This study evaluated the efficacy of albendazole, ivermectin, levamisole, mebendazole and praziquantel on monogeneans of Colossoma macropomum, based on in vitro and in vivo assays. In vitro assays indicated that albendazole (500, 100, 1,500 and 2,000 mg/L), ivermectin (200, 250, 300 and 350 mg/L) and levamisole (50, 75, 100 and 125 mg/L) were 100% effective against Anacanthorus spatulatus, Notozothecium janauachensis, Mymarothecium boegeri and Linguadactyloides brinkmanni, while mebendazole (125, 150, 175 and 200 mg/L) and praziquantel (5, 10, 15 and 20 mg/L) were ineffective. Fish mortality in 24 hr therapeutic baths with 500 mg/L of albendazole was 6.6%, but the behaviour of the animals remained unchanged, while 200 mg/L of ivermectin caused lethargy, signs of hypoxia and 100% mortality within 2 hr, and 125 mg/L of levamisole caused no mortality. The efficacy of 500 mg/L of albendazole was 48.6% in the 24 hr baths, while that of 125 mg/L levamisole was 88.2%. Although ivermectin showed in vitro efficacy, the lowest concentration used in baths was highly toxic to fish. Therefore, we recommend the use of 125 mg/L of levamisole to control and treat monogenean infestations on C. macropomum in fish farming.

In sh, one of the most important interactions is that occur between parasite species and environment.Wild sh interactions with parasites of different taxa can result in diseases for sh and consequently damages to the shing industry. This study investigated the ectoparasite fauna in Mugil curema in Amapá state estuary, in Brazilian coast region. The parasite prevalence was 51.4%, and a total of 282 parasites were collected among Ligophorus brasiliensis (Dactylogyridae), Excorallana longicornis (Corallanidae), larvae of Gnathia sp. (Gnathiidae) and Ergasilus atafonensis (Ergasilidae), but the dominance was of L. brasiliensis. The parasites presented highly aggregated dispersion, except for Gnathia sp. that had a random dispersion. There was a predominance of hosts parasitized by zero and one species. The relative condition factor did not differ between parasitized and non-parasitized sh. The body size of hosts did not in uence the parasite abundance. The community of ectoparasites consisted of low species richness with low infection levels. This is the rst study on parasites of sh from the coast of the State of Amapá and is the rst report of Gnathia sp. for M. curema.

In fish, one of the most important interactions is that occur between parasite species and environment. Wild fish interactions with parasites of different taxa can result in diseases for fish and consequently damages to the fishing industry. This study investigated the ectoparasite fauna in Mugil curema in Amapá state estuary, in Brazilian coast region. The parasite prevalence was 51.4%, and a total of 282 parasites were collected among Ligophorus brasiliensis (Dactylogyridae), Excorallana longicornis (Corallanidae), larvae of Gnathia sp. (Gnathiidae) and Ergasilus atafonensis (Ergasilidae), but the dominance was of L. brasiliensis. The parasites presented highly aggregated dispersion, except for Gnathia sp. that had a random dispersion. There was a predominance of hosts parasitized by zero and one species. The relative condition factor did not differ between parasitized and non-parasitized fish. The body size of hosts did not influence the parasite abundance. The community of ectoparasites consisted of low species richness with low infection levels. This is the first study on parasites of fish from the coast of the State of Amapá and is the first report of Gnathia sp. for M. curema.