Individual trophic specialization in juvenile European seabass: implications for the management of a commercially important species

Abstract

Individual differences in diet can play an important role defining a population's ecological niche and its role within food webs and habitats, but individual trophic specialization is rarely considered in a fisheries context. Stocks of European seabass, Dicentrarchus labrax, have declined in recent years, and policy has focused on managing fishing effort. Inshore nursery grounds represent a critical habitat in terms of recruitment to standing stocks, and improved understanding of the ecology of juvenile seabass at the level of the individual may assist the development of management strategies aimed at maximizing their survival and growth. We quantified levels of individual trophic specialization in juvenile seabass using stomach contents and stable isotope analyses at a monthly resolution over an annual cycle. We found significant, seasonally varying levels of individual specialization in stomach contents, with reduced specialization observed in the spring. This was corroborated by stable isotope analyses, where isotopic variance among seabass individuals was significantly higher compared to that in two other concurrently sampled, sympatric bentho-pelagic predators. Our findings suggest that juvenile seabass form trophic-generalist populations composed of specialized individuals. Considering variation in individual behaviours may improve management strategies aimed at protecting the vulnerable life stages of this commercially important species.

Habitat complexity and individual variation in diet and morphology of a fish species associated with macrophytes

“…However, contrary to our expectation, the highest individual specialisation in the M. forestii diet was found in stands with low macrophyte biomass. This seems likely to be related to the increased intraspecific competition intensified by the lower resource availability that is probably found in less complex habitats (Araújo et al, 2010;Cobain et al, 2019;Kovalenko et al, 2012). During the dry season, when we carried out the sampling, intraspecific competition tends to intensify since resource availability is lower due to the contraction of ecosystems (Correa & Winemiller, 2014;Costa-Pereira, Tavares, Camargo, & Araújo, 2017;Fitzgerald, Winemiller, Sabaj Pérez, & Sousa, 2016;Gomes, Bulla, Agostinho, Vasconcelos, & Miranda, 2012).…”

“…ecomorphological diversity, individual specialisation, macrophyte biomass, Moenkhausia forestii, nested diets niche variation hypothesis (Niche Hypothesis Variation), which suggests that niche expansion may occur due to variation in resource use among individuals of a single population. Thus, species considered generalists may be composed of specialist individuals that use a small subset of the entire niche of the population (Bolnick et al, 2003;Cobain, Steward, Trueman, & Jensen, 2019;Cunha, Wolff, & Hahn, 2018;Latli, Michel, Lepoint, & Kestemont, 2019).…”

Predicting how environmental conditions and smolt body length when entering the marine environment impact individual Atlantic salmon Salmo salar adult return rates

“…This could be caused by additional physiological stress due to a greater difference in marine temperatures and riverine temperatures (Jutila et al, 2005). Another extrinsic variable with a relatively large effect size was sea bass abundance, a species known to predate on S. salar smolts (Riley et al, 2011), and that can be dietary specialists at an individual level, despite being generalists at population levels (Cobain et al, 2019). Riley et al (2011) found that sea bass stomach contents from the tidal River Frome included salmonid smolts, though whether the prey were S. salar or Salmo trutta was difficult to determine.…”

Quantifying spatio‐temporal consistency in the trophic ecology of two sympatric flatfishes

“…If resources are distributed more evenly in space, then competitive interactions are less likely than when they are aggregated, but the likelihood of inter‐ and intra‐species competition increases as resource distributions become more heterogeneous (Ward et al ., 2006), as is typical in coastal environments (Le Pape & Bonhommeau, 2015). Diet studies conducted in coastal and estuarine areas are generally focused on single species ( e.g ., Cobain et al ., 2019) or on several species but in a single location ( e.g ., Cabral et al ., 2002; Carter et al ., 1991). Although such studies provide useful insights into resource partitioning, they do not fully capture the spatial and temporal heterogeneity of consumed prey in these often densely populated and dynamic regions (Buchheister & Latour, 2010; Mariani et al ., 2011), and therefore the degree of consistency in observed dietary behaviours is poorly understood.…”