Morphological and genetic seasonal dynamics of European eel Anguilla anguilla recruitment in southern France

Abstract

The fine scale morphological and genetic dynamics of successive waves of Anguilla anguilla glass eel recruitment was studied over a 2 year period at a southern European Mediterranean location (Camargue, France) with continuous recruitment. Using morphometric [total length (L(T)), mass (M), condition (K) and pigmentation stage] as well as genetic (allozyme) markers, the aim was to test for the existence of temporally separated spawning groups and explore the relation between genetic variability and morphological heterogeneity of recruits. The results showed that L(T), M and K varied over time, being highest from the end of summer to winter (peaking in December) and lowest in spring (lowest in April). The pigmentation stages within monthly samples were highly diverse with a heterogeneous seasonal pattern. Allozyme data showed high genetic variability values within samples, but low genetic differentiation among samples (F(ST) = 0.003, P < 0.05). Pairwise comparisons between samples indicated a positive correlation between genetic differentiation and difference in recruitment time (days), with a marked increase in genetic differentiation around 250 days between monthly recruitment samples. Furthermore, genetic diversity increased with the number of pigmentation stages per sample and was negatively correlated with the North Atlantic Oscillation (NAO) index during the putative year of trans-oceanic migration. No correlation, however, was found between the level of multilocus heterozygosity (MLH) and growth variables. A situation of genetic patchiness with fluctuating parental contribution can thus best explain the patterns observed, although the existence of two separate spawning periods cannot be excluded. More discriminatory and sensitive genetic markers, such as (neutral and adaptive) microsatellites, could probably provide additional insights into the most probable hypothesis explaining the population structure and recruitment heterogeneity of A. anguilla.

Variation of life traits of glass eels of Anguilla anguilla (L.) during the colonization of Ríos Nalón and Minho estuaries (northwestern Iberian Peninsula)

“…However, western Atlantic glass eels show no marked differences in size or in pigmentation stages among locations in Portugal, Spain, France and Ireland although Boëtius & Boëtius (1989) noted that pigmentation stages varied widely with no obvious temporal pattern among several northern Atlantic locations. Studies available for the Mediterranean [La Camargue, southern France (Maes et al, 2009) and Río Arno, northeastern Italy (Gandolfi et al, 1984)] also suggested temporal replacement of pigmentation stages with an increased predominance of more pigmented individuals as the season progressed and interestingly, an overall predominance of more pigmented stages than in the Atlantic glass eels (Table 4). Nonetheless, relative to the whole-season predominance of stage V B in the Iberian Ríos Nalón and Minho, in the Mediterranean Río Arno where pigmentation stages are well documented (Fig.…”

“…On the other hand, the larger size of Atlantic glass eels compared with the smaller Mediterranean individuals may be caused by a greater osmotic exchange cost in the markedly higher-salinity Mediterranean Sea. Nevertheless, a remarkable heterogeneity and a large proportion of the variance unexplained (*75%) may result from genetic heterogeneity (Maes et al, 2009) but still suggests that environmental factors such as water temperature and salinity may affect the pigmentations stages (Briand et al, 2005) and should be taken into account in future investigations on glass eel recruitment.…”

Glass eel (Anguilla anguilla) recruitment to the river Lis: Ingress dynamics in relation to oceanographic processes in the western Iberian margin and shelf

“…Seasonality in mean body length (left) and body condition (right) of glass eels recruiting to western Portugal (1994–2001, open circles), in comparison to published values from France (large closed circles: Atlantic—Guerault et al., ; Desaunay & Guerault, ; small closed circles: Mediterranean—Maes et al., ). Lines and grey shades result from GAM .…”

An integrated genetic-demographic model to unravel the origin of genetic structure in European eel (Anguilla anguilla L.)

“…These studies evidenced that temporal genetic differences between groups of glass eels recruited at the same site within the same year (also referred to as glass eel waves) can exceed between-site large-scale spatial genetic differences of the same recruitment cohort (Maes et al 2006, 2009; Pujolar et al 2006, 2007, 2009). In agreement with these observations, such a small-scale genetic patchiness of glass eel waves would result from independent mating events involving small groups of breeders separated by space or by time (Maes et al 2006; Pujolar et al 2009).…”