RESEARCH ARTICLE Influence of marine reserve size and boundary length on the initial response of exploited reef fishes in the Florida Keys National Marine Sanctuary, USA Aaron Bartholomew Æ James A. Bohnsack Æ Steven G. Smith Æ Jerald S. Ault Æ Douglas E. Harper Æ David B. McClellan Received: 14 July 2007 / Accepted: 18 July 2007 / Published online: 21 August 2007 Ó Springer Science+Business Media B.V. 2007 Abstract We examine the influence of reserve size and boundary length on the relative rate of fish density change in reserves versus fished reference reefs for three exploitable-sized reef fish categories: (1) com- bined fish (34 species of Haemulidae, Lutjanidae, Serranidae, and hogfish Lachnolaimus maximus); (2) Haemulidae (13 species); and (3) Lutjanidae (9 species). If reef habitat boundaries are highly perme- able to fish movements then fish recovery within a reserve would be inversely proportional to: reserve perimeter (RP)/total reserve area (RA) (RP/RA). If, however, reef habitat boundaries are relatively imper- meable barriers to fish movements, recovery within the reserve would be inversely proportional to: reserve boundary that intersects reef habitat (HI)/reef habitat area within the reserve (HA) (HI/HA). From 1994 to 2001 we monitored reef fishes within and outside of no-take marine reserves established in 1997 in the Florida Keys, USA. A significant majority of reserves had greater rates of density change than reference reefs for Lutjanidae and combined fish (22 of 24 reserves for both categories). Significantly higher rates of density change were found in ten reserves for Lutjanidae, two reserves for combined fish, and one reserve for Haemulidae. Reserves appeared to pro- mote an increased density of exploitable fishes. A significant, negative, but weakly correlated relation- ship was found between the relative rate of density change (RDC) for combined fish and the HI/HA ratio. Reserve size and placement appeared to have a minimal effect upon RDC. Keywords Landscape ecology  Fish density  Reserve boundary  Habitat  Perimeter to area ratio  Marine reserve  Conservation Introduction A growing number of theoretical and empirical studies have demonstrated increased density and sizes of exploited species within reserve boundaries (Bohnsack 1998a, b; Murray et al. 1999; National Research Council 1999; Fogarty et al. 2000; Hor- wood 2000; Lindeboom 2000; Roberts and Hawkings 2000; Halpern 2003; Williamson et al. 2004; Ault et al. 2006). Fisheries outside reserves may also benefit from resulting increased reproductive output A. Bartholomew  J. A. Bohnsack  D. E. Harper  D. B. McClellan National Marine Fisheries Service, 75 Virginia Beach Drive, Miami, FL 33149, USA Present Address: A. Bartholomew (&) American University of Sharjah, P. O. Box 26666, Sharjah, United Arab Emirates e-mail: abartholomew@aus.edu S. G. Smith  J. S. Ault University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA 123 Landscape Ecol (2008) 23:55–65 DOI 10.1007/s10980-007-9136-0