World Aquaculture Magazine - September 2021

60 SEP TEMBER 2021 • WORLD AQUACULTURE • WWW.WA S .ORG Control Measures Parasite prevalence is affected by several factors. In marine protected areas (MPAs), habitat heterogeneity, hybrid zones occupied by species and upwelling-directed influx of nutrients contribute to high biodiversity that may reduce the prevalence of parasitic isopods. In an MPA along the Mediterranean coast of Southern Spain (Alboran Sea), Anilocra physodes parasitized only populations of striped bream Lithognathus mormyrus , despite the presence and diversity of other possible fish hosts (Navarro-Barranco et al. 2019). There was an evident degree of the parasite’s host specificity. Moreover, despite a lower mean prevalence rate in MPAs (2 percent) as compared to non-MPAs (16 percent), there was no relationship between population density of striped bream and prevalence rates. However, a direct correlation between fish size and parasitic prevalence was still detected, possibly indicative of detrimental effects of A. physodes parasitism on growth and development of the fish host. Other factors that have plausibly contributed to increasing prevalence rates in non-MPAs could be anthropogenic sources of alteration such as fishing and tourism (Navarro-Barranco et al. 2019). The use of functional and bioactive dietary ingredients or supplements is also a potential control strategy. In farmed Atlantic salmon Salmo salar , two diets —one containing β-glucans to act as an immunostimulant and another with citral to act as a natural counterpart were tested for efficiency against the parasitic prevalence of sea louse Lepeophtheirus salmonis (Jensen et al. 2015). Quantitative histology of the epidermis and proteomic analyses of epidermal mucus of the fish host were assessed after cultured sea lice were administered to the salmon. Salmon growth was similar for both diets. However, salmon fed citral diet had the lowest mean sea louse intensity while salmon fed β-glucan-diet had a mean intensity even higher than that of the control (Jensen et al. 2015). Moreover, salmon fed citral diet exhibited the highest protein concentration in the epidermal mucus. Hence, there is a potential for functional diets to aid in isopod parasite management in fisheries, particularly in decreasing sea louse prevalence in Atlantic salmon populations. Mixed diets containing synergistic natural and artificial immunostimulants, proteomic studies of other tissues, and testing of dietary supplements against other parasitic isopod species in various fishery species are further recommended for possible control measures (Jensen et al. 2015). Better understanding of the life cycle of parasitic isopods could also help in formulating innovative mitigation and management strategies. Notes Tanya Faye S. Muji, Joaquin R. Sorreta, Selwyn B. Briones Jr., Justine Oliver S. Maquirang and Janice Alano Ragaza, Department of Biology, School of Science and Engineering, Ateneo de Manila University, Katipunan Avenue, Loyola Heights, Quezon City, Metro Manila, Philippines 1108 Corresponding author: J.A. Ragaza, jragaza@ateneo.edu References Adorador, V.C., M.A. Bernardo, J.L.L. Gonzales, A.C. Lam, F.A.M. Maijan, R.D.S. Papa and J.R. Castillo. 2006. Morphological and DNA size-based differences among Corallana spp. in Oreochromis sp. found in open waters and fish cages in Taal Lake. The Philippine Biota 39(2):5-11. Anand Kumar, A., G. Rameshkumar, S. Ravichandran, E.R. Priya, R. Nagarajan and A.G.K Leng. 2013. Occurrence of cymothoid isopod fromMiri, East Malaysian marine fishes. Journal of Parasitic Diseases 39(2):206-210. Anand Kumar, A., G. Rameshkumar, S. Ravichandran, R. Nagarajan, K. Prabakaran and M. Ramesh. 2016. Distribution of isopod parasites in commercially important marine fishes of the Miri coast, East Malaysia. Journal of Parasitic Diseases 41(1):55-61. Behera, P.R., S. Ghosh, P. Pattnaik and M.V. Rao. 2016. Maiden occurrence of the isopod, Norileca indica (H. Milne Edwards, 1840) in pelagic and demersal fin fishes of Visakhapatnamwaters along north-west Bay of Bengal. Indian Journal of Geo-Marine Science 45(7):856-862. Boyko, C.B., N.L. Bruce, K.A. Hadfield, K.L. Merrin, G.C.B. Poore, S. Taiti, M. Schotte and G.D.F. Wilson. 2019. WoRMS Isopoda: World marine, freshwater, and terrestrial isopod crustaceans database (version 2019-03-05). In Y. Roskov, G. Ower, T. Orrell, D. Nicolson, A heavy infestation of marine leech Zeylanicobdella arugamensis on a spotted grouper. The dark-colored parasites are attached in large numbers on the fins. Fish infected with Z. arugamensis eventually die within three days due to secondary bacterial infections (Photo: E. Cruz-Lacierda). A female Caligus sp. collected from a grouper. More commonly known as sea louse, the copepod Caligus parasitizes marine fish. The filamentous tails are egg sacs or egg strings that distnguish a female from a male sea louse (Photo: Fish Health Section, Southeast Asian Fisheries Development Center/ Aquaculture Division (SEAFDEC/AQD)).