FISHERY BULLETIN: VOL. 86. NO. 4 



None of the previous studies lasted for more than 

 a few days, and long-term behavioral observations 

 have never been recorded on early juvenile Ameri- 

 can lobsters. There are virtually no field data on sim- 

 ple life history parameters such as their preferred 

 substrate, growth rate, diet, and behavior. It is 

 unwise to proceed with experimental laboratory 

 studies on an organism without having a descrip- 

 tive life history background to provide context. Both 

 Cobb (1987) and Fogarty (1987) recognized the need 

 for more studies on the behavior and ecology of the 

 postsettled prerecruits used in this study. At pres- 

 ent it is difficult to gather such information in the 

 field. However, this study was designed in order to 

 provide such a background by carefully creating 

 naturalistic habitats in the laboratory. We present 

 quantified behavioral observations, survival, and 

 growth of early juvenile American lobsters in three 

 different substrates: mud, rocks, and eelgrass, over 

 an 8-mo period. 



MATERIALS AND METHODS 



Fifteen "ant farm" aquaria (45 cm deep x 30 cm 

 long X 10 cm wide) were constructed to optimize 

 our ability to observe the American lobsters inside 

 their burrows. Five of the aquaria were two-thirds 

 filled with cohesive mud (particle size <0.06 mm) 

 collected from mud flats in the Woods Hole, MA 

 area. Five of the aquaria were two-thirds filled with 

 rocks, collected from subtidal areas in such a way 

 that a representative distribution of rock sizes 

 was obtained (0.1-20 mm diameter). Some of the 

 rocks in each tank had macroalgae Coleus (sp.) 

 and Fucus (sp.), or both growing on them. Eelgrass 

 collected from local eelgrass beds was placed in the 

 last five aquaria; less substrate was used in these 

 latter tanks so that the eelgrass leaves had room 

 to grow. 



The aquaria were randomly distributed in a sys- 

 tem which provided running, unfiltered seawater at 

 ambient temperatures seasonally ranging from 

 23° to 0°C. Plankton were always visible; also the 

 three habitats occasionally had plankton blooms, 

 during which algae and zooplankton were plentiful. 

 The tanks were maintained on an ambient light/dark 

 regime with a light intense enough to keep the 

 eelgrass alive. Removable, opaque, black plastic was 

 placed around each aquarium to the level of the 

 substrate to ensure that the lobster burrows were 

 dark. To establish "natural" benthic communities, 

 the tanks acclimated from 20 July until 16 October 

 1982, before beginning the experiment. 



Stage IV American lobster siblings from the 

 hatchery at St. Andrews, New Brunswick, Canada 

 were introduced, one per day into each aquarium 

 for 3 consecutive days. Thus, the total number of 

 lobsters at the start of the experiment was 45, 15 

 per treatment. Observations were recorded continu- 

 ously for the first half hour after each introduction 

 and then for the following 1.5 hours; observations 

 were recorded by scanning (taking an instantanious 

 reading of the lobsters' behavior) every 10 minutes. 

 Observations were made of the following: 1) loca- 

 tion of the animal in the aquarium, 2) motion (walk- 

 ing, swimming, or resting), 3) burrowing activity 

 (pleopod fanning, bulldozing, or digging), and 4) 

 shape, size, and location of final burrow. This pro- 

 cedure was similar to that used in the substrate 

 choice tests done by Atema et al. (1982). 



During the first introduction of American lobsters 

 into several of the tanks, mud crabs, Neopanope 

 sayi, immediately consumed them. The mud crabs 

 were subsequently removed and new American lobs- 

 ters were placed into these tanks. 



After the American lobsters had been introduced 

 into each of the 15 tanks, long-term observations 

 began of each lobster in each tank at intervals rang- 

 ing from daily to twice per week. The observation 

 periods were at different times during the day with 

 5.1% during the dark period, although it was dif- 

 ficult to see the lobsters in low light because of the 

 cryptic nature of some burrows. There was a total 

 of 195 observations periods. Each lobster that was 

 visible was watched for at least one minute; if the 

 lobster was active, observations lasted until the ac- 

 tivity ended. However, for the quantitative analysis 

 of lobster activity only the first minute of observa- 

 tions were used. A total of 495 hours of observa- 

 tions were made averaging 11 hours per individual 

 lobster. For each lobster we recorded 1) the loca- 

 tion of the lobster in relation to its burrow, 2) 

 whether the lobster had molted, 3) the lobster's ac- 

 tivity, and 4) the shape of the burrow (with a quick 

 sketch). The activities observed are described in 

 Table 1. 



The experiment lasted approximately eight 

 months, from 21 October 1983 to 1 July 1984. The 

 lobsters were not fed during that time; we assumed 

 they would find food from the communities in which 

 they lived. At the end of the experiment, the sur- 

 viving lobsters were weighed and their carapace 

 length was measured. Additionally, the sediment in 

 each tank was sieved through a 1 mm screen, and 

 all organisms were collected, weighed, and identified 

 to the genus or species level. 



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