SOME ASPECTS OF BIOLOGY OF Synodontis schall IN OYAN LAKE, SOUTH WESTERN NIGERIA

Abstract

This study was carried out on natural diets and morphometric characteristics of Synodontis schall from Oyan Lake,
Ogun State, Nigeria. A total of 150 fresh specimens of S. schall comprising 111 males and 39 females were collected
on a monthly basis between February and August, 2017. The samples were preserved in ice-chest and transported to
the laboratory where morphometric and meristic features were examined. Determination of sex and gut content
analyses were also carried out. Frequency of occurrence and numerical method were used for gut content analysis.
Descriptive statistics and correlations were employed to depict the results. Length-weight relationship was analyzed
using regression analysis. Results revealed that the condition factor of male, female and combined sexes of S. schall
were 1.010, 1.000 and 1.000 respectively. The study revealed that male specimens of S. schall exhibited negative
allometric growth pattern with “b” value = 2.83. While, female and combined sexes (3.00 and 2.90 respectively)
exhibited isometric growth pattern with regression values not significantly different (p>0.05) from 3. The highest
positive correlation (0.99) was detected in standard length/fork length while, the least positive correlation (1.19) was
detected in snout length/depth of caudal peduncle. A total of 68 organisms were identified as food items consumed by
this species. Frequency of occurrence showed that Closterium (54.00%) was most consumed organism while
numerically it was Nitzschia (6.95%). This species exhibited omnivorous feeding habit. The ratio of male to female
was (2.9:1) respectively. It was concluded that Oyan Lake supported the thriving fisheries of the species where it
showed a preponderance due to availability of a wider variety of dietary items. There should be reduction of fishing
intensity during the peak spawning period of the fish stock.