tion, but may be influenced by temperature gradients 

 to produce what may seem to be substantial seasonal 

 movements of the population as a whole. 



There is no reason to believe that separate subpopu- 

 lations inhabit these three areas. Any lobster appar- 

 ently adopts the appropriate behavior patterns to the 

 environment in which it finds itself. 



C. Food. 



The important foods of lobsters are not well known. 

 Lobsters are known to be scavengers, and will eat 

 almost any dead flesh available. This characteristic is 

 exploited by the fisherman who baits his trap with 

 dead fish. Some biologists believe that the lobster may 

 supplement such food with microscopic plants combed 

 from the back or collected on the gills, and with sea- 

 weed growing on rocks. Lobsters dig, shuck, and eat 

 soft shell clams and other shellfish. Bait and other 

 lobsters in traps also contribute considerably to the 

 food requirements of lobsters in intensively fished 

 areas. Underwater observations have been made of 

 lobsters retrieving bait from traps. It is estimated that 

 approximately 18,000 to 22,000 metric tons of bait are 

 used in Maine annually. Regardless of the major 

 source of nutrition, the lobster is apparently able to 

 exist for long periods without food. The metabolic rate 

 is slow, and infrequent feeding is the rule. Death from 

 lack of food is unusual except at moult. Shedding the 

 shell is an exhausting process; a weak lobster often 

 dies in the act. 



Living on the ocean bottom, among and under rocks 

 and in burrows, and seeking shelter of rockweeds, 

 kelps, and other marine algae, the lobster is a rela- 

 tively sedentary animal, foraging at night but generally 

 quiescent during daylight. Observations under natural, 

 seminatural, and laboratory conditions indicate that 

 lobsters eat both living and dead fish, moUusks, other 

 marine invertebrates, and small quantities of marine 

 plants. 



D. Migration. 



The lobster in the northern part of its range is a 

 sedentary animal and therefore nonmigratory wher- 

 ever rocky bottom or ledge outcrop provides shelter 

 and where food is available.^ At times, because of lack 

 of shelter, shortage of food, or for unknown reasons, 

 lobsters will be found over considerable areas of 

 smooth mud or sand bottom. Unlike lobsters in a 

 rocky environment, these animals seem to be con- 

 stantly moving. The movements are random, but some 

 tagged individuals may wander many miles from the 

 point of release. Lobsters tagged and released within 

 the limits of restricted hydrographic features are fre- 

 quently and repeatedly recaptured. Random and er- 

 ratic movement of the straggler may reflect inability of 



^Anonymous, 1957; Harriman, 1957; WUder, 1957. 



the captured, tagged, and released lobster to find its 

 burrow after inadvertent displacement. The numbers 

 of such stragglers may also reflect population pres- 

 sures on the available cover. 



The movement of stragglers when it has occurred 

 appears to be coastwise and not inshore or offshore. 

 To what extent this movement has been assisted by 

 man or the counterclockwise, nontidal drift in the Gulf 

 of Maine is not known. When these wanderers find 

 shelter, they burrow in and revert to the more charac- 

 teristic pattern of extended periods of inactivity punc- 

 tuated by foraging expeditions for food. 



In Maine the popularly held belief that extensive 

 inshore-offshore seasonal migrations occur appears to 

 be related to the degree of activity associated with 

 changes in seawater temperature. In the late fall and 

 early winter as air temperature declines, the shallow 

 inshore waters cool first. As these waters cool, lob- 

 sters inhabiting them become less active and ulti- 

 mately cease to forage. Deeper water, farther from 

 shore, is still warming so that lobsters living there con- 

 tinue in activity and are trapable. 



As deeper and more seaward water becomes cooler, 

 lobsters become progressively less active. During the 

 coldest part of the winter lobsters are active only in the 

 deepest and warmest water, which is generally the 

 farthest from shore. In the spring and summer the 

 cycle is reversed, with deep water at its minimum 

 temperature, and creates the false impression that lob- 

 sters are migrating shoreward. 



E. Life History. 



(1) Egg and Larval Stages. — Shortly after moulting, 

 while the new shell is soft, the mature female is in- 

 seminated by a hard-shelled male. Following approx- 

 imately a year, the eggs are extruded from the ovaries 

 and fertilized by the sperm which has been retained in 

 the seminal receptacle. The fertilized eggs are at- 

 tached in an adhesive mass to the swimmerets under 

 the tail (Fig. 2). The number of eggs produced varies 

 geometrically with the size of the female; a range from 

 approximately 6,000 to 40,000 eggs has been reported 

 from measurements at Boothbay Harbor for lobsters 

 with a carapace length range from 82.5 to 127 mm 

 (Taylor, 1950). During the warm months of the follow- 

 ing year the eggs complete incubation and hatch. 



The length of the free-swimming larval period varies 

 largely with seawater temperature from a minimum 2 

 weeks at 20° to 21 °C to a theoretical maximum of ap- 

 proximately 2 mo with low temperatures. 



(2) Moulting. — At periodic intervals throughout life, 

 varying with the rate of growth and commencing at the 

 end of the first larval stage, the lobster moults. The 

 interval of moulting varies with size, occurring several 

 times each year in 1 and 2 yr old juveniles, and 

 averaging approximately once each year among ma- 

 ture males and immature females of legal size. Maine 



