438 
Abstract — Trawling and dredging 
on Georges Bank (northwest Atlantic 
Ocean) have altered the cover of colo- 
nial epifauna, as surveyed through in 
situ photography. A total of 454 pho- 
tographs were analyzed from areas 
with gravel substrate between 1994 
and 2000 at depths of 40-50 m and 
80-90 m. The cover of hydroids, bushy 
bryozoans, sponges, and tubeworms 
was generally higher at sites undis- 
turbed by fishing than at sites classi- 
fied as disturbed. The magnitude and 
significance of this effect depended 
on depth and year. Encrusting bryo- 
zoans were the only type of colonial 
epifauna positively affected by bottom 
fishing. Species richness of noncolo- 
nial epifauna declined with increased 
bottom fishing, but Simpson’s index 
of diversity typically peaked at inter- 
mediate levels of habitat disturbance. 
Species that were more abundant at 
undisturbed sites possessed charac- 
teristics that made them vulnerable to 
bottom fishing. These characteristics 
include emergent growth forms, soft 
body parts, low motility, use of com- 
plex microhabitats, long life spans, 
slow growth, and larval dispersal 
over short distances. After the pro- 
hibition of bottom fishing at one site, 
both colonial and noncolonial species 
increased in abundance. Populations 
of most taxa took two years or more 
to increase after the fishing closure. 
This finding indicates that bottom 
fishing needs to be reduced to infre- 
quent intervals to sustain the ben- 
thic species composition of Georges 
Bank at a high level of biodiversity 
and abundance. 
Manuscript submitted 7 August 2007. 
Manuscript accepted 1 July 2008. 
Fish. Bull. 106:438-456 (2008). 
The views and opinions expressed 
or implied in this article are those 
of the author and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Changes in a benthic megafaunal community 
due to disturbance from bottom fishing 
and the establishment of a fishery closure 
Rebecca G. Asch (contact author ) 1 
Jeremy S. Collie 1 
1 Graduate School of Oceanography 
University of Rhode Island 
Narragansett, Rhode Island 02882 
'Present address for R. G. Asch: Scripps Institution of Oceanography 
University of California San Diego 
9500 Gilman Drive, Mailcode 0208 
La Jolla, California 92093-0208 
Commercial fishing with mobile gear 
(e.g., otter trawls, beam trawls, scal- 
lop dredges) has become such a wide- 
spread practice that it is estimated 
that an area equivalent to approxi- 
mately 75% of the world’s continental 
shelves is trawled annually (Kaiser et 
al., 2002). Because bottom fishing can 
kill and injure benthic invertebrates 
that are either caught as bycatch or 
crushed underneath fishing gear, 
heavily fished areas often exhibit 
decreased abundance, biomass, and 
diversity of epifauna (Collie et al., 
1997). Trawling and dredging can 
modify the composition of marine sed- 
iments through the dispersal of piles 
of boulders (Collie et al., 1997; Freese 
et al., 1999) and the resuspension of 
fine sediments. The latter process may 
subsequently release contaminants 
and excess nutrients, expose anoxic 
sediment layers, smother filter feed- 
ers, and alter biogeochemical fluxes 
(Kaiser et al., 2002). Bottom fishing 
also affects benthic community struc- 
ture by augmenting the abundance 
of scavengers (Ramsay et al., 1998) 
and depleting organisms that serve as 
ecosystem engineers or keystone spe- 
cies (Auster et al., 1996). Similarly, 
ecosystem function and population 
dynamics can be indirectly altered 
because bottom fishing may reduce 
levels of epifaunal productivity (Herm- 
sen et al., 2003), lower the diversity of 
prey available to demersal fish (Jiang 
and Carbines, 2002), and decrease the 
structural complexity of the benthic 
environment (Auster et al., 1996). 
A meta-analysis of the effects of 
bottom fishing revealed that less 
than one-half of the studies address- 
ing this topic examined the long-term 
recovery of the benthic community 
(Collie et al., 2000b). In studies where 
recovery rates were investigated, 
most tracked recovery for a period 
of less than two years, which may 
not be long enough to evaluate the 
final outcome of ecological succession 
in disturbed habitat patches. For ex- 
ample, at the completion of a study 
that involved experimental trawling 
in a Scottish sea loch, physical signs 
of trawl damage had disappeared af- 
ter 18 months, but differences in the 
benthic community structure at treat- 
ment and reference sites persisted 
(Tuck et al., 1998). Similarly, at the 
end of a six-month study of the effects 
of experimental trawling, the poly- 
chaete Terebellides atlantis and the 
nemertean Cerebratulus lacteus had 
not yet returned to pretrawling levels 
of abundance (Sparks-McConkey and 
Watling, 2001). Knowledge of epifau- 
nal recovery from natural and fish- 
ing-induced disturbance is especially 
lacking on the continental shelf, an 
area subjected to heavy bottom fish- 
ing. Compared to intertidal zones and 
shallow subtidal areas where benthic 
responses to natural disturbance have 
long been studied, relatively little re- 
search has been undertaken to track 
the colonization of sessile epifauna 
to hard substrata at depths greater 
than 30 m after natural or anthro- 
pogenic disturbances. In the Gulf of 
Maine, those studies on this subject 
(Sebens et al., 1988; Witman, 1998) 
had relatively short durations (less 
than two years), which may not have 
