Population Dynamics of Mackerel Scad (Decapterus macarellus) Landed at the Sibolga Archipelago Fishing Port

Abstract

This study analyzed the population dynamics of mackerel scad (Decapterus macarellus) landed at the Sibolga
Archipelago Fishing Port, North Sumatra, Indonesia, to assess growth, mortality, recruitment, and exploitation status.
Length–frequency data from 200 specimens were analyzed using the FISAT II software. The asymptotic length (L∞) and
growth coefficient (K) were estimated at 40.4 cm TL and 0.51 year⁻¹, respectively, indicating a moderately fast-growing
species typical of tropical small pelagics. The total, natural, and fishing mortalities were 3.91, 1.08, and 2.84 year⁻¹, resulting
in an exploitation rate (E = 0.73), which exceeds the optimum level (Eopt = 0.5), signifying overexploitation. Recruitment
analysis showed two annual peaks (March–April and September–October), reflecting a bimodal spawning pattern. The
length at first capture (Lc = 16.2 cm TL) was smaller than the length at first maturity (Lm ≈ 17.0 cm TL), suggesting
premature harvesting. The yield-per-recruit model indicated E₀.₁ = 0.607 and Emax = 0.749, reinforcing that the stock is
fully exploited. These findings underscore the urgent need to regulate fishing pressure through mesh-size adjustments and
seasonal closures to sustain D. macarellus fisheries in western Indonesian waters.