Seasonal and depth related variation of parasite communities of Notacanthus bonaparte Risso, 1840 (Notacanthiformes: Notacanthidae) over the northwest Mediterranean slope

Abstract

In the last decades fishing activities have spread from coastal to deeper waters with serious effects on the deep-sea ecosystems and its fauna, which are considered to be highly susceptible to these impacts. The implementation of protection measures is necessary, but the knowledge on this biome is scant, and often limited to species of commercial value. To the best of our knowledge, this study is the first survey to describe and analyse parasite infracommunities of the deep-sea fish Notacanthus bonaparte sampled from three bathymetric strata between the upper and lower slope in the western Mediterranean Sea (Balearic Sea, Spain). The aim of this work was to assess the effect of host specific parameters as well as environmental conditions and spatial and temporal variation on the composition and structure of the parasite communities. We have found poor parasite infracommunities, usually described rather for bathypelagic fishes than observed in fishes with benthic feeding habits such as N. bonaparte, in which two out of five species are considered as accidental infections. The infracommunity composition is determined by the factors, depth and maturity status (size). The dominating taxon, cucullanid larvae, seem to be accumulated throughout the life of the host showing higher abundances in larger fish in deeper waters on the middle and lower slope. The prevalence and abundance of this parasite could be linked to increased water turbidity and it is supposed that these larvae are free-living in the sediment being ingested by N. bonaparte when feeding on benthic organisms. The results suggest that N. bonaparte acts as important intermediate host for this taxon though, the final host is still unknown. The single monogenean species Tinrovia mamaevi was mainly recorded in the upper slope and its higher prevalence in this depth range could be related to higher host densities observed in these depths. The prevalence and abundance of this parasite species could be linked to temperature and salinity, and although measured variations for these parameters were marginal it is supposed that these and probably further additional abiotic factors may influence its distribution pattern. Considering previously published diet data this study indicates potential pathways other than those expected for parasites transmitted via the food web using N. bonaparte as intermediate and definitive host.