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Fish assemblages of Onu–Iyi–Ukwu stream in southeastern Nigeria
Abstract
Ichthyofaunal composition of Onu-Iyi-Ukwu Stream, a first order
stream in Imo State, Southeastern Nigeria was studied from March
2005 to February 2006. A total of 17 fish species belonging to 15
genera and 11 families were encountered. A seasonal pattern was
observed in the species occurrence and abundance; while 15 taxa from
11 families were recorded in the dry months, 11 species representing 7
families were recovered during the rains. Fishes with accessory
breathing organs dominated the community assemblages which points
to oxygen deficiency (range = 2.0 – 8.2 mg/l) as one of the limiting
factors in the stream basin. The length exponent b of the fishes ranged
from 1.826 to 3.845 while condition factor varied between 0.031 and
0.397 in the wet season and 0.031 to 0.634 in the dry season. The poor
taxonomic composition recorded is attributed to the long distance
between the stream and the adjoining Otamiri River which may
preclude the invasion of some occasional visitors including marine
migrants. . More so, it is plausible that synergy between poor
microhabitat diversity, inadequate primary productivity, and habitatage
factors contributes to the low species richness in the stream basin.
Forty one percent of the species recorded are amongst ornamental
fishes that Nigeria exports, which shows that the stream fisheries can
contribute some supplies to the country’s emerging ornamental
fisheries sub-sector.
stream in Imo State, Southeastern Nigeria was studied from March
2005 to February 2006. A total of 17 fish species belonging to 15
genera and 11 families were encountered. A seasonal pattern was
observed in the species occurrence and abundance; while 15 taxa from
11 families were recorded in the dry months, 11 species representing 7
families were recovered during the rains. Fishes with accessory
breathing organs dominated the community assemblages which points
to oxygen deficiency (range = 2.0 – 8.2 mg/l) as one of the limiting
factors in the stream basin. The length exponent b of the fishes ranged
from 1.826 to 3.845 while condition factor varied between 0.031 and
0.397 in the wet season and 0.031 to 0.634 in the dry season. The poor
taxonomic composition recorded is attributed to the long distance
between the stream and the adjoining Otamiri River which may
preclude the invasion of some occasional visitors including marine
migrants. . More so, it is plausible that synergy between poor
microhabitat diversity, inadequate primary productivity, and habitatage
factors contributes to the low species richness in the stream basin.
Forty one percent of the species recorded are amongst ornamental
fishes that Nigeria exports, which shows that the stream fisheries can
contribute some supplies to the country’s emerging ornamental
fisheries sub-sector.
