Stock discrimination and movements of narrow‐barred Spanish mackerel across northern Australia as indicated by parasites

Abstract

The parasite fauna of Spanish mackerel Scomberomorus commerson from 10 sites across northern Australia and one site in Indonesia, was examined to evaluate the degree of movement and subsequent stock structure of the fish. Kupang fish (Indonesia) had very few Terranova spp., Grillotia branchi, Otobothrium cysticum or Pterobothrium sp. compared to Australian fish, indicating that no Australian fish enter the Kupang fishery. Univariate and discriminant function analysis of four ‘temporary’ parasite species, the copepod Pseudocycnoides armatus and the monogeneans Gotocotyla bivaginalis, Pricea multae and Pseudothoracocotyla ovalis, demonstrated little similarity between areas of northern Australia, indicating minimal short‐term exchange between neighbouring groups of S. commerson. Analyses of five ‘permanent’ parasite species, the larval helminths G. branchi, O. cysticum, Pterobothrium sp., Callitetrarhynchus gracilis and Paranybelinia balli, also revealed large differences between areas thus indicating long‐term separation. There are at least six parasitological stocks across northern Australia: Fog Bay/Bathurst Island, Cape Wessel, Groote/Sir Edward Pellew, Mornington Island, Weipa, and the Torres Strait. The occurrence of a few irregular fish in the samples suggested that up to 5% of fish moved between stocks during their lifetime. The similarity of within‐school variability to that between schools showed that the fish do not form long‐term school associations.

The stock structure of grey mackerel Scomberomorus semifasciatus in Australia as inferred from its parasite fauna

“…In a similar study on the closely related S. commerson, Moore et al (2003) found using canonical analysis that there were at least 6 parasitologically distinct stocks of S. commerson across northern Australia, a finding that was supported by otolith isotope analysis on the same fish species ). In S. semifasciatus parasite differences across northern Australia were less marked.…”

“…In addition, they have been used successfully by many authors in earlier studies (e.g. Moore et al, 2003;Williams and Lester, 2006;MacKenzie et al, 2008). To accurately identify these parasites fresh samples were collected from the eastern Gulf of Carpentaria and the east coast of Queensland.…”

The use and abuse of parasites as stock markers for fish

“…At that time the parasites were thought to be directly transmitted but recent studies show that they almost certainly require an intermediate host (Kent et al, 2001) and therefore do not conform to his condition. Many workers have found that the best markers are larvae or juveniles of anisakids and trypanorhynchs, parasites that require at least three host species to complete their life cycles (Boje et al, 1997;MacKenzie and Abaunza, 1998;Moore et al, 2003) so the one-host recommendation should be abandoned.…”

Molecular genotyping of Anisakis Dujardin, 1845 (Nematoda: Ascaridoidea: Anisakidae) larvae from marine fish of Balinese and Javanese waters, Indonesia

“…The author reported that Indonesia is at the centre of the diversity of this group of fish worms, and predatory fish especially can be highly infected. Lester et HELMINTHOLOGIA, 45, 1: 3 -12, 2008 Molecular genotyping of Anisakis Dujardin, 1845 (Nematoda: Ascaridoidea: Anisakidae) larvae from marine fish of Balinese and Javanese waters, Indonesia Moore et al (2003) and Latama (2006) used fish parasites to distinguish between Indonesian and Australian stocks of the narrow-barred Spanish mackerel Scomberomorus commerson, and Jakob and Palm (2006) studied 5 commercially important fish species off the south-western Java coast for fish parasites. The latter recorded 38 different parasite species, among these was Anisakis sp., reaching a prevalence of 100 %.…”