912 resultados para 1927-


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Evolution of fisheries research and FIRRI The earliest approach to fisheries research in Uganda dates from the first fisheries survey of Lake Victoria by Michael Graham between 1927 and 1928 (Graham, 1929). Based on references to the rich fisheries that were reported to Graham, it appears that during the 18th Century, catch per net per night averaged 300 tilapia, a revelation that led Graham to conclude that Lake Victoria is a tilapia lake. The "tilapia" later came to be known as Tilapia esculenta and T variabilis (Oreochromis esculentus and O. variabilis) respectively.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The first fishery survey of Lake Victoria was conducted between 1927 and 1928 (Graham 1929). Atthat time, the lake had a diverse fish fauna and the fishery was dominated by two endemic tilapiine cichlids; Oreochromis esculentus (Graham 1929) and O. variabilis (Boulenger 1906). There were a number of other species such as Protopterus aethiopicus Heckel 1851, Bagrus docmac (Forsk.) 1775, Clarias gariepinus (Burchell), Barbus species, mormyrids, Synodontis spp, Schilbe intermedius (Linn.) 1762 and Rastrineobola argentea Pellegrin, 1904 that were also abundant in the lake most of which made a significant contribution to the fishery (Graham 1929, Worthington 1929, 1932, Kudhongania & Cordone 1974). Haplochromine cichlids were represented by at least 300 species more than 99% of them endemic (Greenwood, 1974; Witte et al., 1992 a & b). The fishery of Lake Victoria was similar to that of lakes Kyoga and Nabugabo (Worthington 1929; Trewavas 1933; Greenwood 1965, 1966; Beadle 1962, 1981). There were also important fisheries on the inflowing rivers of Lake Victoria, the most important of which were Labeo victorianus and Barbus altianalis (Cadwallader 1965). The small sized species notably Rastrineobola argentea and haplochromines cichlids were not originally commercially exploited.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

During the Southeastern Atlantic Expedition of the German fishery research vessel "Walther Herwig" in 1967 the main emphasis lay on selective fishing of the South African hake Merluccius capensis (von BRANDT 1967). Some of the fish were found to be infested by ecto-and endoparasites both of which were collected whenever possible. Large plerocercoids of Dibothriorhynchus grossum whose adult stage lives in the South Atlantic Ocean in Lamna cornubica (L.SZIDAT, personal communication) were quite common as were cysticercoids of a Tetrarhynchus sp., which had also been reported in Cynoscion striatus off the Argentinian coast (MACDONAGH 1927, cited in Szidat, personal communication). Brownish nematodes were infesting the ovaries of several fish, but could not be identified. The most common ectoparasite to be observed was the parasitic isopod Livoneca raynaudii (fam. Cymothoidae) whose early larval stages were also found.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Two little-known nematode species of the genus Spinitectus Fourment, 1883, S. petrowi Belous, 1965 (prevalence 25%, intensity 1-8) and S. gigi Fujita, 1927 (prevalence 10%, intensity 2-3), were collected from the gastrointestinal tract of the yellow catfish, Pelteobagrus fulvidraco (Richardson), from Liangzihu Lake, Hubei Province, central China, in September of 2002. The light and scanning electron microscopical examination of this material, supplemented by a few museum specimens of S. gigi collected from the catfish Clarias fuscus (Lacepede) in southern China, made it possible to study in detail the morphology of these parasite species and to redescribe them. The first species, whose correct name is S. petrowi Belous, 1965, exhibits some morphological features (e.g., unusually short vestibule, shape of pseudolabia and of the left spicule) not found in most other congeners; a unique feature is the presence of peculiar pairs of transversely oriented peg-like cuticular spines with rounded ends on the ventral surface of the female tail. Spinitectus gigi was found to have 28-31 cuticular spines in the first ring, relatively long distances between the 2nd-7th rings of spines, and anterior rings divided into 2 sectors; the excretory pore is located at the level of the 4th ring of cuticular spines; males posses 4 pairs of preanal- and 6 pairs of postanal caudal papillae and a pair of small phasmids. Spinitectus bagri Wang, Wu et Yu, 1993 and S. wulingensis Yu et Wang, 1997 are considered junior synonyms of S. petrowi, whereas S. clariasi Ky, 1971, S. ophicephali Ky, 1971 and S. yuanjiangensis Wang, Wit et Yu, 1997 are regarded to be junior synonyms of S. gigi. Spinitectus petrowi was not previously reported from China.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The present paper comprises a systematic survey of nematodes based on helminthological examinations of 176 specimens of freshwater fishes, belonging to 22 species, from central China (mostly lakes in Hubei Province) collected during the autumn of 2001. The following six species were recorded: Procamallanus (Spirocamallanus) fulvidraconis Li, 1935, Camallanus cotti Fujita, 1927, Dentiphilometra monopteri Moravec et Wang, 2002, Pingus sinensis Hsu, 1933, Proleptinae gen. sp. larv., and Eustrongylides sp. larv. Data on their morphology, morphological variability, host range, prevalence, intensity and distribution are provided. SEM studies of P. fulvidraconis and larval Physalopterinae, used for the first time in these species, revealed some additional morphological details and made it possible to redescribe the former. In contrast to the existing description of P. fulvidraconis, this species was found to possess two spicules and a V-shaped gubernaculum with unequal arms (originally mistaken for the left spicule), as well as deirids, whose location can be considered an important taxonomic feature. Larvae of the Physalopterinae have not previously been reported from fishes in China. The finding of larval Eustrongylides in Paramisgurnus dabryanus represents a new host record. All but one nematode species from this zoogeographically interesting region are briefly described and illustrated.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Fe3O4-polylactide (PLA) core-shell nanoparticles were perpared by surface functionalization of Fe3O4 nanoparticles and subsequent surface-initiated ring-opening polymerization of L-lactide. PLA was directly connected onto the magnetic nanoparticles surface through a chemical linkage. Fourier transform infrared (FT-IR) spectra directly provided evidence of the PLA on the surface of the magnetic nanoparticles. Transmission electron microscopy images (TEM) showed that the magnetic nanoparticles were coated by PLA with a 3-nm-thick shell.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

探索了一种适用于 Pt/CNTs催化剂的纯化方法 .利用比表面积测定、 X射线衍射 ( XRD)、透射电子显微镜 ( TEM)和电化学等手段进行了表征 .研究结果表明 ,经该方法纯化的 CNTs作为载体制备的阳极催化剂表现出明显优于相应的混酸氧化法纯化的 CNTs为载体的催化剂催化性能