Sealworm (Pseudoterranova decipiens) infection in grey seals (Halichoerus grypus), cod (Gadus morhua) and shorthorn sculpin (Myoxocephalus scorpius) in the Baltic Sea

Abstract

Access to the published version may require journal subscription. Published with permission from: Springer Verlag.Standard set statement from the publisher:"The final publication is available at Springer via http://dx.doi.org/ 10.1007/s00436-014-4187-z" Epsilon Open Archive http://epsilon.slu.se or some other variable which correlates with salinity, limits the distribution in the northern part. Sealworm (Pseudoterranova decipiens) infection in grey seals (Halichoerus grypus), cod (Gadus 30Keywords: Baltic Sea, cod, grey seal, Pseudoterranova, sealworm, sculpin. 32 Introduction 33Infection by the larval stages of the parasitic sealworm, Pseudoterranova sp., in commercial fish 34 species has been of great concern in the North Atlantic fisheries (McClelland 2002). So far it has 35 not been raised as an urgent issue in the Baltic Sea area except in the southern parts (Myjak et 36 al., 1994, Szostakowska et al., 2005, Buchmann and Kania, 2012, Nadolna and Podolska, 2014. 37However, with an increasing population of seals, the parasite's final hosts, there are concerns of 38 an increasing problem. Data on the population of grey seals in the Baltic suggest an annual rate 39 of increase of 7.5% since 1990; (Harding et al. 2007) and in 2013 the counted population on 40 shore was 28,000 (www.rktl.fi). The highest density of grey seals in the Baltic is found between 41 latitudes 58° and 61°, which correspond with ICES subdivision 27 in the north to subdivision 31 42 in the south (Figure 1). There are also scattered colonies along the Swedish coast in the southern parasite, the increasing seal population is a problem. 47Pseudoterranova sp. are intestinal roundworms or nematodes belonging to the family Anisakidae 48 and can be considered a cosmopolitan genus, with a confusing taxonomy (Paggi et al. 2000). 49Genetic studies by Buchman and Kania (2012) determined that the nematodes found in cod flesh 50 from the southern Baltic are Pseudoterranova decipiens. The sealworm has a complex life cycle, 51 with a free-living stage and three obligate hosts required for the parasite to complete its life-52 cycle. The eggs are excreted in the faeces of a seal and sink to the sea floor where they hatch into 53 free-living larvae. A benthic invertebrate ingests the larvae. After the infected invertebrate is 54 eaten by a fish, the larvae migrate from the stomach of the fish into the muscle tissue. It is at this 80The spatial distribution in the Baltic Sea is of special interest because of its uniqueness in being a 81 brackish sea. Salinity has been shown to limit the survival of the sealworm larvae (Measures, lower range of salinity in the Baltic Sea, it is not known how well the sealworms survive. 89The aim of this study was to examine the relative presence and distribution of sealworms in the Materials and Methods 99Fish and parasite sampling 100 Fish were collected along the east coast of Sweden, using different types of gear, such as gill In order to support this consistency, the same light table was used throughout the st...

Host size-dependent anisakid infection in Baltic cod Gadus morhua associated with differential food preferences

“…These crustaceans become infected when they feed on nematode larvae released from the parasite eggs delivered by seal. A dominance of adult C. osculatum in Baltic grey seal stomachs was previously documented by Skrzypczak et al (2014) and Lunneryd et al (2015), and the increase of fish infections during the last decades may be caused by the rapidly expanding grey seal population (Haarder et al 2014). Several fish species are able to obtain infection when ingesting the first intermediate hosts, and the present field study documented that more than 10% of the Baltic sprat investigated was infected by up to 8 parasite larvae per fish, which is a higher infection level than previously reported.…”

“…This development has been noted during a period with a marked increase of the grey seal Halichoerus grypus population (Haarder et al 2014). These pinnipeds are final hosts for both C. osculatum and P. decipiens (Marcogliese et al 1996, McClelland 2002, Mattiucci & Nascetti 2008, Skrzypczak et al 2014, Lunneryd et al 2015. Eero et al (2015) suggested that heavy C. osculatum liver infections may partly explain the distress of the eastern population of Baltic cod, where juveniles (< 30 cm total length [TL]) perform successfully but larger cod (> 38 cm TL) show increased mortality.…”

The relevance of larval biology on spatiotemporal patterns of pathogen connectivity among open-marine salmon farms

“…Some pathogens, particularly parasites with a free-living larval stage, possess some movement capabilities. For example, several species of parasitic nematodes (a phylum of generally parasitic round worms) have a free swimming larval stage and several intermediate hosts before ultimately infecting marine mammals or, in some cases, humans (Lunneryd et al 2015). Sea lice, an ectoparasite of commercially and ecologically important fish species (Jones et al 2006;Costello 2006), also possess a free-swimming larval stage, that influences their horizontal dispersal abilities (North et al 2008;Johnsen et al 2016); however, they are still largely dependent on local hydrodynamics for large scale (i.e.…”

Hypoxic areas, density-dependence and food limitation drive the body condition of a heavily exploited marine fish predator

“…The infection intensity has increased in Baltic Sea cod during the past 30 years, probably due to the increase of the population of grey seals ( Halichoerus grypus ) [34–36], that are the final host of these parasites.…”