Reduction of the association preference for conspecifics in cave-dwelling Atlantic mollies, Poecilia mexicana

Cave animals are widely recognised as model organisms to study regressive evolutionary processes like the reduction of eyes. In this paper, we report on the regressive evolution of species discrimination in the cave molly, Poecilia mexicana, which, unlike other cave fishes, still has functional eyes. This allowed us to examine the response to both visual and non-visual cues involved in species discrimination. When surface-dwelling females were given a chance to associate with either a conspecific or a swordtail (Xiphophorus hellerii) female, they strongly preferred the conspecific female both when multiple cues and when solely visual cues were available to the female. No association preference was observed when only non-visual cues were provided. In contrast, cave-dwelling females showed no preference under all testing conditions, suggesting that species recognition mechanisms have been reduced. We discuss the role of species discrimination in relation to habitat differences.     

利用鱼粉废水生产生物絮凝剂及其性能研究

研究了不同培养时间下鱼粉废水中假单胞菌(Pseudomonas sp.)GX4—1菌的生长状况、培养液pH值和絮凝活性变化，发现该絮凝剂产生于菌生长过程中的，培养基灭菌与否对菌合成絮凝剂的特性无大影响．与其它几种常用絮凝剂相比，该絮凝剂对高岭土悬液的絮凝活性较高(絮凝率达95％以上)．发酵液经中速离心获得的上清液作为絮凝剂样品不仅具有良好的热稳定性，且在低温储存170d内活性稳定，对土壤悬液和大肠杆菌悬液表现出良好的絮凝能力。     

Estimator bias and efficiency for adaptive cluster sampling with order statistics and a stopping rule

Practical problems facing adaptive cluster sampling with order statistics (acsord) are explored using Monte Carlo simulation for three simulated fish populations and two known waterfowl populations. First, properties of an unbiased Hansen-Hurwitz (HH) estimator and a biased alternative Horvitz-Thompson (HT) estimator are evaluated. An increase in the level of population aggregation or the initial sample size increases the efficiencies of the two acsord estimators. For less aggregated fish populations, the efficiencies decrease as the order statistic parameter r (the number of units about which adaptive sampling is carried out) increases; for the highly aggregated fish and waterfowl populations, they increase with r. Acsord is almost always more efficient than simple random sampling for the highly aggregated populations. Positive bias is observed for the HT estimator, with the maximum bias usually occurring at small values of r. Secondly, a stopping rule at the Sth iteration of adaptive sampling beyond the initial sampling unit was applied to the acsord design to limit the otherwise open-ended sampling effort. The stopping rule induces relatively high positive bias to the HH estimator if the level of the population aggregation is high, the stopping level S is small, and r is large. The bias of HT is not very sensitive to the stopping rule and its bias is often reduced by the stopping rule at smaller values of r. For more aggregated populations, the stopping rule often reduces the efficiencies of the estimators compared to the non-stopping-rule scheme, but acsord still remains more efficient than simple random sampling. Despite its bias and lack of theoretical grounding, the HT estimator is usually more efficient than the HH estimator. In the stopping rule case, the HT estimator is preferable, because its bias is less sensitive to the stopping level.     

低浓度铅暴露对鲫鱼肝脏抗氧化系统的影响

研究了鲫鱼幼体 (Carassiusauratus)在低浓度铅的长期 ( 4 0d)暴露实验中 ,鲫鱼抗氧化系统所产生的生理生化反应 .结果表明 ,在本实验的剂量范围内 ,铅对鲫鱼肝脏内过氧化氢酶 (CAT)、超氧化物歧化酶 (SOD)的活性 (在暴露浓度达到 0 2mg·l- 1时 )表现为诱导作用 ;而铅对谷胱甘肽硫转移酶 (GST)、谷胱甘肽过氧化物酶 (GSH Px)的活性在低浓度时 ( 0 0 1mg·l- 1)被抑制 ,其中暴露浓度在 0 2mg·l- 1时GSH Px被进一步抑制 .在实验范围内 ,GSH含量无明显变化 .另外 ,对于低浓度铅的长期暴露 ,鲫鱼肝脏中的GST和GSH Px较CAT和SOD敏感 ,可考虑作为水生生态系统中铅低浓度长期暴露的一种生物检测指标 .     

Does the presence of non-breeders enhance the fitness of breeders? An experimental analysis in the clown anemonefish<Emphasis Type="Italic"> Amphiprion percula</Emphasis>

The stability of animal societies depends on individuals decisions about whether to tolerate or evict others and about whether to stay or leave. These decisions, in turn, depend on individuals costs and benefits of living in the group. The clown anemonefish, Amphiprion percula, lives in groups composed of a breeding pair and zero to four non-breeders. To determine why breeders accept the presence of non-breeders in this species I investigated the effect of non-breeders on multiple components of the breeders fitness. Non-breeders did not assist breeders in any obvious way. Experimental removal of non-breeders had no significant effect on the survival, growth, or reproductive success of breeders. Experimental removal of one of the breeding pair showed that non-breeders had little effect on the time taken for a widowed breeder to recommence breeding. The results indicate that the presence of non-breeders neither enhances, nor reduces, the fitness of breeders in A. percula. I suggest that non-breeders might modulate their effect on the fitness of breeders, either by reducing the costs they inflict or by increasing the benefits they provide, such that it just pays breeders to tolerate, rather than to evict, them. This study illustrates that animal societies can be stable even when some individuals gain nothing from the association.Communicated by M. Abrahams     

Experiences of Coal Ash Artificial Reefs in Taiwan

A feasibility study for using fly-ash from Taiwan coal-fired power stations for artificial reef production was started in 1983. Various mixtures of fly ash stabilized with lime, cement, or industrial wastes and formed into blocks were tested in the laboratory. the results showed that the development of compressive strength of those blocks immersed in the sea water was much better than those exposed in the air. Heavy metal (Cd, Cr, Cu, Ni, Pb, Zn) content of the blocks has been monitored routinely to determine the leaching rates. the result indicates that solidification of fly-ash could indeed immobilize heavy metals better than the original fly ash. From March 1984 to February 1987, 3,682 coal ash stabilized blocks with total weight of 300 tons were designed, fabricated and installed at both Hsin-ta, south western coast, and Kuei-hou, northern coast of Taiwan, for field trials. After four years' underwater observations on 100 cubic blocks at Wan-Li, northern Taiwan, it was shown that the physical integrity of the ash reef blocks had been maintained. the compressive strength and durability was better than the concrete artificial reefs nearby. the ash reefs could also attract fishes and the colonization by benthic organisms was similar to that on concrete reefs. Eighty-eight species of fishes were observed, of which 27 were commercially important, comprising more than 80% of the total biomass. These results demonstrate a potential use for stabilized coal ash as artificial reefs to replace traditionally used concrete reefs to protect and enhance the coastal fishery resources in Taiwan in the future.     

广州市场食用鱼和贝类重金属含量及评价

以高氯酸 -硝酸消化法和火焰原子吸收分光光度计测定了广州石牌市场食用鱼类和双壳贝类的Cd、Pb、Cr、Ni、Cu和Zn等重金属的含量。结果表明 ,双壳类对重金属积累的能力高于鱼类。鱼类不同组织器官对各种重金属积累能力明显不同 ,有毒重金属元素Cd、Pb、Cr和Ni主要分布于鳞片、鳃中 ,其食用部分中各重金属含量都远低于“PHNSO”和“人体卫生消费标准” ,具安全的食用价值。但贝类的Cd含量已超过“人体卫生消费标准” ,其中牡蛎的Cu和Zn含量则略超过“人体卫生消费标准” ,其食用价值受到严重威胁 ,应引起重视     

AQUATIC HABITAT CONDITION INDEX,STREAM TYPE,AND LWESTOCK BANK DAMAGE IN NORTHERN NEVADA1

ABSTRACT: The quality of stream habitat varies for a variety of natural and anthropogenic reasons not identified by a condition index. However, many people use condition indices to indicate management needs or even direction. To better sort natural from livestock influences, stream types and levels of ungulate bank damage were regulated to estimates of aquatic habitat condition index and stream width parameters in a large existing stream inventory data base. Pool/riffle ratio, pool structure, stream bottom materials, soil stability, and vegetation type varied significantly with stream type. Pool/riffle ratio, soil and vegetation stability varied significantly with ungulate bank damage level. Soil and vegetation stability were highly cross-correlated. Riparian area width did not vary significantly with either stream type or ungulate bank damage. Variation among stream types indicates that riparian management and monitoring should be stream type and reach specific.     

Analysis of potential impacts to resident fish from Columbia River System Operation alternatives

The US Army Corps of Engineers, the US Bureau of Reclamation, and the Bonneville Power Administration initiated the Columbia River System Operation Review (SOR) in 1990. The SOR will assist agencies in comparing the benefits and risks to Columbia River uses and natural resources from alternative strategies for using Columbia River water. Focusing on 14 federal dams within the basin, the agencies are attempting to improve on the efficient and coordinated use of the Columbia River system. An initial screening of all potential strategies of reservoir operation was necessary to reduce the number of possibilities to a limited set for detailed analysis. To that end, the Resident Fish Work Group of the SOR developed spreadsheet models capable of assessing the impacts of different management strategies on resident fish at six storage reservoirs. The models include biological, physical, and hydrological relationships important to resident fish specific to each reservoir. Alternatives that kept the reservoirs near full pool and held stable during the growing season resulted in positive benefits to resident fish at all locations modeled. Conversely, alternatives designed to improve anadromous fish survival with increased instream flow generally had a negative impact on the resident fish in the reservoirs modeled. The models developed for resident fish in the screening analysis phase of the SOR were useful in assessing the relative impact to resident fish from a large number of alternatives. The screening analysis demonstrated that future analytical efforts must consider trade-offs among river uses/resource groups, among reservoirs throughout the basin, and among resident fish species within a reservoir.Pacific Northwest Laboratory is operated by Battelle Memorial Institute for the US Department of Energy under contract DE-AC06-76RLO 1830.