Studies on the "biology of the Family Schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji, Nigeria.
Studies on the "biology of the Family Schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji, Nigeria.
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Date
1977-10
Authors
OLATUNDE, AKINOLA A.
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Abstract
The biology of the Family Schilbeidae (Osteiehthyes :
Siluriformes) in Lake Kainji, Nigeria was investigated. Eleven
sampling stations located within the central basin of the lake
were sampled monthly with static gill nets of various stretched
mesh sizes, supplemented by netting in Shagunu creek with smallmesh
nets.
Five schilbeid species were found. Eutropius niloticus
RUPPELL and Physailia pellucida BOULENGER were the commonest and
most abundant. Schilbe mystus LINNAEUS was less abundant, but
was far more abundant than Siluranodon auritus (GEOFFROY ST.
HILLAIRE) and Schilbe uranoscopus RUPPELL which were very r a r e.
All species were found in a variety of habitats in the lake and
adjacent in lets; but P. pellucida is pelagic and S. mystus is
riverine.
The pectoral spines display rings which are shown to be annual
so can be used to determine the age and growth of E. niloticus
and S. mystus. Females grow faster, attain greater maximum s i z e,
live longer and attain maturity at a greater length than the
males. Sex ratio varied seasonally with more females in the
population than males. Sex ratios and gonad cycles provided evidence
of breeding pattern for all the species except S. uranoncopus.
P. pellucida spawned several times during a prolonged
breeding season while others spawned once during a short breeding
season from June to November.
Stomach contents showed that although every species would
take a variety of food, Siluranodon auritus is phyto-plonktonivorous;
Physailia pellucida feeds mainly on zooplankton, both
species of Scbilbe are mainly piscivorous and Eutropius niloticus
is omnivorous. Food selection was influenced by age or size of
the fish and seasonal availability of food items. Digestive
enzymes showed a correlation with the dets of the species
studied.
The biochemical and nutritive values of the three common
schilbeids were determined and suggestions are irrade for more
effective harvesting of schilbeids for consumption
Description
Dissertation submitted for the degree of
DOCTOR OF PHILOSOPHY
in
Department of Zoology
Keywords
biology,, Family Schilbeidae,, Osteichthyes,, Siluriformes),, Lake Kainji, Nigeria.