Prehistoric versus modern Baltic Sea codfisheries: selectivity across the millennia

摘要

Combining Stone Age and modern data provides unique insights for management, extending beyondcontemporary problems and shifting baselines. Using fish chronometric parts, we compared demographiccharacteristics of exploited cod populations from the Neolithic Period (4500 BP) to the modern highlyexploited fishery in the central Baltic Sea. We found that Neolithic cod were larger (mean 56.4 cm, 95%confidence interval (CI) ±0.9) than modern fish (weighted mean length in catch = 49.5 + 0.2 cm in 1995,48.2 ± 0.2 cm in 2003), and older (mean ages = 4.7 ± 0.11, 3.1 ± 0.02 and 3.6 ± 0.02 years for Neolithic,1995, and 2003 fisheries, respectively). Fishery-independent surveys in 1995 and 2003 show that meansizes in the stock are 16-17 cm smaller than reflected in the fishery, and mean ages approximately 1-1.5years younger. Modelled von Bertalanffy growth and back-calculated lengths indicated that Neolithic codgrew to smaller asymptotic lengths, but were larger at younger ages, implying rapid early growth. Verysmall Neolithic cod were absent and large individuals were rare as in modern times. This could be owing toselective harvests, the absence of small and large fish in the area or a combination. Comparing modern andprehistoric times, fishery selection is evident, but apparently not as great as in the North Atlantic proper.