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41.
J. Anderson A.J. Jackson A.J. Matty B.S. Capper 《Aquaculture (Amsterdam, Netherlands)》1984,37(4):303-314
Glucose, sucrose, dextrin, starch and a-cellulose were incorporated into experimental rations at three levels (10%, 25% and 40%) and fed to juvenile O. niloticus for 63 days. Inclusion level was adjusted with polypropylene powder. Growth improved as the level of glucose, sucrose, dextrin and starch was increased from 0% to 40%. Carcass fat similarly increased with the addition of assimilable carbohydrate (maximum level 8.2% liveweight). At the 40% level, net protein retention (NPR) was highest on the dextrin diet and lowest on the glucose diet. At 10%, glucose spared more, and at 40%, spared less protein energy in the diet than dextrin, starch or sucrose at corresponding levels. The value of these carbohydrates for replacing protein energy in rations for tilapia is discussed.As a-cellulose was increased from 0% to 40%, growth, food conversion efficiency (FCE), NPR, carcass fat and condition factor were reduced. Growth and FCE on the 25% and 40% a-cellulose diets was lower than the control. The use of a-cellulose as an inert bulker in experimental diets for fish is discussed. 相似文献
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Oceanographic investigation of the American Samoa albacore (Thunnus alalunga) habitat and longline fishing grounds 总被引:1,自引:0,他引:1
RÉKA DOMOKOS MICHAEL P. SEKI JEFFREY J. POLOVINA DONALD R. HAWN 《Fisheries Oceanography》2007,16(6):555-572
The American Samoa fishing ground is a dynamic region with strong mesoscale eddy activity and temporal variability on scales of <1 week. Seasonal and interannual variability in eddy activity, induced by baroclinic instability that is fueled by horizontal shear between the eastward‐flowing South Equatorial Counter Current (SECC) and the westward‐flowing South Equatorial Current (SEC), seems to play an important role in the performance of the longline fishery for albacore. Mesoscale eddy variability in the American Samoa Exclusive Economic Zone (EEZ) peaks from March to April, when the kinetic energy of the SECC is at its strongest. Longline albacore catch tends to be highest at the eddy edges, while albacore catch per effort (CPUE) shows intra‐annual variability with high CPUE that lags the periods of peak eddy activity by about 2 months. When CPUE is highest, the values are distributed toward the northern half of the EEZ, the region affected most by the SECC. Further indication of the possible importance of the SECC for longline performance is the significant drop in eddy variability in 2004 when compared with that observed in 2003 – resulting from a weak SECC – which was accompanied by a substantial drop in albacore CPUE rates and a lack of northward intensification of CPUE. From an ecosystem perspective, evidence to support higher micronekton biomass in the upper 200 m at eddy boundaries is inconclusive. Albacore's vertical distribution seems to be governed by the presence of prey. Albacore spend most of their time between 150 and 250 m, away from the deep daytime and shallow nighttime sonic scattering layers, at depths coinciding with those of small local maxima in micronekton biomass whose backscattering properties are consistent with those of albacore's preferred prey. Settling depths of longline sets during periods of decreased eddy activity correspond to those most occupied by albacore, possibly contributing to the lower CPUE by reducing catchability through rendering bait less attractive to albacore in the presence of prey. 相似文献
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Santana Pedro Henrique Lopes Burak Diego Lang Thiengo Cássio Carlette Peçanha Anderson Lopes Neves Mirna Aparecida Mendonça Eduardo de Sá 《Journal of Soils and Sediments》2020,20(11):4103-4110
Journal of Soils and Sediments - After the greatest environmental disaster in the history of Brazil and the deposition of the iron ore tailings in alluvial regions, the process of revegetation for... 相似文献
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A method tor direct visual or photomicrographic enumeration of soil propagules in soil-agar films and soil smears, stained with a mixture ofeuropium(III) ttienoyltrifluoroacetonate and the disodium salt of 4,41-bis(4-anilino-6-bis(2-hydroxyethyl)amino-S-triazin-2-ylamino)2,21-stilbene disulphonic acid, abbreviated to Eu(TTA)3 and fluorescent brightener (FB), respectively, is described.Soil-agar suspensions at 55–60°C were introduced into haemocytometer sample chambers of 100 μm and 20 μm depth which gave soil-agar film thicknesses of 25 μm and 12 μm, respectively, after air-drying. Soil smears air-dried on 1.25 cm2 and 1.0 cm2 areas of glass slide were 5.2–6.0 μm and 6.0–8.0 μm thick, respectively.The Eu(TTA)3 is best formulated in 50% (v/v) ethanol. The best concentrations of Eu(TTA)3 and FB for staining soil propagules were 2 mM and 25 μM. respectively. A staining period of 18 h for soil-agar films and 90–120 min for soil smears was found to be optimal. The optimum volumes of 50% ethanol for rinsing soil-agar films and soil smears were found to be 12.5 and 5.0 ml. respectively.Lack of in-depth focusing on agar films 25 μm thick resulted in 15–17 per cent error in enumerations. The 12 μm agar films and soil smears required little in-depth focusing and were acceptable for photomicrographic recording of numbers of soil propagules. It is concluded that incident u.v. photomicrographic recording of soil propagule numbers in thin agar films or soil smears is a practical solution to operator fatigue likely to occur during direct microscopy. 相似文献
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Joseph H. Anderson George R. Pess Peter M. Kiffney Todd R. Bennett Paul L. Faulds William I. Atlas Thomas P. Quinn 《Ecology of Freshwater Fish》2013,22(1):30-42
Anadromous fishes are frequently restricted by artificial barriers to movement such as dams and culverts, so measuring dispersal helps identify sites where improved connectivity could promote range expansion and population viability. We used a combination of DNA‐based parentage analysis and mark–recapture techniques to evaluate dispersal by juvenile coho salmon (Oncorhynchus kisutch) in a population in the initial stages of colonisation following installation of fish passage structures at a previously impassable dam on the Cedar River, WA, USA. The spatial distribution of individuals within maternal families revealed that dispersal was common. Among the offspring of radio‐tagged mothers, 28% were collected outside the spawning reach and dispersed up to 6.3 km (median = 1.5 km). Most juveniles captured in a tributary (Rock Creek, where few adults spawned) had immigrated from the Cedar River and represented many different families. Juvenile dispersal therefore provided a secondary phase of spatial expansion following initial colonisation by adults. Consistent with the condition‐dependent dispersal hypothesis, juveniles that dispersed farther upstream in the tributary were larger than fish collected near the tributary mouth. Overall, the results demonstrated widespread dispersal in a system with low coho salmon densities, and this might increase the rate of population growth if it reduces the effects of local density dependence. By implication, juveniles can take advantage of rearing habitats reconnected through barrier removal, even when such areas are located several kilometres from adult breeding grounds. 相似文献
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