Résumé
The demography of a lagoonal population of Lipophrys pavo over a four year period is described. This population exhibited high variability in recruitment and mortality and as a result, in age structure and density. During the study the average size at a given age decreased. This decrease was not linked to growth variation. Changes in demography and length structure are interrelated and could be linked to stressful environmental conditions and to reproductive patterns of this species. Lipophrys pavo (Risso, 1810) is a common species in shallow waters of the rocky littoral of the Mediterranean sea (Zander, 1972; Patzner, 1984). This species differs from other Blenniidae by its ability to colonize biotopes where hard substrates are scarce (Moosleimer, 1980; Almada et al., 1994; Ruchon, 1995), and by its great euryhaline and eurythermal tolerance limits (Marion, 1890; Paris & Quignard, 1971; Zander, 1972; Müller et al., 1973; Moosleitner, 1988; Patzner & Seiwald, 1988). This euryvalence has allowed L. pavo to colonize brackish and soft-bottom lagoons of the Gulf of Lion where it is the single Blenniidae present (personal observation). Lipophrys pavo is a gonochoric species exhibiting strong sexual dimorphism (Zander, 1975; Papaconstantinou, 1979). Males are territorial nest breeders during the spawning season (Patzner et al., 1986), and females are batch spawners (Fishelson, 1963a; Patzner, 1985a).