The Population Dynamics of the Mudskipper, Periophthalmus barbarus (LINNEAUS 1766) (TELEOSTEI, GOBIIDAE) and the Implication for Conservation and Management in the Mangrove Swamp of Iko River Estuary, Southeastern Nigeria

The population dynamics of Periophthalmus barbarus in the mangrove swamp of Iko River estuary,
southeast of Nigeria were obtained from a twenty four month length composition data ranging 4.6 –
14.5 cm total length (TL) (mean 9.1841± 1.6346: n = 2,876) corresponding to 1.16 – 50.6 g total
weight (TW) (mean = 9.9626 ± 5.4796) the growth was exponential. The asymptotic length (L∞) of the
Powell-Wetheral plot (L∞ = 15.03 cm) was seeded into FSAT II (FAO-ICLARM Stock Assessment
Tools II) software to obtain best estimates of vonBertalanfy growth parameters as L∞ = 16.22 cm TL,
growth coefficient (K) = 1.2 year-1, age of fish at zero length, to = 0.071; longevity, tmax = 2.5 years.
The estimated growth performance index, φ' = 2.449. Other FISAT II growth parameters were the
amplitude of growth oscillation, C = 0.6 and the winter point, WP = 0.6, Rn = 0.3127. Mortality
parameters were total mortality, Z = 479 year-1, natural mortality, M = 2.39 year-1 and fishing mortality,
F was 2.40 year-1. Result indicate the fishery is optimally exploited with current exploitation rate, Ecur
= 0.50 < Emax = 0.668 > Eopt = 0.5 which suggests stock optimal exploitation; corroborated by Z/K
ration (3.184). Ecur (0.5) means that 50% of the available stock is being fished annually. The lengthat-
first capture Lc = 7.33 cm TL and Lc/L∞ was 0.45, indicating the fish was yet to complete 55% of
growth as at the time of capture at Lc; hence P. barbarus in the ecosystem is at the optimal level of
exploitation as well as the presence of growth overexploitation. Thus to circumvent the consequences
of growth overfishing, sustainable fisheries measures such as monitoring of fishing effort, use of
selective gears and increase in mesh size should be encouraged, implemented and enforced. The
study has revealed that P. barbarus population residing in the mangrove swamp of Iko River Estuary
is experiencing exploitation rate close to the maximum sustainable yield amidst the presence of heavy
fishing pressure. Moreover, the mudskipper fishery in this ecosystem is currently exhibiting growth
overexploitation signs which could lead to severe implications on the population size and food security
within vulnerable fishing households in the future. Therefore, urgent management interventions in the
form of monitoring fishing efforts, return of captured juveniles back to the water body from the nonselective
fishing gear and use of selective gear with large mesh size (to increase length at first
capture) are needed to safeguard this important fish species from possible collapse in the future.