BARSHAW and BRYANT-RICH: EARLY JUVENILE AMERICAN LOBSTER 



Table 1 .—Description of the different activities observed through- 

 out the experiment. 



Activity 



Description 



Rest No movement for at least 30 seconds. Groom- 



ing was not considered movement, and was not 

 recorded separately from rest. 



Pleopod fan Movement of the pleopods; if the fanning was 



(PPF) being used to repair the burrows, i.e., sediment 



was being moved, then the activity was recorded 

 as burrow repair. 



Burrow repair Any activity which caused sediment to be 



(BR) moved, including bulldozing (pushing sediment 



toward with the claws spread apart), pleopod 



fanning, and digging (loosening sediment by 



pushing claws into it). 



Investigate Standing at the entrance of the burrow with 



(INVEST) antennules out and antennae flicking. 



Feed Eating anything larger than 1 mm. Activity that 



looked like filter feeding was not included in this 

 category (it was part of the pleopod fan). It is 

 discussed in the text. 



Walk Walking on the sediment. Does not include 



"walking" in the burrow. 



Swim Swimming in the water column. 



RESULTS 



Burrowing 



The American lobsters in the eelgrass and rock 

 substrates started burrow construction more quickly 

 than the ones in the mud substrate (1 way ANOVA, 

 Newman-Keuls test, P < 0.05). There was no sig- 

 nificant difference in the time to initial burrowing 

 between lobsters in eelgrass and lobsters in rock 

 substrates (Table 2A). 



American lobsters used the same methods to make 

 burrows in eelgrass as in mud and rocks. They 

 typically started at the base of an eelgrass plant and 

 then established a burrow under the rhizomes by 

 pleopod fanning and bulldozing. The burrows usually 



had two openings although burrows were seen with 

 from one to six openings. These openings were 

 smaller and more difficult to see than similar open- 

 ings in mud or rock substrates. Although lobsters 

 in all substrates had burrows for the majority of the 

 observations, because their burrow had collapsed, 

 the lobsters in the mud substrate were without a 

 burrow for a greater percent of the observations 

 than the lobsters in the eelgrass or rock substrates 

 (arcsine transformation, 1 way ANOVA, Newman- 

 Keuls test, P < 0.05, Table 2B). For this analysis 

 the lobster had to be visible; if neither the lobster 

 nor its burrow were visible during a given observa- 

 tion period, that observation was excluded from the 

 analysis. 



Activity 



American lobsters were not seen to forage out- 

 side of their burrows. If a lobster had a burrow, it 

 was never seen outside of that burrow in any of the 

 treatments during the entire experiment. During 

 the day periods, these lobsters were seen in their 

 burrows 1,503 times, and outside of their burrows 

 times. Therefore, by using sampling theory, one 

 can calculate that the lobsters were spending at least 

 99.8% of their time during light periods in their bur- 

 rows (binomial distribution, P = 0.05). During the 

 night periods lobsters were seen in their burrows 

 103 times, outside of their burrows times. There- 

 fore, the lobsters were spending at least 97.0% of 

 the time in their burrows during the dark (binomial 

 distribution, P = 0.05). The difference between the 

 night and day percentages is a function only of the 

 greater number of observations made during the 

 day. 



The cumulative times that the American lobsters 

 spent at various activities were influenced by sub- 



Table 2. — (A) The average time in minutes that it took each lobster in the 

 eelgrass, rock, and mud treatments to start construction of their burrow 

 (eelgrass vs. mud and rocks vs. mud, P < 0.05). (B) The percent of observa- 

 tions throughout the experiment during which the lobsters in each substrate 

 did not have a burrow. N varied from 160 to 68, depending on how many 

 lobsters were visible (eelgrass vs. mud and rocks vs. mud, P < 0.05). (C) 

 The average weight, in grams, and the carapace length (CL), in mm, of the 

 lobsters in each treatment at the end of the experiment. 



791 



