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印度洋东部金枪鱼延绳钓渔业研究--大眼金枪鱼(Thunnus obesus)的生物学特征 总被引:4,自引:0,他引:4
根据作者在印度洋东部海域的延绳钓生产实践,对渔获的大眼金枪鱼群体的群体构成、摄食、繁殖等基本生物学特征进行了初步探讨.结果表明,渔获群体由纯重10~115kg、叉长80~195cm个体组成,纯重与叉长关系式w=2.000×10-5×L2.969;渔获物以3~5龄个体为主,雄性个体所占比例明显高于雌性个体,且随年龄增长雄性个体所占比例逐步提高.鱼群在该海域产卵期较长,不同年龄组性腺发育节律有明显差异. 相似文献
13.
西边界流在边界“豁口”的形变及其机制 总被引:1,自引:0,他引:1
大洋西边界流在边界豁口处由于失去边界的支持而发生形变。本文将西边界流视为一种惯性射流,遵循绝对涡度守恒原理,推导了流轴及其两侧流体在西边界豁口处不同形式的弯曲,发现在一定的豁口尺度条件下,西边界流自身的相对涡度分布特点和地球旋转的β效应决定了在失去西侧陆坡支持时,其主体会沿反气旋路径发生一段经向的位移而圈回入射点所在的经度位置。主轴变形的经向尺度与初始速度及西边界流的入射角度有关;主轴西侧可能会出现一小部分分支进入邻近的内海并形成气旋或反气旋式环流;主轴东侧的流体则在豁口以东沿反气旋路径弯曲,从而论证了西边界豁口处形成西边界流弯曲的可能性和原因 相似文献
14.
An infinity of conservation laws of fKdV equation is derived in terms of the Miura and Gardner''s transform.The pseudo-mass and energy theorems are studied by the first two conservation laws.As a typical example,the theoretical mean wave resistance and the regional distribution of energy of the precursor soliton generation are determined by means of the first and the second conservation laws. 相似文献
15.
闽南近海尖头斜齿鲨的生殖生物学研究 总被引:12,自引:0,他引:12
尖头斜齿鲨(Scoliodon laticaudus)是暖水性小型鲨鱼,为有胎盘胎生种类.在闽南近海,其雄鱼的性成熟长度为382~448mm,雌鱼的性成熟长度为405~467mm,1994年5月至1995年4月的周年随机采样中,雌鱼在群体中所占比例为53.0%.雌鱼的妊娠开始于1~4月,同年的6~8月分娩,妊娠期为5~6个月.尖头斜齿鲨雌鱼每个子宫一次妊娠怀胚胎1~12尾,其中3~6尾者占67.8%.雌鱼一次妊娠产仔鱼2~24尾,平均9.1尾,其中6~13尾占70%;57%的母体左右子宫内胚胎数相同.胚胎数量随母体全长的增大而呈线性增加.雌性尖头斜齿鲨生殖周期约为2年,一生生殖2~3次,生殖能力较低.尖头斜齿鲨胚胎在分娩时全长138~142mm,与雌鱼性成熟长度的比为0.30~0.35,胚胎的雌雄比为1.17:1.同一子宫内及左右两子宫中的胚胎发育情况均基本相同.另外还讨论了鲨鱼资源的保护和管理问题. 相似文献
16.
Recruitment patterns of Serpula vermicularis L. (Polychaeta, Serpulidae) in Loch Creran, Scotland 总被引:1,自引:0,他引:1
Nicola D. Chapman Colin G. Moore Dan B. Harries Alastair R. Lyndon 《Estuarine, Coastal and Shelf Science》2007,73(3-4):598-606
This study aimed to contribute to conservation management of reefs of Serpula vermicularis by increasing understanding of the factors influencing larval settlement. The study was carried out in Loch Creran, which supports the most extensive known development of S. vermicularis reefs in the world. Settlement plates were deployed to examine the influence of season, depth, reef density, substrate type and orientation. Monthly deployment of plates revealed settlement of S. vermicularis to occur predominantly from mid-June to mid-October, peaking in late August to early September. Settlement of Pomatoceros spp. peaked much earlier, in late May to early June. Deployment of plates at different depths revealed a marked reduction in S. vermicularis settlement intensity between 6 and 12 m. As this corresponds with the deeper limit of the peripheral fringe of serpulid reefs in the loch, it is suggested that this limit is imposed by a depth-correlated settlement response, rather than reduction in available substrata. Comparisons of various substrata showed a preference by S. vermicularis larvae for a slate over a scallop substrate and no evidence of enhanced recruitment to occupied or unoccupied tubes of S. vermicularis, suggesting that gregarious attraction is unlikely to be a factor causing reef formation. Settlement onto the upper side of a horizontal scallop substrate was found to be insignificant in comparison with the underside or a vertically orientated scallop. Evidence for the role of light in controlling the depth and substrate-orientation preferences of S. vermicularis larvae is discussed. Based on the results of this study, recommendations are made regarding remediation of areas suffering reef damage. 相似文献
17.
Richard N. Hey Gary J. Massoth Robert C. Vrijenhoek Peter A. Rona John Lupton David A. Butterfield 《Marine Geophysical Researches》2006,27(2):137-153
Earth’s fastest present seafloor spreading occurs along the East Pacific Rise near 31°–32° S. Two of the major hydrothermal
plume areas discovered during a 1998 multidisciplinary geophysical/hydrothermal investigation of these mid-ocean ridge axes
were explored during a 1999 Alvin expedition. Both occur in recently eruptive areas where shallow collapse structures mark
the neovolcanic axis. The 31° S vent area occurs in a broad linear zone of collapses and fractures coalescing into an axial
summit trough. The 32° S vent area has been volcanically repaved by a more recent eruption, with non-linear collapses that
have not yet coalesced. Both sites occur in highly inflated areas, near local inflation peaks, which is the best segment-scale
predictor of hydrothermal activity at these superfast spreading rates (150 mm/yr). 相似文献
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19.
S. C. Gonalves J. C. Marques M. A. Pardal M. F. Bouslama M. El Gtari F. Charfi-Cheikhrouha 《Estuarine, Coastal and Shelf Science》2003,58(4):901-916
The biology, population dynamics, and production of Talorchestia brito were studied at two sandy beaches located on the Atlantic (Portugal) and on the Mediterranean (Tunisia) coasts, respectively. The seasonal variation in abundance and the overall densities were similar in both populations. Reproduction occurred from February to September in the Atlantic, and from March to early November in the Mediterranean. The sex ratio was male biased in the Atlantic, and female biased in the Mediterranean. Based on data from the Atlantic population, both abundance and the proportion of reproductive females were positively correlated with temperature, while the proportion of juveniles in the population was positively correlated with temperature and sediment moisture. On average, individuals from the Atlantic were larger than the ones from the Mediterranean. Life span was estimated at six to nine months in the Atlantic, and five to eight months in the Mediterranean. Talorchestia brito was shown to be a semiannual species, with iteroparous females producing two broods per year, and exhibited a bivoltine life cycle. The minimum age required for males' and females' sexual differentiation and for female sexual maturation was shorter in the Mediterranean. Growth production (P) was estimated at 0.19 g m−2 y−1 ash free dry weight (AFDW; 4.3 kJ m−2 y−1) in the Atlantic population, and 0.217 g m−2 y−1 AFDW (4.9 kJ m−2 y−1) in the Mediterranean one. Elimination production (E) was estimated at 0.35 g m−2 y−1 AFDW (7.9 kJ m−2 y−1) in the Atlantic, and 0.28 g m−2 y−1 AFDW (6.3 kJ m−2 y−1) in the Mediterranean. The average annual biomass (
) (standing stock) was estimated at 0.032 g m−2 in the Atlantic beach, and 0.029 g m−2 in the Mediterranean one, resulting, respectively, in
ratios of 5.9 and 7.5 and
ratios of 10.8 and 9.6. Like other talitrids, T. brito exhibited geographic variation in morphometrical characteristics, sex ratio, growth rates, life span, and reproduction period, with the Atlantic population presenting a slower life history. 相似文献
20.