Principal component analysis of alimentary canal metrics in developmental stages of the rainbow troutOncorhynchus mykiss (Walbaum, 1792) from Kashmir Valley, India

Abstract

 The primary objective of the research was to ascertain the variations in gut morphometry in
rainbow trout Oncorhynchus mykiss during its life cycle spanning fry, fingerlings, yearlings,
table-sized and brood-sized fish. The gut morphometric parameters viz., total length (a),
standard length (b), weight (c), gut length (d), gut weight (e), intestinal length (f), liver weight (g),
relative length of the gut (h), intestinal coefficient (i), relative gut mass (j), Zihlers index (k),
hepatosomatic index (l) and gastrosomatic index (m) were all significantly correlated,
according to the component pattern profile. The biplots that were created helped to explain
the variations in the data. From the principal components PC1 and PC2, the variable i
(intestinal coefficient) of O. mykiss in all five stages was responsible for the largest variation.
This was followed by variations from PC1 that were related to the variables h (relative length
of the gut), j (relative gut mass), m (gastrosomatic index), d (gut length), e (gut weight) and
f (intestinal length). The largest variation in PC2 was caused by variable b (standard length),
and was followed by variation caused by variable a (total length). As a result, gut length
(d=0.354431), gut weight (e=0.342041), weight (c=0.333106), total length (a=0.320632),
intestinal length (f=0.301986), relative gut length (h=0.241842), Zihlers index (k=0.238940),
relative gut mass (j=0.247716) and gastrosomatic index (m=0.233688) all showed high
positive component loading. Through the use of basic metrics to assess different gut
parameters, we were able to ascertain the feed and nutritional needs of O. mykiss at different
developmental stages. Understanding alimentary canal shape is crucial for fish digestion
and for optimising fish nutrition as fish digestive systems and feeding practices advance.

Keywords:
Fingerling, Gut metrics, Intestinal length, Kashmir, Life cycle, Nutrition, O. mykiss, Raceways