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1.
Results are reported of the growth and yield of the Malawi chambo, Oreochromis karongae (Trewavas, 1941) association, and Oreochromis shiranus (Boulenger. 1896) in polyculture with Clarias gariepinus (Burchell. 1822). Six ponds of 150 m2 were assigned to two replicates of three treatments: C. gariepinus and O. shiranus; C. gariepinus and chambo spawned on station; C. gariepinus and chambo collected from the lake. Total fish stocking density was 3 m?2, and stocking ratio 1:2 (C. gariepinus: titapias). Initial mean body weights were 10.9 g for O. shiranus. 13.2 g for C. gariepinus and 13.3 g for chambo. The ponds were fertilized with chicken manure at the rate of 13.5 kg dry matter ha?1 day?1, representing the daily NPK loading of 0.618.0.186 and 0.191 kg ha?1, respectively. Maize bran was applied at 3% body weight day?1 for 168 days. Fish growth rate for C. gariepinus was significantly higher (P < 0.05) than that of the tilapias. Weight gains were 0.48-0.57 g day?1 for C. gariepinus, 0.30-0.31 g day?1 for chambo and 0.24 g day?1 for O shiranus. There was no difference (P > 0.05) in the growth of chambo despite the source of fingerlings. More fish biomass came from C. gariepinus stocked at 1 m?2 than from the tilapias stocked at 2 m?2. Extrapolated fish yields in the range of 4.37-4.75 t ha?1 year?1 were obtained from the polyculture of chambo and C. gariepinus. Oreochromis shiranus and C. gariepinus gave 3.95 t ha?1 year?1. Low water temperatures for 112 days slowed the growth of tilapias but did not seem to inhibit the growth of C. gariepinus. Chicken manure and maize bran, applied at smallholder farmer's level, has produced higher yields than by using O. shiranus in monoculture at optimal temperatures. The yields obtained show that the polyculture system is feasible during the cold season and may justify investment in aquaculture at semi-intensive level in Malawi. 相似文献
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Abstract – Similarities in the diets of larval, juvenile and adult black-stripe minnow ( Galaxiella nigrostriata ) and salamanderfish ( Lepidogalaxias salamandroides ), collected from ephemeral pools in south-western Australia during the mid-wet, late-wet and dry seasons, were assessed. During the mid-wet season, both intra- and interspecific competition for a diminishing food supply was minimised through differences in prey utilisation by the various developmental stages of both species. During the late-wet season, the pools contained only juvenile G. nigrostriata and juvenile and adult L. salamandroides , the diets of which were vastly different. A shift towards terrestrial fauna by G. nigrostriata and the ingestion of greater proportions of larger benthic prey taxa by L. salamandroides minimised interspecific competition for food at a time when densities of zooplanktors were rapidly declining. Timing differences in the onset of aestivation ensures that no interspecific competition for food occurs during the dry season. 相似文献
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Amusium laurenti is a functional hermaphroditewith well differentiated male and female gonadalareas. The gonadal index varies throughout the yearwith maximum values occurring in January, March andJuly, and minimum ones in August and September. Partial spawning (with respect to the individual andthe population) occurred from January to February andMarch to May. The major spawning event coincided withthe end of the period during which bottom watertemperature increased to temperatures above 26°C(July–August). Subsequently temperature decreased to22°C, with a period of gonadal restoration andincreasing gonadal index. Histological analysis ofthe gonads correlated with the gonadal index. 相似文献
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J.J. Willemse 《Aquaculture (Amsterdam, Netherlands)》1979,17(2):91-103
Morphological detail and topographical relationships of internal organs of the European eel are demonstrated by labelled photographs of microscopical sections and drawings of dissected material. Glass eels were used in the preparation of sections of the head. Blocks were selected from the trunk region of a 35 cm eel. They were sectioned in transverse planes, resulting in a series of complete transverse sections through this region of the body. The macroscopical dissections were made on 50 cm silver eels. 相似文献
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Abstract – Diet composition of Pterodoras granulosus was investigated from June 2004 to June 2005 in the Upper Paraná River floodplain, following invasion by two mollusc species Corbicula fluminea and Limnoperna fortunei . Stomach and intestinal contents analysis showed spatial differences in the diet composition. In the Baía River, P. granulosus diet consisted mainly of C. fluminea , whereas plant items dominated in the Ivinheima River, and L. fortunei was the most important food in the Paraná River. There was little selectivity in shell length consumed. In spite of C. fluminea being a larger mollusc, L. fortunei appears to be energetically more profitable because its shell is more fragile and is rapidly opened and digested. A considerable amount of closed shells of C. fluminea at the end of the digestive tract points to a possible role of P. granulosus as a mollusc disperser. 相似文献
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Juvenile kachlan (Trachinotus ovatus, Linnaeus) were collected with beach seines from the Mediterranean coast of Israel. Length frequency distributions of 1 539 fish were used to indicate the arrival of juveniles. The estimated time of arrival is July–August. Stomach contents of 153 juveniles were determined. The fish ranged from 19 to 90 mm in total length. Percent frequency occurrence of diet contents was determined. Juvenile kachlan ate polychaetes, cladocera, copepods, isopods, amphipods, insects and small fish. 相似文献
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M. A. N. WABUKE-BUNOTI 《Journal of fish diseases》1980,3(3):223-230
Abstract. The prevalence and pathology of the pseudophyllidean cestode, Polyonchobothrium clarias in the gastrointestinal tract of the teleost, Clarias mossambi-cus have been studied. The cestodes were most abundant in the gall bladder where they caused pronounced nodular outgrowths in the mucosa and exhibited a gradual decrease in number distally towards the rectum. Generally the intensity of the infection due to P. clarias was higher in young fish than in old fish. 相似文献
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The melanomacrophage aggregates or cells (MMC) are commonly used as biomarkers of exposure to pollution in fish, albeit their numbers and morphological characteristics can be influenced not only by environmental toxins but also by a range of physiological parameters and pathological conditions. Accordingly, before we can use MMC as biomarkers in any fish species, their normal, 'background' characteristics have to be established in apparently healthy fish. The knowledge of MMC in sharks is minimal. The aim of this study was to characterize MMC from 51 free-ranging, large pelagic sharks from the northwestern Atlantic, including shortfin mako, Isurus oxyrhinchus , thresher, Alopias vulpinus and blue shark, Prionacae glauca . The rationale of this study was twofold. First, because, sharks have life histories predisposing them to the accumulation of environmental toxins they constitute good sentinel species of the health of the global marine ecosystem. Second, because many shark populations are in decline or threatened by extinction, we need to expand our understanding of their health status in order to develop appropriate protective measures. All sharks were collected by sports fishing gear between June and August in 2007. Their health condition was assessed by necropsy, morphometrics, and by microscopic examination of gonads, livers, spleens and kidneys. Routine, haematoxylin and eosin and/or Pearl's reagent-stained paraffin embedded sections were studied by light microscopy. Our results provide the first data on the morphometric and morphological characteristics of MMC in viscera of apparently healthy free-ranging sharks from the northwestern Atlantic. 相似文献
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Jorge Chávez-Villalba María López-Tapia José Mazón-Suástegui & Miguel Robles-Mungaray 《Aquaculture Research》2005,36(14):1337-1344
This is the first evaluation of growth and survival of spat of the Cortez oyster Crassostrea corteziensis (Hertlein) produced under controlled conditions in a coastal area in the state of Sonora, Mexico for aquaculture purposes. A suspended culture technique, used for the Pacific oyster C. gigas, was used. The Cortez oyster has an isometric shell growth during the first 13 months, reaching 71.3±1.9 mm length, 52.6±1.3 mm thickness and 25.1±0.8 mm width. Allometric growth was found between total weight and length, thickness and width (survival was 70%). The relationships between particulate organic, inorganic material, chlorophyll a and environmental parameters with growth are described. Growth rates of C. corteziensis were affected by temperature with retardation at less than 18°C. For aquaculture purposes, it is recommended that spat be sowed after winter, and oyster harvest occur at the end of autumn. According to the von Bertalanffy equation, Cortez oysters would reach the traditional exploitation size of 65 mm (mean length) at harvest. Finally, the results of this study have shown that C. corteziensis is a good candidate for aquaculture projects in this region. 相似文献
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Cristina Milani Adriana Vella Pavlos Vidoris Aristidis Christidis Emmanouil Koutrakis 《水产资源保护:海洋与淡水生态系统》2021,31(Z1):76-86
- The abundance, distribution and diet of the short-beaked common dolphin were investigated as part of the first detailed study on cetacean populations in the North Aegean Sea. Since 2004, the area has been proposed by national and international entities as a marine protected area for common dolphins and other cetacean species owing to its high biodiversity.
- Abundance and distribution were investigated between 2005 and 2013 through dedicated scientific marine transect surveys, covering 14,701 km, in sea conditions of Beaufort sea state 3 and below. The line-transect sampling method was used to estimate relative abundance, using Distance 6.0 software. Encounter rate for this species in the study area was estimated to be 0.24 groups/100 km (1.5 dolphins/100 km), with a mean group size of 6.88 (SE = 1.90).
- Common dolphin sightings were analysed for correlations with eight environmental variables (distance from the coast, depth, slope, median salinity, gradient of salinity, median temperature, gradient of temperature and mean current) using generalized additive modelling. Common dolphin sightings were significantly correlated to depth, temperature and salinity.
- Stomach-content analyses were performed on eight suitable samples from common dolphins stranded in the study area. The trophic level of the species was calculated, indicating that this species is a top predator.
- This research provides the first estimates for abundance and distribution and the first diet analysis for this Mediterranean Endangered dolphin species in the study area based on a year-round long-term study.
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Abstract. Loma salmonae (Putz, Hoffman and Dunbar, 1965), Morrison & Sprague, 1981, in the rainbow trout, Salmo gairdneri Richardson, was studied with the electron microscope. It is morphologically very similar to L. morhua Morrison and Sprague, 1981, in the Atlantic cod, Gadus morhua L., having only minor differences. Loma sp. Morrison and Sprague, 1981, in the brook trout, Salvelinus fontinalis (Mitchill), is more like L. salmonae than the other species of Loma , but was deemed to be distinct. It was named L. fontinalis sp. nov. 相似文献
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ANGEL BORJA ALMUDENA FONTÁN JON SÁENZ VICTORIANO VALENCIA 《Fisheries Oceanography》2008,17(6):477-493
The Bay of Biscay anchovy has experienced, since 2001, a succession of low recruitments, resulting in the collapse of the stock in 2005; this has led to successive closures of the fishery. This study investigates the possible impact of different controlling factors [North Atlantic Oscillation (NAO), East Atlantic (EA) pattern, turbulence, upwelling, and river flow] upon anchovy recruitment and fishery catches. Fifty‐five percent of the recruitment variability of this fishery can be explained by upwelling over the spawning area; this is related, in turn, to the EA pattern. The conceptual understanding of the system proposed for the Bay of Biscay anchovy suggests that negative EA periods are associated with northeasterly wind circulation, which produces weak upwelling over the continental shelf. This pattern results in hydrodynamic stability over the area, leading, probably, to adequate food availability. A positive EA (which extends onwards, from 1998) is associated with southwesterly winds and downwelling over the continental shelf; this leads, probably, to the dispersion of anchovy food and larvae, together with increasing mortality. 相似文献
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C. Pelissero J. Nunez-Rodriguez F. Le Menn O. Kah 《Fish physiology and biochemistry》1988,5(3):109-119
An immunohistochemical study of the sturgeon (Acipenser baeri) pituitary was undertaken using antisera directed against hormones from various classes of vertebrates, including the only pituitary hormone available from sturgeon, gonadotrophin. A positive reaction was obtained after application of antisera towards the following hormones 1–24 synthetic ACTH (1-24 ACTH), melanophore stimulating hormone (MSH), ovine prolactin (oPRL), ovine growth hormone (oGH), salmon growth hormone (sGH), carp gonadotrophin (cGTH) and its beta subunit (cGTH), sturgeon gonadotrophin (aciGTH), carp thyrotrophin (cTSH) and subunit of the human thyrotrophin (hTSH). The results demonstrate that, in general, the sturgeon pituitary resembles that of teleosts as regards the distribution of the different cell types: ACTH and PRL cells in the rostral pars distalis, GTH, TSH and GH cells in the proximal pars distalis and MSH and PAS-cells in pars intermedia. In addition to the topographical organization of the sturgeon pituitary, this study provides data on the immunological relationships between sturgeon pituitary hormones and those of other vertebrates. 相似文献
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A.M. Ajana 《Aquaculture (Amsterdam, Netherlands)》1980,21(2):129-137
The mangrove oyster, Crassostrea gasar, constitutes an important source of animal protein among some communities in the Lagos area. This paper summarises present knowledge of the fishery of the mangrove oyster in the Lagos area, highlights its prospects, and suggests how oyster production for consumption can be improved. 相似文献
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