title: Long-term stability of Sphyrion lumpi abundance in beaked redfish Sebastes mentella of the Irminger Sea and its use as biological marker.
abstract: The main commercial fish species in the Irminger Sea, the beaked redfish Sebastes mentella, is commonly infected with the copepod Sphyrion lumpi. This ectoparasite is often used as a biological marker for stock discrimination to evaluate the still-debated metapopulation structure of beaked redfish. Nevertheless, it is still not understood whether parasite abundances and communities vary over longer time periods. In the present study, we investigated the abundance of S. lumpi in S. mentella of the pelagic zone of the Irminger Sea and adjacent waters. Our analyses revealed that live S. lumpi abundance remained constant during summer over a sampling period from 2001 to 2015, which confirms its validity as a biomarker. As S. mentella forms dense aggregations during mating, our results suggest that host densities are, regardless of a fishery-induced decrease in host biomass, large enough to facilitate the direct transmission of S. lumpi. After correcting for covariate effects, two stock units could be differentiated, which supports a continuation of the current fishery management strategy.
authors.affiliation: Goethe-University, Institute for Ecology, Evolution and Diversity, Senckenberg Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany. r.klapper@em.uni-frankfurt.de.
authors.forename: Regina
authors.initials: R
authors.lastname: Klapper
authors.affiliation: Thünen Institute of Sea Fisheries, Hamburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bernreuther
authors.affiliation: Thünen Institute of Sea Fisheries, Hamburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Wischnewski
authors.affiliation: Goethe-University, Institute for Ecology, Evolution and Diversity, Senckenberg Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Klimpel
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D015415:Biomarkers; D033342:Copepoda / Q000254:growth & development*; D005260:Female; D005393:Fish Diseases / Q000469:parasitology*; D005398:Fisheries; D008297:Male; D010473:Perciformes / Q000469:parasitology*
chemical_list: D015415:Biomarkers
keywords: Biological marker; Long-term parasite abundance; North Atlantic; Parasitic copepods; Stock discrimination; Zero-inflated models