IDENTIFIKASI STRUKTUR STOK IKAN CAKALANG (Katsuwonus pelamis Linnaeus, 1758) DI SAMUDRA HINDIA (WPP NRI 573) MENGGUNAKAN ANALISIS BENTUK OTOLITH

Abstract

Ikan cakalang (Katsuwonus pelamis Linnaeus, 1758) yang tersebar luas di Samudra Hindia selatan Jawa, Bali dan Nusa Tenggara telah dieksploitasi secara terus menerus dengan berbagai alat tangkap. Pengelolaannya saat ini belum rasional karena masih diasumsikan sebagai unit stok tunggal tanpa adanya bukti ilmiah sehingga rentan mengalami lebih tangkap. Penelitian ini bertujuan untuk mengindentifikasi struktur stok ikan cakalang dengan teknik analisis bentuk otolith. Sampel otolith (saggittae) dikumpulkan pada bulan April, Agustus, dan September tahun 2016 di 4 lokasi, yaitu: Binuangeun, Sadeng, Prigi, dan Labuhan Lombok. Rekonstruksi bentuk otolith dilakukan dengan pendekatan outline analysis menggunakan teknik transformasi discrete wavelet. Uji statistik multivariate dengan kluster analisis menggunakan canonical analysis ofprincipal (CAP) dan uji ANOVA-like permutation juga diterapkan untuk menentukan signifikansi antar populasi. Hasil penelitian menunjukkan bahwa analisis bentuk otolith dapat digunakan sebagai penanda yang akurat untuk mengidentifikasi struktur stok. Bentuk otolith ikan cakalang bervariasi khususnya pada bagian rostrum, namun tidak berbeda nyata antar populasi (p>0,001). Hal tersebut berarti struktur stok ikan cakalang di Samudra Hindia (WPP NRI573) terdiri dari 1 populasi yang bergerak mengikuti pola perubahan lingkungan perairan di sepanjang Samudra Hindia. Skipjack tuna (Katsuwonus pelamis Linnaeus, 1758) distributed vastly along the Indian Ocean south of Java, Bali and Nusa Tenggara. It has been exploited by various fishing gear yet it always assumed to be a single stock. It was not based on scientific evidence but merely based on “a scientific assumption”, so that vulnerable to subject of overfishing. This research aims to examine the alternative tool for identifying the stock structure based on the otolith shape. Sampling location took place in four regions, namely: Binuangen, Sadeng, Prigi and Labuhan Lombok. The otolith (sagittae) samples was collected during April, August, and September 2016. The otolith shape was reconstructed using outline analysis with discrete wavelet transformation technique. A multivariate statistic using canonical analysis of principal (CAP) and ANOVA-like permutation test were also used to determine the signification among populations. The result showed that skipjack’s otolith shape was varied from one and another, especially in the rostrum. But it was not statistically different among regions (p>0.001), which means a single stock for skipjack in the Indian Ocean (Indonesian territory of FMA 573). This study also proved that otolith shape can be useful marker tool to identify stock structure for management purpose.

Indeks bentuk otolit ikan cakalang, Katsuwonus pelamis (Linnaeus, 1758) dari Samudra Hindia

“…Canary, Spanyol menggunakan enam deskriptor (Tuset et al 2003(Tuset et al , 2006, tiga spesies Caspian Goby selatan di Pantai Anzali, Iran menggunakan enam deksriptor (Bani et al 2013), dan lima jenis ikan pelagis di Laut Adriatic, Kroasia menggunakan tiga deksriptor (Zorica et al 2010). Penggunaan deskriptor seringkali berkaitan dengan studi lanjutan penggunaan bentuk otolit dalam menginvestigasi struktur populasi ikan peruaya yang tersebar secara luas pada area perairan yang berbeda (Burke et al 2008, Aguera & Brophy 2011, Hussy et al 2016, Wujdi et al 2017.…”

Spawning Potential Ratio (SPR) Approach as a Management Measure of Skipjack Sustainability Record from Cilacap Fishing Port, Central Java, Indonesia

“…Skipjack fish in the Indian Ocean are generally caught with purse seine, longline, handline (Nurdin and Nugraha, 2017), and dominant in FAD locations. According to Wujdi et al (2017), the skipjack fishery in WPP 573 is a population unit that interacts from west to east. Skipjack fisheries management is also faced with problems including invalid and unreliable data, and untraceable fishing grounds.…”

The Size and The Shape of Sagittal Otolith of Redtail Scad, <i>Decapterus kurroides</i> Blekeer 1855 from Kema Bay, North Minahasa Regency, North Sulawesi, Indonesia

“…Wright et al (1990) have firstly reported it on Stolephorus heterolobus in Java Sea, then on several species of eels (Anguilla spp.) around Sulawesi waters and others (Arai et al 2000(Arai et al , 2003Sugeha et al 2001;Kuroki et al 2005;Lee et al 2008;Chino & Arai 2010), bluefin tuna (Thunnus maccoyii) around Bali waters (Shiao et al 2009;William et al 2013;Farley et al 2014), Chinese herring (Tenualosa toil) around Sumatera waters (Milton & Cheney 2001), red snapper (Lutjanus erythropterus) around Nusa Tenggara waters (Fry & Milton 2009), Bali sardinella (Sardinella lemuru) around Bali waters (Wujdi et al 2016), skipjack tuna (Katsuwonus pelamis) in the southern waters of Java and the Sulawesi Sea (Wujdi et al 2017(Wujdi et al , 2018Mogea et al 2019), and Selar crumenophthalmus in Manado Bay (Bahri et al 2018). Otolith study does not merely aim to get information on fish aging and fish growth but also to identify or discriminate the fish stock.…”