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.
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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,
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