The increase in dietary lipid level produced a respdifferent onse in the analyzed digestive enzyme activities (Fig. 2 and Fig. 3). The activity of neutral lipase was stimulated in fish fed with diet L25, but this increase (P = 0.015) was only detected in the total activity per segment (or segmental activity; Fig. 2A). Segmental activity is thus defined as the total activity per digestive tract (hepatopancreas and gut) or segment, and it reflects the digestive capability of an organism. In addition, a significant decrease (P = 0.011) was measured in the specific activity of pancreatic lipase in group L25 ( Fig. 3B), although segmental activities did not change significantly (P = 0.124; Fig. 2B). The increase in dietary lipid levels also produced an increase in the proteolytic capability of the fish ( Fig. 2C and D). Thus, whereas the total activity of alkaline proteases was not significantly different between groups L10 and L25 ( Fig. 2C), the maximum activity for trypsin corresponded to group L10 (P = 0.004; Fig. 2D). No significant differences were detected in the specific activities for both enzymes (P > 0.05; Fig. 3C and D), although the specific activity of trypsin ( Fig. 3D) followed a similar trend to its segmental activity ( Fig. 2D). The decrease in dietary starch (to maintain the energy levels) as a consequence of the increase in dietary lipids was followed by a parallel and significant decrease (P = 0.007) in the specific activity of amylase in fish fed with diet L25 ( Fig. 3E). This decrease was clearly related to the significant decrease in the secretion of this enzyme [55.6 ± 6.16b (L6), 43.3 ± 3.20b (L10), and 28.5 ± 4.22a (L25); P = 0.001]. The secretion rates of all the other analyzed digestive enzymes were not significantly affected by the dietary treatments (P > 0.05; data not shown).