Necessary elements of precautionary management: implications for the Antarctic toothfish

We review the precautionary approach to fisheries management, propose a framework that will allow a systematic assessment of insufficient precaution and provide an illustration using an Antarctic fishery. For a single‐species fishery, our framework includes five attributes: (1) limit reference points that recognize gaps in our understanding of the dynamics of the species; (2) accurate measures of population size; (3) ability to detect population changes quickly enough to arrest unwanted declines; (4) adequate understanding of ecosystem dynamics to avoid adverse indirect effects; and (5) assessment of the first four elements by a sufficiently impartial group of scientists. We argue that one or more of these elements frequently fail to be present in the management of many fisheries. Structural uncertainties, which characterize almost all fisheries models, call for higher limit points than those commonly used. A detailed look into the five elements and associated uncertainties is presented for the fishery on the Antarctic toothfish in the Ross Sea (FAO/CCAMLR Area 88.1, 88.2), for which management was recently described as ‘highly precautionary’. In spite of having features that make the Ross Sea fishery ideal for the application of the precautionary approach, gaps in our knowledge and failure to acknowledge these gaps mean that current regulation falls short of being sufficiently precautionary. We propose some possible remedies.     

火烧对黄土高原典型草原地上植被和繁殖更新的影响

火烧影响着草地植物种群的繁殖策略和形成过程,控制着群落的组成、外貌特征、动态变化和演替进程。本文通过对比黄土高原典型草原未火烧区和火烧区火后第一年地上植被特征、群落结构、物种组成和繁殖更新,探讨了黄土高原典型草原地上植被和繁殖更新对火烧的响应机制。结果表明,火烧显著降低了群落盖度、枯落物厚度与生物量,显著提高了群落的密度。火烧对物种丰富度影响不显著,却显著降低了4个物种多样性指数(Margalef指数、Shannon-Wiener指数、Simpson指数和Pielou指数)。火烧干扰明显改变了植物群落结构和物种组成。火烧显著提高了草地的繁殖更新密度和无性繁殖密度,而对有性繁殖密度和草地繁殖更新的物种丰富度影响不显著。火烧显著提高根茎型和分蘖型植物的密度,而对根蘖型、分枝型和匍匐型植物密度影响不显著。黄土高原典型草原是以多年生克隆植物为主的草原生态系统,地上植被的繁殖更新更依赖于无性繁殖。植物繁殖更新贡献高低与火烧无关,而与草地群落物种组成相关。     

First‐year survival of North East Atlantic mackerel (Scomber scombrus) from 1998 to 2012 appears to be driven by availability of Calanus,a preferred copepod prey

Mackerel (Scomber scombrus) is one of the ecologically and economically most important fish species in the Atlantic. Its recruitment has, for unknown reasons, been exceptional from 1998 to 2012. The majority (75%) of the survivors in the first winter were found north of an oceanographic division at approximately 52°N, despite the fact that mackerel spawns over a wide range of latitudes. Multivariate time series modelling of survivor abundance in the north revealed a significant correlation with the abundance of copepodites (stage I–IV) of Calanus sp. in the spawning season (April to June). The copepodites were a mix of C. helgolandicus (dominating) and C. finmarchicus. The growth of mackerel larvae is known to be positively related to the availability of nauplii and copopodites of preferred prey species, namely, large calanoid copepod species such as Calanus. The statistical relationship between mackerel survivors and abundance of Calanus, therefore, most likely, reflected a causal relationship: high availability of Calanus probably reduced starvation, stage‐specific predation and cannibalism (owing to prey switching). The effects of other abundant, but less preferred zooplankton taxa, (Acartia sp., Branchiopoda spp. and Echinodermata spp. larvae), as well as stock size, temperature and wind‐induced turbulence were not found to be significant. However, stock size was retained in the final model because of a significant interaction with Calanus in oceanic areas west of the North European continental shelf. This was suggested to be a consequence of a density driven expansion of the spawning area that increased the overlap between early life stages of mackerel and food (Calanus) in new areas.     

Ecological assessment of populations of Juniperus phoenicea L. in the Al-Akhdar mountainous landscape of Libya

The Phoenician juniper (Juniperus phoenicea L.) has long been common in the Al-Akhdar mountain range in NE Libya. Juniper trees in the region are showing signs of dieback, and minimal successful seedling recruitment has occurred. We investigate this effect at the level of individual trees, tree size classes, and populations. At ten sites, population size, growth and reproductive traits, and percentage dieback in different size classes were evaluated. Elevation, distance from the sea, and the interaction between these factors had a significant effect on tree volume, and number of branches, number of female cones per branch and number of female cones per tree. Two groups of populations were recognized: the first (Sites 2, 3, and 4) were near the coast. They appeared to be more recently established, with no individuals in the largest size class, and, at this point, less severe dieback. In contrast, in the rest of the sites there were no individuals (Sites 1, 5, 6, and 9) or very few individuals (Sites 7, 8, and 10) in the smallest size class, indicating widespread failure of recruitment in recent years. Mature female cones containing seeds were abundant at these sites (except for Site 8); therefore, this was not attributable to failure of sexual reproduction, but rather was associated with higher levels of intra- and inter-specific competition, combined with more variable rainfall in recent years. Smaller trees are particularly susceptible to dieback throughout the region. Conservation initiatives should include restrictions on clearing these natural forests for conversion to agriculture and, where harvesting is necessary, preferential harvesting of larger individuals.     

Demography of Rumex acetosella in lowbush blueberry (Vaccinium angustifolium)

The demography of Rumex acetosella ramets and seedlings was monitored within and between blueberry clones over the two‐year lowbush blueberry production cycle in Nova Scotia, Canada. Overwintering ramets constituted the majority (>70%) of the flowering ramet population. A small proportion of ramets emerging in May and June flowered, but no ramets emerging between July and November flowered in the year of emergence. Emergence of new ramets was season‐long and ramet populations were regulated by a cycle of birth and death in each production year. Ramet populations in blueberry patches had higher growth rates and lower mortality than ramet populations in bare soil patches in the non‐bearing year, resulting in large net gains to ramet populations in blueberry patches during this production year. Ramet population growth rates and mortality were similar in blueberry and bare soil patches in the bearing year and net ramet populations declined during this production year. Survival rates of overwintering and new ramets varied, but ramets from both the overwintering and monthly cohorts contributed to a distinct ramet age structure at the end of each season. Seedling survival ranged from 6 ± 6 to 51 ± 12% across sites, and no seedlings flowered in the year of emergence. Transition probabilities of ramets and seedlings were used to develop a life‐cycle model of R. acetosella for the 2‐year lowbush blueberry production cycle. This model has utility in developing new management strategies for R. acetosella in lowbush blueberry.     

西藏日喀则地区越冬黑颈鹤的数量和分布(英文)

我们在西藏自治区日喀则地区越冬的黑颈鹤(Grus nigricollis)进行了三个冬季的数量调查,结果确认日喀则地区是黑颈鹤最为重要的越冬地。在一些年份,这里越冬的黑颈鹤可占其世界种群的39%。计数的最高数量为2007年1月份的4240只,最低为2009年2月的2636只。幼鹤新增率(100只鹤类中幼鹤的数量)最低为2010年1月的8.2,最高为2007年1月份的11.3。在3个冬季,黑颈鹤分布最为集中的是拉孜至彭措林之间60km长的雅鲁藏布江河谷地带。为了评估距日喀则市西约50km的谢通门铜矿对黑颈鹤带来的潜在影响,我们在铜矿投产前对日喀则市和下布曲河谷之间的研究区重点进行了监测,在这个研究区记录到820±83只鹤(SE;n=8)。随着谢通门铜矿渐趋开工,雅鲁藏布江北岸的交通和和经济将会快速发展,由此极有可能导致北岸黑颈鹤分布区的移位,使得黑颈鹤离开北岸到附近其它适宜栖息的地方。基于我们调查的结果,建议把矿区附近的黑颈鹤数量集中的3个地区(包括聂日雄乡的聂日雄和甲庆则村以及下布曲河谷)纳入到雅鲁藏布江中游河谷黑颈鹤国家级保护区范围内。     

Dynamics of wood recruitment in streams of the northeastern US

Wood is an important component of forested stream ecosystems, and stream restoration efforts often incorporate large wood. In most cases, however, stream restoration projects are implemented without information regarding the amount of wood that historically occurred or the natural rates of wood recruitment. This study uses a space-for-time analysis to quantify large wood loading to 28 streams in the northeastern US with a range of in-stream and riparian forest characteristics. We document the current volume and frequency of occurrence of large wood in streams with riparian forests varying in their stage of stand development as well as stream size and gradient. Linear models relating stream wood characteristics to stream geomorphic and forest characteristics were compared using Akaike's Information Criterion (AIC) model selection. The AIC analysis indicated that the volume and frequency of large wood and wood accumulations (wood jams) in streams was most closely associated with the age of the dominant canopy trees in the riparian forest (best models: log₁₀(large wood volume (m³ 100 m⁻¹)) = (0.0036 × stand age) − 0.2281, p < 0.001, r² = 0.80; and large wood frequency (number per 100 m) = (0.1326 × stand age) + 7.3952, p < 001, r² = 0.63). Bankfull width was an important factor accounting for wood volume per unit area (m³ ha⁻¹) but not the volume of wood per length of stream (100 m⁻¹). The empirical models developed in this study were unsuccessful in predicting wood loading in other regions, most likely due to difference in forest characteristics and the legacy of forest disturbance. However, these models may be applicable in other streams in the northeastern US or in streams with comparable riparian forests, underlying geology, and disturbance regimes—factors that could alter long-term wood loading dynamics. Our results highlight the importance of understanding region-specific processes when planning stream restoration and stream management projects.     

湿地植物繁殖库的研究进展

繁殖库由土壤基质中有活力的种子(种子库)和具有营养繁殖潜力的芽(芽库)共同组成。繁殖库是潜在的植物群落,其物种组成、密度和动态直接影响地表群落组成、更新潜力及演替方向。当前湿地植物繁殖库研究主要关注种子库,而对芽库研究较少,限制了对湿地植物群落更新和演替机理的认识。根据最新研究成果,本文从以下三个方面对湿地植物繁殖库进行了归纳研究。1)繁殖库的建成机制,主要包括种子库和芽库的形成方式、寿命和扩散能力。2)繁殖库的规模、空间格局和季节动态。繁殖库主要分布在表层土壤中(0-10cm),物种组成及密度呈明显季节性变化。种子库密度一般高于地表群落,但芽库密度可能会低于地表群落,表明地表群落更新和替代可能会受到芽库限制。3)繁殖库对水位、泥沙淤积、土壤含水量以及动物取食等湿地生境变化的响应。植物可通过调节繁殖库中种子和芽的产生、萌发、休眠和死亡等适应一定程度的湿地生境变化。将来应加强种子库与芽库生产的权衡、预测模型、繁殖库在湿地演变中的作用机理及其在湿地植被恢复中的应用等方面的研究。     

Oceanographic factors affecting interannual recruitment variability of Pacific saury (Cololabis saira) in the central and western North Pacific

Pacific saury (Cololabis saira) has a short life span of 2 years and tends to exhibit marked population fluctuations. To examine the importance of sea surface temperature (SST) and mixed layer depth (MLD) as oceanographic factors for interannual variability of saury recruitment in early life history, we analyzed the relationship between abundance index (survey CPUE (catch per unit of effort)) of age‐1 fish and the oceanographic factors in the spawning and nursery grounds of the previous year when they were born, for the period of 1979–2006, in the central and western North Pacific. Applying the mixture of two linear regression models, the variability in the survey CPUE was positively correlated with previous year's winter SST in the Kuroshio Recirculation region (KR) throughout the survey period except 1994–2002. In contrast, the survey CPUE was positively correlated with the previous year's spring MLD (a proxy of spring chlorophyll a (Chl‐a) concentration) in the Kuroshio‐Oyashio Transition and Kuroshio Extension (TKE) during 1994–2002. This period is characterized by unusually deep spring MLD during 1994–1997 and anomalous climate conditions during 1998–2002. We suggest that saury recruitment variability was generally driven by the winter SST in the KR (winter spawning/nursery ground), or by the spring Chl‐a concentration (a proxy of prey for saury larvae) in the TKE (spring spawning/nursery ground). These oceanographic factors could be potentially useful to predict abundance trends of age‐1 saury in the future if the conditions leading to the switch between SST and MLD as the key input variable are elucidated further.