Authors:
Gbaaondo, T.
, Obande,R.A.
, Olufeagba, S.O.
, Ataguba, G.A.
and Anongo,T.T., Nigeria
|
Abstract:
Data on three freshwater fish species: Chrysichthys nigrodigitatus, Bagrus bayad, and
Synodontis clarias from lower river Benue were gathered between July 2018 and June 2019. This
study aims to estimate the population parameters of the species and assess the stocks based on
length frequency data collected and analysed using FiSAT II software. The length-weight
relationships were determined to be: Log10Wt = -0.524+1.8516Log10L; Log10Wt =
0.4609+1.0963Log10L and Log10Wt = 0.3399+1.0399Log10L for C. nigrodigitatus, B. bayad
and S. clarias respectively. The condition factors (K) were not significantly different (p>0.05)
between the two seasons for C. nigrodigitatus and B. bayad but were significantly different
(p<0.05) for S. clarias. The asymptotic lengths (L?) derived from the von Bertalanffy growth
curves were 42.52cm, 41.50cm, and 39.38cm for S. clarias, C. nigrodigitatus, and B. bayad. The
annual growth coefficient (K) was 0.57y-1, 1.30y-1, and 1.50y-1. The growth performance index
(ø) was estimated as 2.99 for C. nigrodigitatus, and 3.37 for both B. bayad and S. clarias. The
estimated values of the total, natural and fishing mortalities were Z = 1.77, 2.232, and 2.449; M=
0.993, 1.248, and 1.963; F = 0.77, 0.984 and 0.486 for C. nigrodigitatus, B. bayad and S. clarias
respectively. The current exploitation rates of the species were 0.439, 0.441, and 0.198
respectively. Although these rates were less than the threshold level of 0.5, they were higher than
Emax and E0.1. it was conclud there is overfishing and lends credence to the arguments that
more accurate biological reference points need to be utilized. Based on the findings of this study
I recommend that strict measures should be employed to discourage overfishing to avoid
extinction on these species. |
