Impacts of Flounder Trawls on the Intertidal Habitat and Community of the Minas Basin, Bay of Fundy

Abstract

Four experimental trawls were made at highwater over the intertidal zone of the Minas Basin and the effects assessed when the tide was out to determine the physical and biological impacts of groundfish trawling on the benthos. The trawl doors made furrows 30–85 cm wide and up to 5 cm deep. The rollers compressed surficial sediments but did not scour a depression. The bridle caused no obvious disturbance. Door furrows and roller marks remained visible for 2–7 mo. No significant impacts were observed on either benthic diatoms or macrobenthos. The macrobenthos was dominated by polychaetes, some of which may have the ability to take evasive action as a trawl approaches. There were few molluscs, crustaceans, or echinoderms present; these taxa have been shown to be more susceptible to trawling damage in studies done elsewhere. Nematode numbers were initially depressed in the door furrows but did recover with time. It is not known whether nematodes were killed or displaced but the latter is thought more likely. Overall, the impacts in this particular environment are judged to be minor, especially since the intertidal sediments of the Minas Basin are already exposed to similar natural stresses imposed by storms and winter ice.

The impact of habitat disturbance by scallop dredging on marine benthic communities:what can be predicted from the results of experiments?

“…However, fishing effects on macrofaunal communities a r e not always apparent. Brylinsky et al (1994) found no significant effects on intertidal macrofauna after flounder trawling, even though physical conditions were visibly impacted for 2 to 7 mo. The lack of significant effects was attributed to the predominance of subsurface feeding polychaetes and the naturally high levels of storm and ice disturbance in the habitat.…”

“…The lack of significant effects was attributed to the predominance of subsurface feeding polychaetes and the naturally high levels of storm and ice disturbance in the habitat. In ad.dition the power to detect significant effects was not considered by Brylinsky et al (1994).…”

“…indirect effects on community structure that can occur in response to predator removal; Sih et al 1985, Kneib 1991 and larger-scale environmental features (e.g. variations in the frequency and intensity of storm disturbance of the seabed; Hall et al 1990, Brylinsky et al 1994, Hall 1994 which are likely to influence the identification of any fishing effects. Apart from the influence of physical and biological environmental features, the intensity, frequency and gear used in a particular fishery also needs to be considered in developing hypotheses about potential fishing impacts.…”

Experimental beam-trawling in Lanice conchilega reefs: Impact on the associated fauna

“…Brylinski et al, 1994;Kaiser et al, 2006). The impact of beam-trawling on soft-sediment systems has already triggered considerable attention (e.g.…”

“…The quick overall recovery from disturbance is possibly related to the dynamic intertidal environment, where communities are known to recover very quickly from disturbances (Kaiser and Spencer, 1996). In Brylinski et al (1994), impacts of otter trawling in these high-energy environments also appeared to be minor.…”