Feeding indices of Isfahan toothcarp (Aphanius isfahanensis) in Zayandeh River in Iran (Teleostei: Aphaniidae)

The feeding characteristics of Aphanius isfahanensis in the Zayandeh River of Isfahan Province were studied by collecting 440 specimens (220 males and 220 females) from July 2016 to May 2017. The specimens were anesthetized in 1% clove oil, fixed in 10% buffered formalin and transferred to the laboratory. The average condition factor for males was 1.7, for female 1.26 and showed significant difference between different months in both sexes (P<0.05). The average length and weight for all specimens were 38.57±5.24mm and 1.00±0.41g, respectively. The average length of gut (RLG) for all fish was 0.54±0.17 during the year. The mean RLG in different length classes showed significant differences (P<0.05). The highest Gastrosomatic Index value was in July (0.05) and the lowest in August (0.03) and showed significant differences in different months (P<0.05). A total of 181 empty stomachs were observed amongst the 440 fish and there were significant differences in different months (P<0.05). Therefore, it can be concluded that this is a carnivorous fish (mainly aquatic insect larvae) with a modest feeding throughout the year