In the 1976-1986 period Branchiostoma lanceolatum was widely spread outside the near-coastal zone and reached densities of 600 ind./m2 maximally in that area. In the 1994-2001 period the distribution of the species was remarkably more limited and lower densities were observed: B. lanceolatum was exclusively found near the Hinder Banks in densities of maximum 120 ind./m2.
Degraer, S.; Wittoeck, J.; Appeltans, W.; Cooreman, K.; Deprez, T.; Hillewaert, H.; Hostens, K.; Mees, J.; Vanden Berghe, E.; Vincx, M. (2006). The macrobenthos atlas of the Belgian part of the North Sea. <em>Belgian Science Policy. D/2005/1191/3. ISBN 90-810081-6-1.</em> 164 pp. (look up in IMIS)