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<p>The integration of theoretical biology, particularly through mathematical modeling, alongside qualitative approaches within fisheries dynamics, offers pertinent factors, thereby enabling mechanistic techniques in crafting effective policy and management measures. We present updated information on the stock status of Frigate Tuna (<i>Auxis thazard</i>) in the Southern Philippines. The average fork length was 25.00&#xa0;cm ± 4.45&#xa0;cm FL, with a sex ratio of 1:1.16. Growth analysis showed positive allometry, with b-values of 3.1179 for males and 3.2502 for females. Reproductive biology analysis indicated two gonadosomatic index (GSI) peaks in July and February (males: 2.54% ± 1.23; females: 2.40% ± 1.33), with an estimated absolute fecundity of 335,982 eggs per gravid female. The length at first maturity (Lm<sub>50</sub>) was 26.90 cmFL, and length selectivity (SL<sub>50</sub>) was 23.46 cmFL, indicating premature harvesting before adequate reproduction. Mortality parameters derived from the Length-Converted Catch Curve using the Von Bertalanffy Growth Function revealed a total mortality rate (<i>Z</i>) of 1.65&#xa0;yr<sup>−1</sup>, a natural mortality rate (M) of 1.06&#xa0;yr<sup>−1</sup>, and a fishing mortality rate (<i>F</i>) of 0.59&#xa0;yr<sup>−1</sup>, resulting in an exploitation rate (<i>E</i>) of 0.36. Estimates of natural mortality (<i>M</i>) varied slightly depending on the method used, with Pauly’s M equation providing an estimate of 1.05857&#xa0;yr<sup>−1</sup>, the Beverton and Holt model estimating M at 0.954&#xa0;yr<sup>−1</sup>, and the Ault and Ehrhardt model yielding 0.924&#xa0;yr<sup>−1</sup>. Combining these methods produced an average natural mortality rate of 1.764&#xa0;yr<sup>−1</sup>, offering a comprehensive understanding of the species' natural mortality dynamics. The spawning potential ratio (SPR) was 35%, aligning with Maximum Sustainable Yield. We also profiled gonadal organogenesis, focusing on morphological and histological features. We present the first comprehensive assessment of the Frigate Tuna stock in the Southern Philippines, highlighting the critical need for continued management efforts to conserve the species' biomass and sustain its fisheries productivity. </p>

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Shedding Light in the Intricate Relationship Between Reproductive Biology and Some Structural Stock Dynamics: Current Status of Frigate Tuna in Southern Philippines

  • 期刊论文

  • 发表日期：

    2025年8月31日

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  • John Christian D. Entia,
  • Niña Mae B. Nabre,
  • Glennville A. Castrence,
  • Red Arthur Duke A. Amoncio,
  • Edna P. Guevarra

摘要

The integration of theoretical biology, particularly through mathematical modeling, alongside qualitative approaches within fisheries dynamics, offers pertinent factors, thereby enabling mechanistic techniques in crafting effective policy and management measures. We present updated information on the stock status of Frigate Tuna (Auxis thazard) in the Southern Philippines. The average fork length was 25.00 cm ± 4.45 cm FL, with a sex ratio of 1:1.16. Growth analysis showed positive allometry, with b-values of 3.1179 for males and 3.2502 for females. Reproductive biology analysis indicated two gonadosomatic index (GSI) peaks in July and February (males: 2.54% ± 1.23; females: 2.40% ± 1.33), with an estimated absolute fecundity of 335,982 eggs per gravid female. The length at first maturity (Lm50) was 26.90 cmFL, and length selectivity (SL50) was 23.46 cmFL, indicating premature harvesting before adequate reproduction. Mortality parameters derived from the Length-Converted Catch Curve using the Von Bertalanffy Growth Function revealed a total mortality rate (Z) of 1.65 yr−1, a natural mortality rate (M) of 1.06 yr−1, and a fishing mortality rate (F) of 0.59 yr−1, resulting in an exploitation rate (E) of 0.36. Estimates of natural mortality (M) varied slightly depending on the method used, with Pauly’s M equation providing an estimate of 1.05857 yr−1, the Beverton and Holt model estimating M at 0.954 yr−1, and the Ault and Ehrhardt model yielding 0.924 yr−1. Combining these methods produced an average natural mortality rate of 1.764 yr−1, offering a comprehensive understanding of the species' natural mortality dynamics. The spawning potential ratio (SPR) was 35%, aligning with Maximum Sustainable Yield. We also profiled gonadal organogenesis, focusing on morphological and histological features. We present the first comprehensive assessment of the Frigate Tuna stock in the Southern Philippines, highlighting the critical need for continued management efforts to conserve the species' biomass and sustain its fisheries productivity.