长江口环境条件对日本鳗鲡(Anguilla japonica)鳗苗溯河洄游的影响

长江口是日本鳗鲡鳗苗的手要产区,利用2007年1-5月在长江口的长兴岛、横沙和杭州湾小洋山4个取样点得到的日本鳗鲡鳗苗渔获量数据,初步研究了鳗苗的补充时间分布以及补充量与潮汐、月相等环境因素之间的关系.发现鳗苗在长江口的补.充时间从1月下旬开始到5月中旬结束,鳗苗日产量峰值出现日期从长江口外向内逐渐推迟,与其洄游路线致.长江口附近潮汐为半月潮,每月有两次涨落潮,鳗苗溯河量与潮汐周期呈现一定的节律性,每月有两次鳗苗峰值.河口区鳗苗溯河具有潮流选择性,长江口内鳗苗溯河量起汛潮多于落汛潮:长江口外鳗苗溯河量和潮汐振幅呈现正相关趋势.日本鳗鲡鳗苗的溯河量与月相变化也有一定的关系;朔月望月的平均单网捕捞量之和占总平均单网捕捞量的93.13%,而上下弦只占6.87%.经过方差检验,朔月鳗苗溯河量多于望月,且二者之间存在极显著差异(P<0.01).     

Fish community structure of the St Lucia Estuarine System under prolonged drought conditions and its potential for recovery after mouth breaching

The St Lucia Estuarine System, South Africa, has been under pressure due to recent drought conditions, which have led to closure of the mouth, extremely low lake levels and hypersaline conditions. The estuary mouth closed in June 2002 and remained so for almost 5 years before being breached by Cyclone Gamede in May 2007. After mouth closure in August 2007, salinities in South and North Lake gradually increased to reach highs of 68 at the end of 2008, while salinities in the Narrows gradually declined during the study. Fish were sampled biannually during 2006–2008 with seine and gill-nets at six sites throughout the system. A total of 20,422 fish from 72 species were recorded, with the number of species and CPUE gradually decreasing from the Narrows throughout the system to Hells Gate in the upper parts of the system. The fish community was dominated by the freshwater species Oreochromis mossambicus, and two estuarine species, Ambassis ambassis and Hyporamphus capensis. The fish community was dominated in terms of species numbers by marine spawning species, but in terms of fish abundance by freshwater and estuarine breeding species. Recruitment of post-larvae of 20 marine species into the system occurred following opening of the mouth in March 2007, highlighting the importance of the system as a nursery area for marine species. The fish community was structured by spatial differences between sampling areas and between the three main compartments of the system, and not by temporal changes during the study period.     

Fish assemblages and rapid colonization after enlargement of an artificial reef off the Algarve coast (Southern Portugal)

Artificial reefs (ARs) have been deployed in Algarve (Southern Portugal) coastal waters to contribute to the sustainability of local nearshore fisheries. Herein, we describe the colonization process of the recently deployed Faro/Ancão AR, and assess the time until the fish assemblage reaches stability and their seasonal patterns. In addition, we compare the results from the present study with those previously reported for an older AR. The fish assemblages were monitored monthly over a 2‐year period by means of visual census. A rapid increase in fish colonization occurred within the first 4 months. After this initial period the assemblage structure showed high similarity (> 73%). The high rate of colonization of the AR was related to the maturity already achieved by the nearby 14‐year‐old AR and to the fish migration from the Ria Formosa lagoon, a nearby nursery habitat. The reef fish assemblage structure showed a seasonal pattern, mainly associated with recruitment episodes of occasional demersal species (Boops boops, Trachurus trachurus and Pagellus spp.) in spring and summer. A total of 66% of the species found in AR are of commercial and recreational importance. The overall mean density and biomass were 2.8 ind·m^?3 and 207 g·m^?3. The occasional demersal species accounted for 42% of the fish density. The most important species in terms of biomass belong to the Sparidae family along with Dicentrarchus labrax. The fish assemblage of the new ARs showed higher mean number of species, diversity, density and biomass values than those reported for the older AR. This result was associated with enlargement of the AR area and with the fishing exploitation of the isolated, small and patchy old AR. Moreover, the high biomass values recorded in the new ARs were mainly due to the increased density of D. labrax after AR enlargement. The results of the present study are used to define guidelines for suitable management strategies for the AR areas that are exploited by the local commercial and recreational fisheries.     

煤炭地质单位人才招聘浅议

招聘工作是企业人力资源管理活动的一个基础性环节,它是企业人力资源获取的高素质人才的主要途径,招聘工作的好坏关系到企事业单位的生存和发展。在日益竞争激烈的社会里,企业的招聘工作一旦失误单位将蒙受巨大的损失。针对煤炭地质单位在招聘环节中存在的一些问题,结合航测遥感局人才招聘工作的实践,对煤炭地质单位如何做好人才招聘工作进行了思考和探讨。     

Succession and seasonal onset of colonization in subtidal hard‐bottom communities off northern Chile

Although there is extensive information concerning the colonization sequences of benthic communities, little is known about the successional development of subtidal hard‐bottom habitats in highly productive coastal upwelling areas. In these systems, succession is predicted to be fast due to high growth rate of the later dominant colonizers. Using artificial hard substrata a field experiment was conducted in a rocky subtidal area off Northern Chile (Humboldt Current System) and monitored at 3‐month intervals to test the following hypotheses: (i) epibenthic succession may proceed through consecutive replacement of species, (ii) there is a fast convergence rate towards natural communities, and (iii) different seasonal starting points for the colonization will produce different community structure over a 1‐year period of exposure. Panels were installed on a vertical wall at 17 m water depth. Three replicate panels were sampled every 3 months over a period of 27 months. As a reference, six haphazardly selected plots from the surrounding natural community were surveyed at each sampling date. To evaluate how seasonally varying substratum availability affects community development, further panels were exposed for a 12‐month period, starting in four different seasons (n = 3 replicates per season). Community succession was slow and occurred through progressive changes, between early encrusting red corallines, middle Balanus flosculus and late Lagenicella variabilis. After 27 months, the community composition, but not its structure, was similar between experimental and reference communities on surrounding rocky bottoms. Seasonality had no effects and after 1 year of exposure the experimental communities converged towards a common structure. This study indicates that succession of subtidal epibenthic communities follows a slow and predictable pattern with a dominant late colonial species. In addition, aseasonal variability might be more relevant during colonization and succession in this upwelling ecosystem.     

Seed predation and moisture limit germination of recalcitrant Dobera glabra (Salvadoraceae) seeds in the Afar rangelands, Ethiopia

We studied current recruitment failure of Dobera glabra, an important famine-food throughout the dryland parts of the Horn of Africa. The species has previously been found to have recalcitrant seeds, a strategy not common for plants in dryland areas. We experimentally tested (1) how germination capacity of D. glabra is affected by seed form, storage period and moisture under nursery conditions, and (2) how seed predation by vertebrate herbivore and seed exposure at germination site affect germination under field conditions in northern Afar rangelands, Ethiopia. D. glabra seeds that received either mulching or supplementary watering (3 days/week) had a higher germination success than controls. The seeds are probably desiccation sensitive since stored seeds had poor germination performance compared to fresh seeds. Seeds in the rangeland plots protected from herbivores had significantly higher germination success compared to open plots. Our findings demonstrate that seed predation and moisture limitation highly reduced the germinability of the recalcitrant D. glabra seeds, indicating that the species might have persisted due to past wetter periods and low herbivore density in dry environments.     

Understanding the association between the non-geniculate coralline red alga Spongites discoidea and the mollusc Oxystele sinensis

Nearly all adult winkles Oxystele sinensis encountered in the Kalk Bay (Western Cape province, South Africa) shallow subtidal zone were observed to bear a thick, convoluted form of the non-geniculate coralline red alga Spongites discoidea. To understand this association, various data were collected. The results show that O. sinensis is for the most part restricted to the shallow subtidal zone and rockpools, whereas the morphologically similar O. tigrina is largely restricted to the intertidal zone. Fleshy macroalgae were absent from all habitats sampled, with much of the primary substratum being occupied by encrusting algae. Spongites discoidea was restricted to intertidal rockpools and the shallow subtidal zone where O. sinensis was the most abundant winkle. Subtidal specimens of S. discoidea were generally thicker (7.24?mm [SE 0.55] on shells, 6.02?mm [SE 0.67] on boulders) than intertidal specimens (2.39?mm [SE 0.21] on boulders, 1.02?mm [SE 0.09] on bedrock), were more heavily burrowed into (44% [SE 3.32] for subtidal shells, 36% [SE 3.94] for subtidal boulders), and were more weakly attached (2.2?kg [SE 0.58] for subtidal shells, 8.4?kg [SE 0.77] for subtidal boulders). Experimental evidence showed that the coralline has no preference for shells of O. sinensis and that, contrary to our assumption, there is no apparent advantage to the winkle bearing the coralline, other than perhaps for camouflage to avoid predation. The high frequency of the association is more likely due to the substantial overlap in the niches of the coralline and the winkle.     

Use of environmental parameters to explain the variability in spawnerrecruitment relationships of Namibian sardine Sardinops sagax

This study attempts to explain the variability in recruitment of sardine in the northern Benguela and to develop potential models by including environmental information to predict recruitment. Two different recruitment and spawner number datasets were available: a VPA-developed dataset, for the period 1952-1987, and data from a simple age-structured model for 1992-2007. In all, four environmental indices were used: the degree of the intrusion of the warm Angola Current into northern Namibia, termed the Angola-Benguela front index; the extent of the upwelling area off central Namibia; average sea surface temperature (SST) over the northern and central Namibian shelf; and wind stress anomalies at Luderitz as an indicator of upwelling strength. Contrary to general belief, it was found that extremely high recruitment can happen at low spawner levels. This occurred in years in which a large upwelling area existed in association with the minimum southward intrusion of the Angola Current. These effects override the normal negative linear relationships with SST and the positive linear relationship with wind. However, when the area of upwelling is average or small, the effects of spawner biomass, SST and wind become important factors in the variability of recruitment. To estimate exceptional recruitment, the upwelling and front indices were included in the model. To measure medium and weak recruitment, spawner numbers and the SST and wind anomaly formed part of the model. These models can be used simultaneously to predict recruitment before annual acoustic surveys take place and thus aid management decisions.     

Physico‐chemical features of pupu springs

The physical and chemical features of Pupu Springs (40 51’ S, 172° 46’ E), near Takaka, the largest cold springs in New Zealand and one of the largest in the world, were investigated by scuba diving. The springs have a maximum depth of 6.9 m and a mosaic of substrate types (bedrock, boulders, and gravel). The temperature of the springs water is constant at 11.7°C, water velocities are generally moderate to very strong (25–100 cm.s^‐1), and average water discharge is about 9.6 m³.s^‐1. Mean holding time for water in the springs is 4.4 min. The water is extremely clear, with a vertical extinction coefficient (log10) of 0.09. The springs water flows from an artesian basin in Arthur Marble and is low in dissolved oxygen. The water is rich in calcium (64 g.m^‐3), with a high specific conductivity (65 mS.m^‐1). Information on water temperature, discharge, and chemistry is provided for five other cold springs in New Zealand: Hamurana Springs, Rotorua; Otangaroa Springs, near Putaruru; Three Springs, near Fairlie; Western Springs, Auckland; and a spring at Lake Hayes, Queenstown.