The migration patterns of the European flounder Platichthys flesus (Linnaeus, 1758) (Pleuronectidae, Pisces) at the southern limit of its distribution range: Ecological implications and fishery management

Plasticity of European flounder life history patterns discloses alternatives to catadromy

“…Kalish 1990, Volk et al 2000. A similar pattern was found in flounder otoliths, which was also attributed to sea-run mothers (Morais et al 2011). Thus, the assignment of a coastal signature in the otoliths must be made with caution since a 'maternal' effect caused by a marine mother may exist.…”

“…Previous work showed that Ba incorporation into otoliths was negatively correlated to growth rate during ontogeny (Walther et al 2010), while other studies concluded that Ba incorporation was mostly environmentally driven (Elsdon & Gillanders 2003a,b). For European flounder, there is no evidence to date that suggest an ontogeny effect on the incorporation of elements to the otolith (Morais et al 2011). However, it is unlikely that ontogeny has a greater effect than the surrounding environment.…”

“…However, there is still controversy about classifying flounder as catadromic, semi-catadromic, estuarine migrant, marine-estuarine opportunistic (Elliott et al 2007) or even as a truly estuarine resident species (Elliott & Dewailly 1995). Recent works clearly proved that flounder is not an estuarine resident species (Daverat et al 2011, Morais et al 2011, although field observations confirmed that flounder use estuarine habitats (Jager 1999, Marchand et al 2003 as well as freshwater habitats for extended periods (Radforth 1940, Beaumont & Mann 1984. Indeed, freshwater was found to trigger the metamorphosis of flounder (Hutchinson & Hawkins 2004), and larvae are able to migrate upstream efficiently to their estuarine nursery ground using selective tidal transport (Bos 1999).…”

“…A recent study has shown that there are genetic differences between flounder from the northern and southern part of the Baltic, corresponding to the outlined ecological types (Florin & Höglund 2008). Further south in the species' distribution area, in the Minho basin (NW Iberian Peninsula), it was hypothesized that flounder used both the coastal area and the estuary as spawning grounds (Morais et al 2011). Alternative habitat use was also suggested in the Gironde estuary population (W France), where most flounder used freshwater habitat in the juvenile stage, although a smaller proportion of the sample was resident in the brackish estuary or undertook several movements between coastal, estuarine and freshwater habitats (Daverat et al 2011).…”

“…The studies conducted in the Minho (Morais et al 2011) and Gironde basins (Daverat et al 2011) inferred the migration patterns and habitats used by flounder by analyzing trace elements incorporated in the sagittal otoliths of fish (Campana 1999, Gillanders 2005. Sagittal otoliths (hereafter, otoliths) are 1 of 3 pairs of otoliths that fish have in their inner ear and are composed of calcium carbonate (CaCO 3 ) in a non-collagenous matrix (see Campana 1999 andElsdon et al 2008 for a comprehensive review of otoliths and otolith microchemistry).…”