tank were fed by a self-feeder (84 days, 208C, 16L : 8D, 30 g NaCl/l). A second experiment was performed to better understand the relation between individual food intake, individual growth and growth heterogeneity, using the model as a tool for a hypothetico-deductive approach on growth heterogeneity (135 passive integrated transpondertagged fish, same rearing conditions as above and individual food intake measured by X-ray every 14 days). The tested hypotheses were that food intake was (a) homogeneous, (b) proportional to the fish weight (i.e. to W 1.00 ) X-ray (c) proportional to W 0.66 and (d) reflected by the X-ray measurements of food intake. For each hypothesis, a simple linear regression between experimental and simulated results was produced. The Fitness indicators of these analyses, together with their confidence intervals (calculated by bootstrapping), allowed testing the relevance of these hypotheses. The analysis indicated that growth heterogeneity was largely accounted for by individual variations of food intake, as revealed by the X-ray analysis, and that food intake was proportional to W 1.00 , which suggests a dominance hierarchy where small fish are incapable of feeding maximally.Keywords: sea bass, growth, heterogeneity, energetic model IntroductionSize heterogeneity is a recurrent issue in aquaculture, since it largely facilitates the exercise of cannibalism (Baras and Jobling, 2002;Kestemont et al., 2003) and frequently imposes grading practices. Growth dispersal among cultured animals is not specific to fish, but it is generally more intense among fish than among other taxa. According to Gjedrem (2000), the coefficient of variation for body weight typically ranges from 7% to 10% in livestock farm animals, whereas it varies between 20% and 35% in most cultured fish species. Size heterogeneity has been extensively studied and attributed to a broad series of factors, of intrinsic or extrinsic nature. In brief, individual fish are likely to exhibit genuine capacities for growth that differ slightly, e.g., because their standard metabolic rates (Cutts et al., 2001;Bang et al., 2004) or digestive abilities are different (Lemieux et al., 1999), growth dispersal can be dependent on the degree of heterozygosity (Tiira et al., 2006). These factors are likely to be buffered or amplified by between-individual variations in food intake, which have been demonstrated on several occasions to be the driving factor behind growth depensation (e.g. Jobling and Baardvik, 1994). In theory, all environmental factors that impact on food intake and growth can impact directly on growth heterogeneity (Gelineau et al., 1998;Jo...

The effects of rearing density on growth, size heterogeneity and inter-individual variation of feed intake in monosex male Nile tilapia Oreochromis niloticus L.

“…Stocking density has been shown to affect behavioural interactions in several fish species such as intraspecific competition (Martins et al, 2005) and may influence the inter-individual variations of FI. This intraspecific competition and social hierarchy have been demonstrated on several occasions to be the driving factor behind growth heterogeneity (Campeas et al, 2009). To the best of our knowledge, thus far, such an effect has not been reported previously among tilapias, which are one of the major contributors to world aquaculture nowadays (Food and Agriculture Organization of the United Nations - FAO-FishStatPlus, 2012).…”

Effect of size grading on sea bass (Dicentrarchus labrax) juvenile self-feeding behaviour, social structure and culture performance

“…In our study, this idea is supported by the fact that correlations between initial and final weights tended to be lower in T low groups, but at the end of experiment, when CV w increased, correlations reached the same values as those of the T high groups. Indeed, Campéas (2009) showed that this tendency was related to a modification of fish rank (weight rank between the beginning and the end of the studied period) in low CV w groups.…”

“…Indeed, in exploitation competition, there are no direct interactions between competitors; instead, one individual exploits and depletes a food patch before a second individual arrives (Ward et al 2006). Recent work based on growth heterogeneity modelling in fish rearing systems rejected the hypothesis of competition decrease within time (Campéas 2009). According to this author, growth heterogeneity stability is not correlated with the stabilisation of social interactions (i.e., size had little or no effect on fight determinism), and CV w stability is the result of the dominance pressure of large fish on small fish.…”

Individual growth trajectories of sibling Brycon moorei raised in isolation since egg stage, and their relationship with aggressive behaviour

“…Growth heterogeneity between individuals appears to be the rule rather than the exception in wild and cultured fish populations (Huston & DeAngelis, 1987; Kestemont et al , 2003; Campeas et al , 2009). An individual fish has an intrinsic capacity for growth that is governed by its genome and by epigenetic factors such as yolk size of embryos.…”