ABSTRAK
Tingginya permintaan pasar terhadap ikan cakalang mengakibatkan aktivitas penangkapannya dilakukan secara terus-menerus sepanjang tahun sehingga dapat mengancam kelestariannya. Tujuan penelitian yaitu mengetahui distribusi frekuensi panjang ikan cakalang secara temporal dan menganalisis tingkat selektivitas alat tangkap purse seine pelagis besar di fishing ground Samudera Hindia bagian timur. Data yang digunakan adalah data panjang cagak ikan cakalang selama Januari s/d Desember 2016 yang didaratkan di PPS Nizam Zachman Jakarta. Analisis data frekuensi panjang dilakukan dengan membandingkan sebaran individu ikan dalam bentuk histogram, dan analisis selektivitas dengan metode skoring berdasarkan komposisi hasil tangkapan, persentase hasil tangkapan layak tangkap dan membandingkan nilai Lc dan Lm. Hasil penelitian menunjukkan pada bulan juli sampai oktober distribusi frekuensi panjang cagak cakalang terbanyak pada rentang kelas 40-45 cm dengan panjang rata-rata 43 cm atau diatas nilai Lm (42,9 cmFL). Sedangkan pada bulan november sampai juni distribusi frekuensi panjang cagak cakalang berada pada nilai dibawah nilai Lm. Panjang ikan cakalang pertama kali tertangkap (Lc) diperoleh nilai 40,83 cmFL dibawah nilai pertama kali matang gonad (Lm) sebesar 42,9 cmFL. Hasil tangkapan utama purse seine pelagis besar selama penelitian yaitu ikan cakalang 42,6% dan hasil tangkapan sampingan sebesar 57,4%. Jumlah cakalang layak tangkap sebesar 26%, sehingga berdasarkan analisis selektivitas, selektivitas alat tangkap purse seine pelagis besar di perairan Samudera Hindia bagian timur memiliki selektivitas rendah.

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ABSTRACT
The high market demand for skipjack tuna has resulted in its catching activities continuously throughout the year so can be threaten its sustainability. The objectives of this research are to know the temporal length frequency distribution of skipjack tuna and to analyze the level of selectivity of large pelagic purse seine in the Eastern Indian Ocean fishing ground. The data used were length data of skipjack tuna wich unloaded during January to December 2016 at Nizam Zachman Jakarta Fishing Port. Length frequency data analysis was done descriptively by comparing the distribution of individual fish in the form of histogram, whereas the selectivity analysis done by scoring method based on the catch composition, the capture catch percentage and compare the Lc and Lm values. The results of this research showed that in July to October, highest distribution of the length frequency of skipjack tuna was in the 40-45 class range, with average length value was higher than Lm value of 43 cmFL and 42.9 cmFL, respectively. While from November until June, the length frequency distribution value of skipjack tuna was lower the Lm value. The skipjack tuna minimum length of caught (Lc) was lower than its minimum length of gonad mature (Lm) of 40.83 cmFL and 42.9 cmFL, respectively. The major catches of large pelagic purse seine during this research was skipjack tuna as much as 42.6%, and by-catch by 57.4%. The amount of catchable fish is 26%, so based on selectivity analysis, the selectivity of the large pelagic purse seine fishing gear in the waters of the East Indian Ocean has low selectivity.