A LONG-TERM STUDY ON THE BEHAVIOR AND SURVIVAL OF 



EARLY JUVENILE AMERICAN LOBSTER, HOMARUS AMERICANUS, IN 



THREE NATURALISTIC SUBSTRATES: EELGRASS, MUD, AND ROCKS 



Diana E. Barshawi and Donald R. Bryant-Rich^ 



ABSTRACT 



An 8-month study on the behavior, growth, and survival of early juvenile American lobsters, HoTnarus 

 americanus, was conducted in three different naturalistic habitats of mud, rocks with algae, and eelgrass. 

 Fifteen narrow aquaria (10 cm wide) allowed visual observations of American lobster's activities in five 

 replicates of each of the three habitats. After a 3-month acclimation period to establish "natural" ben- 

 thic communities which entered through the water supply, three stage IV American lobsters were intro- 

 duced into each aquarium. Observations were made on the settling, burrowing, activity, and feeding 

 behavior of these lobsters. 



American lobsters in eelgrass and rock habitats settled into the substrate more quickly, had burrows 

 a greater percent of the time, and spent less time repairing their burrows than lobsters in mud habitats. 

 The lobsters in eelgrass had a lower mortality rate than lobsters in either rocks or mud. None of the 

 lobsters in any substrate were observed foraging for food outside of their burrows. However, the behavior 

 of these American lobsters indicated that they were able to capture plankton drawn into their burrows 

 by pleopod fanning. Six lobsters molted during the coldest part of the year when the water temperature 

 was approximately 1° to 2°C. 



Stage IV of the American lobster, Homarus ameri- 

 canus, is best described as transitional between 

 larval and juvenile (Phillips et al. 1980). During this 

 stage major behavioral changes take place, which 

 coincide with the morphological changes occurring 

 in the molt. These behavioral and morphological 

 changes cause the stage IV lobsters to descend from 

 the upper layers of the water column to the bottom 

 where they build a burrow (Botero and Atema 1982; 

 Ennis 1975). 



Knowledge of the American lobster's behavior 

 from the onset of settlement until they reach a size 

 of approximately 20 mm in carapace length (CL) 

 remains Hmited because juveniles of this size 

 range have been found in the field only sporadi- 

 cally. 



Several laboratory experiments sought to deter- 

 mine the substrate preferences of stage IV Ameri- 

 can lobsters. Howard and Bennett (1979) found that 

 lobsters [H. gammarus) generally choose the largest 

 size of gravel provided (approximately 20 mm in 

 diameter), because larger rocks have more available 



'Boston University Marine Program, Marine Biological Labora- 

 tory, Woods Hole, MA 02543; present address: Marine Field Sta- 

 tion, Rutgers University, Great Bay Blvd., Tuckerton, NJ 08087. 



^Boston University Marine Program, Marine Biological Labora- 

 tory, Woods Hole, MA 02543. 



space between them for burrows. If given a choice 

 between a gravel substrate or a silt/clay substrate, 

 American lobsters prefer the gravel (Pottle and 

 Elner 1982). In choice tests, stage IV American 

 lobsters preferred rocks with macroalgae, followed 

 by, in order of decreasing preference, mud, rocks 

 on sand, and sand. If not afforded a choice, the 

 lobsters settled most quickly on the rocks with 

 macroalgae, followed by rocks on sand, mud, and 

 sand (Botero and Atema 1982). 



MacKay (1926) recorded observations on the 

 lobsters' ability to burrow in mud. Subsequently 

 Cobb (1971), Berrill and Stewart (1973), and Botero 

 and Atema (1982) have described the methods 

 by which juvenile American lobsters make burrows 

 in both mud and rocky substrates. No observa- 

 tions have been made on American lobsters burrow- 

 ing into other substrates, such as eelgrass or 

 peat. 



Cobb et al. (1983) followed stage IV H. ameri- 

 canus for short periods of time following their re- 

 lease into the field. They observed behavior which 

 may indicate that American lobsters test different 

 substrates and continue moving if they are on un- 

 satisfactory substrates such as sand or mud; how- 

 ever, only two lobsters were actually seen reject- 

 ing a substrate. 



Manuscript accepted July 1988. 



FISHERY BULLETIN: VOL. 86, NO. 4, 1988. 



789 



