Do bigger fish arrive and spawn at the spawning grounds before smaller fish: Cod (Gadus morhua) predation on beach spawning capelin (Mallotus villosus) from coastal Newfoundland     

F. Vandeperre  D.A. Methven   《Estuarine, Coastal and Shelf Science》2007,71(3-4):391-400

A relationship between body size and time of spawning has often been described for both pelagic and non-pelagic fish species that migrate for the purpose of spawning. The present study investigates this relationship for capelin (Mallotus villosus), a pelagic smelt-like species that spawns on the beaches of Newfoundland. Simple linear regressions were carried out separately for three groups of capelin: ovid females, spent females and males in three successive years (1982–1984). Bigger fish arrived near the spawning grounds first, for all three groups in all three years and was most obvious for female capelin. Analyses of stomach contents of Atlantic cod (Gadus morhua), an important predator of capelin in the Newfoundland area, showed a similar decrease in mean size of capelin throughout the capelin spawning season in June, July and August. Furthermore, analyses strongly suggest that early in the spawning seasons, when capelin abundance was high, cod selected for bigger capelin, whereas towards the end of the spawning seasons, when capelin abundance was low, cod did not show any size preference.  相似文献   

Probabilistic Analysis for Seismic Stability of Beach Earth Embankment     

He Guangne Yang Bin Professor  Dalian University of Technology  Dalian Engineer  Design  Research Institute of Shanghai Harbour Engineering  Shanghai 《中国海洋工程》1995,(4)

The current safety factor method for evaluating earth embankment stability is not very rational since the assessment of slope stability is really an uncertainty problem. In order to consider the random property of this problem, the probabilistic analysis is introduced herein. Finally, the stability of a real beach earth embankment is analysed by means of the suggested probabilitic approach. It may be seen that the results of analysis can represent the numerical assessment of the degree of seismic stability.  相似文献   

黄河三角洲及邻区的风暴潮沉积   总被引：8，自引：0，他引：8  

丁东  任于灿 《海洋地质与第四纪地质》1995,15(3):25-34

黄河三角洲及邻区具有形成风暴潮灾的环境和条件。风暴潮作用在河口淤积区、蚀退型海岸和相对稳定型海岸会形成不同的地貌现象，其沉积物也会因不同的岸段而有差别。本区风暴潮沉积有别于其它的沉积物。  相似文献   

海岸带滩涂地貌演变遥感方法研究   总被引：2，自引：0，他引：2  

胡平香  张鹰  姜杰 《海洋技术学报》2004,23(4):130-133,139

遥感技术是进行海岸带资源调查的有效技术手段,对水利工程规划、防灾减灾、滩涂开发利用等方面有较大的实用价值。在海岸带资源调查中,传统的地面调查方法不仅工作量大,而且实施起来非常困难;遥感技术由于具有感测范围大、获取信息快、更新周期短的特点,为海岸带资源调查和地貌演变的分析和研究提供了较好的方法和手段。文章探讨了遥感技术在江苏省安台线(海安、东台之间海域界线)勘界工作中的运用,采用较新的卫星遥感影像作为工作底图,同时利用1988—2003年之间不同时相的七景影像监测滩涂的演变,在提供了准确的滩涂地形、地貌资料的基础上,通过监测潮沟的变化推断出滩涂的演变,为海域勘界工作提供了有力而可靠的依据。  相似文献   

海滩均衡剖面的概念及相关问题的讨论--以日照实测海滩剖面为例     

印萍  吕京福  夏东兴 《海洋科学进展》2001,19(2):39-45

海滩均衡剖面是海洋动力和海滩泥沙充分作用下的一个具有统计意义上的相对均衡的海滩形态。绝对意义上的、理想的均衡海滩剖面在自然界是难以找到的 ,而统计意义上的海滩均衡特征可以满足海岸变化和海滩过程研究需要。海滩均衡剖面的形态主要受控于国海滩泥沙的粒度特征 ,该剖面的形态指数是海滩泥沙沉降速率的函数 ,海滩粒度越粗 ,海滩坡度越陡。本文研究的日照海滩存在统计意义上的均衡剖面。由于海滩沉积物粒度具有明显的分带特征 ,海滩剖面不是一个理想的均一平面 ,而是由与海滩泥沙粒度相适应的两个均衡剖面组成。这两段海滩的表层粒径分别为 4.8Φ和 7.5Φ ,观测剖面的海滩形态指数分别为 0 .0 75和 0 .0 1 5,理论海滩形态指数分别为 0 .0 77和 0 .0 2 ,理论值和观测值有很好的一致性。  相似文献   

A Numerical Wave Tank for Nonlinear Waves with Passive Absorption   总被引：1，自引：2，他引：1  

Chung-Ren CHOU 《中国海洋工程》2001,(2):253-268

  相似文献   

长乐国际机场附近沙滩潮间带的生态     

李荣冠  江锦祥 《台湾海峡》1994,13(3):290-296

本文研究了福建长乐国际机场附近漳港沙滩潮间带的生态。结果表明，该区生物６０种。其中，多毛类动物１９种，软体动物２４种，甲壳动物１１种，棘皮动物２种，其他动物４种；种类性质以热带，亚热带种占优势。平均生物量４．３４ｇ／ｍ＾２，平均栖息密度１５个／ｍ＾２。数量以中潮区较大。群落结构不大稳定，初步认为与沙滩特殊生境有关。  相似文献   

季节性波浪动力作用下南湾弧形岸滩泥沙横向输运特征     

戴志军  陈建勇  李春初  王世俊  路海亭 《海洋工程》2007,25(4):39-45

响应季节性波候作用的泥沙输运特征是研究弧形海滩地貌变化及港工建筑的重要内容。基于南湾弧形海滩实际测量的冬、夏各11条剖面高程变化资料,将其划分为低潮间带、低中潮带、中潮带、高潮间带、低冲流带、中冲流带及其海滩后滨等7带,在此基础上利用经验正交函数(EOF)方法对各个带的体积变化进行分析,结果表明:1)南湾弧形海滩的泥沙以单向输运为主,并具有季节性变化特征,其中冬季泥沙在东南浪作用下,自陆向海输运,夏季泥沙在西南浪作用下自海向陆输运;2)南湾弧形海滩的泥沙分别在高潮带与中潮带、低冲流带与中冲流带之间存在频繁的双向输运;3)南湾弧形海滩不同岸段泥沙的横向输运因岬角的遮蔽能力、地形以及波浪作用的方向而有所差异。  相似文献   

The formation of offshore ripples in the zone under irregular waves   总被引：1，自引：0，他引：1  

K Günayd?n  M.S Kabda?l? 《Ocean Engineering》2003,30(3):297-307

In this article, results obtained from an experimental investigation conducted to determine the wave-induced geometric characteristics of offshore ripples and bars are presented. The experiments were performed using irregular waves. Natural beach sand was used in the study, where the mean diameter was 0.35 mm and the specific gravity was 2.63. The initial slope of the beach was 1:5. Different wave groups were generated over the initially flat beach, and a number of characteristics were determined. These include the ripple number, individual and average ripple heights, individual and average ripple lengths and the length of the offshore bar. The results of the experimental study were evaluated and empirical expressions based on the results were formulated.  相似文献   

Forcing of large-scale cycles of coastal change at the entrance to Willapa Bay, Washington     

Robert A. Morton  H. Edward Clifton  Russell L. Peterson 《Marine Geology》2007,246(1):24-41

Anomalous morphological features within large estuaries may be: (1) recorders of external forces that periodically overwhelm the normal morphodynamic responses to estuarine energy fluxes, and (2) possible predictors of cycles of future coastal change. At the entrance to Willapa Bay, Washington, chronic beach erosion and frequent coastal flooding are related to the historical northward channel migration that destroyed the protective sand spits of Cape Shoalwater. Northward channel migration since the late 1800s conforms to the long-term net sediment transport direction. What requires explanation is periodic southward relocation of the trunk channel by as much as 5 km, and attendant construction of moderately large sand spits on the north side of the bay such as Kindred Island, Tokeland Peninsula, and Cape Shoalwater.Both autocyclic and allocyclic processes may have been responsible for trunk channel realignment and associated spit deposition. Channel recycling may occur when the main channel becomes overextended to the north and the tidal flow is inefficient because of its decreased gradient and increased susceptibility to shoaling by the growth and migration of tidal sand ridges. Under those conditions trunk channel relocation would be facilitated by increased wave heights and water levels of El Niño winter storms. However, co-seismic subsidence is the most likely mechanism for abruptly increasing sand supply and longshore transport that would favor discrete periods of channel relocation and spit deposition. Unless external forcing changes sand supply and predominant sediment transport directions in the future, the relative rise in sea level, frequent winter storms, and local deficit in the sand budget assure that beach erosion will continue at the mouth of this large estuary.  相似文献