Parasites of flounder Platichthys flesus (L.) from the German Bight, North Sea, and their potential use in ecosystem monitoring

Abstract

The analysis of fish-parasite community structure and the use of ecological richness and diversity measurements are commonly used for the evaluation of environmental stress in aquatic ecosystems. As part of an integrated biological-effect monitoring, the parasite community of flounder Platichthys flesus (L.) was investigated for various locations in the German Bight during spring and autumn of 1995-2000, using established ecological methods. Although the parasite-community composition was very similar at the component-community level, the number of component species as well as the species accumulation curves showed clear differences among the sites. On the infra-community level, all of the ecological measurements showed significantly lower values in flounder from the Elbe estuary, the most polluted site, than in flounder from Helgoland. This was seen during a single season or during both seasons. When the data were pooled over the years, gradual differences between the sites, which were seldom detected at individual sampling periods, became evident for different measurements of species richness and species diversity and corresponded to a contamination gradient established between Elbe > Inner Eider, Outer Eider > Helgoland. Despite seasonal variations, which were observed in almost all measurements, these gradual differences were found in both seasons.

Seasonality of metazoan ectoparasites in marine European flounderPlatichthys flesus(Teleostei: Pleuronectidae)

“…Indeed, all reported studies on flounder's ectoparasites either concern estuarine environments (van den Broek, 1979 ;Schmidt et al 2003) or the Baltic Sea (Chibani and Rokicki, 2004), which is known as the world's largest brackish water sea area (Leppäkoski et al 2002).…”

Parasites and hystopathology of <i>Mullus barbatus</i> and <i>Citharus linguatula</i> (Pisces) from two sites in the NW Mediterranean with different degrees of pollution

“…M. barbatus showed higher diversity and richness values in Barcelona than in Blanes. Although pollution and stress are usually associated with a reduction in species richness and diversity of parasites (Schmidt et al, 2003), this is not a rule for all host species (Zander and Kesting, 1996;Landsberg et al, 1998). In fact, a wide range of positive and negative responses of parasite species to pollutants has been observed (Overstreet, 1997;Lafferty and Kuris, 1999;Dzikowski et al, 2003); since it is not always clear how diversity varies with particular impacts, because some species or parasite populations may increase while others decline (Poulin, 1992;Lafferty, 1997;Marcogliese, 2005), drawing conclusions based exclusively on a direct comparison of parasite indices is unreliable (Lang et al, 1999).…”

“…Since fish parasites can reflect adverse effects of complex and variable environmental stresses (Lafferty, 1997;Landsberg et al, 1998;Lafferty and Kuris, 1999;MacKenzie, 1999;Dzikowski et al, 2003;Williams and Mackenzie, 2003), the study of fish parasite community structure has been proposed as a more sensitive indicator than the study of fishes themselves (Landsberg et al, 1998). However, although evidence supports the view of a relationship between parasitic load of fish and exposure to pollutants (Zander and Kesting, 1996;Schmidt et al, 2003), the potential use of parasites as bioindicators for pollution biomonitoring is still controversial, since many natural factors also influence prevalence, infection intensity and biodiversity of parasites (Williams and Mackenzie, 2003) and both hosts and parasites can interact differently with each stressor (Lafferty and Kuris, 1999). This notwithstanding, from parasitological data obtained either from the field or following experimental treatment, Blanar et al (2009) and Vidal-Martinez et al (2010) point out the usefulness of parasites as bioindicators of environmental impacts.…”

Survey of the Metazoan Ectoparasites of the European Flounder Platichthys flesus (Linnaeus, 1758) along the North-Central Portuguese Coast

“…Both copepods were dominant off Matosinhos, Aveiro, and Figueira da Foz, whereas off Viana do Castelo the highest prevalence value was recorded for gnathiid pranizae. In the North Sea, Lepeophtheirus pectoralis and A. cornuta also appear to be common parasites of the European flounder (Boxshall, 1974;Schmidt, 2003). All other identified parasites, i.e., C. diaphanus, Caligus sp., H. confusus, and N. orbignyi, exhibited comparatively lower prevalence and total intensity values, indicating that they are probably not common in flounders from the studied area.…”

“…Moreover, all were absent from FF, the sampling location where older fish, i.e., fish possessing higher mean total weight and length values, were collected. The absence of Lernaeocera branchialis, a parasite that can constitute a severe pest with significant economic impact (Kabata, 1979), is noteworthy, since this species is a common parasite on flounders from the North (Schmidt, 2003) and Baltic Seas (Køie, 1999). This result is probably related to the absence of the main definitive host species (gadoid fishes) from the area under study (Kabata, 1979;Svetovidov, 1986 …”