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All Journal Acta Aquatica: Aquatic Sciences Journal Journal of Marine Studies
Konoyima, Komba Jossie
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Agriculture, Biological Sciences & Forestry Biochemistry, Genetics & Molecular Biology Chemistry Earth & Planetary Sciences Environmental Science Materials Science & Nanotechnology Other

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Evaluating the stock status of Trachurus trecae (Cadenat, 1950) in the Eastern Central Atlantic Ocean based on an extended surplus production model incorporating life history and fishery selectivity Konoyima, Komba Jossie
Journal of Marine Studies Volume 2, Issue 3 (November, 2025)
Publisher : Universitas Malikussaleh

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29103/joms.v2i3.22956

Abstract

This study on Trachurus trachurus used data from the Regional Committee (CECAF). It employs JABBA-Select, a model that balances age-structured and traditional surplus production models, uniquely incorporating life history and fishery selectivity. Sensitivity scenarios included single and combined catch per unit effort (CPUE) data (1999-2017) for demersal and pelagic fisheries under logistic and dome-shaped selectivity functions. Results indicated that the demersal CPUE under logistic selectivity performed best, leading to a single-fleet analysis as the base case. Model results were robust against variations in natural mortality (M) compared to other input parameters, including steepness (h), while stock status perceptions remained consistent. The base case revealed an overexploited stock (SB/SBMSY = 66%) with a slow growth rate (r = 29%) in 2017. Catches exceeding 15,744 tons from 2022 to 2030 may not be sustainable. JABBA-Select is recommended for future assessments; however, careful consideration of input parameters is essential to minimize uncertainties.
Growth, Mortality and Exploitation Rate of Pagellus bellottii Harvested from the Marine Territorial Waters of Sierra Leone Konoyima, Komba Jossie; Seisay, Lahai Duramany
Acta Aquatica: Aquatic Sciences Journal Acta Aquatica: Jurnal Ilmu Perairan, Vol. 8: No. 2 (August, 2021)
Publisher : Universitas Malikussaleh

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29103/aa.v8i2.4774

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 (Lˆž = 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 < Lˆž) 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 
Co-Authors Seisay, Lahai Duramany