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proportion of piscivorous fish in the standardized hauls from 29.3% to 0% of the catch (Tang et al., 2003). In contrast, planktivorous species increased from 4.75% to 58.0% of the catch in the same hauls.

Finally, Jennings and Blanchard (2004) used the theoretical abundance–body mass relationship derived from macroecological theory to estimate the pristine biomass of fishes in the North Sea in comparison with the size and trophic structure of heavily exploited populations in 2001. The estimated total biomass of all fishes 64 g to 64 kg declined 38% while the mean turnover time of the population was estimated to have dropped from 3.5 to 1.9 years. Large fishes 4–16 kg were estimated to have declined by 97.4%, and species 16–66 kg were estimated to have declined by 99.2%. The great importance of these calculations is that they are entirely independent of all of the assumptions and controversies surrounding fisheries catch data and models, and yet lead to predictions entirely consistent with the most extreme estimates of fishery declines.

Habitat Destruction by Trawling and Dredging

Trawling reduces the three-dimensional structure and complexity of sea floor habitats to bare sediment; reduces the size, biological diversity, and turnover time of dominant species; and results in entirely new associations of species that may persist for decades even if trawling is halted

FIGURE 1.1 Impact of trawling on the seafloor at ≈18 m depth in the Swan Island Conservation Area, northern Gulf of Maine (Auster, 1998). The straight lines are furrows made by the trawl, and the debris is polychaete worm tubes.

FIGURE 1.1 Impact of trawling on the seafloor at ≈18 m depth in the Swan Island Conservation Area, northern Gulf of Maine (Auster, 1998). The straight lines are furrows made by the trawl, and the debris is polychaete worm tubes.



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