Investigating Feeding Regimen of Brown Trout Fario in Tonekabon River, Northern Iran
The present study was conducted in a four-season period, from September 2016 to 2017, in Tonekabon River,
northern Iran. A total of 91 brown trout fish were collected from five stations using electrofishing
equipment. They composed 40 females, 41 males, and 10 of unknown sex. Their age ranged from 1 to 3 years, and
they had a minimum and maximum length of 41 mm and 175 mm, respectively. The preys identified within their
gastrointestinal tract included insect larvae of Ephemeroptera, Diptera, Liponeura, Simulium, Hydropsyche, Coleopteran,
Trichoptera, flying insect, spawn, Odonata, Oligochaeta, Plecoptera taxonomic groups. The collected fish were classified
into three age groups including 1- and <1-year, 2-years, and 3-years old as a scale to define their feeding intensity. The
consumption percentage of Hydropsyche and Liponeura was significantly different among three classes. However, there
was no significant difference in the consumption intensities of Ephemeroptera, Plecoptera, and Simulium. The
reproduction season of brown trout fish is within fall. Maximum feeding intensity occurs in spring, whereas
minimum feeding takes place within summer and fall seasons. Classes 1 and <1-year-old had higher feeding intensity
than other classes (classes 2 and 3 years old). In general, Plecoptera, Ephemeroptera and Simulium constitute primary
preys of the fish, while Liponeura, Hydropsyche, Dipteral, Trichoptera, and Oligochaete, Coleoptera, Oligochaeta, Odonatan,
flying insects, and spawn are considered as the subordinate prey for the feeding regimen of brown trout. The highest
amount of prey for stations 1, 2, 3, 4 and 5 included Simolium, Ephemeroptera, Simolium, Simolium and Liponeura,
respectively. Station 2 had the highest glutting stomach index, followed by station 1, both of which were located on
the Se-Hezar River.
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