Herring abundance

The map of herring relative abundance is mainly based on Baltic International acoustic surveys (BIAS), years 2011-2016 (ICES WGBIFS reports), reported as millions of herring / ICES rectangle. Also herring landings data were used to complement the data. For ICES rectangles surveyed by BIAS, values shown are the mean values per ICES rectangle based on BIAS data, average for 2011-2016. For ICES rectangles not surveyed by BIAS, values are calculated as: MAX-value x Weighting factor. The weighting factor is specific to each ICES rectangle, calculated as the ratio between the commercial landings in that rectangle and the commercial landings in the ICES rectangle with highest landings (based on averages for 2011-2016). MAX-value = millions of herring according to BIAS in the ICES rectangle with highest landings. ICES rectangles outside the BIAS survey area with no reported herring landings were given the value 0. The relative abundance values in each ICES rectangle were divided by the area of the rectangle to obtain values per 1km2. If the values in small coastal ICES rectangles (outside BIAS area) became unrealistically large due to high herring landings, the value of the neighboring rectangle was given. The final layer was converted to 1 km x 1km grid cells. Values were first log transformed and normalized.鲱鱼相对丰度分布图主要基于2011-2016年波罗的海国际声学调查（Baltic International acoustic surveys，BIAS）数据，数据来源于ICES WGBIFS报告，统计单位为百万尾鲱鱼/ICES矩形（ICES rectangle）。同时辅以鲱鱼商业捕捞上岸数据以补充数据集。 对于经BIAS调查覆盖的ICES矩形，图中数值为2011-2016年基于BIAS数据计算得到的单ICES矩形平均丰度。对于未被BIAS调查覆盖的ICES矩形，其数值按如下方式计算：最大值×加权系数。其中加权系数为各ICES矩形专属，以该矩形的商业捕捞上岸量与捕捞量最高的ICES矩形的商业捕捞上岸量之比计算（数据均取自2011-2016年平均值）；此处最大值指捕捞量最高的ICES矩形经BIAS调查得到的鲱鱼百万尾数。 对于BIAS调查范围外且无鲱鱼捕捞上岸记录的ICES矩形，其丰度值设为0。 将每个ICES矩形内的相对丰度值除以该矩形的面积，得到每平方公里的丰度值。若位于BIAS调查范围外的小型近岸ICES矩形因鲱鱼捕捞上岸量过高导致数值出现不合理偏高，则采用其相邻矩形的数值替代。最终图层被转换为1km×1km的网格单元。 所有数值首先经过对数变换与归一化处理。