BARSHAW and BRYANT-RICH: EARLY JUVENILE AMERICAN LOBSTER 



lobsters in eelgrass were not smaller perhaps also 

 because the eelgrass substrate ameliorated the 

 effects of higher density. We did not observe any 

 differences in the activity budgets of the lobsters 

 owing to higher density (Fig. 1). 



This study shows that early juvenile American 

 lobsters differ dramatically in their behavior from 

 older lobsters. They seldom, if ever, forage for food 

 outside of their burrows, but instead remain inside 

 of them. This was true even though there were no 

 predators present other than other juveniles. 



The lobsters' main activities within their bur- 

 rows reflected their needs. Because they did not for- 

 age outside of their burrows, all of the early juve- 

 niles' nourishment must have been found inside 

 of their burrow, or within reach of the entrance. 

 Lobsters could forage on polycheates, meiofauna, 

 and on any other organisms residing inside their bur- 

 rows or draw plankton in by pleopod-fanning. In this 

 study lobsters were seen to catch swimming am- 

 phipods at the entrance to their burrow, and Ber- 

 rill (1974) observed similar behavior. Besides rest- 

 ing, the lobsters mainly "investigated" for anything 

 edible in the entrance of their burrow and pleopod- 

 fanned to draw in plankton. If they were forced to 

 burrow in a relatively unstable substrate, such as 

 mud, they spent a significant amount of time main- 

 taining that burrow. 



The claws of early juvenile American lobsters are 

 smaller and weigh less relative to the abdomen than 

 those of older lobsters, and, by external appearance 

 the two claws are not differentiated from each other. 

 Furthermore, the speed of the tail flip reflex is faster 

 at sizes smaller than 20 mm carapace length (Lang 

 et al. 1977). These morphological characteristics 

 along with the behavioral results from this study, 

 and field observations that juveniles become easier 

 to find at a carapace length of 20-40 mm (Cooper 

 and Uzmann 1980; Able et al. in press), indicate that 

 the juvenile stage of the American lobster can ac- 

 tually be divided into two substages: 1) the early 

 juvenile stage, spanning settlement to the time un- 

 til claws begin to differentiate, during which period 

 the lobsters seldom, if ever, leave their burrow; and 

 2) the late juvenile stage, starting when the claws 

 are differentiated and become larger in relation to 

 the abdomen and ending with sexual maturity. At 

 this stage, the lobsters start to forage for food 

 outside of their burrows, and behave more similar- 

 ly to adults (Cooper and Uzmann 1980; Able et al. 

 1988). 



We suggest the following scenario for the life 

 history of early juvenile American lobsters. After 



settling onto a suitable substrate the lobsters build 

 a burrow where they remain for the duration of the 

 "early juvenile" substage. By catching food, both 

 in the substrate around their burrow entrance and 

 by drawing plankton into their burrow by pleopod- 

 fanning, the early juvenile lobsters manage to sur- 

 vive without foraging outside their burrow. 



ACKNOWLEDGMENTS 



We thank Diane Cowan and Ruth lannazzi for help 

 with observations and maintenance of the system. 

 We also thank Mike Eagles then of the St. Andrews 

 Marine Biological Field Station, New Brunswick, 

 Canada for supplying us with stage IV American 

 lobsters. We also thank Kenneth W. Able for review- 

 ing the manuscript and Judith Capuzzo and Stanley 

 Cobb for reviewing an earlier draft. This research 

 was supported in part by a National Wildlife Feder- 

 ation - American Petroleum Institute, Environmen- 

 tal Conservation Fellowship to Diana Barshaw. 



LITERATURE CITED 



Able. W. K., K. L. Heck, Jr., M. P. Fahay, and C. T. Roman. 

 1988. Habitat utilization of juvenile lobsters in a Cape Cod 

 estuary: evidence for the importance of salt marshes. Estu- 

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 Atema, J., D. F. Leavitt, D. E. Barshaw, and M. C. Cuomo. 

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In press. Growth and survival of early juvenile lobsters, 

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Botero, L., and J. Atema. 



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Cobb, J. S. 



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Cobb, J. S., and G. R. Tamm. 



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