In the present study gut type was described and intestinal indices (i.e. mean gut length, relative gut length and Zihler's index) were estimated and compared for 58 fish species from the North Aegean Sea. A strong relationship between gut length (GL) and total length (TL) (significant relationships (P < 0.05) for 52 species) was found, whereas the hypothesis of the allometric growth of GL with TL was confirmed for 27 out of the 52 species. For the same TL, GL differs for species with different feeding habits (in omnivores > carnivores), as previously reported. Finally, for the same TL, GL also differs for species with different habitats (reef-associated > pelagic > benthopelagic > demersal) and gut types (Z-shaped with multiple loops > looped Z-shaped > Z-shaped >straight > convoluted > short with spiral valve).
