257 
Abstract — For many fish stocks, 
resource management cannot be based 
on stock assessment because data are 
insufficient — a situation that requires 
alternative approaches to manage- 
ment. One possible approach is to 
manage data-Iimited stocks as part 
of an assemblage and to determine the 
status of the entire unit by a data-rich 
indicator species. The utility of this 
approach was evaluated in analyses of 
15 years of commercial and 34 years 
of recreational logbook data from reef 
fisheries off the southeastern United 
States coast. Multivariate statisti- 
cal analyses successfully revealed 
three primary assemblages. Within 
assemblages, however, there was 
little evidence of synchrony in popu- 
lation dynamics of member species, 
and thus, no support for the use of 
indicator species. Nonetheless, assem- 
blages could prove useful as manage- 
ment units. Their identification offers 
opportunities for implementing man- 
agement to address such ecological 
considerations as bycatch and species 
interrelations. 
Manuscript submitted 6 August 2007. 
Manuscript accepted 26 February 2008. 
Fish. Bull. 106:257-269 (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. 
Fish assemblages and indicator species: 
reef fishes off the southeastern United States 
Kyle W. Shertzer (contact author) 
Erik H. Williams 
Email address for K. W. Shertzer: Kyle.Shertzer@noaa.gov 
National Oceanic and Atmospheric Administration 
Southeast Fisheries Science Center 
Center for Coastal Fisheries and Habitat Research 
101 Pivers Island Road 
Beaufort, North Carolina 28516 
Most approaches to fishery man- 
agement rely on results from stock 
assessment. Data-limited situations, 
however, may not conform to conven- 
tional assessment methods, necessitat- 
ing other approaches to management 
(Kruse et al., 2005). One possible 
approach with data-limited stocks is 
to assign them to assemblages that 
are managed as units. Ideally, each 
assemblage would include at least 
one data-rich species that could be 
assessed and serve as a status indi- 
cator of the entire unit. Managing 
assemblages by means of indicator 
species is arguably a small but prac- 
tical step in the direction of ecosys- 
tem-based management (Hall and 
Mainprize, 2004). 
Assemblages may be defined by 
similarities in such biological charac- 
teristics as life history, trophic behav- 
ior, or home range. For the purpose 
of fishery management, however, an 
assemblage should consist of spe- 
cies caught together, if regulations 
on fishing are to benefit assemblage 
members. This is particularly true if 
regulations are focused on an indica- 
tor species but the intent is also to 
control the harvest of other species 
in the assemblage. 
Indicator species have been used 
in management of both terrestrial 
and marine systems (Simberloff, 
1998; Zacharias and Roff, 2001). The 
term “indicator species” has no single 
definition (Landres et al., 1988); it is 
used here as suggested by the Na- 
tional Standard Guidelines of U.S. 
federal fishery management, which 
states that where maximum sustain- 
able yield (MSY) cannot be specified 
for each stock of a mixed-stock fish- 
ery, then “MSY may be specified on 
the basis of one or more species as 
an indicator for the mixed stock as a 
whole or for the fishery as a whole.” 
(Federal Register, 1998) According 
to this usage, the stock status of the 
indicator is extrapolated to represent 
that of other species in the assem- 
blage, or analogously, other stocks of 
the same species. Such an approach 
requires the assumption that popu- 
lation trends of an indicator species 
reflect those of others in the assem- 
blage. 
The approach of managing multi- 
species assemblages by means of in- 
dicator species raises two fundamen- 
tal questions. First, can assemblages 
be identified? As mentioned, species 
of an assemblage would need to be 
caught together if regulations are to 
affect the entire unit. Second, if an 
assemblage can be identified, do its 
members have similar stock dynam- 
ics? If not, focusing management on 
the indicator species may not pro- 
vide the intended benefits to other 
stocks. 
We address both questions, using 
as a case study the snapper-grouper 
complex off the southeastern United 
States. As defined for management, 
the complex contains 73 species (Ap- 
pendix), the majority of which cannot 
be assessed with currently available 
data. The objectives of this study are 
1) to identify assemblages of finfish 
species within the snapper-grouper 
complex and 2) to examine synchrony 
of stock dynamics within assemblag- 
es. To accomplish the first objective, 
multivariate statistical techniques 
