Behavioral interactions between black mudfish (Neochanna diversus Stokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinis Baird & Girard, 1854)a

The behavior of black mudfish (Neochanna diversus Stokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinis Baird & Girard, 1854: Poeciliidae) was investigated in laboratory tanks. Black mudfish are indigenous to northern New Zealand, and mosquitofish are introduced; both species are sympatric in wetlands in the Waikato region. By comparing position, feeding rates and aggressive behavior of both species, we found that black mudfish were increasingly able to compete with mosquitofish as they grew from fry to adults. Mosquitofish were more aggressive towards mudfish fry and juveniles than were these two life stages towards mosquitofish, but adult mudfish were aggressive towards mosquitofish. Both small (18–24 mm total length (TL)) and large mosquitofish (25–36 mm TL) showed high aggression towards mudfish fry (13–18 mm TL), and fry were eaten by large mosquitofish. However, 3 interspecific differences appear to allow coexistence of these two species. Firstly, mudfish reproduce in winter, whereas mosquitofish reproduce in summer, resulting in mudfish fry being present when mosquitofish are at their lowest abundance. Secondly, mudfish can survive in seasonally dry habitats by aestivation, while mosquitofish cannot. Thirdly, adult black mudfish are nocturnal, whereas mosquitofish are primarily diurnal.     

A simple model for predicting ecological impacts of introduced aquatic organisms: a case study of common carp, Cyprinus carpio L., in the Sepik-Ramu River Basin, Papua New Guinea

Abstract Practical models for predicting the impacts of introduced biota are urgently required to assess the benefits and risks of introductions. The simple method described predicts the ecological consequences of an introduction through potential competition between species based on elementary niche classifications. The model's predictions are tested against field data for common carp, Cyprinus carpio L., which escaped from fish farms during a study of the feasibility of fish stock enhancement in a large river basin. Recorded effects of carp are based on pre- and post-carp gillnet catches, observations of local villagers, socio-economic censuses and other sources of data. The predicted ecological interactions of common carp are in broad agreement with those recorded. The method can assist pre-introduction assessments and is particularly useful where limited data exist. In this particular study, common carp have contributed significantly to an improved capture fishery by fortuitous accident; production from aquaculture was negligible. High niche overlap between carp and certain resident fish species is predicted and this may be of more consequence in highland than lowland regions. Organisms introduced/transferred for aquaculture should be assessed within a much wider forum. The intended impacts of an introduction/ transfer, which in the case study were entirely erroneous, is an area in need of considerable attention.     

Catch performance of the small prawn pot in terms of entry and escape of the Oriental river prawn Macrobrachium nipponense

ABSTRACT: The entry and escape behavior of prawn Macrobrachium nipponense in relation to the pot may be controlled both by its design and population process in the pot's given interior space. To obtain the basic data on how the population process affects the number of individuals in the pot without bait, a comparative study of the experimental results obtained in the actual fishing ground and calculated values was conducted. The variation pattern in the number of individuals in a pot was consistent with that of the calculated value. The model equation proposed in this study might be effective for evaluating the daily variations in the number of individuals in a pot. The results suggest that both the population process and the pot's design control the entry and escape behavior of the prawn.     

The large‐scale capture of eastern grey kangaroos (Macropus giganteus) and red kangaroos (Osphranter rufus) and its application to a population management project

Objective: A large‐scale capture method was developed to enable sterilisation of a macropod population in western Sydney from 2005 to 2018. Methods: Until March 2007, free ranging eastern grey kangaroos and red kangaroos were herded into purpose‐built 15 m diameter capture yards (CYs) for darting with a projectile syringe. From March 2007 onwards, animals were free‐range darted in large areas without herding. Kangaroos were darted with 1.33–5.10 mg/kg tiletamine/zolazepam and 0.01–0.02 mg/kg medetomidine, ± 0.03 mg/kg acepromazine. Deaths were monitored. Population counts were performed annually. Results: There were 5825 capture events involving 3963 kangaroos. Over 85% of all captures occurred from 2005 to 2008. Of all reported deaths (n = 523), 135 were attributed to ill health. Musculoskeletal injuries incurred during capture were the main project‐related cause of death (n = 116). Post capture myopathy was uncommonly diagnosed following capture (n = 19). Conclusion: The herding and capture method enabled a large number of kangaroos to be mobilised and captured with low mortality rates, and the use of CYs resulted in fewer capture‐related injuries and deaths than free‐range capture. The drug doses and combinations used for darting were safe and effective, and the capture technique was successfully applied to a population management project.     

Monitoring tigers with confidence

With only 5% of the world's wild tigers (Panthera tigris Linnaeus, 1758) remaining since the last century, conservationists urgently need to know whether or not the management strategies currently being employed are effectively protecting these tigers. This knowledge is contingent on the ability to reliably monitor tiger populations, or subsets, over space and time. In the this paper, we focus on the 2 seminal methodologies (camera trap and occupancy surveys) that have enabled the monitoring of tiger populations with greater confidence. Specifically, we: (i) describe their statistical theory and application in the field; (ii) discuss issues associated with their survey designs and state variable modeling; and, (iii) discuss their future directions. These methods have had an unprecedented influence on increasing statistical rigor within tiger surveys and, also, surveys of other carnivore species. Nevertheless, only 2 published camera trap studies have gone beyond single baseline assessments and actually monitored population trends. For low density tiger populations (e.g. <1 adult tiger/100 km²) obtaining sufficient precision for state variable estimates from camera trapping remains a challenge because of insufficient detection probabilities and/or sample sizes. Occupancy surveys have overcome this problem by redefining the sampling unit (e.g. grid cells and not individual tigers). Current research is focusing on developing spatially explicit capture-mark-recapture models and estimating abundance indices from landscape-scale occupancy surveys, as well as the use of genetic information for identifying and monitoring tigers. The widespread application of these monitoring methods in the field now enables complementary studies on the impact of the different threats to tiger populations and their response to varying management intervention.     

基于Libpcap的数据包捕获机制的实现

网络数据包捕获分析是进行网络安全检测和流量计费的基础。论文研究了以太网数据包监听过滤机制和Libpcap分组捕获函数库,并在Linux平台上设计实现了一个小型的网络数据包的捕获分析器,该捕获分析器运行简单、高效、准确。     

大连近海光棘球海胆生殖周期的初步研究

１９９０年对大连近海光棘球海胆生殖腺指数进行周年调查,并对其生殖腺发育进行了组织学观察。结果表明：该海区光棘球海胆的自然系列期为７月末至９月下旬,盛期为８月中下旬至９月上旬,这一时期的水温为２２～２３℃,处于水温自然下降季节。雄性成熟略早于雌性。全年生殖腺肥满期出现在６～８月,消瘦期为１０月至年４月,因而海胆的采捕期以６～８月初为宜。     

振荡浮子式波浪能转换装置的优化计算

对振荡浮子式波浪能转换装置进行初步设计，并通过数值计算对装置结构进行优化，找出影响装置性能的主要因素，确定出在中国南海工况下装置性能最优的参数。结果显示，在中国南海常波周期5—6S附近，前港长Lfp和浮子长Lb对装置性能影响最大，是决定装置性能的主要因素；浮子吃水深度D和港内水深Dp是影响装置性能的次要因素，通过调整这两个参数，可在局部范围内改善装置性能；等深域水深H对装置性能几乎没有影响，建造装置选址时可不考虑这方面的因素。使装置性能最优的参数取值依次为：Lfp=4m，Lb=3m，D=2．5m，Dp=4．3m。     

我国海洋捕捞渔业经营机制实证研究

选择全国海洋渔业重点市——浙江省舟山市作为典型,运用经济模型对我国海洋捕捞渔业经营机制的改革与海洋捕捞渔业生产力发展的关系进行了实证分析,并结合目前我国海洋捕捞渔业经营机制中的个体独资经营、股份合作经营和股份制公司存在的制度缺陷,对经济模型分析的结论进行了现实层面的探讨,并提出了进一步完善和创新海洋捕捞渔业经营机制的基本思路。