The occurrence and behaviour of Pseudoterranova decipiens and Anisakis simplex (Nematoda) in Gadus morhua and their impacts on commercial processing

• Main Author: Milligan, Rosanna J.
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: QH301 Biology; QL Zoology; Gadus morhua
• Online Access: http://theses.gla.ac.uk/252/; http://theses.gla.ac.uk/252/1/2008milligan-MSc.pdf; https://eleanor.lib.gla.ac.uk/record=b2630584

A Scottish seafood processor commissioned this study because the high prevalence of parasitic nematodes in their cod fillets meant they were unable to meet the standards demanded by their retailer. The aims were to determine which species of nematode were present, and whether the detection or mortality rates could be improved during processing with a view to eliminating ‘live worm’ complaints by consumers. Anisakis simplex, Pseudoterranova decipiens and Hysterothylacium aduncum (Anisakidae) were identified from a total of 4920 specimens. All species were more abundant within the viscera, but H. aduncum was absent from the musculature. In the flesh, significantly more A. simplex were recovered from the abdominal flaps than the fillets; there was no difference for P. decipiens. Type of capture vessel, sea area, somatic condition and season had no effect on the abundance of nematodes. Of the experimental treatments trialled, light, desiccation, temperature, electrocution and modified atmosphere packing had no significant effect on either the behaviour or mortality of the nematodes. Only high hydrostatic pressure (HHP) affected the mortality of the Anisakis simplex and Pseudoterranova decipiens. A pressure of 400MPa for 90 seconds caused 100% mortality of A. simplex. Lower pressures are likely to be as effective but will require further investigation. 240MPa for three minutes was the minimum treatment required to kill 100% of P. decipiens after 72 hours. Using published literature, it may be possible to reduce initial numbers of nematodes by only fishing areas that are known to have a low prevalence of parasites during a given season. Avoiding regions where the final hosts (cetaceans and pinnipeds) are known to congregate would also be beneficial. Candling remains the only commercially viable method for detecting nematodes in fish flesh, but other techniques are in development. Of these, the most promising appear to involve electromagnetic detection and imaging spectroscopy although they are not yet ready for industrialisation.