(4) Highlighting 400 years of shifting species distribution

RUC ( Denmark )

(Please click to enlarge, jpg 372 KB)

Download dataset 51, Limfjord, Norwegian, North and Baltic Seas

Time series showing the estimated total catch of herring in the Limfjorden, 1667-1999. Catches have been reconstructed using custom records and account books as proxy-data, supplemented by modern statistics. Blank spaces mean that no data are available.

Explanation

Data relating to species composition in the Limfjord, Denmark , reveal that during the last 400 years there have been four distinct periods, as follows:

The ‘same’ water produced four very different ecosystems over the long run. Various factors interacted to force transitions from one phase to the next, including regime shifts, fishing mortality, hydrographical change, episodic events and societal change. Measuring such change over time is highly dependent upon which variable is chosen to serve as a baseline.

One key species throughout the 400-year period is herring. Although the abundance of the resident stocks of herring have not been assessed, total extractions from 1667-2007 show that total removals in the 18 th and early 19 th centuries were at least as large as those in the 20 th century. This result derives from deploying species distribution and abundance indices as baselines.

(Bo Poulsen)