- O'Day, Nafpaktitis 1967
- A study of the effects of expatriation on the gonads of two myctophid fishes in the North Atlantic Ocean. Bull. Mus. comp. Zool. Harv., 136 (5): pp. 70-90, 9 fig., 2 pl.
- O.C.D.E. 1966
- Projet de dictionnaire multilingue des poissons et produits de la peche. Mimeo, vii+1019 p., Paris (publ., 1968, Fishing News (books), London: 431 p.).
- Oberg 1871
- Acantholabrus couchii Cuv. et Val. en for Skandinaviens Fauna ny Fiskart. K svenska VetenskAkad. Handl., 1870 [
- Odhelius 1788
- Chinensia lagerstroemiana: 230-260, pl. III. In: C. Linne, Amoen. Acad., IV, ed. 2a, no. LXI.
- Ojaveer 1962
- [On differentiation of the herring seasonal races in the North Eastern Baltic by means of otoliths]. Izv. Akad. Nauk. Est. SSR, ser. biol., 11(3) :193-208, 3 fig., 2 microph. (in Russian, with English summary).
- Okada 1955
- Fishes of Japan. Illustrations and descriptions of fishes of Japan. Tokyo, 434+28 p., 391 fig.
- Okada 1960
- Studies on the Freshwater Fishes of Japan. J. Fac. Fish. pref Univ. MieTsu, 4: 860+II p., 133 fig., 111 pl.
- Okada, Matsubara 1938
- Keys to the Fishes and Fish-like Animals of Japan. Tokyo and Osaka, 40: 584 p., 113 pl.
- Oken 1817
- V Kl. Fische. Isis oder Encyclopadische Zeitung, 8 (148) :1181-1183 (misprinted 1781-83).
- Okiyama 1972
- Morphology and identification of the young ipnopid, 'Macristiella' from the tropical western Pacific. Jap. J. Ichthyol., 19 (3): 145-153.
- Okiyama 1979
- Morphology of juveniles and phyletic relationships among the Myctophiformes. Oceanography Science, 11 (2): 131-145.
- Okiyama 1970
- Revision of the family Macrisiiidae. Jap. J. Icthyol., 17: 89-90.
- Okiyama 1973
- The larval taxonomy of the primitive myctophiform fishes. In: J. H. S. Blaxter (ed.), The early life history of fish, p. 609-621.
- Olafsen 1774
- Des Vice-Lavmands Eggert Olafsens und des Landphysici Biarne Povelsens Reise durch Island, veranstaltet von der Königlischen Societät der Wissenschaften in Kopenhagen und beschrieben von bemeldten Eggert Olafsen. Aus dem Dänischen übersetzt. Mit 25 Kupfertafeln und einer neuen Charte über Island versehen. Kopenhagen und Leipzig, 1:14 not numb.+1-328, 25 pl., map.
- Olafsen 1772
- Vice-Lavmand Eggert Olafsens og Land-Physici Biarne Povelsens Reise igiennem Island, 1:1-618, 51 pl.
- Olfers 1831
- Die Gattung Torpedo in ihren naturhistorischen und antiquarischen Beziehungen erlautert. Berlin, 35+1 p., 3 pl.
- Oliva 1953
- Prispevek k prehledub nasic mihuli (Petromyzones Berg, 1940). Vestn. Kral. cesk.spol.náuk, 1952 [
- , 1952
- La alacha y la sardina de Baleares. Investigaciones en 1950 y 1951. Boln Inst. esp. Oceanogr., (58) :1-49, 8 fig.
- Olney, Markle 1979
- Description and occurrence of vexillifer larvae of Echiodon (Pisces, Carapidae) in the western North Atlantic and notes on other carapid vexillifers. Bull. Mar. Sci., 29: 365-379.
- Ondrias 1971
- A list of the fresh and sea water fishes of Greece. Hellenic Oceanol. Limnol., 10: 23-96.
- Oppenheimer 1954
- Transplantation experiments on the eggs of Gobius. Publ. Staz. zool., Napoli, 25 :18-25.
- Orbigny 1841-1849
- Dictionnaire universel d'Histoire naturelle. Paris, 13 vol., 3 vol. color. plates (Fishes: 18 pl.).
- Orkin 1950
- A history of the opah Lampris guttatus (Brunnich). Scott. Nat., 62: 129-141, fig.
- Orsi 1971
- Primo ritrovamento di un adulto di Oculospinus brevis Koefoed, 1927 (Pisces, Brotulidae) in Mediterraneo. Annali Mus. civ. Stor. nat. Giacomo Doria, 78: 247-255, 5 fig.
- Orton 1964b
- New information on a rare eel larva, Leptocephalus hyoproroides Stromman. Copeia, (2): 434-444, 4 fig.
- Orton 1963
- Notes on larval anatomy of fishes of the order Lyomeri. Copeia: 6-15, 4 fig.
- Orton 1964a
- The eggs of Scomberesocid fishes. Copeia, (1) :144-150.
- Orton 1955
- Separation of eggs of Synentognath and Allotriognath fishes in early embryonic stages. Calif: Fish Game, 41:103-105, fig.
- Osbeck 1771
- A voyage to China and the East Indies. 2 vol., White, London.
- Osbeck 1765
- Reise nach Ostindien und China [transl. from Swedish by J. G. Georgi], Rostock: xxvi+552 p.+13 ff. n. num., 13 pl. [Orig. ed. (Swedish): 1757, Engl. transl.: 1771].
- Osorio B. 1917
- Nota sobre algumas espécies de Peixes que vivem no Atlântico Ocidental. Archos Mus. Bocage. 4 :103-131, 8 pl.
- Osorio B. 1888
- Additamento ao catálogo dos Peixes de Portugal. J. Sci. Math. Phys Nat., 12:
- Ostroumoff 1896b
- Détermination des Poissons de la mer Noire et de la mer d'Azov. Bull de l'lndustrie poissonniere, 7-9: 45 p.
- Ostroumoff 1897
- Résultats scientifiques de l'expédition 'Atmanai'. III. Poissons de la mer d'Azov. Izv. imp. Akad. Nauk, 5 (7): 251-267, 2 fig.
- Ostroumoff 1896a
- Zwei neue Relicten-Gattungen im Azowschen Meere. Zool Anz., 19: 30.
- Otterstrøm 1914
- Fisk II. Blødfinnefisk. Danmarks Fauna. Copenhagen, 351 p., 150 fig.
- Otterstrøm 1912
- Fisk. I. Pigfinnefisk. Danmarks Fauna, 6: 198 pp. Gadsforlag, Copenhagen.
- Otto 1821a
- Conspectus animalium quorundam maritimorum nondum editorum. Inaug. Dissert. Vratislaviae, 20 p.
- Otto 1821b
- Animalium quorundam maritimorum nondum editorum. Pars prior. Isis (Oken), 2, Heft 9, Beylage 18: 5 p. n. num.
- Ovchinuikov 1970
- Swordfishes and Billfishes in the Atlantic ocean. Atlanticheskii Nauchno-issledovatel'skii Institut rybnogo Khozyaistva i Okeanografii, KalininFad, 77 p., 40 fig. (Engl. transl., I.P.S.T. Jerusalem, 1971.)