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Here, on the basis of published information upon over 800 species from 39 orders and 202 families, we analyse how the size of oil globules in fish eggs varies between reproductive guilds and environments with contrasting salinities. About 80% of marine fishes produce eggs with oil globules, the volume of which (VO) never exceeds 9% of the egg reserves and averages 2%. These proportions vary very little between marine fish species producing pelagic or demersal eggs. Fewer freshwater fishes (about 40%) produce eggs with oil globules, but their globules are much larger (mean VO of 10%) and their volumes vary considerably between reproductive guilds: VO is on average 3–10 times lower in freshwater species with demersal eggs than among freshwater pelagophils and aphrophils (i.e., bubble nesters), where it averages about 40% (range of 23%–69%) of the egg reserves. These results support the idea that oil globules serve to hydrostatic lift in fresh waters, but not or very little in marine waters, where egg buoyancy can be achieved at a lower energy cost through egg hydration. Advantages and constraints of oil globules in fish eggs are discussed in the light of species producing eggs with very large oil globules (VO > 20%): access to oxygen‐rich water layers that are indispensable for egg development vs. smaller size of larvae at first feeding, since the saturated lipids contained in oil globules essentially serve very little to tissue construction.

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ABSTRAKIkan baung (Hemibagrus nemurus Val. 1840) termasuk kelompok catfish bernilai ekonomis, di Asia populer dengan nama "green catfish". Informasi tentang variasi genetik dan keragaan bioreproduksi dari ketiga kandidat populasi hasil kegiatan 2011, yaitu: populasi Cisadane (Sdn), Cirata (Crt), dan Serayu (Sry) telah dijadikan informasi dasar dalam keperluan seleksi atau persilangan antar strain agar diperoleh ikan yang cepat tumbuh. Populasi Serayu menunjukkan tingkat variasi genetik paling kecil, namun memiliki aspek bioreproduksi lebih baik, sementara populasi Cirata menunjukkan kekerabatan dan variasi genetik lebih tinggi dari populasi Serayu dan Cisadane. Penelitian ini bertujuan untuk mengetahui keragaan bioreproduksi dan pertumbuhan hasil persilangan dari tiga populasi yang digunakan. Keturunan hasil persilangan antara ketiga populasi telah diamati pada aspek Spesific Growth Rate (SGR), bobot akhir, dan sintasan (SR) pada stadia benih umur 42 hari, serta parameter bioreproduksi dari masing-masing populasi induk antara lain: perkembangan gonad, fekunditas, dan indeks ova somatik. Hasil persilangan antara populasi Sdn x Sry menghasilkan nilai heterosis tertinggi pada parameter SGR (8,72%); heterosis sintasan tertinggi dicapai oleh persilangan Sry dengan Sdn (45,45%); sedangkan bobot akhir dicapai oleh persilangan Crt dengan Sdn (22,08%). Persilangan dua arah antara populasi Cisadane dan populasi Cirata adalah persilangan dengan respons tertinggi pada parameter SR dan bobot akhir nilai IOS (Indeks Ova Somatik) Cisadane 15,9% dan Cirata 20,7%. KATA KUNCI: ikan baung, persilangan, intraspesifik, heterosis ABSTRACT:Bioreproduction

Variasi genetik dan morfometrik beberapa ras ikan baung yang dikoleksi dari Jambi, Wonogiri, dan Jatiluhur telah diteliti dengan menggunakan polimorfisme mitokondria DNA D-loop dan metode truss morphometric. Berdasarkan kedua metode tersebut terdapat perbedaan yang nyata antara ras ikan baung dari Jambi dengan Wonogiri dan Jatiluhur, dan tidak berbeda nyata antara ras Jatiluhur dengan Wonogiri.

Study about tambra fish, Tor tambroides (Bleeker, 1854) or mahseer were conducted in Muller Mountain areas Central Kalimantan. The aims of study were to know status and structure of population, habitat types, and preferences. The methods are catch per unit of effort, visual, and experimental. The results were caught 29 tambra fish, consist of 4 males, 8 females, and 17 juvenile size; the population is rare; the habitat type were grouped to three groups; this fish more prefer to deep waters, the water quality was suitable for living of tambra fish.

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