Ichthyoplankton composition from PC-BELAP cruise 2, Southern Brazilian Shelf, in 1982@en

The PC-BELAP project was coordinated by Laboratório de Crustáceos Decápodos and Laboratório de Ictiologia of the Department of Oceanography of the Federal University of Rio Grande between the 31º49'S and 33ºS extending to the 60 m isobath in the years 1982 and 1983 ((Calazans, 1992; Ibagy & Sinque, 1995). Five cruises were conducted aboard NOc. Atlantico Sul, but in the first cruise (August / September 1982) no ichthyoplankton samples were analyzed. Plankton samples were collected with oblique trawls made from 1 m above the bottom to the surface with a conical 0.6 m diameter and 2.5 m long 330 ?m mesh-net coupled with a flowmeter (General Oceanics ) and a 20 kg hydrodynamic depressor. In shallow stations (i.e., with depths of 10 m or less), double oblique trawls were performed to increase the volume of filtered water (Ibagy & Sinque, 1995). The trawl velocity was estimated to be maintained between 1.5 and 2 ms-1 and vessel velocity constant at 1 ms-1 (approximately 2 kt) (Calazans, 1992). The samples were fixed and preserved in formaldehyde solution, buffered with sodium tetraborate, diluted in sea water with a final approximate concentration of 4%. The volume of filtered water was calculated and used to standardize the abundance of fish eggs and larvae per 100 m3. The identification of the eggs and larvae of fish was complete from the second cruise (November 1982) up to the 22nd station of the third cruise (January 1983). From the 23rd station of the third cruise the focus of identification was on the Clupeiformes and Sciaenidae.本PC-BELAP项目由里约格朗德联邦大学海洋学系十足目甲壳动物实验室（Laboratório de Crustáceos Decápodos）与鱼类学实验室（Laboratório de Ictiologia）牵头协调，研究区域覆盖南纬31°49'至33°S、水深延伸至60米等深线的海域，调查时段为1982年至1983年（Calazans, 1992; Ibagy & Sinque, 1995）。本次调查共依托"大西洋南"号（NOc. Atlantico Sul）海洋考察船开展5次巡航，其中1982年8-9月的首次巡航未分析鱼类浮游幼体（ichthyoplankton）样本。浮游生物样本采用斜拖网（oblique trawls）采集，拖网作业范围从距海底1米处至海面，使用的网具为锥形结构，直径0.6米、长2.5米，网目尺寸330μm，配套搭载General Oceanics公司生产的流量计（flowmeter）与20kg水动力压重器（hydrodynamic depressor）。对于水深≤10米的浅海站位，采用双斜拖网作业以提升过滤水体体积（Ibagy & Sinque, 1995）。拖网作业速度控制在1.5~2 m·s⁻¹，考察船航速恒定为1 m·s⁻¹（约2节）（Calazans, 1992）。样本采用经四硼酸钠（硼砂）缓冲的甲醛溶液固定保存，该溶液以海水稀释至终浓度约4%。通过计算过滤水体体积，将鱼卵与仔鱼的丰度标准化为每100立方米水体的个体数。自1982年11月的第二次巡航起，至第三次巡航的第22站位，已完成全部鱼类卵与仔鱼的鉴定工作；自第三次巡航第23站位起，鉴定工作的重点集中于鲱形目（Clupeiformes）与石首鱼科（Sciaenidae）。