The self-organizing map (SOM), which is widely used in economics and engineering applications, is a type of artificial neural network trained without supervision. SOM is used to represent multidimensional data in much lower dimensional spaces-usually in two dimensions (2D)-while preserving the topological properties of the input space. In this study, 2D maps were produced by using SOM to display the relationship between seasons, length, weight, and isopod infestation of goldblotch grouper (Epinephelus costae Staindahner, 1878). This is first study of gnathiid isopod praniza larvae infesting goldblotch grouper (E. costae Staindahner, 1878) in the northeast Mediterranean Sea (36A degrees 36' N-36A degrees 07' E, 35A degrees 52' N-36A degrees 25' E) in Iskenderun Bay. Fish were sampled monthly from Iskenderun Bay for a period of 12 months from 2006 May to 2007 April (Nt = 331, Wt +/- SD (range) = 392.92 +/- 72.76g (169 - 927g), TLt +/- SD(range) = 30.85 +/- 3.88 cm (17 - 48.3 cm). Gnathia sp. was only extracted from the epithelium of the buccal cavity and internal side of the gills arch. The monthly patterns in infested fish samples (Np = 109, Wp +/- SD (range) - 349.25 +/- 182.79g (169 - 853g), TLt +/- SD(range) - 26.05 +/- 12.68cm (18.2 - 45.0cm)) infestation rates (mean prevalence, P = 28.12% (0-60) and mean intensity (MI +/- SD - 23.69 +/- 14.78(4 - 82), the relationship between length-weight and infested/non-infested fish were calculated. Although the gnathiid parasite high intensities were observed in fish, there was no significant effect on the growth and general health condition of infested fish.