THE ROLES OF PRIOR RESIDENCE AND 



RELATIVE SIZE IN ( OMPEII LION FOR 



SHELTER BY LHE MALA^ SLAN I'RAW N, 



MAC ROliltKLlULM KOSISBHRGIl^ 



Behavorial dominance, tenitoiiality. and their re- 

 lationship to survival and population density have 

 been the subject of extensive research (reviewed 

 by Brown and Orians 1970; Ito 1970; Brown 1975). 

 Generally dominance (behavioral) hierarchies 

 imply some form of ranked order (reviewed by 

 Marler and Hamilton 1966; Eibl-Eibesfeldt 1970; 

 Ito 1970) whereby the alpha animal(s) has prefer- 

 red access to food, shelter, or mates. Dominance 

 may develop within a short time after an initial 

 encounter (Dingle and Caldwell 1969), is partially 

 controlled by differences in relative size (Marler 

 and Hamilton 1966). and in some species is mod- 

 ified by relative location in space (Brown 1963). 

 This latter modification is related to Noble's 

 ( 1939) original concept of territory. Noble referred 

 to territory as "any defended area." This area 

 could serve as a "retreat" ( in contrast to a sexual or 

 nesting area) that "is occupied because it is famil- 

 iar and defended because any newcomer is irritat- 

 ing to the resident." 



Such space-related aggressive behavior has 

 been reported in numerous animals (Brown and 

 Orians 1970). Territorial behavior can be related 

 to "defense" of 1 ) a breeding area ( Buechner 1 96 1 ; 

 Watson 1964); 2) a renewable resource such as 

 food (Stimson 1970); or 3 ) a physical shelter 

 I Crane 1958; Reese 1964; Fielder 1965; Hughes 

 1966; Dingle and Caldwell 1969). Often the out- 

 come of such a defensive action is exclusion of the 

 intruder by the resident. Since this area is "famil- 

 iar" to the resident and unfamiliar to the "new- 

 comer," it follows that the resident has some type 

 of advantage. This "prior resident effect" has been 

 observed in a number of species (Braddock 1945, 

 1949; Miller 1958; Hughes 1966; Baird 1968; 

 Dingle and Caldwell 1969; Selander 1970). Thus 

 in many animals, spacing behavior is a powerful 

 mechanism that can regulate resource utilization 

 and influence distribution patterns. 



Many of the above-mentioned studies and re- 

 views dealt with animal populations in natural 

 open systems subject to both immigration and 

 emigration. In contrast, aquaculture systems are 



'Contribution No. 544 from the Hawaii Institute of Marine 

 Biology, University of Hawaii, Kaneohe, Hawaii. 



closed and deal with confined high-density popula- 

 tions. In the case of Macrobrachi ion rosenbergii, 

 ponds are stocked with postlarvae, and harvesting 

 of adults begins 9-12 mo later. The same space- 

 related behavioral mechanisms observed in open 

 systems may be operating in these high-density 

 ponds. Circumstantial evidence indicates that this 

 is occurring in ponds containing M. rosenbergii. 

 Animals of the same age exhibit large variation in 

 size at the end of several months of growth 

 (Fujimura nad Okamoto 1970). Malecha (1977) 

 reported that small M. rosenbergii can greatly in- 

 crease their size when larger animals are absent. 

 This has been called the "Bull Effect" by Fujimura 

 and Okamoto (1970). Similar observations have 

 been reported for carp (Nakamura and Kasahara 

 1955, 1961; Wohlfarth and Moav 1972), trout 

 (Brown 1946), and salmon (Symons 1971). One 

 hypothesis advanced by Nakamura and Kasahara 

 ( 1961) is that the larger animals are outcompeting 

 the smaller subordinates for food. 



Maerobraehiiini rosenbergii is a large freshwa- 

 ter prawn. Its native distribution ranges from 

 Pakistan to Papua, New Guinea, and Palau 

 (Johnson 1960; McVey 1975). Usually it is found 

 in fresh and brackish streams and pools. The eggs 

 hatch near ocean waters, and the adults are found 

 up to 200 km from the coast (Ling 1969). Generally 

 males are thought to stay in upstream waters 

 while the females undergo a seasonal migration, 

 moving downstream and into brackish waters 

 (Raman 1967). Relatively little is known of M. 

 rosenhergii's behavioral ecology but Raman ( 1964) 

 reported juveniles "hiding in crevices or among 

 submerged plants along river banks." In order to 

 understand how social behavior affects resource 

 utilization by M. rosenbergii. three experiments 

 were conducted in which shelter was the limiting 

 resource, and relative size and prior residence 

 were measured as variables. 



Methods 



The three experiments consisted of: a prior resi- 

 dent experiment, a simultaneous introduction ex- 

 periment, and a control experiment. The prior res- 

 ident experiment was used to test for the role of 

 prior residence and relative size in competition for 

 shelter. The simultaneous introduction experi- 

 ment tested for the role of relative size on competi- 

 tion in the absence of a "prior resident effect." The 

 control experiment tested for the effect of handling 

 and capture. 



FISHERY BULLETIN: VOL. 76. NO. 4. 1979. 



905 



