954 



Abstract.— Understanding the rela- 

 tive importance of pre- and postsettle- 

 ment processes is critical to under- 

 standing the population dynamics of 

 marine fishes. Our goals in this study 

 were 1 1 to examine habitat preference 

 and habitat use of newly settled Atlan- 

 tic croaker, Micropogonias undulatus, 

 and 2) to determine if postsettlement 

 growth or predation varied with habi- 

 tat type. Field surveys showed no dif- 

 ference in croaker abundance among 

 three estuarine habitats: marsh edge, 

 seagrass, and sand. Behavioral e.xperi- 

 ments in laboratory mesocosms sug- 

 gested that the pattern of similar use 

 of habitats in the field results from a 

 lack of preference among habitats. In a 

 field experiment, croaker recruitment 

 was greater to artificial seagrass than 

 to sand habitats, but there was no dif- 

 ference in fish density in habitats with 

 or without food supplementation. More- 

 over, growth rates were similar in both 

 sand and artificial seagrass habitats 

 and in habitats with or without food 

 supplementation. In a second experi- 

 ment, we were unable to detect a dif- 

 ference in the density of newly settled 

 croaker between sand and artificial 

 seagrass habitats, or between habitats 

 with predator access limited by cages and 

 cage controls. Our results demonstrate 

 that newly settled croaker use different 

 estuarine habitats similarly, and there 

 does not appear to be a fitness conse- 

 quence of using many habitats. We sug- 

 gest that for habitat generalists, such as 

 the Atlantic croaker, variability in larval 

 supply will be a stronger predictor of 

 population dynamics than will variabil- 

 itv of habitat attributes. 



Recruitment of Atlantic croaker, 



Micropogonias undulatus: 



Do postsettlement processes disrupt 



or reinforce initial patterns of settlement?* 



Rachel Petrik 



Phillip S. Levin 



Institute ol Marine Science 



University of California, Santa Cruz 



Santa Cruz, California 95064, 



E-mail address (for P S Levin, contact author) levinraJbiology ucsc edu 



Gregory W. Stunz 



Department of Marine Biology 



Texas A&M University, Galveston, Texas 77553 



John Malone 



Department of Biology 



University of California, Los Angeles, California 90095 



Manuscript accepted 21 .^pril 1999, 

 Fish. Hull. 97:9,'')4-961 1 1999). 



Understanding the causes of fluc- 

 tuations in population abundance is 

 critical for ecologists and fishery 

 biologists. For marine fishes with 

 life histories in which adults have 

 limited home ranges and larvae are 

 pelagic and advected vast distances 

 from natal sites, an understanding of 

 variability in larval supply to local 

 populations is critical for tmderstand- 

 ing the mechanisms that produce dy- 

 namics in populations (Caley et al., 

 1996). In addition, habitat selection 

 by settling fish (Carr, 1991; Levin, 

 1991; Wellington, 1992; Tolimieri, 

 1995), and habitat-specific growth 

 and mortality (Heck and Orth, 1980; 

 Hixon and Beets, 1993; Levin et al., 

 1997 ) may ultimately reinforce or dis- 

 loipt patterns created by variable lar- 

 val supply (Jones, 1997). Thus, 

 knowledge of the degree to which pro- 

 cesses such as habitat selection, com- 

 petition, or predation modify initial 

 patterns of lai'val settlement is im- 

 portant in understanding the popu- 

 lation dynamics of marine species. 



The importance of variability in 

 postsettlement growth or mortality 

 and the level to which postsettlement 



processes alter initial patterns of 

 larval settlement can be a function 

 of habitat structure. For example, 

 on coral reefs, holes provide a ref- 

 uge from predation, and on reefs 

 with large numbers of holes, the 

 importance of predation is reduced 

 (Shulman, 1984; Hixon and Beets, 

 1993). Similarly, Atlantic cod settle 

 in equivalent densities in a variety 

 of habitats but suffer lower preda- 

 tion rates in structurally complex 

 habitats (Tupper and Boutilier, 

 1995). Thus, habitat-specific mor- 

 tality disrupts initial patterns of 

 larval settlement. Differences in 

 habitat structtu'e may also impact 

 growth rates or the ability offish to 

 procure food (Nelson, 1979; Heck 

 and Thoman, 1981; Stoner, 1982). 

 As examples, 1 ) pinfish have greater 

 success capturing amphipods in 

 shoal grass iHalodule wrightii) 

 than in similar densities of turtle 

 grass ( Thalassia te^tudin iiin ) ( Stoner, 



' Contribution 10 of the Partnership for Inter- 

 disciplinary Studies of Coastal Oceans 

 I PISCO I: a long-term ecological consortium 

 funded by the David and Lucile Packard 

 Fiiundation. 



