Selected fishery and population parameters of eight shore-angling species in the Tsitsikamma National Park no-take marine reserve

An eight-year research angling dataset collected between February 1998 and December 2005 in the Tsitsikamma National Park marine protected area (MPA), along the south-eastern Cape coast of South Africa, was examined to provide estimates of important fishery and population parameters for eight important shore-angling species. Five different estimates of natural mortality (M), and the coefficients of variation (CVs) of catch per unit effort (CPUE) and size measurements were calculated. There was no consistency in estimates of M between methods, highlighting the difficulty in obtaining reliable estimates of this parameter for per-recruit assessments. The CVs of CPUE measurements were generally higher than those for size measurements. Estimates obtained for the most abundant species, blacktail Diplodus capensis, with a mean CPUE of 0.252 fish h^–1, yielded the lowest CVs for CPUE (0.806) and size (0.130) measurements. Therefore, blacktail is considered the preferred indicator species for making comparisons with estimates obtained for shore-angling fish in exploited areas and other MPAs along the South African coastline. The large inter annual variations in mean CPUE and size for all species indicated that a minimum assessment period of four years is required to obtain reliable estimates.     

Phytoplankton models and life history strategies

Phytoplankton models generally do not consider the initial phases of seed stocks and deal only with the vegetative growth phase, ignoring life history strategies. Some quantitatively important diatoms, such as species of Chaetoceros and Skeletonema, have special strategies with respect to the timing of the planktonic phase that cannot be explained purely on the basis of environmental clues. In Norwegian waters and elsewhere, the first Chaetoceros bloom of the growth season usually starts in mid March, initiated by C. socialis. Other Chaetoceros species appear in the water column later. Species of dinoflagcllates like Alexandrium also bloom at certain times of the year. In many cases, phytoplankton inocula originate from resuspension of bottom-dwelling spores or cysts rather than from residual planktonic vegetative cells, and it is probable that, in some species, inoculation events are controlled by endogenous biological clocks. The sequential appearance of different Chaetoceros species may be related to day-length-regulated germination of spores. Most Chaetoceros species have few generations, but they appear at opportunistic times in the plankton. In contrast, Skelelonema costatum and Scrippsiella trochoidea appear at any time of the year. Some modelling results can be improved by including the dynamics of phytoplankton seed stocks in the sediments.     

Quantifying commercial catch and effort of monkfish Lophius vomerinus and L. vaillanti off Namibia

Abundance and exploitation patterns of monkfish Lophius vomerinus and L. vaillanti were investigated for use as inputs into a stock assessment framework to be used for management of the Namibian monkfish resource. Total numbers of monkfish caught per size-class were estimated using industry records of tail products classified into six commercial categories. The proportions per category varied each year. Analysis of the commercial data suggests that large numbers of juvenile monkfish are harvested annually. Catch-per-unit-effort (cpue) data of vessels targeting monkfish and sole (the two species are combined in terms of Namibian fleet legislation) for the period 1991–1999 were analysed using two different methods to construct indices of abundance. Both indices, one standardized on vessel horsepower and the other standardized by means of a Generalized Linear Model, showed an increase in catch rate of monkfish from 1991 to 1994 and between 1996 and 1998, but a decline from 1994 to 1996 as well as during 1999. Conversion factors for landed or tail weight to whole weight for four different tail products of monkfish were estimated. Results obtained from the study suggest that the factor of 3.04 currently applied in Namibia to all tail-weight classes is not appropriate for the current fishery and needs to be amended. For management purposes it is also suggested that four different conversion factors, one for each monkfish tail product, be implemented.     

养殖水中氮物质与欧洲鳗鲡血氯离子的关系

用不同浓度的无机氮，以水浴和注射两种方法对正常欧鳗进行攻击，抽取其心脏血液测定电解质的变化，结果所有实验组的血氯离子均比正常组的低，下降幅度为20％～35％，"狂奔病"症欧鳗的血氯离子也比正常鱼的下降了20％～45％.警示欧鳗配合饲料蛋白质效率(PER)和给饲技术管理的重要性.     

淡水湖泊中类蛭弧菌的分离方法

从贵州阿哈湖、百花湖及云南滇池不同深度的湖水中筛选出2株宿主菌株。经16SrRNA基因序列分析,这2株宿主菌分别鉴定为肠杆菌(Enterobacteriales)和黄色单胞菌(Xanthomonadales)。分别利用这2株宿主菌,从湖水样品中获得到了类蛭弧菌噬菌斑。通过吸光度分析、用淡水类蛭弧菌的特异性引物进行基因扩增、DNA序列分析等一系列方法,证实了所分离的菌株为类蛭弧菌。建立了用同一生长环境中的宿主菌来分离类蛭弧菌的方法,并用该方法从淡水湖泊中分离出了不同类群的类蛭弧菌菌株。