Bullet tuna

Abstract: Summary A tuna larval survey (TUNALEV) in the Northern Levantine Basin (Cilician Basin) was conducted onboard a trawler from 5 to 18 June 2004. To determine the spatial distribution and abundance of tuna larvae, Bongo 60 and Bongo 90 nets were used. Ichtyoplankton samples from 104 stations were taken. In total, 121 bluefin tuna (Thunnus thynnus), 94 bullet tuna (Auxis rochei) and 22 Atlantic black skipjack (Euthynnus alletteratus) larvae were collected. In comparison with the other tuna larvae, the concentration of bluefin tuna larvae was highest in the Bay of Mersin. The collected larvae in this area were composed mainly of 5–9 mm size specimens.

Abstract: The complete mitochondrial DNA sequence of the frigate tuna Auxis thazard and two divergent mitotypes (Mitotype I and Mitotype II) of the bullet tuna Auxis rochei have been determined. The total length of the mitogenomes was 16,506, 16,501 and 16,503 bp, respectively. All mitogenomes had a gene content (13 protein-coding, 2 rRNAs and 22 tRNAs) and organization similar to those observed in most other vertebrates. The major non-coding region (control region) ranged between 843 and 847 bp in length, and showed the typical conserved blocks. Phylogenetic analyses revealed a monophyletic origin of Auxis with respect to other tuna fish. Molecular data here presented provide a useful tool for evolutionary as well as population genetic studies.

Abstract: Myoglobin (Mb) was isolated from bullet tuna (Auxis rochei) skeletal muscle and characterized from the viewpoint of the thermostability-structure relationship. Differential scanning calorimetry (DSC) measurement showed that the thermostability of bullet tuna Mb was the lowest among all the scombridae fish Mbs so far examined. The highest value (72.8 degrees C) of melting temperature (Tm) was obtained at pH 6.52. alpha-Helical content at 10 degrees C was 34.5%, clearly lower than that of horse Mb (55.3%). The amino acid sequence was then deduced by cloning cDNA which encodes bullet tuna Mb. Bullet tuna Mb consisted of 147 amino acids, and the sequence identity was very close to that of skipjack (Katsuwonus pelamis) Mb (91.8%). A few amino acid substitutions, which could be involved in stability difference of Mb, were recognized. By mass spectrometry of lysyl endoproteinase digest of Mb, the N-terminus was found to be acetylated like that of other fish Mbs.

Abstract: This synopsis of biological and technical data on frigate tuna, Auxis thazard, and bullet tuna, A. roche i, includes information on identity, distribution, bionomics, life history, population, and exploitation. Over 200 published and unpublished reports, up to and including those published in 1978, are covered. Genus Auxis Cuvier 1829 (type-species: Scorn ber rochei Risso) by subsequent selection by Gill (1862). The description of the genus Auxis under "Les Scombres" first appeared in Cuvier's Règne Animal in 1829. From the time of Cuvier's work to the present, however, the genus A uxis has had several reclassifications. For example, in classifying the genus Auxis, Kishinouye (1915) first included it in the family Thunnidae. However, in a later work (1917), he placed Thunnidae and Katsuwonidae in a new order called Plecostei and placed the families Scombridae and Cybiidae in the order Teleostei. The genus Thunnus fell under Thunnidae and the genera Katsuwonus, Euthynnus, and Auxi came under Katsuwonidae (Kishinouye 1923). The primary characteristic subcutaneous blood vessels; a secondary characteristic of Plecostei was the presence of well-developed subcutaneous blood vessels; a secondary characteristic was the development of dark red lateral tissues in relation to the subcutaneous blood vessels. Many scientists disagreed with Kishinouye's new order and its subdivision. Takahashi (1924) argued that Plecostei was established only on partial differences in the highly variable vascular system and cannot exist on an equal status with the other four orders of Teleostorni. Jordan (1923) and Herre (1953) placed the scombroid fishes in two families--Scombridae and Thunnidae. Fraser-Brunner (1950), on the other hand, rejected any division of the family Scombridae arguing that attempts to subdivide this family "have resulted in arrangements which are artificial and have left the classification in an uneasy, shifting state." de Sylva (1955), Collette and Gibbs (1963b), and most other recent workers recognize a single family Scornbridae with various subdivisions. Collette and Chao (1975) placed Auxis in the tribe Thunnini of the subfamily Scombrinae. The following description of the genus Auxis is from Jordan and Evermann (1905): "Body oblong, plump, most naked posteriorly, anteriorly covered with small scales, those of the pectoral region enlarged, forming a corselet; snout very short, conical, scarcely compressed; mouth rather small, the jaws equal; teeth very small, mostly in a single series, on the jaws only; tail very slender, depressed, with a rather large keel on each side; first dorsal short, separated from the second by a considerable interspace; second dorsal and anal small, each with 7 or 8 finlets; pectorals and ventrals small; no airbladder; branchiostegals 7; pyloric coeca dentritical; gillrakers very long and slender, numerous; vertebrae 39 in number, peculiarly modified . . . Auxis is the most primitive genus among the higher tunas that have developed a prootic pit and a partial subcutaneous circulatory system (Collette and Gibbs 1963b). All the Thunnini, except Auxis, have a common cutaneous artery that divides into dorsal and ventral branches lateral to the aorta; in Auxis, however, the dorsal and ventral branches originate separately with the latter being very poorly developed (Collette 1978). The haemal spines of the thoracic vertebrae do not form a haemal arch and the first vertebra is not sutured to the 2 cranium as in the higher members of Thunnini. Also, compared with Euthynnus, Katsuwonus, and Thunnus, Aux is lacks the frontoparietal fenestra, which is an additional pair of openings present in the cranium and has a lateral countercurrent system for heat exchange that is not as well developed phylogenetically (Collette 1978). All members of the tribe Thunnini have a swim bladder as juveniles; however, the bladder degenerate with growth in Auxis, Euthynnus, and Katsuwonus. Several other characters distinguish members of the genus Auxis, the smallest of the higher tunas, from other scombrids (Collette and Gibbs 1963b; Fitch and Roedel 1963; Williams 1963). In Auxis, there is a single interpelvic process which is between and about as long as the pelvic fins. In other tunas, but not in other scombrids, the interpelvic process is bifurcate and much less than half the length of the pelvic fins (it is single but small in Grammatorcynus and Gyrnnosarda). The number of dorsal and anal finlets (seven or eight) distinguishes Auxis from Scorn ber, which has only five of each. Auxis can also be distinguished from Rastrelliger by the lack of a corselet and a body entirely covered with moderate-sized scales in the latter. Species Auxis thazard (Lacepède) 1802 The following description of A. thazard (Fig. 1, upper photo) is from Williams (1963). Major morphological features described under the genus are omitted from the account of the species. "Depth 3.9 to 4.5, head 3.2 to 3.8 in standard length.. Eye 5.0 to 5.85 in head, 1.25 to 1.66 in snout and 1.25 to 1.7 in the flatly rounded interorbital space. Snout 3.62 to 4 in head. Maxilla reaches to a point under the anterior half of the eye and is 3 in head. Single row of small pointed teeth in each jaw, none on palate. Jaws almost equal. First and second dorsal spines subequal, equal to snout and eye; following spines rapidly decreasing in size, eighth usually shorter than the pupil. Second dorsal fin very low, about three times its base distant from first dorsal; first ray of second dorsal about 5 in head. Anal similar to second dorsal, first ray about 5.2 in head. Pectorals short, roughly triangular, about 2 in head and shorter than postorbital; origin of pectoral before that of first dorsal. Pelvics thoracic, about 2.5 in head, origin somewhat behind that of pectorals. Caudal lunate, upper lobe about 1.8 in head. Body naked except for the corselet of scales anteriorly. Rear margin of the corselet runs from base of second dorsal to above end of pectoral; thence there is a posterior prolongation of the corselet along the lateral line; below the pectoral tips the corselet margin curves to above the pelvic base from where it turns posteriorly and finishes well behind the tips of the pelvics. The prolongation of the corselet along the lateral line tapers abruptly between first and second dorsal fins, and under the origin of the second dorsal is not more than 4 irregular scale rows wide. Scales large and imbricated above pectoral base. Gill rakers about 1.75 in length of gill filaments." Species Auxis rochei (Risso) 1810 The description of A. rochei (Fig. 1, lower photo) is from Jones (1958), who originally referred to the specimen as A. tapeinosoma. "Body robust, rounded, almost circular in crosssection. Dorsal outline moderately and evenly curved. Ventral outline evenly curved when fresh but slightly flattened abdominally after preservation in formalin. "Height 5.38 in standard and 5.55 in furcal [ fork] length. Head 3.77 in standard and 3.88 in furcal length. Snout, pointed 3.9 in the head, longer than eye diameter. Eye 4.91 in the head, 1.27 in the snout, 1.27 in the almost flattened interorbital space. Mouth moderate, oblique, end of maxillary reaching vertical from anterior margin of eye. Jaws nearly equal, the lower jaw projecting almost imperceptibly beyond the upper. Teeth Figure l.Auxis thazard (upper photo) from the eastern Pacific, collected at Morgan Bank, Baja California, and A. rochei (lower photo) from near Santa Catalina Island, Calif. (Fitch and Roedel 1963)