Table 5.6. Effects of otter
trawls on gravel/rock substrate habitat: summary of published studies. (S =
statistically significant; citations in bold print are peer-reviewed
publications.)
| No. |
Reference |
Location |
Depth |
Sediment |
Effects |
Recovery |
Approach |
| 1 |
Auster et al. 1996 |
Jeffreys Bank, Gulf of Maine |
94 m |
Gravel/boulder with thin mud veneer. |
Gravel
base exposed; boulders moved; reduced abundance of erect sponges and
associated epifaunal species; changes attributed to trawling. |
|
Submersible
and video observations in same location in 1987 and 1993. |
| 2 |
Freese et al. 1999 |
Gulf of Alaska |
206-274 m |
93% pebble, 5% cobble, 2% boulder. |
Boulders
displaced; groundgear left furrows 1-8 cm deep in less compact sediment;
layer of silt removed in more compact sediment; S reductions in abundance of
sponges, anemones, and sea whips; damage to sponges, sea whips and brittle
stars. |
|
Video
observations from a submersible 2-5 hr after single trawl tows in area
exposed to little or no commercial trawling for about 20 yr. |
| 3 |
Dolah et al. 1987 |
Georgia, SE U.S. coast |
20 m |
Smooth rock with thin layer of sand and attached
epifauna. |
Damage
to sponges and corals, mostly to sponges; S reductions in density of
undamaged barrel sponges in high-density transects; no S effects on densities
of vase sponges, finger sponges, or stony corals. |
Full
recovery of damaged organisms and density within 12 mo. |
Experimental
study using diver counts of large sponges and corals before, immediately
after, and 12 mo after, a single tow of a “roller” trawl in an unexploited
area. |