NATURAL HISTORY OF THE LOBSTER.
Although the lobster has been of great value to the New England States and the British Provinces as a food commodity, but little was known of its life-history and habits until within the last few years. To this ignorance has been due quite largely peculiar (and in some instances useless) laws enacted by some States. The gradual enlightenment of the public on this subject has borne good fruit, however, and most of the present State laws are founded on substantial facts instead of theories. Prof. Francis H. Herrick has been one of the most prominent of the investigators, and his summary of the present knowledge on this subject is quoted below from the Fish Commission Bulletin for 1897:
(1) The fishery is declining, and this decline is due to the persistence with which it has been conducted during the last twenty-five years. There is no evidence that the animal is being driven to the wall by any new or unusual disturbance of the forces of nature.
(2) The lobster is migratory only to the extent of moving to and from the shore, and is, therefore, practically a sedentary animal. Its movements are governed chiefly by the abundance of food and the temperature of the water.
(3) The female may be impregnated or provided with a supply of sperm for future use by the male at any time, and the sperm, which is deposited in an external pouch or sperm receptacle, has remarkable vitality. Copulation occurs commonly in spring, and the eggs are fertilized outside the body.
(4) Female lobsters become sexually mature when from 8 to 12 inches long. The majority of all lobsters 10½ inches long are mature. It is rare to find a female less than 8 inches long which has spawned or one over 12 inches in length which has never borne eggs.
(5) The spawning interval is a biennial one, two years elapsing between each period of egg-laying.
(6) The spawning period for the majority of lobsters is July and August. A few lay eggs at other seasons of the year—in the fall, winter, and probably in the spring.
(7) The period of spawning lasts about six weeks, and fluctuates slightly from year to year. The individual variation in the time of extrusion of ova is explained by the long period during which the eggs attain the limits of growth. Anything which affects the vital condition of the female during this period of two years may affect the time of spawning.
(8) The spawning period in the middle and eastern districts of Maine is two weeks later than in Vineyard Sound, Massachusetts. In 1893 71 per cent of eggs examined from the coast of Maine were extruded in the first half of August.
(9) The number of eggs laid varies with the size of the animal. The law of production may be arithmetically expressed as follows: The number of eggs produced at each reproductive period varies in a geometrical series, while the length of lobsters producing these eggs varies in an arithmetical series. According to this law an 8-inch lobster produces 5,000 eggs, a lobster 10 inches long 10,000, a 12-inch lobster 20,000. This high rate of production is not maintained beyond the length of 14 to 16 inches. The largest number of eggs recorded for a female is 97,440. A lobster 10½ inches long produces, on the average, nearly 13,000 eggs.
(10) The period of incubation of summer eggs at Woods Hole is about ten months, July 15-August 15 to May 15-June 15. The hatching of a single brood lasts about a week, owing to the slightly unequal rate of development of individual eggs.
(11) The hatching period varies also with the time of egg-laying, lobsters having rarely been known to hatch in November and February.
(12) Taking all things into consideration, the sexes appear about equally divided, though the relative numbers caught in certain places at certain times of the year may be remarkably variable.
(13) Molting commonly occurs from June to September, but there is no month of the year in which soft lobsters may not be caught.
(14) The male probably molts oftener than the female.
(15) In the adult female the molting like the spawning period is a biennial one, but the two periods are one year apart. As a rule, the female lays her eggs in July, carries them until the following summer, when they hatch; then she molts. Possibly a second molt may occur in the fall, winter, or spring, but it is not probable, and molting just before the production of new eggs is rare.
(16) The egg-bearing female, with eggs removed, weighs less than the female of the same length without eggs.
(17) The new shell becomes thoroughly hard in the course of from six to eight weeks, the length of time requisite for this varying with the food and other conditions of the animal.
(18) The young, after hatching, cut loose from their mother, rise to the surface of the ocean, and, lead a free life as pelagic larvae. The first larva is about one-third of an inch long (7.84 mm). The swimming period lasts from six to eight weeks, or until the lobster has molted five or at most six times, and is three-fifths of an inch long, when it sinks to the bottom. It now travels toward the shore, and, if fortunate, establishes itself in the rock piles of inlets of harbors, where it remains until driven out by ice in the fall or early winter. The smallest, now from 1 to 3 inches long, go down among the loose stones which are often exposed at low tides. At a later period, when 3 to 4 inches long, they come out of their retreats and explore the bottom, occasionally hiding or burrowing under stones. Young lobsters have also been found in eelgrass and on sandy bottoms in shallow water.
(19) The food of the larva consists of minute pelagic organisms. The food of the older and adult stages is largely of animal origin with but slight addition of vegetable material, consisting chiefly of fish and invertebrates of various kinds. The large and strong also prey upon the small and weak.
(20) The increase in length at each molt is about 15.3 per cent. During the first year the lobster molts from 14 to 17 times. At 10½ inches the lobster has molted 25 to 26 times and is about 5 years old.
As the purpose of this article is to deal more particularly with the commercial side of the lobster question all interested more particularly in the natural history of the animal are referred to the following works:
The Fisheries and Fishery Industries of the United States, sec. I, pp. 780-812.
The American Lobster, by Francis H. Herrick. Bull. U. S. Fish Com. for 1895, pp. 1-252.