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Research Technical Report

Effects of Commercial Trawling on Infaunal Community Structure and Flatfish Diets

Engel, J., and R. Kvitek (December 1997)

Presentation at Western Society of Naturalists Annual Meeting, Monterey, CA


We compared an area within Monterey Bay National Marine Sanctuary under high levels of trawling intensity (HT) to an area under low levels of trawling intensity (LT). Three seasons of infaunal data was collected and significant differences included 30 to 70% more oligochaetes in the HT area, 25% more ophiuroids in the HT area, and over 25% fewer polychaete species in the HT area Fall seasons. The polychaete, Chloeia pinnata, was 3 times more abundant in the HT vs. LT area Fall seasons and had 25 to 75% higher biomass in the HT vs. LT area. Polychaete community trophic structure shifted from sedentary, deposit feeding worms in the LT area to motile, carnivorous worms in the HT area. C. pinnata was a dominant prey item in flatfish. The positive relationship between C. pinnata abundance and biomass and trawling intensity along with C. pinnata dominance in flatfish diets suggests that some prey species and commercially important fish may be enhanced by trawling disturbance. This research helps clarify potential impacts of commercial trawling and provides incentive to conduct large scale, long-term manipulative studies in marine reserves that will more broadly assess the effect of trawling on marine bottom communities.


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