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Diet, size and reproductive biology of the silver catfish, Chrysichthys nigrodigitatus (Siluformes: Bagridae) in the Cross River, Nigeria

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dc.coverageCRCen
dc.creatorObeten Offem, Benedict
dc.creatorAkegbejo Samsons, Yemi
dc.creatorTunde Omoniyi, Isaac
dc.date2008-02-01
dc.date.accessioned2016-05-03T15:34:00Z
dc.date.available2016-05-03T15:34:00Z
dc.descriptionThe 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 1248 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 11.5cm (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 Lt2.206 (Zone I), W = -2.831 Lt3.040 (Zone II) and Wt= -2.245 Lt2.995 (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 I), 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.en-US
dc.formatapplication/pdf
dc.identifierhttp://revistas.ucr.ac.cr/index.php/rbt/article/view/5759
dc.identifier10.15517/rbt.v56i4.5759
dc.identifier.urihttps://hdl.handle.net/10669/27510
dc.languageeng
dc.publisherUniversidad de Costa Ricaen
dc.rightsCopyright (c) 2014 International Journal of Tropical Biology and Conservationen
dc.sourceRevista de Biología Tropical/International Journal of Tropical Biology and Conservation; Vol. 56 (4) December 2008en
dc.sourceRevista de Biología Tropical/International Journal of Tropical Biology and Conservation; Vol. 56 (4) December 2008es
dc.sourceRevista Biología Tropical; Vol. 56 (4) December 2008pt-PT
dc.source2215-2075
dc.source0034-7744
dc.source10.15517/rbt.v56i4
dc.titleDiet, size and reproductive biology of the silver catfish, Chrysichthys nigrodigitatus (Siluformes: Bagridae) in the Cross River, Nigeriaen
dc.titleDiet, size and reproductive biology of the silver catfish, Chrysichthys nigrodigitatus (Siluformes: Bagridae) in the Cross River, Nigeriaes
dc.typeartículo original

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