417 
Abstract — We examined the effect of 
habitat and shrimp trawl bycatch on 
the density, size, growth, and mor- 
tality of inshore lizardfish (Synodus 
foetens), a nonexploited species that 
is among the most widespread and 
abundant benthic fishes in the north 
central Gulf of Mexico. Results of 
quarterly trawl sampling conducted 
from spring 2004 through spring 
2005 revealed that inshore lizardfish 
are most abundant on sand habitat, 
but larger fish are more common on 
shell rubble habitat. There was no 
significant difference in fish density 
between habitats exposed to shrimp 
trawling on the open shelf versus 
those habitats within a permitted 
artificial reef zone that served as 
a de facto no-trawl area; this find- 
ing indicates that either inshore liz- 
ardfish experienced minimal effects 
from trawling or, more likely, that 
fish moved between trawled and non- 
trawled habitats. Exploitation ratio 
(bycatch mortality/total morality) 
estimates derived from catch curve 
analysis ranged from 0.43 inside 
the artificial reef zone to 0.55 out- 
side the reef zone, thus indicating 
that inshore lizardfish are subject 
to significant fishing mortality in the 
north central Gulf of Mexico despite 
the lack of a directed fishery for the 
species. We infer from this result that 
effects of shrimp trawl bycatch may 
be significant at the population level 
for nonexploited species and that a 
broader ecosystem-scale examination 
of bycatch effects is warranted. 
Manuscript submitted 7 November 2007. 
Manuscript accepted 23 June 2008. 
Fish. Bull. 106:417-426(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. 
Habitat and bycatch effects on 
population parameters of 
inshore lizardfish ( Synodus foetens ) 
in the north central Gulf of Mexico 
Sarah A. Jeffers 1 
William F. Patterson, III (contact author ) 1 
James H. Cowan Jr . 2 
Email address (for W. F Patterson): wpatterson@uwf.edu 
1 Department of Biology 
University of West Florida 
11000 University Parkway 
Pensacola, Florida 32514 
2 Department of Oceanography and Coastal Studies 
Louisiana State University 
Baton Rouge, Louisiana 70803 
Habitat degradation and bycatch of 
adult or younger life-stage indviduals 
of nontargeted species are among the 
greatest ecosystem effects of fishing 
(Hall et al., 2000; Pauly et al., 2002, 
2003; Thrush and Dayton, 2002). In 
fact, bycatch of nontargeted species or 
life stages may pose an even greater 
threat to marine ecosystem health 
than direct the harvest of targeted 
species (Crowder and Murawski, 
1998; Baum et al., 2003; Harrington 
et al., 2005). Therefore, biologists, 
conservation groups, and fisheries 
agencies have called for a transition 
away from single species manage- 
ment to a more holistic ecosystem- 
based fisheries management (EBFM) 
approach (Zabel et al., 2003; Francis 
et ah, 2007; Marasco et ah, 2007). A 
single-species approach traditionally 
has been applied to estimate maxi- 
mum sustainable yield (MSY) and 
to subsequently set total allowable 
catch (TAC) for most fisheries, but 
that approach does not account for or 
mitigate against direct and indirect 
ecosystem effects of fishing. 
The shortcomings of single species 
management are evident when con- 
sidering management of the penaeid 
shrimp trawl fishery in the northern 
Gulf of Mexico (GOM). That fishery 
has operated near its estimated MSY 
since the 1950s, averaging approxi- 
mately 130 xlO 6 lbs/yr in total land- 
ings of brown (Farfantepenaeus az- 
tecus), white ( Litopenaeus setiferus), 
and pink (Farfantepenaeus duorarum) 
shrimps, but greater than 1 x 10 9 lbs/ 
yr of bycatch have also been associ- 
ated with those landings (Diamond, 
2004; Ortiz et ah, 2000; Strelcheck 
and Hood, 2007). Although that level 
of bycatch is clearly substantial, its 
effects on fishes at the population 
level have been studied for only a few 
commercially important fishes (Dia- 
mond et ah, 2000; Porch, 2007). Per- 
haps a more comprehensive approach 
would be to analyze the effects of by- 
catch on the community (e.g., Wells, 
2007), as well as to examine species- 
specific effects for nonexploited but 
ecologically important fishes. 
Inshore lizardfish ( Synodus foetens) 
is an ideal model species for examin- 
ing the effects of shrimp trawl bycatch 
on the population demographics and 
dynamics of an ecologically but not 
commercially important species. In- 
shore lizardfish are ubiquitous on the 
northern GOM shelf and are among 
the ten most frequently encountered 
benthic fishes in trawl samples there 
(Wells, 2007). The ecological impor- 
tance of inshore lizardfish has been 
assumed to be significant given their 
abundance on the shelf and carnivo- 
rous habits (Garcia-Abad et al., 1999); 
however, relatively little is known 
about their population ecology in the 
