Abstract
Salmo trutta fario is the most important fish species of family Salmonidae inhibited in cool waters all over the world including the nortern parts of Pakistan. This study was aimed to find out the prey selection and feeding habits of the species. One hundred and eighty five Salmo trutta fario were captured from March 2016 to April 2017. Feeding intensity as represented by a fullness index (FI), changing with various length groups and season. Out of 185 Brown trout 24 fish stomaches were found empty. The most important and common food items of brown trout were Brachycentridae, Blepharocera, Hydropsychidae, ephemerella spp. Kruskal Wallis H-test were applied on feeding intensity groups consisting of three month group. The test statistic for K.W-H-test were (H=8.13 with df =3) had a p-value of 0.043 < (alpha=0.05 indicates favor of the alternative hypothesis of at least one difference among the feeding intensity groups. The linear relationship of N with index of relative importance and %IRI denoted by least square regression line (N = 35.2 + 22.1%IRI), shows that for 22 prey there is 1% change in IRI. The relationship between total length (mm) and fish body weight (gm) is expressed by Pearson correlation coefficient (r = 0.976), showed that total length (mm) and fish body weight (gm.) is highly correlated. Descriptive statistics are used for the stomach fullness, which shows that feeding intensity was recorded higher from March to May. A total of 2289 preys was recorded including the most common were; Trichoptera, Hydropsychidae, Brachycentridae, diptera, blepharocera, ephemerala, chironomida, honey bees, grass hopper, locust, trout egg, trochanter, plant tissue, stones were retrieved from the gut contents of brown trout. According to index of relative importance IRI% four preys represents major components of the diet. The highest IRI% was recorded in Brachycentridae (39.38%), followed by blepharocera (13.23%), Hydropsychidae (10.76%) and ephemerella spp (8.28%). The relationship between IRI and FO is (r =0.556) is moderately correlated with coefficient of determination (r2=0.31). This study will help in the development of an artificial diet for the species for better growth performance in captivity.
Highlights
Information on food and feeding habits of fish is very important for the artificial development in culture system which provide a potential source of food
Studies on ecto and endo parasitic fauna of snow trout of river Swat and river Panjkora have been published by Khalid et al (2020) and Ahmad et al (2020) while there is no study on food and feeding habit of the species
The presents study aimed to determine the prey selection and feeding habits of Salmo trutta fario in upper parts of river Swat, Pakistan and the data were taken from March 2016 to April 2017
Summary
Information on food and feeding habits of fish is very important for the artificial development in culture system which provide a potential source of food. Rainbow trout occupied the cold waters of Swat, Dir, Chitral Shangla and Kohistan in Pakistan (Hassan et al, 2007). Socio-economically and tourist point of view this fish play a very vital role on commercial level (Butler et al, 2009). Salmonids are transporter of energy from lower to higher trophic levels lies on the top-consumers list in freshwater environments (Karlsson and Byström, 2005). Studies on ecto and endo parasitic fauna of snow trout of river Swat and river Panjkora have been published by Khalid et al (2020) and Ahmad et al (2020) while there is no study on food and feeding habit of the species. Feeding habit of a fish is essential as it does not shows its diets and indicate relationship of various ecological components like behavior, habitat use, energy intake and inter/intra specific competition (Zachariah and Abdurahiman, 2010)
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