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Estimates of Life-History Parameters and Population Dynamics of Bagrus
Docmak (Forsskål, 1775) in Lake Abaya, South Ethiopia

Buchale Shishitu Shija
South Ethiopia Agricultural Research Institute, Arba Minch Agricultural Research Center
Corresponding author: buchale.shishitu@yahoo.com
ORCiD: https://orcid.org/0000-0001-9134-8085

Abstract:
Sufficient knowledge is necessary for the responsible exploitation of inland fisheries. However, decision-making for
fisheries management is unreliable since many inland fisheries lack monitoring. The purpose of this study was to estimate
life-history parameters and population dynamics of B. docmak from Lake Abaya. The length-weight data were collected
from a total of 1033 fish samples from commercial fisheries of Lake Abaya. The life-history parameters and population
dynamics were analyzed with SPSS, and FiSAT II software. An estimate of the length-weight relationship was W =
0.0085L3.04; R2= 0.9118. The mean condition factor was 0.99, 1.01, and 1.00 for females, males, and combined sexes,
respectively, and it was highly significant by months’ interaction (P = 0.000). The estimated growth parameters were
asymptotic length L∞ = 99.75 cm, growth rate K = 0.55 yr-1, theoretical age to = -0.21, growth performance index Φ′ =
3.74 and life-span tmax =5.24 years. The mortality related parameters were estimated as Z = 1.43 yr-1, M = 0.57 yr-1, E =
0.60, and Z/K = 2.6. The length at first maturity (L50), the length at first capture (Lc), and the optimum length (Lopt) was
52.02 cm, 44.27 cm and 64.37cm, respectively. With biannual pulses in March and September, the recruitment pattern
was year-round. It was also estimated that the length at first recruitment (Lr) was 32 cm, and the corresponding age at
first recruitment (Tr) was 0.5 years. About 39.5% of the fish in this study were caught before reaching their length at first
maturity (L50), and they were subject to overfishing in terms of both recruitment and growth. The exploitation rate (E) in
the current investigation was 0.60, while the exploitation rate derived from Y΄/R for E0.5 was 0.35. The current rate of
exploitation suggested that B. docmak from Lake Abaya was overexploited. From the management point of view, the
exploitation rate should be reduced from 0.60 to 0.35 (42%) to obtain sustainable yield from the fishery of Lake Abaya.
Keywords: Condition factor, Exploitation rate, Growth pattern, Life-history parameters, Population dynamics