Research papers
1975 · Journal of Fish Biology · 142 citations
An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1–7 m deep. Adult fishes (over 8 cm standard length) are usually absent from water deeper than 12m and shallower than 0–5 m, whereas juveniles may occur at all depths, and fry only in very shallow water. T. mossambica inhabits the littoral and sublittoral in the warm and transition periods (August–April) but moves into deep water in the cool season (May–July). Exposed and sheltered areas are utilized for different purposes by adult fishes, the former for nesting, and latter for feeding and mouth–brooding. Habitat selection by males is governed by the availability of suitable nest sites. Nests are most common in sparsely–vegetated sheltered areas. Brooding females preferred sheltered littoral areas but ventured onto the terrace to release the fry. Juveniles and fry inhabited exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour is described. The biology of T. mossambica in Lake Sibaya is compared to data on the same, and similar species, in other systems. The utilization of available resources in the lake by T. mossambica is discussed and reference is made to the importance of the retention of generalized characters for the successful habitation of the cyclically–renewed habitat of the littoral.
1979 · Journal of Fish Biology · 108 citations
The biology of filter feeding teleosts in St Lucia, was studied for two years from 1976 to 1978. The three common species, Gilchristella aestuarius, Hilsa kelee and Thryssa vitrirostris were studied with the composition and cyclical nature of the zooplankton which formed their food. Stolephorus commersonii and Hepsetia breviceps which were rare were only briefly examined. The zooplankton was dominated by the calanoid Pseudodiaptomus stuhlmanni which formed > 70 % of the calorific value of the zooplankton for 70 % of the study period. The mysid Mesopodopsis africana was second in importance in terms of calorific contribution while the amphipod Grandidierella lignorum was relatively abundant. Larval forms, particularly post‐veligers of Assiminea bifasciata were also important. There was a close correlation between the zooplankton cycles, both diel and annual, and the feeding, reproduction and recruitment of the three common filter feeding teleosts. G. aestuarius spent its whole life‐cycle in the system and spawned in early summer when the resulting juveniles could feed on the summer zooplankton peaks. They grew at 0.5 cm month −1 and attained maximum size in one year. They were non‐selective taking mainly P. stuhlmanni and post‐veligers. H. kelee spawned in the sea and juveniles were common in St Lucia during 1978 when they fed non‐selectively, chiefly on P. stuhlmanning the summer before disappearing over the winter. The resulting offspring went through a sequence of dietary changes which were closely related to zooplankton cycles. The importance of P. stuhlmanni in the pelagic food web of St Lucia is illustrated. The species supports not only the filter feeding teleosts but indirectly the predatory fish Argyrosomus hololepidotus and Elops machnata which feed on G. aestuarius and T. vitrirostris .
1972 · Journal of Fish Biology · 69 citations
The biology of the population of Ethmalosa fimbriata occurring in the Lagos lagoon was investigated. Three size groups, 35–69 mm (Yoyo), 70–169 mm (Efolo) and 170 mm and above (Agbodo) occur in the lagoon and the spatial distribution of these size groups and the length frequency distribution of the species is given. The relationship between length, weight, age and growth is discussed and the food and feeding intra‐relationship of the size groups is shown. Information on the fecundity and possible spawning periods is discussed.
1980 · Journal of Fish Biology · 65 citations
In ‘runted’ populations of Tilapia zilli positive correlations were found between maturation stages and the following: gonadosomatic index, gonad weight, fish weight and fish length. The minimum size at maturity was 9·0 cm in males and 11·0 cm in females. The mean fecundity in the ‘stunted’ females was 2359 eggs and it increased with length ( L ) weight (HO and depth ( D ) of the fish. There was, however, no correlation between fecundity and egg size. The results indicated that growth in this ‘stunted’ T. zilli population was not isometric. The relative condition factor ( Kn ) which approached one indicates good condition.
2018 · Fisheries and aquatic sciences · 38 citations
A preliminary investigation of length-weight relationship, condition factor and reproductive ecology of African pike fish, Hepsetus odoe , was conducted between June to August 2010 in Lake Eleiyele. A total of 90 samples of the fish species were caught by fishermen using gill nets. The results obtained showed that fish species had isometric growth pattern (contrary to negative allometry expected) with the growth exponent, b value of 2.64, that is not statistically different from 3 and with high statistical power of 0.866 when tested. The mean condition factor, K , was found to be 2.6, indicating that the fish species were in good condition in the study area. For reproductive biology, mean fecundity and gonadosomatic index were found to be 1349 eggs and 3.53% respectively. This study was necessary to fill the knowledge gap and provide information for management and conservation of the investigated species in the lake system. This study recommended that further research needs to be conducted because the sampling was carried out in the rainy season period and within a quarter of a year.
2008 · Revista de Biología Tropical · 32 citations
The silver catfish, Chrysichthys nigrodigitatus (Lacépède: 1803) is a highly valued food-fish included among the dominant commercial catches exploited in major rivers of Africa. To provide useful biological data for management, samples were collected monthly between January (2005) and December (2007) in three zones: I: Upper Cross River (grassland), II: Middle Cross River (mixed forest and grassland), and III: Lower Cross River (rainforest)] along 200 km length of the Cross River, Nigeria. Data from 1 248 specimens were processed using: allometric coefficient (b), gonado-somatic index, Fulton's condition factor and diversity indices. Male dominance was observed in all populations; C. nigrodigitatus reached maturity at 11.5 cm (male) and 16.7cm (female) total length. Gonado-somatic index was higher for females with a peak in the early rains. The breeding period was between April and August with mean fecundity ranging between 4522 +/- 1924 eggs and 20321 +/- 5543 eggs. This was directly related to total length and weight by the regression models: F = 2365.88 + 560.22 log L and F = 5025.81 +56.34 log W respectively. Exponential equations for length-weight relationships were Wt = -1.997 Lt(2.206) (Zone I), W = -2.831 Lt(3.040) (Zone II) and Wt = -2.245 Lt(2.995) (Zone III). The mean allometric coefficient (b) showed significant departure from cubic value (negative allometry) for Zone I while Zones II and III showed no difference, indicating isometry. Dominant items in the diet were fish and fish parts constituting 21.6% with Food Richness and Gut Repletion Index of 18 and 100% respectively, in all zones. Diet Breadth of 0.802 (Zone 1), 0.922 (Zone II) and 0.910 (Zone III) indicate a high trophic flexibility that enables switching from one diet to another according to availability. Mean condition factor for males varied from 0.718 +/- 0.117 minimum in Zone I to 0.996 +/- 0.062 maximum in Zone III. Forest inland wetlands (Zone II and III) of Cross River provided better condition for C. nigrodigitatus.
2011 · African Journal of Food Agriculture Nutrition and Development · 14 citations
Between October 2000 and March 2001, a preliminary study on the aspects of the biology of Parachanna obscura, was carried out. Sex ratio revealed female preponderance (÷2 = 4.733, df = 1, P < 0.05). There was no variation in sex ratio during the wet season but there were more females than males in the dry season (÷2=4.735, df = 1, p =