共查询到20条相似文献，搜索用时 31 毫秒
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On the rational utilization of the Icelandic cod stock 总被引：1，自引：2，他引：1
Baldursson Fridrik M.; Danielsson Asgeir; Stefansson Gunnar 《ICES Journal of Marine Science》1996,53(4):643-658
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A Procrustean assessment of the European eel stock 总被引：1，自引：1，他引：1
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《African Journal of Marine Science》2013,35(1):499-512
Attempts are made to consolidate current information on estimates of standing stock, production and consumption of meso- and macrozooplankton from the shelf region of the west and south coasts of southern Africa for inclusion in a network analysis of carbon flow in the Benguela system. The meso- and macrozooplankton communities consist chiefly of copepods and euphausiids respectively. Although geographic and seasonal differences in standing stock are reasonably well described for the inner shelf (<200 m), knowledge of production and rate processes affecting standing stock is limited, and extrapolation to the whole shelf area (<500 m) provides only a crude appraisal of the real situation. Despite the uncertainties, direct measurements have improved on estimates previously inferred. It seems likely that grazing by meso- and macrozooplankton plays a minor role in phytoplankton losses in the Benguela system. However, it would appear that predation by macrozooplankton, particularly under swarming conditions, has an appreciable impact on mesozooplankton biomass. 相似文献
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利用1998和1999年引进的海湾扇贝(Argopecten irradians irradians)原种F1进行了连续2 a的原种保持实验,包括实验性及生产性两种规模,并用所得原种F3与对照群体进行比较,以探讨在国内进行原种保持的技术措施。2000年,实验性原种制备共培育出M贝(来源于Massachusetts州)原种F2330 kg,V贝(来源于Virginia州)原种F2320 kg,生产性原种制备共培育出原种F255 000 kg。2001年,实验性原种制备共培育出M贝原种F3和V贝原种F3均为280 kg,生产性原种制备共培育出原种F315 000 kg,原种F3的肉柱得率(15.42%)明显高于对照组(13.16%),依然保持了引进群体肉柱得率高的特性,因此在国内进行原种保持是可行的。 相似文献
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《African Journal of Marine Science》2013,35(1):181-203
Orange roughy Hoplostethus atlanticus are unusual fish. They form dense aggregations that have fuelled lucrative fisheries at great depths (600–1 400 m), especially off Namibia, New Zealand and Australia. They are thought to be very long-lived (>100 years, maturity at 22 – 40 years), and to have exceptionally low natural mortality (M = 0.045–0.064 year?1) and slow growth rates (K = 0.055–0.070 year?1). In addition, they spawn large eggs and have low fecundity. These factors combine to make orange roughy highly susceptible to overfishing; most stocks are below 30% of pristine levels. Assessments are obtained from indices of catch rate and trawl, acoustic and egg surveys. Acoustic estimates are the most direct, but are confounded by the species' low target strength (?50 to ?53 dB)–attributable to the wax-filled swim bladder. Extracellular wax esters are stored in abundance and comprise mostly mono-unsaturated fatty acids, with low concentrations of the ω-3 fatty acid family. This unusual composition (resultant from the species' diet) ensures neutral buoyancy. Stock separation has been inferred mainly from biological studies, but genetic studies have also found differences among stocks within New Zealand and Australia. Deep-water habitat may be damaged by trawling operations and may take many years to recover, so in some quarters there is a call for a portion of suitable habitat to be set aside for preservation. Although Namibian orange roughy are shallower, smaller and younger than those in other stocks, the Namibian fishery sustained high catches for only a few years before quotas were reduced, from 12 000 to 1 875 tons. Three management lessons are suggested for developing orange roughy fisheries based on the Namibian experience: (1) imposition of catch limits during exploratory fishing; (2) starting the acoustic surveys earlier in the fishery, if possible; (3) greater reliance on trends in catch rate until a survey series has been established. 相似文献
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近年来的研究指出红树林在海岸带碳固定和碳储存方面发挥着重要的作用。尽管印度尼西亚的红树林面积在全球占很大的比重,对于该地区红树林的有机碳储量和土壤有机碳来源的认识仍有限。本研究调查了印度尼西亚北苏拉威西海洋型的Wori红树林中生态系统有机碳储量及其空间分布特征,以及土壤有机碳的来源,以期加深该地区红树林“蓝碳”功能的认识。研究结果显示,Wori红树林0-50cm深度土壤中有机碳储量为15.4 kg/m2,占生态系统碳储量的主要部分（65%）。红树植物生物量和生态系统碳储量分别为8.3 kg/m2和23.7 kg/m2。土壤有机碳储量在不同离岸距离的采样站位中未表现出显著的空间分布差异,而生物量碳储量则在外滩最高。13C稳定同位素分析结果表明红树林土壤中蓄积的有机碳主要来源于红树林有机质,而潮水中的悬浮有机质和红树林外缘的海草并不构成红树林土壤有机碳的重要来源,它们的贡献者都低于20%。研究结果进一步证实了热带地区海洋型红树林湿地在碳储存以及红树植物对碳固定方面的重要性。 相似文献