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Background <p>Tusk (<i>Brosme brosme</i>) is a demersal species of increasing commercial importance in Norwegian fisheries, yet information on its parasite fauna remains limited. This study represents the first systematic investigation of ascaridoid nematodes infecting tusk from six localities across a wide latitudinal gradient in Norwegian waters, spanning from the North Sea to the Barents Sea.</p> Methods <p>A total of 187 fish from commercial catches were examined using the UV press method, and 225 anisakid larvae were genetically identified through mitochondrial DNA (cox2) sequencing.</p> Results <p>Nine species were recorded: <i>Anisakis simplex</i> (s.s.), <i>Phocanema decipiens</i> (s.s.), <i>P. krabbei</i>, <i>P. bulbosum</i>, <i>Contracaecum osculatum</i> B, <i>Phocascaris cystophorae</i>, <i>Phocascaris</i> sp., <i>Hysterothylacium aduncum</i>, and <i>Hysterothylacium</i> sp. <i>Anisakis simplex</i> (s.s.) occurred at 100% prevalence and was detected in all examined tissues, including viscera, muscle, liver, and gonads. Notably, 42% of larvae were located in the musculature, with 92% of flesh invading larvae concentrated in the belly flap region. <i>Phocanema</i> spp. were also consistently present, with <i>P. decipiens</i> (s.s.) and <i>P. krabbei</i> predominantly infecting muscle tissue, whereas <i>Contracaecum</i>, <i>Phocascaris</i>, and <i>Hysterothylacium</i> spp. were restricted to the viscera. Distinct geographic patterns were observed among <i>Phocanema</i> species, including the occurrence of <i>P. bulbosum</i> in Arctic samples.</p> Conclusions <p>Spatial differences in parasite assemblages between northern and southern sampling areas suggest ecological structuring, likely reflecting variation in definitive host distribution and trophic interactions, and support the use of anisakid parasites as biological tags for supplemental stock discrimination. The observed infection patterns further suggest that tusk trophic ecology may involve a stronger piscivorous component than previously assumed. High infection levels and the frequent occurrence of zoonotic anisakids in the musculature highlight potential food safety and product quality concerns.</p> Graphical Abstract <p></p>

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Nematode parasite assemblages in tusk (Brosme brosme) along the Norwegian continental shelf: indicators of fish host feeding ecology and stock structuring

  • 期刊论文

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  • 发表日期：

    2026年7月8日

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  • Paolo Cipriani,
  • Miguel Bao,
  • Lucilla Giulietti,
  • Julia E. Storesund,
  • Kristin Helle,
  • Arne Levsen

摘要

Background

Tusk (Brosme brosme) is a demersal species of increasing commercial importance in Norwegian fisheries, yet information on its parasite fauna remains limited. This study represents the first systematic investigation of ascaridoid nematodes infecting tusk from six localities across a wide latitudinal gradient in Norwegian waters, spanning from the North Sea to the Barents Sea.

Methods

A total of 187 fish from commercial catches were examined using the UV press method, and 225 anisakid larvae were genetically identified through mitochondrial DNA (cox2) sequencing.

Results

Nine species were recorded: Anisakis simplex (s.s.), Phocanema decipiens (s.s.), P. krabbei, P. bulbosum, Contracaecum osculatum B, Phocascaris cystophorae, Phocascaris sp., Hysterothylacium aduncum, and Hysterothylacium sp. Anisakis simplex (s.s.) occurred at 100% prevalence and was detected in all examined tissues, including viscera, muscle, liver, and gonads. Notably, 42% of larvae were located in the musculature, with 92% of flesh invading larvae concentrated in the belly flap region. Phocanema spp. were also consistently present, with P. decipiens (s.s.) and P. krabbei predominantly infecting muscle tissue, whereas Contracaecum, Phocascaris, and Hysterothylacium spp. were restricted to the viscera. Distinct geographic patterns were observed among Phocanema species, including the occurrence of P. bulbosum in Arctic samples.

Conclusions

Spatial differences in parasite assemblages between northern and southern sampling areas suggest ecological structuring, likely reflecting variation in definitive host distribution and trophic interactions, and support the use of anisakid parasites as biological tags for supplemental stock discrimination. The observed infection patterns further suggest that tusk trophic ecology may involve a stronger piscivorous component than previously assumed. High infection levels and the frequent occurrence of zoonotic anisakids in the musculature highlight potential food safety and product quality concerns.

Graphical Abstract