Abstract:
Linear regression analysis of length-weight relationships (LWRs) were studied to reveal the growth
patterns of 380 specimens belonging to 10 species, 9 genera and 5 families of local fish in Vavuniya
reservoir, Sri Lanka during January, 2013 to August, 2014. The regression coefficient value ‘b’ from
LWR and statistical comparison from the ideal value (b=3) were used to find the growth patterns. Most
of the local species showed isometric growth except Amblypharyngodon melettinus, Puntius sarana and
Heteropneustes fossilis. Only Channa striata (b= 2.996, p=0.396) and females of Puntius dorsalis (b=
3.076, p=0.234) appeared in the catch throughout the study period and showed a strong correlation between
length and weight. Combined sexes of, Glossogobius giuris (b= 3.178, p=0.216), Labeo dussumieri (b=
2.752, p=0.069) and females of Mystus keletius (b= 2.823, p=0.078) showed isometric growth. However,
positive allometric growth for P. sarana females (b= 3.182, p=0.000) and negative allometric growth
for combined sexes of H. fossilis (b= 2.613, p=0.001) were observed. During the drought period (July to
August, 2014), A. melettinus, Esomus thermoicos (endemic) and Rasbora daniconius were observed at the
sluice. E. thermoicos (b= 3.163, p=0.181) and R. daniconius (b= 3.065, p=0.393) obeyed the cubic law
and showed an isometric growth pattern. However, A. melettinus showed a negative allometric growth
(b= 2.367, p=0.002). Although, most of the local fish indicated isometric growth that reflected successful
thriving, allometric growth reflected the sensitivity for environmental and habitat characteristics.
Therefore, this study revealed the baseline evidence on the LWRs and the growth patterns, which could
be considered for studying the survival of local fish to reach the optimal species richness and abundance.
