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<p>The size selectivity of experimental longlines for two commercially important grouper species viz., Brown lined grouper, <i>Epinephelus undulosus</i> and Malabar grouper, <i>E. malabaricus</i> was investigated in the Gulf of Mannar, southeast coast of India. J-type hooks of three different sizes (hook no. #12, #9 and #6) were evaluated during experimental longline trials conducted between February 2020 and January 2022 in fishing grounds of 20&#xa0;m to 30&#xa0;m depth. Eight different models namely, Normal location, Normal scale, Lognormal, Gamma, Logistic, Richards, Binormal and Bilognormal were fitted using the SELECT method. Model selection based on Akaike’s Information Criterion (AIC) indicated that the lognormal model provided the best fit for <i>E. malabaricus</i>, while the binormal model best described selectivity for <i>E. undulosus</i>. The estimated mean lengths increased consistently with hook size, indicating a shift towards larger individuals with increasing hook size. Comparison of estimated mean lengths with length at first maturity revealed a substantial reduction in the probability of capturing immature fish with larger hooks. These results suggest that the use of larger hook sizes can reduce the capture of undersized individuals without compromising catch, thereby improving both selectivity and sustainability of grouper fisheries in the Gulf of Mannar.</p>

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Hook Size Optimization and Selectivity Modelling for Epinephelus undulosus and E. malabaricus in Experimental Longline Fisheries

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • Thangaraji Ravikumar,
  • Neethirajan Neethiselvan,
  • Esakkimuthu Dineshkumar,
  • Rajarajan Tamilselvan,
  • Natarajan Jayakumar,
  • Pandurangan Padmavathy,
  • Thavasiyandi Umamaheswari,
  • Soosaiantony Emiema,
  • Boominathan Manikandan

摘要

The size selectivity of experimental longlines for two commercially important grouper species viz., Brown lined grouper, Epinephelus undulosus and Malabar grouper, E. malabaricus was investigated in the Gulf of Mannar, southeast coast of India. J-type hooks of three different sizes (hook no. #12, #9 and #6) were evaluated during experimental longline trials conducted between February 2020 and January 2022 in fishing grounds of 20 m to 30 m depth. Eight different models namely, Normal location, Normal scale, Lognormal, Gamma, Logistic, Richards, Binormal and Bilognormal were fitted using the SELECT method. Model selection based on Akaike’s Information Criterion (AIC) indicated that the lognormal model provided the best fit for E. malabaricus, while the binormal model best described selectivity for E. undulosus. The estimated mean lengths increased consistently with hook size, indicating a shift towards larger individuals with increasing hook size. Comparison of estimated mean lengths with length at first maturity revealed a substantial reduction in the probability of capturing immature fish with larger hooks. These results suggest that the use of larger hook sizes can reduce the capture of undersized individuals without compromising catch, thereby improving both selectivity and sustainability of grouper fisheries in the Gulf of Mannar.