Abstract
Notwithstanding the nutritional, economic and fisheries importance of Chrysichthys nigrodigitatus, and its relatively high abundance and propagation in Lake Ahozon (South Benin), nothing is known about the well-being of the species in this water body. Thus, this study investigated length and weight frequency distributions, length-weight relationships and condition factors of C. nigrodigitatus. A total of 1020 individuals of C. nigrodigitatus were sampled with seines, cast nets, gill nets and hooks during a 15 month period, from August 2014 to October 2015. Total length (TL) and body weight (W) frequency curves showed a unimodal distribution. The longest TL and highest W recorded were 324 mm and 456.1 g, respectively. In Lake Ahozon, C. nigrodigitatus population exhibited a significant (P≤0.01) isometric growth pattern, indicated by the power function (W = 0.011TL2.99; r=0.96) and the log-transformed linear regression equation (LogW = 2.99 LogTL - 1.94; r=0.96). Growth models varied spatially, sexually, ontogenetically, and seasonally, while corresponding subpopulations showed allometric or isometric growth trends, with slopes b ranging between 2.47 and 3.21. The population showed conditions factors (K) ranging between 0.8 and 3.08 which significantly varied with habitats (F1,1018 = 7.613, P = 0.006), seasons (F2,1017 = 29, P = 0.0001) and life stage categories (F2,1017 =5.583, P = 0.004). The active breeding that provided an important stock of offspring for recruitment, the isometric growth model and the relatively high condition factors indicated the perfect establishment of C. nigrodigitatus in the artificial lake of Ahozon. The sustainable exploitation of fisheries in this non-conventional medium-environment requires an integrated approach of lake management. Key words: Claroteid, condition factor, establishment, fisheries, isometric growth, length-weight model, man-made lake.
Highlights
The silver catfish Chrysichthys nigrodigitatus (Lacepède, 1803) is widely distributed in the Western African inland waters, and occurs to a lesser extent in Central, Northern and Southern Africa (Azeroual et al, 2010).Afr
Two years and half after its introduction in the sand-dragged manmade lake of Ahozon, C. nigrodigtatus efficiently exploited the existing food resources and spawned actively to become one of the prominent fishable species in this special water body (Adite et al, 2017). Management evaluation tools such relative abundance, length and weight frequency, length-weight relationships and condition factors globally indicated a perfect establishment of this catfish in Lake Ahozon
Length/weight frequencies and growth patterns In Lake Ahozon, C. nigrodigitatus made about 29.40% of the fish biomass and numerically accounted for 11.22% of the fish community (Gbaguidi et al, 2016)
Summary
The silver catfish Chrysichthys nigrodigitatus (Lacepède, 1803) is widely distributed in the Western African inland waters, and occurs to a lesser extent in Central, Northern and Southern Africa (Azeroual et al, 2010). C. nigrodigitatus provides highly nutritive proteins and nutrients, such as the omega-3 fatty acid, required by human body to maintain its cardiovascular health and to reduce tissue inflammation (Abowei and Ezekiel, 2013). C. nigrodigitatus is known for its ecological role in determining the dynamics and the structure of aquatic ecosystems (Abu and Agarin, 2016)
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