Publication Date:
2023-09-22
Description:
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.
Keywords:
Comment; Conversion factor; DATE/TIME; Eutrigla gurnardus, catch per unit effort; Gadus morhua, catch per unit effort; German_Bight; German Bight, North Sea; Limanda limanda, catch per unit effort; Melanogrammus aeglefinus, catch per unit effort; Merluccius merluccius, catch per unit effort; MULT; Multiple investigations; Pleuronectes platessa, catch per unit effort; Raja clavata, catch per unit effort; Solea vulgaris, catch per unit effort; Squalus acanthias, catch per unit effort
Type:
Dataset
Format:
text/tab-separated-values, 693 data points
Permalink
