Samples were taken weekly at one station on the Balgzand (a tidal flat area near Den Helder, the Netherlands) from the beginning of July to mid-November; in addition 12 sections of 1 km each were sampled twice during this period. The variation in occurrence of young shore crabs (Carcinus maenas (L.)) was studied. The growth was recorded by measuring and weighing the animals, and the meat production was estimated; the latter was also recorded for the older crabs, which were probably in their second growth season. A size-frequency distribution analysis clearly showed the first six moulting stages. To begin with the third stage, the mean carapace-width of each moulting stage appears to decrease in the course of the season. The log-log relationship between width and meat weight appears to be linear. For the animals taken at the station, the slope of the line and ints intercept with the vertical, changed significantly during the season. The meat production at the station was 0,28gr/square meter, as estimated with an "Allencurve". The production for the whole Balgzand area, as calculated from the mean of all sections, was 0,11gr/square meter. A more accurate estimation was made by calculating the production for four characteristic parts of the Balgzand area separately; this gave a mean production of 0,08gr/square meter. However, high accuracy in these calculations isn't necessary, since the annual fluctuation of the production is much greater than the deviation in these methods. The production of older crabs was etimated to be 0,3gr/square meter for the whole year. |
