Abstract
The study investigated growth, mortality and exploitation rate of Pagellus bellottii collected off Sierra Leone, aimed to support efficient management of its stock. A total of 8, 216 specimens of Pagellus bellottii were collected at random from January-November, 2016 on-board a demersal trawler. Data analysis employed methods implemented in the computerized FiSAT II software using pooled length-frequencies in constant class size. Growth parameters gave asymptotic length (L∞ = 33.63cm), growth rate (K = 0.63yr-1), growth performance index (ɸ = 2.85), theoretical age (to = -0.6years) and life-span (tmax = 5.50years) whereas the length (Lm50) and age (tm50) at first maturity were estimated as 22.40 cm and 2.30years respectively. Besides, the current fishing mortality rate (F = 6.58yr-1) exceeded the optimum (Fopt = 0.50yr-1), limiting (Flimit = 0.81yr-1) and natural (M = 1.22yr-1) mortality rates, and the current exploitation rate (Ecurrent) was 0.84yr-1. Results depicted low life expectancy, fast growth and late first maturity (Lm50 = 33.4%, but < L∞) in Pagellus bellottii. Also, the stock of P. bellottii was overexploited (Ecurrent > 0.5), buttressed by the alarming current fishing mortality beyond optimal and permissible limits. This was very worrisome and the current exploitation rate should be reduced to 0.5yr-1 (40.5%) and fishing mortality rate to 0.5yr-1 (92.4%) in order to achieve at least optimal level of exploitation (Ecurrent = 0.5) and fishing mortality rate (Fcurrent = Fopt) respectively, through institution of closed fishing seasons and reduction in fleets targeting the species.Keywords: Exploitation; growth; life-span; mortality; stock
Highlights
Pagellus bellottii (Steindachner, 1882) is commonly known as the red Pandora, a demersal fish species of the Sparidae family that inhabit hard or sandy bottoms in coastal marine waters at depths between 10m and 50m but could move up to 250m depth (Kouame et al, 2018)
The current fishing mortality rate (F) should be reduced to a rate of 0.5yr-1 (92.4%) and the current exploitation rate (Ecurrent) to 0.5yr1 (40.5%) in order to achieve at least an optimal fishing mortality rate (Fcurrent = Fopt, Gulland, 1971) and exploitation rate (Ecurrent = 0.5, Pauly 1984) respectively
Pagellus bellottii was of low life expectancy, fast growth and late first maturity (Lm50 = 33.4% < L∞)
Summary
Pagellus bellottii (Steindachner, 1882) is commonly known as the red Pandora, a demersal fish species of the Sparidae family that inhabit hard or sandy bottoms in coastal marine waters at depths between 10m and 50m but could move up to 250m depth (Kouame et al, 2018). Pagellus bellottii is one of most economically important and diverse marine teleost of the West African Coast (Kouame et al, 2018), and constitutes a critical component of the multi-species coastal demersal fisheries in Sierra Leone (Showers,1995; Seisay 2014) and the Eastern Central Atlantic (Russell and Carpenter, 2014). Biological studies are known to provide unwavering information for fisheries resources management (Amponsah et al, 2017; Konoyima et al, 2020). Study of fish growth inform of the instantaneous growth rate, growth performance and age (Ghanbarzadeh et al, 2015; Baset et al, 2020), whereas mortality and exploitation rates provide invaluable information about the status of fish stocks, required for recalibrating management measures for exploitation within efficient limit (Amponsah et al, 2016; 2017; Asadollah et al, 2017; Wehye et al, 2017; Baset et al, 2020)
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