Substrate composition determines emergence success and development of European nase larvae (Chondrostoma nasus L.)

European nase (Chondrostoma nasus) is a specialist riverine fish, characterised by a complex life cycle making it vulnerable to habitat degradation. Recent findings indicate that, analogously to salmonids, the interstitial zone quality may pose a serious bottleneck for successful recruitment of this species. In this study, nase eggs were exposed to different substrate qualities. First, standardised substrate mixtures with differing fine sediment additions were used. Second, we tested different homogenous gravel fractions for their influence on egg development and emergence success. In both setups, substrate composition significantly affected emergence success, timing of emergence and larvae size at emergence. In the substrate mixtures, emergence was most successful in substratum with no fine sediment addition (98%) and decreased to 55% in substratum with 20% fine sediment addition. Emergence was most successful in the coarsest fraction (93%) and decreased to 47% in the finest fraction. Over all treatments, the time between hatching and emergence from substrate differed by up to 156 degree days, thereby indicating that free embryos of nase use the shelter of the interstitial zone for early ontogeny. These results suggest that a loose and porous stream bed can positively contribute to the development success of eggs and larvae and thereby potentially improve the recruitment of nase populations. It is thus important to consider the substrate and interstitial conditions in the conservation and restoration management of this rheophilic cyprinid.     

Population decline in the endemic Atlantic salmon (Salmo salar) in Kapisillit River,Greenland

Atlantic salmon, Salmo salar L., is found throughout the North Atlantic, with thousands of rivers having spawning populations. In Greenland, spawning is limited to one river in West Greenland, the Kapisillit River (64?N), and the salmon are limited to the lower few kilometres of the system. Using mark–recapture, it was estimated the parr population was 5,953 individuals, and that the population size has declined by 52% since 1959. In spite of this decline, parr density remains high, being between 0.26 and 0.62 parr/m². Using a historical age‐length key, an estimated minimum of 635 smolt will have descended to the sea in 2017. These will be caught in a fishery currently subject to no regulatory measures and fishing remains the most likely driver of the population decline. The genetically distinct population is endemic to Greenland, and managers should implement measures to conserve this genetic integrity and local biodiversity.     

An assessment of catches of shore sport fishing competitions along the coast of the Maltese Islands: Implications for conservation and management

Competitive shore‐based sport fishing is a popular recreational activity in the Maltese Islands. However, prior to this study, no scientific research surveys had been carried out during sport fishing competitions to investigate catches. Collaboration with Maltese sports fishermen was developed to target sustainable management. Recreational fishing catches were recorded between July 2012 and December 2015 by means of 1,633 roving‐access creel surveys, conducted during 79 sport fishing competitions, totalling a fishing effort of 7,548 hr. A total of 29,916 fish belonging to 80 species from 26 different families were caught at a mean catch‐per‐unit‐effort (CPUE) of 4.16 fish angler/hr (SD ± 3.79) and 0.18 kg angler/hr (SD ± 0.17) but with seasonal variation. Catch‐and‐release practices were implemented by all Maltese sport fishing clubs, however, the mean mortality rate stood at 35.5% (SD ± 42.1), indicating that more effort is required to improve survival of fish. The study outcomes provide conservation recommendations.     

Salty stories,fresh spaces: Lessons for aquatic protected areas from marine and freshwater experiences

1. Marine protected areas (MPAs) and freshwater protected areas (FPAs), collectively aquatic protected areas (APAs), share many commonalities in their design, establishment, and management, suggesting great potential for sharing lessons learned. However, surprisingly little has been exchanged to date, and both realms of inquiry and practice have progressed mostly independent of each other.
2. This paper builds on a session held at the 7^th World Fisheries Congress in Busan, South Korea, in May 2016, which explored crossover lessons between marine and freshwater realms, and included case studies of four MPAs and five FPAs (or clusters of FPAs) from nine countries.
3. This review uses the case studies to explore similarities, differences, and transferrable lessons between MPAs and FPAs under five themes: (1) ecological system; (2) establishment approaches; (3) effectiveness monitoring; (4) sustaining APAs; and (5) challenges and external threats.
4. Ecological differences between marine and freshwater environments may necessitate different approaches for collecting species and habitat data to inform APA design, establishment and monitoring, but once collected, similar spatial ecological tools can be applied in both realms. In contrast, many similarities exist in the human dimension of both MPA and FPA establishment and management, highlighting clear opportunities for exchanging lessons related to stakeholder engagement and support, and for using similar socio‐economic and governance assessment methods to address data gaps in both realms.
5. Regions that implement MPAs and FPAs could work together to address shared challenges, such as developing mechanisms for diversified and sustained funding, and employing integrated coastal/watershed management to address system‐level threats. Collaboration across realms could facilitate conservation of diadromous species in both marine and freshwater habitats.
6. Continued exchange and increased collaboration would benefit both realms, and may be facilitated by defining shared terminology, holding cross‐disciplinary conferences or sessions, publishing inclusive papers, and proposing joint projects.

     

海参捕捞装置导航中低成本陀螺仪的降噪研究与试验

针对MEMS陀螺仪输出信号中含有的随机漂移噪声造成海参捕捞装置惯性导航精度明显下降的问题,采用时间序列分析法和Kalman滤波算法,对MEMS陀螺仪随机漂移噪声的削减问题进行研究。以MEMS惯性测量单元的实测数据和三维电子罗盘测量的姿态角为样本,对本研究的低成本陀螺仪的降噪效果进行测试,试验结果表明:1)经过降噪处理后的陀螺仪随机漂移信号的方差比陀螺仪原始采样信号的方差降低1个数量级,显著改善了陀螺仪随机漂移数据的精密度;2)以高精度三维电子罗盘实测的姿态角作为参考基准,将降噪后的陀螺仪随机漂移数据导入捷联惯导姿态更新算法程序,在300s时间内,解算出的俯仰角、横滚角和航向角的均方根误差RMSE全部小于1°;与降噪前相比,相应的俯仰角、横滚角、航向角的RMSE分别降低了170.5、97.6和42.5倍,明显提高了惯性导航精度。     

The decline of fisheries on the Madeira River,Brazil: The high cost of the hydroelectric dams in the Amazon Basin

Despite being considered beneficial by providing a clean and renewable source of energy, the construction of hydroelectric dams has extremely negative implications for Amazonian fisheries. This study investigated the impacts of the Santo Antônio and Jirau hydroelectric dams on the fishery stocks of the Madeira River. This investigation was based on fish catch data from the Z‐31 fishing colony, located in the municipality of Humaitá, in Amazonas State, Northern Brazil. Data were collected daily and provided information on the date of return from each trip, the fish species targeted, and the total catch (kg) between January 2002 and September 2017. The results indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. These results highlight the high price paid by local fish communities for the development of hydroelectric power in the Amazon basin.     

断裂错动与水作用下的地层位移及应力变化

[目的]在断裂活动和地下水位变化条件下,对地裂缝上下盘地层的沉降位移与应力变化进行分析,为深入研究地裂缝的形成机理提供参考。[方法]以北京市高丽营地区地裂缝为研究背景原型,基于其活动特征,分析了该地裂缝的发育与断裂构造及地下水水位变化之间的关系,并运用数值模拟方法分别研究了两种诱因作用下模型地层的沉降位移及土体内部应力的变化规律。[结果]断裂错动作用下,地裂缝上盘土层的沉降变形响应程度大于下盘,地表竖向位移变化曲线近似呈反"S"形态,且上盘应力降低区的范围大于下盘应力增强区的范围;地层沉降量随地下水位的下降而不断增加,其土体应力变化曲线呈"中心对称"。[结论]断裂两侧附近的土体沉降位移和应力变化的差异较明显,且差异沉降与水位降深呈正相关,地下水位下降易诱发地裂缝的影响范围是上盘45m和下盘35m,研究成果可为地裂缝灾害地区的防灾减灾提供科学的理论依据。     

Does full protection count for the maintenance of β‐diversity patterns in marine communities? Evidence from Mediterranean fish assemblages

1. Although it is widely recognized that protection may enhance size, abundance, and diversity of fish, its effect on spatial heterogeneity of fish assemblages and species turnover is still poorly understood.
2. Here the effect of full protection within a Mediterranean marine protected area on β‐diversity patterns of fish assemblages along a depth gradient comparing a no‐take zone with multiple unprotected areas is explored. The no‐take zone showed significantly higher synecological parameters, higher β‐diversity among depths, and lower small‐scale heterogeneity of fish assemblages relative to unprotected areas.
3. Such patterns might likely depend on the high level of fishing pressure outside the no‐take zone, as also abundance‐biomass curves seemed to indicate. Results suggested that full protection could play a role in maintaining high β‐diversity, thus reducing the fragility of marine communities and ecosystems, and spatial heterogeneity may represent a reliable predictor of how management actions could provide insurance against undesirable phase shifts.

     

乳山近海渔业资源种类组成及变化

根据2013—2015年乳山近海拖网渔船的渔捞日志,分析了乳山近海的单位捕捞努力量渔获量、渔获种类组成及生物多样性等特征。结果表明:(1)乳山近海渔获物共有36种,隶属于19目28科33属。其中鱼类有26种,虾蟹类4种,头足类4种,水母类1种,贝类1种。(2)2013—2015年全年优势种差异明显。其中,蓝点马鲛3年均为优势种,鳀鱼是2014年和2015年优势种,网纹狮子鱼为2013年和2015年的优势种。(3)乳山近海渔获物主要集中在休渔期前后的4—5月、9—11月,渔业生产存在明显的春汛和秋汛。2013—2015年乳山近海单位捕捞努力量渔获量逐年增加,但与历史单位捕捞努力量渔获量相比还是存在明显下降;多样性指数和均匀度指数变化趋势一致,多样性指数和丰富度指数较高值出现在秋季;春汛和秋汛期间,渔业资源种属组成及群落结构相似性较高。     

滑县花生新黑地蛛蚧的发生与防治技术

花生新黑地蛛蚧是近年来滑县花生田新发现的一种地下害虫，对花生造成危害，影响花生的 品质和产量。本文主要介绍新黑地蛛蚧的形态特征、发生规律、生活习性、为害症状及防治措施。