Benedict Obeten OFFEM, Yemi AKEGBEJO-SAMSONS, Isaac Tonde OMONIYI

Aspects of ecology of Clarias anguillaris (teleostei: clariidae) in the Cross River, Nigeria

Nijerya’daki 200 km uzunluğundaki Cross Nehrinde Clarias anguillaris’in yaşam hikayesi araştırıldı. Mevsimsel değişkenlerin; dağılım, üreme, besin ve büyüklük üzerindeki etkisi Cross River’da 24 aylık sürede av örneklerinden tespit edildi. Balıklar, kuru ve nemli mevsimlerde nehrin menbası, orta kesimi ve mansabında eşit bir dağılım göstermediği tespit edildi. En yüksek bolluk, erken ve geç yağmurlarda olurken daha düşük değerler orta kısım ve mansaptan ziyade menbada görüldü. Erkek sayısı, dişilerden fazla (1:0,6) olduğu gibi, gece avları, gündüz avlarından daha yüksekti. Üreme dönemi Haziran– emmuz’da olduğu belirlendi. Balıklar, besinin yararlanırlığına bağlı olarak trofik esnekliği olan omnivor balıklardı. Üç yerdeki ortalama allometri katsayıları, izometrik bir büyüme modelinin olduğunu belirtti. Balıkların kondisyonu üç istasyonda da aynı olmakla beraber kuru mevsim boyunca azaldı ve erken ve geç yağmurlarda iyileşti. Bu nedenle balıklar yağmurlu mevsim boyunca kondisyonları gelişti ve çevresel değişikliklerden etkilenmediler.

Anahtar Kelimeler:

populasyon dağılımı, döllenme gücü, alansal değişim, eşey oranı, Nigeria, ekoloji, mevsimsel bolluk, mevsimsel değişimler

Cross River’da (Nijerya) Clarias anguillaris (teleostei: clariidae) biyoekolojisinin belirlenmesi

The life history of Clarias anguillaris was studied over 24 months in the upper, middle and lower reaches of the 200 km length of Cross River, Nigeria. The influence of spatial and seasonal variables on the distribution and abundance, reproduction, diet and size was determined from catch samples over 24 months in the 200 km length of the Cross River, Nigeria. Fish occurred unevenly in the three reaches and over the dry and wet seasons, with peak abundances during the early and late rains and lower values in the upper reach than in the middle and lower reaches. Night catches were higher than day catches, with males being more common than females. The peak breeding period was June - July. The fish were omnivorous with trophic flexibility being related to food availability.Mean allometric coefficients in the three reaches indicated an isometric growth pattern. The condition of the fish was the same in the three reaches but declined during dry season and improved during early and late rains. Fish was therefore in better condition during the rainy season and was not affected by spatial changes.

Keywords:

population distribution, fecundity, spatial variation, sex ratio, Nigeria, ecology, seasonal abundance, seasonal variation,

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