Study on the food habits of Crested Loach, Metaschistura cristata in the northeast of Iran

Metaschistura cristata is a small nemacheilid loach species found only in Turkmenistan and Iran. The present study reports data on its feed habits and preferences, based on 1029 specimens collected in the northeast of Iran. Maximum age, based on opercula readings, was 6+ years for both sexes. Specimens ranged in size from 24 to 98 mm total length and weighted from 0.08 to 7.32 g. Length-weight relationships implied positive allometric growth for both sexes and sex ratio was 1:1. Small relative gut length (<1) confirmed that M. cristata is a carnivorous species. The values of relative gut length (13.2-86.4%) and gastrointestinal index (53.6-94.4%) increased significantly (P<0.05) with an increase in the age class from 0+ to 6+. The highest value of gastrointestinal index was observed in May. Based on the Ivlev index, the preferential feed ingredients were blood worm (chironomidae) and ephemeroptera. Overall, the present study provides evidence that the population of Metaschistura cristata in the northeast of Iran is in the unique condition; however, more experimentation is necessary to determine biological effects of this species on the ecosystems.