Spiny lobster, continued 



It preys on a wide variety of slow-moving and sedentary 

 animals such as molluscs, crustaceans, and echino- 

 derms. Young juveniles can be considered general 

 opportunistic feeders that consume a large variety of 

 organisms (Andree 1 981 , Herrnkind et al. 1 988). The 

 only major difference between the diets of younger and 

 older juveniles is the size of the prey; smaller lobsters 

 feed on smaller species of gastropods, bivalves, and 

 crustaceans as well as smaller size classes of com- 

 monly eaten larger species. Small quantities of algae, 

 sea grass, detritus, foraminiferans, polychaetes, and 

 sponges have also been found in fecal samples. Older 

 juveniles were found to feed on molluscs, crustaceans, 

 and other fauna that exist on the algal clumps in which 

 they reside (GMFMC 1 982, Marx and Herrnkind 1 985a). 

 Larger juveniles and adults are higher trophic level 

 carnivores that forage considerable distances from 

 their dens in search of prey, principally bivalves, snails, 

 hermit crabs, other crustaceans, and fish (Crawford 

 and DeSmidt 1923, Davis 1977, GMFMC 1982, 

 Schomerand Drew 1982, Marx and Herrnkind 1986). 



Biological Interactions 



Predation : Larvae are preyed on by a number of 

 pelagic fishes, including skipjack tuna (Katsuwonus 

 pelanus) and blackfin tuna (Thunnus atlanticus) 

 (GMFMC 1 982). Postlarvae are preyed on most heavily 

 as they cross the reef track (Acosta 1 997). Blue crabs 

 and octopuses have been observed eating early juve- 

 niles (Andree 1 981 ). Juveniles are presumably subject 

 to predation by numerous fishes while occupying the 

 mangrove and grass flat habitats (GMFMC 1982). 

 Major predators of adult and sub-adult stages include 

 skates (Dasyatis species), sharks (especially nurse 

 shark, Ginglymostoma cirratum), various snappers 

 (Lutjanus species), grouper (Mycteroperca and 

 Epinephelus species), jewfish, grunts, barracudas, 

 and octopus (Andree 1 981 , GMFMC 1 982, Smith and 

 Herrnkind 1992). Dolphins (Tursiops) and loggerhead 

 turtles (Caretta caretta) also prey on lobster. A small 

 snail, Murexpomum, is known to kill lobsters in traps by 

 boring through the carapace (GMFMC 1982). The 

 degree of predation risk in an area appears to influence 

 the distribution and abundance of lobsters present 

 there (Eggleston and Lipcius 1 992, Mintz et al. 1 994). 



Factors Influencing Populations : Extreme tempera- 

 tures and salinities (Field and Butler 1994) and sedi- 

 mentation (Herrnkind et al. 1988) reduce survival of 

 postlarvae and juveniles. The cascading effects of 

 environmental disturbance can result in declines in 

 lobster populations (Butler et al. 1995). Although 

 Florida Bay is a major nursery area for juvenile spiny 

 lobster, recruitment within the northern portion of the 

 bay may be limited by physical hydrology, and by 

 seasonal extremes of temperature and salinity (Field 

 and Butler 1994). Illegal harvest out-of-season and of 



undersize lobsters (shorts) are no longer considered 

 serious problems in the now-limited entry fishery (Lyons 

 pers. comm.). The widespread use of shorts as trap 

 attractants by commercial fishermen may have an 

 adverse impact on recruitment to the adult population 

 due to increased mortality of the shorts (GMFMC 1 982, 

 Lyons 1986). However, this impact may diminish as 

 the number of traps in the fishery is reduced consider- 

 ably by limited entry (Lyons pers. comm.). Ocean 

 dumping of dredged material creates silt that settles 

 over larvae and suffocates them (GMFMC 1982). Oil 

 and tar pollution of marine waters can potentially 

 impact the open ocean epipelagic habitat of larvae 

 (GMFMC 1982). Shallow water mangrove and grass 

 flat nursery areas are subject to abuses of dredge and 

 fill, modified discharges, and coastal development, all 

 of which destroy necessary habitat needed to sustain 

 spiny lobster population levels (Herrnkind et al. 1 988). 

 Damage to reef areas from pollution, ship groundings, 

 anchors, and collectors also remove habitat necessary 

 for sustaining this species (Andree 1981, GMFMC 

 1 982). Large amounts of rainfall that significantly lower 

 the salinity of estuarine nursery areas can cause 

 mortality in postlarval lobsters, affecting their recruit- 

 ment to these areas (Witham et al. 1968, Field and 

 Butler 1994). Loss or degradation of inshore nursery 

 habitat could have a serious effect on continued lobster 

 recruitment and production (Little 1977, Butler et al. 

 1995, Butler and Herrnkind 1997). However, artificial 

 habitats that mimic mimic natural shelters are useful in 

 mitigating loss of shelter (Herrnkind et al. 1997). The 

 inability of lobsters to survive low temperatures (<10° 

 C) probably limits latitudinal and depth distribution of 

 this species and prevents its spread northward and 

 across deep ocean basins (Witham 1974, Marx and 

 Herrnkind 1986). The density of lobsters in a given 

 habitat can enhance gregariousness, which in turn can 

 influence the relative impact of lobster size, shelter 

 size, and predation risk upon den choice (Eggleston 

 and Lipcius 1992). 



Personal communications 



Butler, Mark J. Old Dominion University, Norfolk, VA. 



Hockeday, D. Pan American University, Edinburg, TX. 



Hunt, John H. Florida Div. Marine Resources, Mara- 

 thon, FL. 



Jury, Steven H. NOAA SEA Division, Silver Spring, 

 MD. 



92 



