Groundfish survey data from the German Bight from 1902-08, 1919-23, and 1930-1932 and ICES International Bottom Trawl Survey (IBTS) quarter 3 data from 1991 to 2009

Groundfish survey data from the German Bight from 1902-08, 1919-23, and 1930-1932 and ICES International Bottom Trawl Survey (IBTS) quarter 3 data from 1991 to 2009 were analysed with respect to species frequencies, maximum length, trends in catch-per-unit-effort, species richness parameters (SNR) and presence of large fish (Phi40), the latter defined as average presence of species per haul with specimens larger than 40 cm given. Four different periods are distinguished: (a) before 1914 with medium commercial CPUE and low landings, Phi40 approx. 2, high abundance in elasmobranchs and SNR conditions indicating highly diverse assemblages, (b) conditions immediately after 1918 with higher commercial CPUE, recovering landings, Phi40 at > 4 in 1919, and SNR conditions indicating highly diverse assemblages, (c) conditions from 1920 to the early 1930's with decreasing commercial CPUE, increased landings, decreasing Phi40, SNR conditions similar to later years indicating less diverse assemblages, and a decrease in elasmobranchs. In the IBTS series (d), Phi40 remains low indicating an increased rarity of large specimens, and SNR characteristics are similar to the third period. Dab, whiting and grey gurnard have increased considerably in the IBTS series as compared to the historic data. Phi40 is suggested an alternative indicator reflecting community functional diversity when weight based indicators cannot be applied.本研究对1902-1908年、1919-1923年及1930-1932年德国湾的底栖鱼类调查数据，以及1991-2009年的国际底拖网调查第三季度数据（ICES International Bottom Trawl Survey, IBTS quarter 3）开展分析，分析维度涵盖物种频率、最大体长、单位捕捞努力量渔获量（catch-per-unit-effort, CPUE）的变化趋势、物种丰富度参数（SNR）以及大型鱼类出现率（Phi40）；其中Phi40被定义为每拖网站位中体长超过40cm的物种平均出现频次。 研究划分出四个不同阶段：(a) 1914年以前阶段：商业性CPUE处于中等水平，上岸渔获量较低，Phi40约为2，软骨鱼类丰度较高，且SNR参数表明群落物种组成高度多样；(b) 1918年战后初期阶段：商业性CPUE有所提升，渔获量逐步恢复，1919年Phi40大于4，SNR参数仍显示群落具有高度多样性；(c) 1920年至20世纪30年代早期阶段：商业性CPUE持续下降，上岸渔获量增加，Phi40逐步降低，SNR参数与后期阶段相近，反映群落多样性下降，同时软骨鱼类丰度出现衰减；(d) IBTS序列阶段：Phi40始终维持较低水平，表明大型个体已愈发罕见，SNR特征与第三阶段相似。 相较于历史调查数据，IBTS序列中的黄盖鲽（Dab）、牙鳕（whiting）及灰鲂鮄（grey gurnard）种群丰度显著提升。研究提出，当基于重量的群落功能多样性指标无法适用时，Phi40可作为替代指标反映群落功能多样性。