This study determined the minimum inhibitory concentrations (MICs) for oxytetracycline hydrochloride (OTC) and erythromycin (Em), along with the a-glucosidase (a-glu) activities in 110 Nocardia seriolae strains isolated in Miyazaki and Kagoshima prefectures in 2008-2009. The strains were examined for the presence of the tet(K), tet(L), tet(M), tet(O), tet(S), erm(A), erm(B), mph(A), mef(A), and msr(D) genes. All the a-glu-positive strains (n = 15) were OTC resistant and Em sensitive, with MICs of 32-64 and \0.125 lg/ml, respectively. All the aglu-negative strains (n = 95) were OTC sensitive, with MICs of 2-4 lg/ml, and most of them (93 of 95) were Em resistant, with MICs of [128 lg/ml. The MICs for Em in the remaining 2 a-glu-negative strains were \0.125 lg/ml. The 15 OTC-resistant strains possessed the tet(K) and/or tet(L) gene(s), and all of the 93 Em-resistant strains possessed both the mef(A) and msr(D) genes. The relationship between a-glu activity and drug sensitivity of the N. seriolae strains may explain the difference in prevalence of each phenotype. Nevertheless, the relationship should be further explored using N. seriolae isolates collected from more prefectures and farms.

Characteristics and frequency of cannibalism were investigated in the juvenile orange-spotted grouper Epinephelus coioides in order to obtain information to reduce mortality and, therefore, improve the seed production and culture of this species. In the present study, cannibalism was classified into three types: C-1: prey nipped in the head or body, C-2: prey swallowed whole, head first, and C-3: predator suffocated to death with the prey in its mouth. As size-grading is widely known to minimize fish cannibalism, experiments were also conducted on 30-, 40-, and 50-mm-TL size groups of the fish. In the results of both groups that had and had not been size-graded, cannibalism was more prevalent in the 30-mm group than in [40-mm groups. Size-grading demonstrated a tendency to minimize mortality in [40-mm groups, whereas there was no effect in fish of the 30-mm group. These results suggest that dominant juvenile grouper attack subordinates regardless of their size differences, and the size-graded technique is therefore ineffective in reducing cannibalism in the 30-mm group.

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The meat quality of farmed yellowtail Seriola quinqueradiata fed on extruded pellets (EP) containing 0.5%