THE BIOLOGY OF THE SOMPAT GRUNT, POMADASYS JUBELINI (CUVIER, 1830) IN THE NEW CALABAR-BONNY RIVER, RIVERS STATE, NIGERIA
THE BIOLOGY OF THE SOMPAT GRUNT, POMADASYS JUBELINI (CUVIER, 1830) IN THE NEW CALABAR-BONNY RIVER, RIVERS STATE, NIGERIA
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Date
2014-07
Authors
AGBUGUI, Marian Onwude
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Abstract
The biology of the Sompat grunt Pomadasys jubelini (Cuvier, 1830) from New Calabar-
Bonny River was studied from June 2011 to May 2013. Pomadasys jubelini belongs to the
family Haemulidae, genus Pomadasys. This species is common in costal and brackish
waters of Nigeria. It is affordable, tasty with high economic and nutritional value.
Specimens caught using gill nets, hook and line and traps were used to study the
biometrics, growth, fecundity and stomach contents using standard procedures. Physicochemical
parameters of water from the River were determined by using a Multi-insitumeter
at the three stations and results obtained were temperature 28.62±0.62°C, 28.37±0.7°C and
28.41±0.57°C; pH 6.36±0.34, 6.19±38 and 6.27±0.74; salinity 11.50±7.71ppt,
12.15±5.24ppt and 0.58±0.94ppt; and dissolved oxygen 6.88±0.51mg/l, 6.92±0.58mg/l and
6.88±0.63mg/l for Stations 1, 2 and 3 respectively. There were significant differences (P≤
0.05) in salinity among the three Stations, Station 1 was salt water, Station 2 brackish/tidal
and Station 3 predominantly freshwater. The standard length of P. jubelini ranged from
8.50cm to 47.60cm and the weight from 17.00g to 2320g. There was a high positive
relationship (r = 0.91) between fish length and weight in males and females (r = 0.99). The
b-value (b<3) indicated a negative allometric growth. The monthly condition factor (K)
ranged from 0.00–2.15 in both males and females. The male to female ratio of Pomadasys
jubelini was 1:2.1. The age range was 0+ to 4+ and the immature fish were found in the
5.0cm-15.00cm length class. Sub-adults occurred in the 15.10cm-30.00cm length class
while the adults were between 30.10cm-55.00cm. More of class length 20.10cm-50.00cm
(40%) were obtained from Station 2 and most from Station 3 (60%), an indication that
juveniles inhabit brackish water and the adults salt water. Ageing structures such as
otoliths, scales and transverse section of spines did not show definite patterns of annuli
formation. The occurrence of gravid females in September and October indicates that
spawning coincided with the end of the rainy season. The minimum and maximum
fecundity were 9,085 and 37,926 eggs respectively; there was a significant correlation
(r=0.94) between fish weight and fecundity. The mean gonado-somatic index (2.89%)
revealed that this species uses up to 2.89% of its total body weight for egg production. The
terminal mouth in P. jubelini with a gape of up to 10% of its total body length, allows the
fish to seize its prey easily. The setiform teeth in multiserial bands enable the fish to grip
its prey firmly in the mouth before swallowing, and the pharyngeal teeth on the roof and
floor of the mouth are smooth and pebble-like and adapted for crushing prey before
swallowing. The long and hard gill rakersconfirm that P. jubelini is a carnivore. Stomach
content analysis showed that Callinectesamnicola(crabs) 73.1%, Sardinellamaderensis
(0.69%), Scomberomorustritor (1.51%), Ethmalosafimbriata(0.56%),
Macrobrachiummacrobrachion(24.08%), and Littorinaanguilifera(0.02%) were the main
food items consumed by P. jubelini;most of the food items were found intact, indicating
that preys are swallowed whole. In conclusion, there are variations in the physico-chemical
parameters of water of the New Calabar-Bonny River; P. jubelini shows a negative
allometric growth pattern and its attainable age is 0+ to 4+. Pomadasys jubelini is a total
spawner, and a carnivorous fish species that shows transition from consumption of
invertebrates at the immature and sub-adult stages to piscivorous diets at adult stage. It is
recommended that relevant/appropriate government agencies monitor and control activities
that may pollute the New Calabar-Bonny River. The breeding grounds of P. jubelini,which
is most likely at the freshwater zone, will thus be protected. The juveniles of P. jubelini are
recommended for cage culture in the marine environment, and its feed should comprise
invertebrates and smaller fish species.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY IN PARTIAL FULFILMENT OF THE
REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHILOSOPHY DEGREE IN
FISHERIES
DEPARTMENT OF BIOLOGICAL SCIENCES, FACULTY OF SCIENCE,
AHMADU BELLO UNIVERSITY, ZARIA
JULY, 2014
Keywords
BIOLOGY,, SOMPAT GRUNT,, POMADASYS,, JUBELINI,, CALABAR-BONNY,, RIVER,