PART II
WORKING PAPERS

INS/80/005/TWl

PREPARATORY ASSISTANCE IN SEAFARMING - INDONESIA
(UNDP/FAO - INS/80/005)

TRAINING WORKSHOP ON SEAFARMING
Denpasar, Bali, Indonesia
March 1981

BUDIDAYA RUMPUT LAUT¹

by

Hasan Mubarak²

Abstract

Seaweeds are utilised as food and medicine and also for various industrial purposes. Species of the genus Eucheuma are an important export commodity for the Philippines, Malaysia and Indonesia. Gracilaria and Gelidium species are also economically important seaweeds in Indonesia, the bulk of which is consumed locally.

The general biology of Eucheuma seaweeds including taxonomy, morphology, reproduction and distribution, is described. Eucheuma is the only group of seaweeds which has been successfully cultivated and which is considered feasible for production on a commercial scale.

The culture method for, and the ecological requirements of, Eucheuma are presented. Bottom, off-bottom and floating methods of culture, including the need for the monitoring of the culture media and the harvesting methods, are described. Pronounced fluctuations in water temperature have been found to be a limiting factor on growth.

The major postharvest activity is primarily concerned with the drying of the product. Generally, the moisture content of the treated product is set at or below 30%, while the amount of undesirable substances including sand and coral fragments at or below 5%.

¹ Seaweed culture.

² Marine Fisheries Research Institute, Jakarta, Indonesia

1. PENDAHULUAN

Istilah “rumput laut” adalah terjemahan dari “seaweed” yang merupakan nama dalam dunia perdagangan internasional untuk jenis-jenis alga (e) yang dipanen dari laut. Sebenamya penamaan rumput laut tidak tepat karena algae secara botanis tidak termasuk dalam golongan rumput-rumputan (Graminae). Nama agar-agar juga diberikan kepada jenis-jenis algae ini berdasarkan kandungan kimianya. Di perairan pantai P. Jawa umumnya yang disebut agar atau ager adalah jenis Gracilaria verrucosa yang memang mengandung agar. Di Sulawesi, Maluku dan Nusa Tenggara nama agar diberikan kepada jenis Eucheuma yang kandungan kimianya bukan agar melainkan karaginan. Terlihat bahwa dalam penamaan terhadap algae laut ini terdapat banyak kesalahan. Mungkin yang lebih tepat adalah istilah ganggang laut untuk menterjemahkan seaweed atau algae laut. Ganggang berasal dari bahasa Jawa (ganggeng) yang ditujukan kepada jenis-jenis tanaman air.

Manfaat rumput laut

Rumput laut telah dimanfaatkan sebagai sayuran terutama oleh penduduk di sepanjang pantai sejak ratusan tahun yang lalu. Sejak sebelum Perang Dunia II rumput laut telah mulai di ekspor. Jenis rumput laut Indonesia yang banyak dimanfaatkan mempunyai kandungan karbohidrat yang tinggi, sedikit protein dan vitamin. Karena karbohidrat dari rumput laut ini sukar diuraiken aleh enzym pencernaan manusia, maka sebagian besar rumput laut tidak dimanfaatkan sebagai makanan, akan tetapi sebagai bahan tambahan dalam industri makanan, abat-abatan dan kosmetika. Untuk ketiga jenis industri tersebut yang penting adalah Eucheuma, karena mempunyai kandungan kimia yang disebut karaginan, berguna sebegai stabilizing, gelating, dan thickening agent. Proses ekstraksi karaginan dari rumput laut rupanya cukup rumit sehigga terbatas sekali perusahaan yang bisa mengerjakannya. Tiga perusahaan besar di dunia yang mengekstrak karaginan deri rumput laut Eucheuma dan Chondrus adalah Marine Colloids (A.S.), Kopenhagen Pectin Fact Fitty Auby (Perancis). Ketiga perusahaan ini berasosiasi dengan kantornya di Singapura untuk pembelian Eucheuma di Philippina, Indonesia dan Malaysia. Sekitar tahun 1973 sebelum budidaya Eucheuma berkembang, tercatcat jumlah Eucheuma di pasaran dunia sebenyak kira-kira 4.000 metric ton. Pada waktu itu Indonesia mengekspor sekitar 5.000 mt dan Philipina hanya 300–400 mt. Sejak tahun 1973–1974 budidaya Eucheuma dimulai di Philipina dan berkembang pesat sekali sehingga produksinya jauh melampaui produksi Eucheuma Indonesia.

Disamping Eucheuma yang merupakan komoditi ekspor dan tidak di konsumsi langsung di dalam negiri dipanen juga dari alam dalam jumlah yang tidak sedikit jenis-jenis Gelidium dan Gracilaria yang mengandung agar untuk industri agar-agar dan sebegian besar di konsumsi dalam negeri.

Taksonomi

Dalam, taksonomi, ganggang atau algae termasuk ke dalam phylum Thallophyta yang terbagi ke dalam 7 (tujuh) divisi yaitu Euglenophyta, Chlorophyta, Chrysophyta, Phaeophyta, Rhodophyta, Pyrrophyta den Cyanophyta. Ciri-ciri dari dari phylum ini yaitu tidak menpunyai akar, batang dan daun sejati, alat reproduksi terdiri dari satu sel, dan zygote yang merupakan hasil pembuahan sel betina oleh sel jantan hanya akan tumbuh sesudah keluar dari alat kelamin betina. Deri ke tujuh divisi ini yang terpenting dalam dunia perdagangan adalah Rhodophyta.

Morfologi

Seluruh begian tanaman yang dapat menyerupai akar, batang, daun ataupun buah, semuanya desebut thallus. Bentuk thallus ini bermacam-macam yaitu: bulat seperti tabung, pipih, gepeng, bulat seperti kantong, seperti rambut dan lain-lain. Susunan thallus ada yang terdiri dari satu sel dan ada yang terdiri dari banyak sel. Percabangan thallus ada yang dichotomous (dua-dua tarus menerus) pinnate (dua-dua berlawanan sepanjang thallus utama), pectinate (berderet searah pada satu sisi thallus utama), ferticillate (berpusat melingkari aksis atau batang utama), dan ada juga yang sederhana tanpa percabangan. Sifat substansi thallus juga bermacam-macam antara lain lunak seperti gelatin (gelatinous), keras diliputi atau mengandung zat kapur (calcareous), seperti tulang rawan (cartilagenous) dan berserabut (spongious). Semua sifat-sifat thallus itu membantu dalam pengenalan jenis atau species dalam klasifikasinya.

Reproduksi

Perkembang biakan rumput laut pada dasarnya ada dua macam yaitu secara kawin dan tidak kawin. Pada perkembang biakan secara kawin, gametophyt jantan melalui pori spermatangia menghasilkan sel jantan yang disebut spermatia. Spermatia ini akan membuahi sel betina pada cabang carpogonia dari gametophyt betina. Hasil pembuahan ini kemudian keluar sebagai carpospora. Sesudah terjadi proses germinasi kemudian tumbuh menjadi tanaman yang tidak beralat kelamin yang disebut sporophyt. Perkembang biakan dengan cara tidak kawin terdiri dari penyebaran tetraspora, vegetatif dan conyugatif. Sporophyt dewasa menghasilkan spora yang disebut tetraspora yang sesudah proses germinasi tumbuh menjadi tanaman beralat kelamin yaitu gametophyt jantan dan gametophyt betina. Perkembangan vegetatif ialah dengan cara stek. Potongan-potongan seluruh bagian dari thallus akan membentuk percabangan baru dan tumbuh berkembang menjadi tanaman biasa. Sedangkan conyugasi adalah peleburan dinding sel dan percampuran protoplasma antara dua thally.

Penyebaran

Rumput laut tumbuh hampir di seluruh bagian hidrosfir sampai batas kedalaman kurang lebih 200 meter, dimana batas syarat-syarat hidup untuk tanaman air masih memungkinkan. Jenis-jenis rumput laut ada yang hidup di perairan tropis, subtropis dan ada yang tumbuh di perairan dingin. Disamping itu ada beberapa jenis yang hidup kosmopolit antara Ulva lactuca, Hypnea musciformis, Colpomenia sinuosa dan Gracilaria verrucosa. Karena tidak mempunyai akar sebenarnya, rumput laut menempel pada substratnya (fitobentes) dan selutuh bagian thallus mengambil makanan dari air sekitarnya dengan cara osmosa. Substrat itu dapat merupakan lumpur, pasir, karang, framen karang mati, kulit kerang, batu atau kayu. Tumbuhan yang melekat pada tumbuhan yang melekat pada tumbuhan lainnya disebut epiphyt. ZANEVELD (1955) mencatat lebih dari 50 species rumput laut Indonesia yang dapat dimanfaatkan, sebagian besar sebagai sayuran. Jenis-jenis yang mempunyai nilai ekonomis lebih tinggi seperti yang disabutkan di atas adalah Eucheuma, Gracilaria, Gelidium dan Hypnea. Dari ke empat jenis ini, Eucheuma talah berhasil dibudidayakan secara teknik, dan ekonomis menguntungkan. Dalam uraian selanjutnya akan dikemukakan segala sesuatunya mengenai budidaya Eucheuma ini. Gracilaria rupanya juga mempunyai harapan untuk dibudidayakan dengan teknik yang sama. Sedangkan Gelidium, karena sifatnya yang tumbuh di tempat dengan ombak yang besar dan angka pertumbuhannya yang rendah maka sulit di budidayakan untuk memperoleh keuntungan ekonomis dalam jangka waktu pendek.

2. METODA BUDIDAYA

Sebelum memulai suatu usaha budidaya rumput laut sudah barang tentu ditetapkan dulu jenis apa yang akan di budidayakan dan apakah sudah ada metoda yang secara teknis dan ekonomis dapat digunakan untuk jenis tersebut. Selanjutnya hal-hal yang harus diperhatikan adalah area yang memenuhi syarat-syarat budidaya tersedienya material budidaya secara mudah dan murah, dan ada bibit untuk penanaman.

Area budidaya

Eucheuma hidup di alam di daerah pasang surut dengan menempel pada suatu substrat agar dapat bertahan supaya tidak hanyut terbawa arus atau ombak. Untuk dapat menyerap makanan dari air laut, tumbuhan ini memerlukan pergerakan air yang cukup.

Dasar perairan yang hanya terdiri dari pasir menunjukkan pergerakan air yang sedikit, dan lumpur menunjukkan pergerakan air yang lebih rendah lagi. Dasar perairan yang terdiri dari karang yang keras selalu atau sering menerima pergerakan air yang kuat terutama pukulan ombak yang besar. Bila terdapat suatu perairan yang terdiri dari potongan-potongan karang mati dan pasir berarti pergerakan airnya cukup tidak rendah dan tidak terlalu kuat. Keadaan dasar perairan yang dasarnya atau tumbuh-tumbuhan yang terdapat di situ banyak ditempeli endapan (silt), mempunyai pergerakan air yang kurang. Hendaknya perairan yang demikian tidak dipilih dalam penentuan area budidaya. Bila budidaya dilakukan juga, seperti halnya tanaman yang tumbuh alami akan ditutupi oleh endapan-endapan air. Tertutupnya permukaan thallus tanaman menyebabkan kurangnya sinar matahari yang diterima yang diperlukan untuk proses fotosynthesa. Selain itu karena sedikitnya pergerakan air, maka jumlah makanan yang dapat diserap juga sedikit. Sehingga dangan demikian pertumbuhan tanaman di tempat yang demikian menjadi rendah. Di tempat yang pergerakan airnya kuat, angka pertumubuhan tanaman akan tinggi, akan tetepi bila pergerakan air (ombak atau arus) itu terlalu kuat, tanaman akan rusak patahpatah dan bahkan bangunan budidaya bisa rusak. Seperti diterangkan diatas, desar perairan yang hanye terdiri dari pasir mempunyai pergerakan air yang kurang. Di tempat seperti ini pananaman diatas dasar memberikan hasil yang kurang baik. Akan tetepi bila Eucheuma ditanam dekat permukaan air, mungkin pergerakan airnya cukup karena pengaruh ombak, maka pertumbuhan tanaman akan lebih baik.

Sutau perairan yang merupakan terusan dan terletak di antara dua pulau atau gugusan pulau-pulau karang biasanya mempunyai arus kuat dan baik sekali untuk area budidaya. Di perairan yang menghadap lautan bebas, bila terdapat barrier reef juga bagus sekali dipilih karena tanaman akan mendapat pergerakan air baik sekali dari ombak samudera yang sudah pecah di karang sebelum mencapai tanaman. Di suatu perairan karang yang luas sekali dapat terjadi alur-alur atau kanal yang waktu surut rendah merupakan anak sungai. Di bagian ini arusnya lebih dari di bagian lainnya sehingga bagus juga untuk area budidaya.

Untuk dapat memperoleh makanan, Eucheuma harus berada dalam air. Dialam, tumbuhnya biasanya persis pada garis surut terendah atau tidak lebih dalam dari satu meter di bawah garis surut terendah. Kadang-kadang masih terdapat juga ditempat-tempat yang kekeringan sampai satu jam pada waktu surut. Untuk menentukan area budidaya dalam hubungannya dengan kedalaman, perlu diperhatikan bahwa pada waktu pasang surut terendah area tersebut tidak kekeringan (exposed). Apabila area demikian sukar diperoleh, bisa juga dipilih area yang kekeringan hanya sekitar satu atau dua jam. Kedalaman maksimum akan ditentukan bardasarkan pada metoda penanaman apa yang akan digunakan. Bila digunakan metoda lepas dasar maka maksimum kedalaman pada surut terendah adalah sedemikian rupa sehingga pekerjaan penanaman pemeliharaan dan panen dapat dikerjakan dengan mudah. Maksimum kedalaman ini kira-kira satu meter. Bila akan digunakan metoda terapung maka kedalamannya dapat lebih dalam, karena pemeliharaan dan panen dapat dilakukan di atas perahu. Walaupun demikian, pemeliharaan panen dari atas perahu lebih sulit dari pada bila dikerjakan sambil berdiri di dasar perairan.

Diatas telah disebutkan syarat-syarat kedalaman, pergerakan air dan kecerahan air. Hal-hal lain yang perlu diparkatikan pula adalah salinitas, temperatur, organisma pengganggu, pencemaran dan alur pelayaran. Dalam hubungannya dengan salinitas, Eucheuma memelukan kadar garam yang agak tinggi disekitar 30 permil atau lebih. Hendaknya tidak dipilih lokasi yang dekat dengen muara sungai. Dua hal yang merugikan dari muara sungai ini yaitu suplai air tawar yang dapat merusak tanaman dan endapan atau lumpur yang dapat menutupi permukaan thallus tanaman. Temperatur air laut dipengeruhi oleh arus, pasang dan kedalaman. Adanya arus terus menerus, apalagi bila massa airnya berasal dari parairan dalam maka temperatur cukup baik, mungkin 25–27°C atau lebih rendah lagi. Dan yang penting dari temperatur ini fluktuasinya yang rendah. Pada waktu pasang surut, tidak terjadi aliran air, kedalaman hanya bebarapa cm pada siang hari yang cerah, maka temperatur air cukup tinggi dapat mencapai sampai 35°C. Hal ini dapat merugikan tanaman apalagi bila berlangsung lama sampai 3 atau 4 jam.

Organisma penganggu terdiri dari ikan-ikan herbivour, penyu dan bulubabi (sea-urchin). Lokasi penanaman handaknya bebas deri semua organisma tersebut. Lumut sering menyerang dan menempel serta menutupi seluruh tanaman. Ini terjadi terutama pada perioda dimana pergerakan air kurang sekali dan temperatur air tinggi. Perairan yang mengalami pencemaran karang terutama merupakan alur pelayaran tidak dianjurkan untuk dipilih sebgai lokasi pananaman.

Seperti halnya dengan tanaman di darat, tanaman air laut ini memerlukan kesuburan. Kesuburan perairan ditentukan oleh tersedianya makanan (unsurunsur hara) secara terus menerus. Adaya pergerakan air yang tetap menjamin tersedianya makanan yang tetap pula. Suatu indikasi perairan yang subur untuk penanaman rumput laut yaitu banyaknya jumlah species tumbuhan (vegetasi) yang terdapat, dan tumbuh-tumbuhan tersebut tidak ditempeli endapan air. Sea grass yang bersih dan tumbuh miring ke satu arah menunjukkan adanya arus yang baik. Demikian juga adanya bentic coelenterata menunjukkan area mempunyai pergerakan air yang baik dan tidak kekeringan.

Bibit tanaman

Tersedianya bibit tanaman di lokasi penanaman mempunyai satu keuntungan. Karena bila di tempat itu secara alami sudah terdapat jenis rumput laut yang akan ditanam, tentu perairan itu cocok (suitable) untuk tanaman tersebut. Disamping itu tidak detemui kesulitan untuk memperoleh bibit tanaman. Berdasarkan pengalaman, tidak terdapatnya bibit tanaman di suatu perairan, tidak berarti perairan bersebut tidak cocok untuk pertumbuhan tanaman. Karena ditempat yang demikian, sesudah dicoba ternyata tanaman dapat tumbuh dengan baik. Hanya saja yang perlu diperhatikan adalah bahwa bibit dapat diperoleh dengan mudah walaupun harus didatangkan dari tempat lain. Tergantung dari jarak dan sarana, maka pengangkutan dapat mekan waktu beberapa jam atau bahkan berharihari. Dalam pengangkutan ini harus diperhatikan agar bibit tanaman tidak terkena sinar matahari langsung, selalu basah, tidak terkena air tawar atau minyak behan bakar dan terhindar dari sumber panas. Bila pangangkutan dengan perahu atau sampan, bibit tanaman cukup ditaruh di dasar perahu dan ditutup agar tidak terkena sinar matahari. Bila diperlukan pengangkutan dengan kendaraan di darat maka bibit dapat dimasukkan ke dalam kotak karton dengan dilapisi plastik agar airnya tidak marembes keluar. Diperlukan lapisan kapas yang dibasahi dengan air laut agar tanaman tetap basah. Dalam keadaan demikian bibit tanaman dapat tahan sampai 2 × 24 jam.

Material budidaya

Dari metoda-metoda budidaya yang dikenal dapat dilakukan, maka material budidaya yang diperlukan antara lain nilon monofilamen (No. 2000, Æ 1.5 mm), tali pengikat bibit, kayu (Æ 5 – 7,5 cm) dan bambu (Æ 10 cm). Kayu dipilih yang lurus. Bambu yang lebih tebal dan tua dapat lebih tahan lama dalam air dan dapat bertahan sampai 6 bulan. Kayu dapat digunakan sampai satu tahun. Plastik pengikat bibit tanaman selalu diganti hampir setiap panen dan penanaman baru.

3. METODA BUDIDAYA

Pada prinsipnya ada tiga metoda budidaya menurut posisi tanaman yaitu:

• Metoda didasar (bottom method)
• Metoda lepas dasar (off-bottom method)
• Metoda terapung (floating method)

Masing-masing metoda ini mempunyai keuntungan-keuntungan dan kerugian-kerugian. Metoda penanaman dipilih berdasarkan keadaan perairan, tujuan budidaya dan jenis rumput laut yang dibusidayakan.

Metoda di dasar (bottom method)

Pada penanaman dengan metoda ini bibit tanaman diikatkan pada batu-batu karang dan disusun berbaris di dasar perairan. Keuntungan dengan cara ini adalah murahnya biaya budidaya dan tidak diperlukan banyak pekerjaan pemeliharaan. Kerugian yaitu mudah diserang bulu babi (sea-urchin). Mungkin di suatu area sulit diperoleh batu-batu karang lepas dengan ukuran cukup. Metoda ini baik digunakan untuk jenis Gelidium yang tumbuhnya diperairan terbuka dan menerima pukulan ombak besar terus menerus. Metoda lain sulit dilakukan untuk jenis Gelidium ini karena bangunan budidaya tidak dapat bertahan. Bila metoda ini digunakan untuk jenis Gelidium maka tujuannya bukan untuk suatu usaha karena pertumbuhannya yang lambat. Cara ini berguna untuk memperluas daerah penyebaran dan mempertahankan kelestarian stok.

Metoda lepas dasar (off-bottom method)

Jenis-jenis Eucheuma dan Gracilaria dapat ditanam dengan metoda ini. Mula-mula bibit tertanam diikat tali plastic (rafia) masing-masing dengan berat kirakira 20 cm dan direntangkan kira-kira 20–30 cm diatas dasar perairan dengan menggunakan kayu-kayu pancang. Bebarapa diikatkan langsung pada kayu-kayu yang berjarak 5 m. Masing-masing monoline jaraknya kira-kira ½ meter. Kedua pada kayu-kayu pancang direntangkan 2 m nilon multifilamen (Æ 6 – 7 mm). Dalam barisan, jarak nilon multifilamen kira-kira 2-½ m. Nilon monofilamen direntangkan dengan mengikatkannya pada nilon multifilamen dengan jarak 20 cm. Modifikasi ketiga, dibuat jaring dari nilon monofilamen dengan lebar mata 20 cm. Bibit tanaman diikatkan pada simpul-simpulnya. Jaring ini direntangkan dengan kayu-kayu pancang.

Metoda ini mempunyai keuntungan yaitu terhindar dari bulu-babi. Penanaman dapat dilakukan di area dengan dasar perairan terdiri dari pasir sehingga mudah menancapkan pancang, sulit di lakukan diperairan dengan dasar perairang karang. Kerugian dengan metoda ini ialah, sering diserang ikan-ikan herbivour pada waktu pasang dalam.

Metoda ini memberikan nilai pertumbuhan yang baik bila di areanya terdapat arus yang baik. Karena bila pergerakan air di area penanaman didominasi oleh ombak, maka tanamen tidak atau sedikit manerima pergarakan air selama perioda pasong dalam, sehingga pertumbuhannya kurang baik.

Metoda terapung (floating method)

Dibuat rakit-rakit dari bambu dan kayu dengan ukuran 2 sampai 4 meter. Ada dua modifikasi dangan metoda ini yaitu monoline den net seperti halnya dengan metoda lepas daser. Ditempat-tempat yang pergerakan airnya terutama terdiri dari ombak, sebaiknya digunakan metoda ini. Demikian juga bila dasar periran terdiri dari karang yang keras dimana sulit menancapkan pancang, dapat dwgunakan metoda ini. Untuk mempertahankan agar rakit-rakit tidak hanyut, digunakan jangkar. Untuk efisiensi area, beberapa rakit dijadikan satu. Makin banyak jumlah rakit, makin tinggi efisiensi area. Pengaruh penyatuan sejumlah rakit terhadap pertumbuhan adalah negatip di mana makin banyak jumlah rakit yang disatukan makin banyak pula jumlah rakit yang berada di tengah dengan pertumbuhan tanaman jelek. Jumlah yang sebaiknya ialah 10 rakit (2 × 5) rakit dijadikan satu.

Pemeliharaan dan panen

Dalam kegiatan-kegiatan rumput laut, instalasi bangunan budidaya dan pananaman memerlukan banyak tenaga kerja. Selanjutnya kegiatan pemeliharaan mudah sekali dilakukan, asal dikerjakan secara teratur setiap hari. Pekerjaan pemeliharaan terdiri dari membersiihkan tanaman dari tumbuhan penempel atau benda-benda lainnya, menggantikan tanaman yang rusak atau hilang dengan yang baru dan memperbaiki bagian-bagian bangunan budidaya yang rusak seperti monoline yang putus, bambu atau kayu yang patah, tiang-tiang pancang yang tercabut dan lain-lain. Apabila kegiatan ini dilakukan setiap hari maka kerusakan kerusakan berat dapat dihindari sehigga kerugian yang lebih besarpun tidak akan terjadi.

Pertumbuhan tanaman pada umumnya tidak seragam. Sesudah sebulan masa penanaman biasanya akan terlihat tanaman yang sudah mencapai ukuran besar, sementara ada tanaman yang masih tetap kecil. Karena itu beberapa tanaman sudah dapat dipanen. Di P. Samaringa, Sulawesi Tengah pada bulan-bulan tertentu tanaman diserang lumut. Pembersihan tanaman dari lumut ini harus dilakukan dengan hati-hati agar tidak sampai merusak thallus. Bila tanaman telah merata mencapai ukuran kira-kira 600 grams sudah waktunya untuk dipanen. Panen dilakukan dengan memotong dan meninggalkan sebagian tanaman untuk dapat tumbuh besar lagi. Kadang-kadang dilakukan juga pengangkatan seluruh tanaman kalau pengikatnya sudah tidak kuat lagi.

Monitoring

Penanaman rumput laut dilakukan dengan memanfaatkan sifat pertumbuhan vegetatif. Pertumbuhan tanaman diukur dengan pertambahan beratnya tiap hari dan dapat dihitung dengan rumus :

Untuk dapat memberikan kebijahsanaan-kebijaksanaan yang diperlukan masyarakat nelayan/petani rumput laut sehubungan dengan keadaan tanaman sebagai akibat dari lingkungan perairan maka diperlukan monitoring lingkungan perairan yang meliputi sifat-sifat hidrologis dan biologis, serta monitoring pertumbuhan tanaman. Monitoring pertumbuhan dilakukan dengan penimbangan tanaman contoh yang diberi label setiap minggu sekali.

Penanganan lepas panen

Rumput laut di ekspor dalam bentuk raw-material. Sesudah dipanen baik dari alam maupun dari budidaya, rumput laut dikeringkan dengan penjemuran sinar matahari yang dilakukan masyarakat nelayan satu atau dua hari penjemuran sesudah panen dari laut kemudian dijemur lagi sampai kering. Dengan care denikian dihasilkan rumput laut yang bersih dangan warna kekuningan. Akan tetapi cara demikian dimana dilakukan pencucian sesudah penjemuran setengah kering menyebabkan berkurangnya kadan karaginan.

Penjemuran langsung diatas pasir tanpa alas menyebabkan tercam-purnya butir-butir pasir pada rumput laut. Halini dapat mengurangi mutu perdagangan rumput laut. Sebagai alas yang murah untuk penjemuran ini dapat digunakan daun kelapa. Dalam standar perdagangan rumput laut antara lain diyatakan bahwa benda-benda asing yang terdiri dari pasir, batu karang dan lain-lain tidak lebih dari 5 persen. Kandungan air (moisture content) tidak lebih dari 30 persen. Pengepakan biasanya cukup dengan menggunakan karung yang dapat diisi sampai beratnya 90 kg. Dalam penyimpanan di gudang harus dijaga agar tidak sampai kena air hujan. Demikian pula dalam pengangkutannya.

Pemasaran

Tujuan pengembangan budidaya adalah peningkatan taraf hidup nelayan melalui peningkatan produksi. Usaha ini baru dapat dikatakan mencapai sasaranya apabila secara langsung dapat dirasakan manfaatnya oleh masyarakat nelayan. Pengalaman di P. Samaringa, Sulawesi Tengah menunjukkan bahwa ketika budidaya ini mulai dikembangkan maka pedagang-pedagang atau tengkulak mulai mengusahakan penyediaan material budidaya. Harga material ini semakin meningkat karena permintaan yang memang tinggi. Nelayan yang dalam pemenuhan kebutuhannya sehari-hari tergantung dari para tengkulak itu tidak punya pilihan lain selain dari membeli dengan harga berapapun yang diminta. Demikian pula dengan hasil panen, nelayan hanya menjualnya kepada tengkulak yang telah memberinya hutang sehingga harga hasil panennyapun ditentukan oleh tengkulak. Keadaan demikian tidak menjamin tercapainya tujuan pengem-bangan budidaya. Sebagian besar keuntungan tidak dinikmati oleh nelayan/ petani. Untuk mamjamin tercapainya tujuan tersebut diperlukan suata badan dalam bentuk koperasi, sehingga segala masalah yang dihadapai nelayan/petani dapat dimasyarahkan bersama.

Permitaan pasaran dunia terhadap rumput laut saat ini sedang dalam keadaan krisis sehingga terjadi kegoncangan-kegoncangan harga yang meresahkan masyarakat nelayan. Tampak juga spekulasi-spekulasi dari para pedagang yang ternyata tidak menguntungkan. Hal ini perlu mendapat perhatian pemerintah di tingkat pusat.

INS/80/005/TW2

A SUMMARY OVERVIEW OF THE PRINCIPAL PROBLEMS PRESENTLY CONFRONTING THE CAGE CULTURE OF MARINE FINFISHES IN THE SOUTH CHINA SEA REGION

by

W. L. Chan¹

1. OVERALL PROBLEMS

1.1 Being a recent introduction, the coastal culture of marine finfishes in floating net cages (hereafter referred to as cage culture) is still in its early phases of development in the South China Sea region. Despite the amount of research inputs, the diverse variety of finfishes (hereafter understood as fish) and the habitats of the individual species, have made it difficult and in some cases almost impossible to transfer what is being practised (with relatively successful performance) in one country to another without due consideration of local constraints.

1.2 Cage culture, as its name suggests, actually means the artificial confinement of wild fish stocks densely in “selected” bodies of water. For all intents and purposes, site selection criteria, no matter how objectively determined, invariably include a number of “convenience” factors, ranging from proximity to market outlet and facility sources to cost considerations. There is also the need to stress on socio-economic requirements in development planning. For small scale investments, these can perhaps be tolerated; but attention should be given to subsequent risk factors arising from mismanagement of the grounds on the one hand, and the potential adverse effects of human and other land-based activities on the other.

¹ Fishcage/pen Culture Specialist, Preparatory Assistance Project in Seafarming (INS/80/005), Jakarta, Indonesia

Present address: UNDP/FAO South China Sea Fisheries Development and Coordinating Programme, P.O. Box 1184 MCC, Makati, Metro Manila, Philippines

1.3 Artificial confinement of the wild fish deprives the fish of their optimal conditions for survival, creates and indeed accelerates ecological stresses (a point often neglected by many culturists), and renders disease outbreak uncontrollable. Within such a confinement, the complicated problem of “competition” within a species or among species is another major problem area. Under these circumstances, coupled with inadequate back-up by applicable scientific information, adverse effects of varying magnitude, ranging from stunted and uneven growth, to disease infection and mass kills, have already been a common phenomenon under mismanaged conditions.

1.4 From a problem-solving angle, the manageability of the caged fish is indeed the first and foremost concern. Suitably designed production management, for any size of investment, based on realistically adopted strategies to overcome identifiable constraints, then becomes the prerequisite to successful development planning.

1.5 The purpose of this paper can, therefore, be said to be two-fold :

1. the identification of the principal constraints presently confronting coastal cage culture; and

2. the identification of a workable strategy in development planning to overcome the identified constraints.

1.6 Unlike animal husbandry with many decades of well-coordinated research and development advancements, there is no ready-made technology package in coastal cage culture in the region. In this consideration, our lack of knowledge of the population ecology of the cultured species is indeed another major obstacle in itself.

1.7 With these sad notes, it does not imply that coastal cage culture is not feasible or viable. On the contrary, it is a highly profitable engagement irrespective of the scale of investment. The above-noted views merely call our priority attention to realistic planning and indeed honest “soul searching” of past failures and successes - and the reasons for them.

1.8 In undertaking this task, perhaps culturists should ask :

1. What have been responsible for past failures and successes ?

2. Is the current back-up, in terms of both research/development programmes/resources/coordination and existing infrastructures, adequate? And if not, what should the requirements be?

3. Is the current arrangement for the dissemination of applicable information to facilitate development needs, realistic and effective? If not, what could be the alternatives?

4. Indeed, are we satisfied that the primary producers find their engagement manageable? Though not known at this time, do we need to monitor the situations as they arise? And if so, how?

2. IDENTIFIABLE PROBLEMS

2.1 Preservation of the long-term productivity of grounds

Two major factors affect the long-term interest of a selected ground.

1. Pollution. This embraces industrial effluents, domestic sewage, and the associated categories of pollutants such as microbes and heavy metals.

   To avoid this problem, a culture site should, therefore, be located away from these pollutant sources.

2. Mismanagement. This arises from carelessness on the part of the operator in using the sea as a recipient of trashes and micro- and macro-debris. This leads to the tipping of the ecological balance of the substrate and if non-biodegradable substances are involved (e.g. plastic bag), this could lead to a number of adverse consequences. (Anaerobes have been recorded from polluted substrates which later attacked the caged fish). Feeding if mismanaged is another problem leading to the overloading of nutrients in the substrates. In less serious cases, this situation affects the level of dissolved oxygen in the water column, and in serious cases this has been recorded as being responsible for diatom blooms.

2.2 The need to grant rights to the operator to his facilities and his fish

This is a legal problem that can only be resolved through the introduction of appropriate legislation. Apart from granting legal recognition of the property of the operator, this also facilitates government control of this new activity on the one hand and enables an organized approach to deal with the future problems of poaching and sabotage on the other.

2.3 Business management

Irrespective of the scale of investment, the operator should be aware of the importance of managing his operations along the principles of business engagement. In the first instance, he should be aware of the need to maintain a high gross prifit. In attaining this, he should monitor the priority and justification of each expenditure in his annual running costs, and he should also take into consideration the annual depreciation rate of each of his facility items with a view to attempting an appropriate approximation of annual saving for future development.

2.4 Stock and facility management

This is of direct concern with the operator's level of success in attaining a high annual gross profit. This also forms the main workload in his day-to-day operations.

2.5 Crisis management

At times of adverse situations where full effort should be directed to resolve/handle such situations. Of particular note, situations arising from adverse weather conditions, disease outbreak, and any other aspects that may be at the detriment of his stocks. This is, therefore, a task oriented problem.

2.6 Fry/fingerling supply

Fry and fingerling supply is a major constraint throughout the region. While cost of these to the operation is a major constraint with respect to his running costs, the quality of fry/fingerling is over and above everything else by virtue of the fact that sub-quality fish are difficult to handle and often-times have low survival rate (if without quarantine and special care and treatment).

2.7 Future development rate in this new fishery activity will largely depend upon the availability of fry/fingerlings, and the sources/grounds of these may or may not be conveniently located at or near the growout sites. Under this circumstance, it would be necessary to divide fingerling supply and fry nursery into two inter-dependent activities. Arising from this, there is the associated need to consider a network of low-cost but efficient:

1. fry/fingerling catching programme (functional) ; and
2. a fry/fingerling transport/relay system.

2.8 The cultured fish species

There are the hardy fish and there are also the “more-difficult-to-hand” fish from a cage culture point of view. In the beginning, therefore, the selection of the hardy species with potentially high market value and demand, and with faster growth rate, should be attempted.

2.9 In dealing with a species, one should have a general appreciation of the species especially its habits and its handling requirements - a subject dealt with in a separate paper.

2.10 Farm management

The management of a cage culture farm must take into consideration and integrate all the above-noted problems. In production planning, it would be advisable to attempt manpower planning based on:

1. task definition;
2. team formation;
3. recruitment;
4. deputisation (test assignment);
5. work schedule; and
6. task integration.

This should be done in accordance with budgetary considerations, scale of operation, and availability of technical back-up, progress review, and marketing support.

INS/80/005/TW3

THE MANAGEMENT OF CAGE CULTURE OF MARINE FINFISHES AND ASSOCIATED OPERATIONAL ASPECTS FOR PLANNING IN THE SOUTH CHINA SEA REGION

A summary case presentation for the southern
Bintan Island area, Indonesia

by

W. L. Chan¹

1. INTRODUCTION

1.1 Need for management

Experience has shown that irrespective of the scale of investment, the culture of marine finfishes in floating net cages (hereafter referred to as cage culture) requires:

1. on the part of the operator, a comprehensive understanding of the potantial range of problems and tasks involved and also the inter-relationships among them, with a view to

2. identifying and integrating these tasks and problems in the design of a manageable, functional and effective organization of the required and/or given manpower, facility and other supporting resources, and at the same time

3. built into such an organization standing arrangements as specific as possible, to tackle urgent tasks in crisis management with timeliness and effectiveness.

The need for management in the betterment of the region's fisheries, capture or captive, has for some time been an important issue in fisheries development objectives of the region's countries. In the early phase of cage culture development, advantage should therefore, be taken to introduce management practices to the prospective operators in addition to culture methods and techniques.

¹ Fishcage/pen Culture Specialist, Preparatory Assistance Project in Seafarming (INS/80/005), Jakarta, Indonesia

Present address: UNDP/FAO South China Sea Fisheries Development and Coordinating Programme, P.O. Box 1184 MCC, Makati, Metro Manila, Philippines

Constraints, risks and other local problems inherent in an area to be selected for cage culture play a vital role in attempting a successful, realistic production management programme. Thus, their identification at the onset is absolutely essential. Similarly, technical backup to help resolve these problems is equally necessary. All this (ref. INS/80/005/TW2) is directly concerned with site selection (ref. INS/80/005/TW4), and coupled with other management considerations (Fig. 1) is directly and/or indirectly responsible for the optimization of the eventual annual gross profit through the minimization of “losses” on the one hand and the upgrading of product quality on the other.

In addition to these factors, Fig. 1 also summarizes other direct or indirect factors affecting the level of success in cage culture management and the inter-relationships of all these factors by the major category of activities. For the purpose of illustrating the role of each of these factors, Table 1 attempts a preliminary pro-forma statement of income using the southern Bintan Island area as a test case. In quantitative terms, for example, if an operator engages also in the acquisition of fingerlings for stocking and feeds for feeding, the annual total production expenditure can be considerably reduced, resulting of course in a much higher profit margin. It can also be visualized that a mistake or wrong decision made in running a cage culture investment could in fact tip the balance of a cost and benefit estimate - no matter how carefully and skillfully such an estimate is arrived at.

Mistakes and wrong decisions are expected to come up from time to time due to human and sometimes other circumstantial factors (e.g. biological, environmental and in fact also ignorance or a lack of foresight). But lessons should be learned from such unfortunate cases - and not to be repeated.

Emphasis on management planning must therefore, take into consideration all constraints, risks, etc. so that a realistic, functional strategy can be designed to overcome them.

For different sites/circumstances, a management schedule applicable to one may not necessary be applicable to another. But in essence, the same principles do hold true. A management design must therefore be reviewed and assessed for its usefulness and applicability from time to time, and refinement is indeed a very necessary ongoing process.

1.2 Constraints

All existing aquaculture systems have their respective constraints. This is also true to the same system practised in different parts of a country, or of an area. In generalizing however, one can identify the following common problems.

1. Available scientific, particularly of an applied nature, information in the tropical region is inadequate for a number of basic reasons inherent in this region.

2. In this regard, disease and nutritional problems then become difficult to resolve. This indirectly dictates the variety of fishes to be chosen, the design of a culture system, and in fact all practices vital to the optimization of yield rate.

3. The supply of fish seedlings has to depend on the wild stock of the species. Although the relative abundance of the seedling stock may be high, the cost of their acquisition and the subsequent distribution is often high, and in many countries unfeasible.

4. This in turn affects the production schedule and therefore, also the annual level of gross profit.

5. Orderly development would appear to be difficult in the absence of legal recognition of the rights of the operator to his fish and legal protection of his properties. Poaching and sabotage are well-known common problems in fish culture.

6. The low priority of fisheries and the absence of vital backup provisions to facilitate development in both the short and long term, will create conflicting situations and in fact competition with other higher priority national activities (viz., industrial and other forms of land development). This also refers to the potential threats of present and future pollution sources that are allowed to co-exist with fish culture. Pollution is a strange word to many who as often as not, fail to command its practical implications in real terms. Even if anti-pollution policy and programme were in existence, the lack of, or slip-shod way in, implementation and control is equally unhelpful.

7. The absence of a suitable infrastructure including product disposal and distribution systems can be expected to adversely affect the culturists and the profit margin of investments. Availability and cost of ice, packaging materials and methods, wholesaling system, percentage of the end value of the fish to the producer, and indeed the role of the middleman, are all unknown variables to the future development of cage culture.

Solutions to these constraints must be attempted if cage culture is to be successful.

1.3 Risks

As for other fish culture systems, risks in cage culture can be readily identifiable and many of them can be aliminated at the time of site selection (INS/80/005/TW4). For pilot culture trial purposes however, the need to accept certain “convenience” factors in selecting pilot sites (ref. INS/80/005/TW2) makes it difficult to eliminate all risks. In either event, the uncertainty of the future pollution level in a presently unpolluted site could in the course of time lead to considerable adverse situations to a potentially good site.

The major risks in cage culture are:

1. Exposure of facilities to the adverse effects of strong weather quarters.

2. Exposure to the adverse effects of strong tidal current movement.

3. Contamination of the caged fish by pollutants (viz., oil, diatom bloom, microbial infection, etc.)

4. The potential danger of pests (e.g., sharks, large predatory pelagic fishes, puffers, otters and any other organisms causing potential damage to both the culture facilities and the confined fish stocks.)

5. Stratification in the water column during slack tidal periods and the associated dynamics of hydrographic parameters often resulting in oxygen depletion.

The control of these risks are difficult. As far as possible these should be eliminated at the time of site selection, and if this is not possible attempts should be made to prevent them from causing unnecessary losses of fish stock through a system of task-oriented crisis management. Timeliness and effectiveness in the execution of each of the individual task will be most essential.

1.4 Development opportunities

Through good management control and practices, cage culture is a potentially viable engagement. Good management depends upon the outcome of a number of dependent and independent variables (Fig. 1). Of particular note are:

1. The cost of fish seedlings (Table 1) forming about 33% of the total annual cost of goods. Apart from this high percentage, the fund has to be expended in two payments. As far as possible a prospective operator should also undertake seedling acquisition to reduce cost.

2. Similarly, feed cost (Table 1) forms 60% of the total goods cost. This is a daily expenditure item. The prospective operator should also undertake his own feed acquisition using labour non-intensive gear such as the gill net. If a daily feed ratio of 8% of the total fish biomass is planned, the daily feed requirement only ranges from 107.5 kg to 400.4 kg per day, a weight that can be attained in gill net catches.

3. If the cost reductions under (a) and (b) above were possible, this would automatically reduce the total annual production costs and at the same time increase the annual gross net profit by a very significant percentage.

In the estimate (Table 1) a figure of 10 kg/cu. m. of fish biomass at harvest is used. But in the southern Bintan Island area, fast flowing currents and tidal water exchange could enable an optimum biomass carrying capacity of 15 kg/cu. m. subject to good management of the net cages. This higher figure is not presently proposed since less densely stocked cages are in many ways more manageable particularly in the beginning of this new development.

Using an eight-cage unit for a family size of, say, 6 persons, of whom 3 are fully functional, a family earns from wages Rp 720 000 per year, and on top of this there is a net profit of Rp 10 119 895. But the family would require an initial grant of Rp 5 000 000 for the initial capital cost, and an annual cost of Rp 9 732 905 to cover items B and C in Table 1. It is therefore, of great importance that the suggestions made under paragraph 1.4 (a) and (b) above should be followed as far as possible to reduce running costs.

With two crops a year, cash flow will be fast, and coupled with the need to control expenditures involved, good accounting will then be absoutely necessary.

The demand of the cage produced fish and the effect of supply on the current demand characteristics, are two major factors requiring investigation before embarking upon the expansion of this new engagement. The problem of distribution of the product to the better marketing centers of higher demand and better value should also play a key role in this consideration. Needless to say, the quality and freshness of the product to fetch an optimum value are also important issues in development. Associated with these will also be the need to improve packaging and transport technology.

With the extremely long coastline and numerous large river systems, the supply of wild seedlings would not appear to be a major problem at this time. But the acquisition of wild seedlings still necessitates good organization to minimize seedling acquisition cost on the one hand, and to begin to arrive at a viable arrangement in seedling acquisition for the longer term to facilitate the expansion of cage culture operation.

In this consideration, it is particularly important to draw our attention to:

1. the spawning and nursery, and therefore the fry grounds of the desired species of finfishes may in all probability be spaced out along the very long coastline of the country, and under such a circumstance it would appear to be essential to consider national fry holding and nursery centers; and

2. of many of the percoid fishes of culture value, fry nursery requires such higher technological inputs than the growout operation, which may or may not be handled by the operators themselves, including problems ranging from cannibalism, need for grading, disease infection, special feeding arrangements, and other problems associated with the young fish.

In considering the future prospects of the island province, it is not optimistic to contemplate an annual total production of 25 000 matric tons of premium fish through cage culture practices. In the present test case of an eight-cage culture unit, an annual yield of 5 metric tons has been estimated. To attain this 25 000 metric tons target, it requires 5 000 such units to be spaced out among the numerous islands.

Similar development undertaken elsewhere along the long coastline of the country could in fact yield at a rate of 100 000 metric tons per year.

Expansion must however, be realistically planned taking into consideration the constraints noted in the aforesaid, and also the viability of future operation as a measure of the rate of expansion. Expansion means increasing demand for seedlings and fish feeds, it also means increasing costs of these essential production inputs. Higher production cost would render cage culture non-viable, and coupled with over supplying the markets the consequences could then be serious.

If cage culture is meant to stay, it would be prudent to

1. consider ways and means to minimize production costs;

2. consider seedling supply centres both through the utilization of the wild fry stocks and the production of seedlings using modern hatchery techniques;

3. consider alternatives for fresh fish feed;

4. consider national infrastructure in support of this new venture; and

5. consider the introduction of legislation to control and protect this new development.

2. CULTURE FACILITIES

2.1 A unit of floating net cage(s) comprises four principal components: the raft structure, the floatation device, the net cage, and the mooring system. The design and choice of materials for each of these components depend on a number of factors inherent in the individual sites concerned (ref. INS/80/005/TW5). The choice of materials in family-scale operation, is often times a compromise between cost of the materials and the required material strength that can withstand the extreme of local weather conditions.

2.2 Raft structure

1. In the southern Bintan Island area, good quality hard wood is readily available and much less costly than bamboo and any form of metallic material. If properly rigged and reinforced, it is a choice material. For this reason it is chosen.

2. The eight-cage unit comprises two rafts, each of which is divided into four square spaces to hold net cages each of a dimension of 2.4 m (length) × 2.4 m (width) × 5 m (depth).

2.3 Floatation device

1. An assortment of floatation devices are presently used ranging from oil drum, plastic container, to especially manufactured styrofoam floats and styrofoam reinforced pvc tubings. Again the choice of these is a cost consideration and also the reliability of the device under adverse weather conditions.

2. For the southern Bintan Island area, the oil drum is readily available and cost is comparatively cheaper even considering its maximum life span to be just a year.

2.4 Net cage

1. In the absence of information on foulers, it is difficult to decide on the materials to be used. For the Bintan sites, monofilament netting material is suggested for two reasons first, it gives less surface for foulers to settle and second, it has a longer life span than most of the multifilament trawl net type materials.

2. For ease of management and especially harvesting and stock manipulation, it is not suggested to distend the net cage with a wooden or other types of stiff frame. To maintain a consistent shape of the net cage, a bottom square galvanized water-pipe frame and other riggings are used instead.

2.5 Outer cage for protection

1. Information from fishermen concerned with the frequenting of large pelagic fishes in the inter-islet channels necessitates the incorporation of an outer heavy duty monofilament net cage for the protection of the fish stock in the inner cage.

2. This outer cage also enables the prevention of the distortion of the fish cage by strong moving currents.

2.6 Mooring system

1. The mooring system is as shown in INS/80/005/TW5.

3. FISHES FOR CULTURE

3.1 In general the species of fish selected for culture should meet with the following criteria (Table 2) that:

1. Its optimal requirements for survival and normal growth can be met by the conditions inherent in the aquatic environment of a chosen site.

2. It should be a fast growing fish capable of fatching a good value from conveniently located market outlets.

3. It should be a hardy fish, easy to handle and with the least problem arising from confinement (INS/80/005/TW2).

4. Its fry and/or fingerlings should occur in the area or its vicinity in adequate numbers for utilization.

3.2 For the Bintan areas, the following species are suggested:

1. Epinephelus tauvina or the estuarine grouper. It is widely distributed in the South China Sea region. Its early larvae and fry are found commonly in coastal seas adjacent to the outfall of river systems where salinity values may range from 15 to 25% or slightly above. In some parts of the region, nearly all sizes are found in large, very much enclosed water bodies receiving the discharges of fresh water from rivers. Thus, it is difficult to generalize the ecology of this species. Juvenile and adult stages are however, known to inhabit marine waters. Subject to further survey results, this species appears to show two spawning peaks, with the main one in October-December and a minor one possibly in April-May. From hatchery results, the time required for fertilized eggs to reach 5 cm fry is 50 days. Like other serranoids, it is cannibalistic especially in its early stages of development. Grading of a caged stock of young fish to size groups is therefore absolutely essential to prevent unnecessary losses. As other Epinephelus species, it is a bottom-dwelling species and prefers to hide themselves under rocks, macro-debris and among algal growths. Under confinement in net cages, it stays on the bottom net and especially corners. On feeding, it makes fast lunges to get at the feed. It can tolerate fresh or near fresh water, which serves as an easy means to rid the fish from harmful parasites and bacteria in its stomach.

2. Plectropomus maculatus and P. leopardus, or commonly called coral trouts. Unlike the epinephelids widely distributed in different habitats, the plectropomids are all confined to coral reef areas. They also differ in being off-bottom swimmers although feeding behaviour is similar to that of the epinephelids. Very little is known about its spawning behaviour and season, although in some areas April-June is known to be the peak spawning period. In March, gonad maturation reaching stage 4 and above has been observed. It is a difficult fish to culture outside coral reef area irrespective of similarities in the aquatic regime. This is largely due to its vulnerability to the mirobial flora and fauna outside coral reef area. But under cage culture conditions in coral reef area, it is a fast growing fish and maintains its normal condition factor. It is therefore, a good species (either P. maculatus, or P. leopardus) to be mixed with the epinephelids in taking up the off-bottom and “off-side” water column.

3.3 For the pilot culture trials in the Bintan area, these two hardy, fast-growing species are recommended. Other epinephelids viz., E. fuscoguttatus and E. malabaricus can also be considered if their fingerlings can be obtained. Both these species are also coral reef fishes of a hardy, fast-growing nature. But the black spots and blotches would appear to be less presentable as a market fish.

3.4 For Teluk Lampung, these same species can also be used. But the lack of information on the availability and relative abundance of their fingerlings has presented the major problem in making this proposal. In addition, the emphasis on the use of the kakap (Lates calcarifer) presents also a major problem to the present recommendation for this area. In the opinion of the author, the culture of kakap in net cages should be delayed until experiences have been gained after the pilot culture trial, since the culture of kakap necessitates very intensive care particularly at its early phases of development from the fry stage. For the present purpose, the following species are proposed:

1. Epinephelus tauvina (estuarine grouper).

2. Epinephelus malabaricus (Malabar grouper). A coral-reef serranid, it grows equally fast as E. tauvina and also equally hardy to handling. Very little is understood of its habits and spawning season.

3. Lutjanus argentimaculatus (mangrove snapper). It should occur in abundance in Teluk Lampung. From elsewhere in the region, its main spawning peak falls between May and July and its early fry invade brackish mangrove waters and the larger juvenile move into marine habitats. (In one area, this species has been known to enter a freshwater lake and stay and propagate there). It is a fast grower, but like other fishes with medium to large-sized scales, it has to be handled with care to avoid the falling off of scales. This could lead to subsequent bacterial infection.

4. Lutjanus sanguineus (red snapper). This is a marine and coral reef snapper which is found in the Teluk Lampung area. It is a fast grower and like the mangrove snapper has to be handled with care. This name, according to most taxonomists, refers to a “red-coloured” complex of snappers of at least two species. For this reason, it is difficult to suggest what might be the spawning season of this fish in the area. According to the author, what he saw should be the real L. sanguineus. If so, its spawning season according to information elsewhere should fall within the November-January period.

5. Lutjanus johni (John's snapper). Its habits and other ecological characteristics are fairly similar to those of L. argentimaculatus.

3.5 In Teluk Lampung, any one of these species or their combination can be tried. As far as the kakap is concerned, the author does not rule out its potential as a cage culture species, but rather emphasizes its great potential as a brackish pond culture species for the following reasons:

1. Cannibalistic behaviour. Though many of serranoids show this behaviour in confinement, the giant sea perch is perhaps the most aggressive fish in this sense. This behaviour is exhibited as from some time after metamorphosis. If grading to size groups is not done every 5 days, and if the fish are not fed more than three times a day, mortality suffered could exceed 90%.

2. Nursery. Intensive stock manipulation backed up by functional, qualified technical assistance are necessary and essential in the nursery of the early fry of this species up to a stocking size of not less than 4 inches in total length.

3. Density problem. Under crowded condition, one could see a rapid reduction in the number of fish in net cages as the fish gain in size. Grading to different size groups is therefore necessary, but grading itself is a physical process in which unnecessary bodily damage (notably loss of scales and operculum, and damage to skin of the nape) could incur a mortality (handling) of up to 3% per grading. In the pond environment, where the stocked fish can resort to “sanctuary” like inside a hole in the mud, among growths of aquatic weeds, etc. would tend to prevent cannibalistic losses. Moreover, the presence of benthic animals in a pond environment can provide not only additional feeds but also other “attractions” to the larger fish.

4. Salinity. Although this fish is a euryhaline one, the effect of high salinity on it can sometimes be a stress in itself as suggested by the wide ranging variety of diseases it contracts (including virus, bacteria, protozoans, sporozoans and parasites). This is particularly true to the fry and fingerling stages.

4. SPECIES SELECTION IN CAGE CULTURE

4.1 Apart from the point on manageability, availability of stocking materials and feeds, and the required technical know-how in management, the selection of the species for culture is not as straightforward as some normally believe. Table 2 attempts to summarize the inter-relationships of the main points for serious consideration. Apart from the suitability of the environmental setting to the chosen species, notes should also be taken of the total annual value of the harvested fish on a per-cubic-meter basis. As shown in Table 2, this depends on a number of variables. This line of thought is directly related to the case presented in Fig. 1.

5. MANAGEMENT OF CAGE CULTURE OPERATION

5.1 Task identification

Routine tasks can be classified into the following categories:

1. Feed acquisition and feeding. This forms the major daily work to be carried out without fail. Records of the cost of feed, amount of feed administered per cage, and the objective assessment of the feeder of the general well-being of the stock in each cage, should be taken.

2. Stock manipulation. This is a periodic task to be carried out as and when required, with the purpose of grading the caged stock to different size groups to reduce the adverse effects of uneven growth, loss of fish through cannibalism and disease, and optimize growth for each individual fish. Depending on the situation in each of the cages, grading should be scheduled on a monthly basis.

3. Material facility maintenance. On a daily basis, lose objects, twine, etc. should be checked and repaired. Periodically, net cages should be monitored for the relative abundance of settled foulers, and cage changing should then be carried out on siting the attachment of especially hard foulers at an early stage.

4. Maintenance of supporting facilities. This is concerned with the motorized boat, watchman hut, and any of land-based facility.

5. Precautionary measures. Before the onset of poor weather, if predictable, additional anchors should be attached to the rafts, and all anchoring ropes tied to the corners of each raft should be chacked to ensure security. All cover nets should be tightly secured.

6. Crisis management. This refers to unexpected happenings that could do serious damage of the caged fish. Such happenings may include fish disease outbreak, oil spillage in the neighbourhood or within the farm itself, strong weather conditions, etc., which require the deployment of all resources to resolve the problem.

5.2 Task integration

These tasks should be integrated with a view to making all farm hands interchangeable in their assignments, thereby maximizing efficiency in operation. Task integration is also a good, practical way to identify the potential capacity of development and therefore, leadership of each of the farm workers. It is especially useful when it comes to resolve problems during crisis periods.

5.3 Work schedule

Good managements means many things, one of which is that people involved must know what they are expected to do ahead of time. The adoption of daily, and better still weakly, schedule of work would facilitate the development in this direction.

5.4 Team formation

The formation of a functional working team with the given labour force is essential. This enables a practical organizational approach to undertake the given tasks, to generate a team spirit approach towards the solving of problems, and to make events accountable.

5.5 Deputisation

The overall responsibility of a pilot culture trial and the eventual functional family-level culture farm, would require leadorship in the enforcement and implementation of the day-to-day and other duties inherent in a cage culture farm. Leadership qualities of the farm “manager” must be carefully assessed from time to time, and the “manager” should be given the chance to know his strengths and weaknesses. Through an appropriate training scheme, the “manager” can then be given all the basic essentials to enable his development in this direction.

6. A SUMMARY OF CAGE CULTURE OPERATION

6.1 Acquisition of stocking materials

In this undertaking, experiences of fishermen are extremely important insofar as the identification of fry or fingerling grounds is concerned. For smooth bottom grounds, beach seine and traps are considered the best gear to deploy. On rugged grounds, traps are the only method of capture. These gear are emphasized because they are expected to incur the least damage to the captured fish.

The live fish should be placed in a small “portable” floating not cage, and at the end of a day of capture the fish can then be relayed to the farm in aerated wide containers, or in plastic bag with oxygen, or in live tanks inside the hull of a motorized craft. To transfer the fish use only knotless, soft dip nets.

6.2 Treatment of fish before stocking

First, the fish selected for stocking must have all scales intact, fins undamaged, skin and eyes in normal conditions. Second, by kind they can then be sorted out visually to different size groups. Before stocking such materials in a cage, it may be necessary to immerse them in good-quality freshwater for 1 or 2 minutes inside a tub or other forms of container.

6.3 Stocking rate

To facilitate the development of this new engagement, it is suggested that:

1. For the Bintan situation, each cage should be stocked with 1 344 numbers of fish (Table 1). Assuming an average initial stocking weight of 125 gm per fish, and a 30% mortality by harvesting time, this should yield 941 605-gm fish. If stock manipulation is carried out and feeding regular, this is considered to be the minimum number of fish at harvest.

2. For the Teluk Lampung situation, each cage should be stocked with 307 numbers of fish (Table 2). Using the same assumption as for (a) above, each cage should yield 236 numbers of 1-kg fish. Again, if management is effective this number can be considered the minimum.

6.4 Feeding

Feeding should be done twice per day, the first at 8 a.m. and the last at 5 p.m. The total quantity of feed given per day should be at 8% of the total fish biomass inside each cage. This biomass figure could be extrapolated from visual judgment of the average weight of the caged fish and, if records of mortality were kept for each cage, this quantity could easily be arrived at. This also means that this 8% is to be shared between the two feedings.

All fish feeds must be fresh and cut into pieces to suit the mouth size of the caged fish. Adopt a “spraying” movement with one's hand in feeding to obtain as wide a spread of the feed as possible. This gives an equal chance for each fish to have a bid for the feed, and at the same time, avoid overcrowding of fish at a small area. Overcrowding in feeding can incur physical injuries which later promote bacterial growth. As soon as the “urge” of the caged fish to feed is lessened, begin to stop feeding. This is known as an 80% satiation.

Records of feed quantity applied to each cage, number of dead fish in each cage, and the general conditions of the caged fish in each cage, should be treated as a daily routine information keeping for future reference. Do not underestimate the usefulness of this information.

6.5 Grading

The grading of the caged fish must be done periodically to reduce stress on the smaller fish, to minimize adverse effects of cannibalism, and to maximize output. Details of each grading exercise should also be recorded.

Lift a cage and gilt it to one side with the help of a bamboo pole. With a soft dip net take out the smaller fish and put them into a known cage. Rotate this work until all the fish are graded and accommodated in the eight cages.

After grading the fish may not feed for one or at the most two feedings.

6.6 Cage changing

If hard foulers are seen attached to the net, it is always important to get rid of them before they grow to a larger size. This has two benefits in one maintain a longer life span of the cage and in the other protect the fish from getting scars on their body. Of course, it will also allow better exchange of seawater and therefore, increase the level of dissolved oxygen in the confinement.

Detach part of the fouled cage, life up the fouled cage just more than half its depth, attach a clean cage, and put the detached part of the fouled cage over the part of the clean cage still unattached. Lift up the fouled cage after detaching the remaining part, and herd the fish over to the clean cage. Remove the fouled cage and entirely rig up the clean cage. The fish after this handling would not feed for one or at the most two feedings.

6.7 Cleaning the fouled cage

To avoid as far as possible beating off the foulers, it is advisable to soak the net cage in freshwater on land. This would kill the hard foulers and at the same time render their attachment to the netting material easier to be removed with the use of a squarish block of wood. (Ideally, a freshwater jet should be used, but such a machinery is too expensive).

After drying the cleaned net, store it away from the direct effect of the sun to retain its material strength.

6.8 Maintenance of the floating raft

Before the onset of strong weather period, precautionary action should be taken to ensure that the floating raft should have adequate floatation force, anchoring ropes properly attached to the raft, and additional anchors are prepared to give better security to the raft if weather deteriorates.

Checking of the oil drums is essential. Bad ones should be replaced and good ones to be further secured. Changing oil drum is a one-man job if the person is skilled. It is always advisable to put in a new drum before an old one is detached.

6.9 Crisis management : strong weather precautionary schedule

Before the onset of strong weather seasons, take precautionary actions along the lines noted in paragraph 6.8 above.

When strong weather arises, repeat the same procedures. Throw in additional anchors on the weather side to give the raft a better resistance to the action of strong seas and winds.

Secure all cover nets, oil drums, wooden planks and all ropes. Feeding has to be stopped. All farm hands on duty on a rotation basis, and alert all hands in case of the need to perform emergency work.

6.10 Crisis management : oil spillage

An oil spillage may occur under different circumstances and at varying magnitude. The oil involved may also be extremely diverse in the level of toxicity resulting in either mass kills of the caged fish or disease infection and tainting the flesh of the fish. Oil kills fish without having to get into direct contact with the fish as many western oil spillage experts insist to claim. When the spilled oil is located or gradually drifting towards the proximity of a cage culture farm, the aromatic or volatile contents of the oil get into solution with the seawater may at times reach the caged fish. In trying desperately to avoid this, the fish hurt themselves on their sides, snout, fins and head by rubbing hard against the net cage material. At the same time, the dissolved aromatic contents of the oil begin to be taken up by the fish through the gill filaments. In serious cases involving a high aromatic content, an oil spillage has been found to kill the fish without actually entering to a farm area. This situation is worsened if detergent particularly that of the third generation is used without taking advantage of wind drift, current flow direction and a “containing” strategy with the aid of booms.

If the spilled oil has low aromatic contents, it can still kill the fish without getting into direct contact with them. This would happen if again unacceptable detergent is used without the use of common sense. The partially dispersed oil droplets once drifted over to the caged fish would again incur similar avoidance behaviour of the fish resulting in considerable physical damages which subsequently lead to disease infections.

The presence of oil over the area of a farm is a disastrous situation. Irrespective of the oil's toxicity level or the use of detergent, the oil could incur mental, physical and chemical stresses on the caged fish, coupled with the lack of oxygen transfer between air and water, render such a case insalvageable.

From crisis management point of view, the following procedures whether effective or ineffective should be followed:

1. Take careful note of the wind direction and subsurface current direction (from 1 m to bottom) for the prediction of the possible invasion of the spilled oil into the farm area. If there are indications that the site could be affected, detach all anchoring ropes (each tied to a float for subsequent identification), and move the raft to another area which is suspected not to be affected by the oil. When moving the rafts, do not tow them, but “push” them with the bow of a motorized vessel.

2. If the fish are approaching the target marketable size, harvest them immediately for sale before they get contaminated.

3. Authorities responsible for handling oil spillage must adopt intelligent strategies in coping with the problem. Spillage occurred in areas where cage culture exist, must be tackled using different methods other than overreliance on the use of detergents. Even outside cage culture areas, a spillage must be “contained” using appropriately designed booms and utilizing information of wind, current and tidal water direction and speed. There should be a standardized procedure to tackle oil spillage, and there must also be special procedure for handling spilled oil likely to enter or affect cage culture areas. In this consideration, there must also be a policy to choose the least toxic detergents, to prohibit the use of detergents in cage culture areas, and to have special arrangements to tackle spilled oil in these areas (e.g., booming, mopping, etc.).

6.11 Crisis management: oxygen depletion

The high biomass carrying capacity and therefore, the high yield of fish per cubic volume of water in cage culture are attributed by the natural flow of tidal waters and currents, which essentially thin out metabolites and replenishes a good level of dissolved oxygen supply. But at times of slack water movement periods, coupled with the presence of a high planktonic population or collapse of such a population, have been found to incur oxygen depletion phenomenon. There are other factors coming into play Overcast sky, low atmospheric pressure, high air and water temperatures, etc., are all associated with such a phenomenon. Two established cases of fish kill as a result of oxygen depletion have been recorded:

1. In one, subsequent to a short period of heavy downpour, a strong halocline was formed at the upper 6 inches of the water column. The slack water movement, and lack of transfer of oxygen between air and water, coupled with high water temperatures, had caused a sudden increase in trapped metabolites and bacterial activities, followed by a rapid decline in dissolved oxygen content and also the value of pH and abrupt increase in ammonia. Fish died within a matter of several hours with the young fish first taking the pinge.

2. In the other, water movement was minimal, atmospheric pressure low, air temperature high, and the sky with 100% overcast. A similar phenomenon took place with fish killed within a few hours' time.

The symptoms of the fish were exactly those of the fish in eutrophic pond water all surfacing to gulp for air. At the same time they swam blindly and bruised themselves by hitting hard against the netting material.

In the beginning of this phenomenon, all farm hands should try as hard as possible to stir the water inside a cage to create air bubbles at the surface and through convection transfer these to the lower layers in the water column. If a motorized boat is in hand, start its motor, put its gear in neutral and allow the propeller to create water movements through the cages This is quite effective.

The ideal situation is of course to be able to have an aerator, but there is the question of whether or not electric power source is available. (A highly functional marine type aerator of 1 hp has been developed recently).

6.12 Crisis management. diatom bloom

In nutrient rich areas, diatom blooms must be expected to take place from time to time. One may see coloured waters coming in red, yellow and brown patches of varying sizes. These have been responsible for some of the worst mass fish kills in cage culture in this region, responsible by the Noctiluca, Ceratium and Prorocentrum groups.

It is very difficult to tackle diatom blooms because of the following reasons :

1. A bloom may shift from place to place depending on the direction of wind drift and surface currents.

2. A bloom would stay for as long as nutrients and trace elements are present.

3. A bloom kills the fish not only through the uptake of dissolved oxygen but also through the emitted toxin.

Precautionary actions can be one of several whichever that may appear to be the right one to take :

1. Aerate the caged water as vigorously as possible with aerators.

2. Seal and secure cover net and lower fish cage to deeper than at least 5 m.

3. Move the floating rafts with cages to an open channel where daily current flows are expected to at least thin out the density of diatom.

4. As a good practice to avoid complete loss, sell the fish if they are approaching optimum-value size.

6.13 Crisis management : disease infection/outbreak

Disease infection or outbreak in a fish stock is costly. Invariably, some percentage of mortality is suffered and at the same time the after effect of stresses on the surviving fish is always a sad sight. Unlike in animal husbandry where quarantine and cure/control of the disease are manageable, the task of having to treat the sick fish is altogether a very different game and problem in fish culture. It is therefore always prudent to adopt the policy of disease prevention than to attempt disease treatment in cage culture, as closely as possible.

Very little is indeed known about fish disease in tropical marine percoids. The need for information is real and urgent, but very little sympathy is received from national authorities (medical and university fields) or from international fishery agencies. Perhaps, solutions to our present problems are expensive on the one hand, and indeed the great challenge of having to be confronted by the diverse variety of species.

Fish disease includes a wide spectrum of organisms, including fungus, virus, bacteria, protozoa, and a wide range of parasites. Fish contract a disease through contaminated feeds, through environmental stress(es), and through direct contact with the disease itself.

The seriousness of a fish disease case depends on whether it is a primary or secondary infection. The management of fish disease problems would necessitate the support of professional inputs. Unlike other problems, fish disease is one that can only be resolved through multidisciplinary efforts.

+ Items 1 and 2 are based on direct purchase in theory. In practice, these costs should be lower if operator also engages in these acquisitions on his own.

# Based on 30% mortality as a safeguard, but this estimation is on the high side for groupers. The value per 605-gm fish to operator at S$8 could be increased by direct involvement in the delivery of product to Singapore where 605-gm groupers are sold for S$10–12 per catty wholesale.

(1) A summary list of potential cage culture fish species for the southern Bintan Island area and the likely events (if collectively considered) to justify the selection of species. Justification emphasizes on likely economic return.

(2) Based on likely value to the fish farmer from Singapore-based fish collectors/agents for sales in Singapore. 605-gm or catty size fetching optimum value.

(3) A size from which optinal growth begins, based on serranids and lmtjanids.

(4) Attainable through good, effective management.

(5) A likely event depending on availability of fingerlings and the dedicated efforts of the fish farmer.

(6) Value of 605-gm fish x number of fish per m³ at harvest x number of crops per year, being annual gross revenue from each m³.

(7) To generalize the distribution of the fry, juvenile and adult of the species with a view to illustrating the relative suitability of a site for each of the listed species.

(8) This species is a fast-growing one, but there are many problems requiring intensive technical input particularly at the fry stages.

Fig. 1 Factors Concerned with the Eventual Optimisation of Annual Gross Profit, with Special Emphasis on the Role of Dependent and Independent Variables in Cage Culture Investments