Stock discrimination of mackerel scad Decapterus macarellus (Cuvier, 1833) in the eastern Indonesia based on metazoan fish parasite composition

Abstract

Mackerel scad Decapterus macarellus (Cuvier, 1833), a small pelagic species, is the major catch in Asia, particularly in Indonesia. Despite a high catch volume, its utilization status is relatively unknown since stock assessment is mostly conducted for the entire small pelagic group without separating the species. Studies on population biology and stock distribution of mackerel scad in Indonesia so far involved catch-based production models, growth parameter analyses, otoliths, and fish genetics. We herewith discriminate eastern Indonesian fish stocks of D. macarellus by comparing the respective metazoan parasite community. We collected 105 specimens of mackerel scad from three closely connected fishing grounds representing two Indonesian fisheries management areas. Recorded metazoan parasites belonged to the Monogenea (4 species), Digenea (8 species), Acanthocephala (1 species), and Crustacea (2 species), with the two Monogenea Allopseudodiclidophora opelu (Yamaguti, 1965) and Pseudodiclidophora decapteri (Yamaguti, 1965) being the most prevalent. A multidimensional scaling analysis revealed the clustering pattern of the hosts based on the parasites, identifying two major fish stocks, the North Sulawesi group and the North Maluku group. The strength and weaknesses of the so far applied stock assessment methodologies for this small pelagic fish in Indonesia are discussed.