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BULLETIN OF THE UNITED STATES FISH COMMISSION 1886 Vol. VI, No. 2. Washington, DC Feb. 8, 1886. Notes on Lobster Culture Part 3 ........ Back to Part 1
Most of the British maritime provinces abound in lobsters which are especially plentiful on both the ocean and gulf coasts of New Brunswick and Nova Scotia, these two countries now affording the most extensive lobster fishery in the world. They appear to be much less common in Newfoundland and Labrador, possibly because they have been less fished for there. Lobsters are not known to migrate, excepting over very short distances, mainly in the spring and fall, when they change their grounds, moving into deeper water on the approach of cold weather, and returning nearer to the shore in the late spring. The fall migrations are solely for the purpose of escaping the cold of winter, the shallower summer grounds probably furnishing a better supply of food. The extent of the movements depends more or less upon the character of the coast, for where the bottom slopes off very gradually they will need to go a much greater distance to reach a suitable depth of water than where deep holes occur near their summer grounds. The summer fishery is mainly in depths of a very few to 15 or 20 fathoms, the winter fishery in 25 to 60 fathoms. On the coast of Maine the traps are sometimes set in such shallow water that they lie partly exposed at low tide. Formerly some fishing was done along the shores by means of gaffs and dip-nets, but lobsters rarely occur in such favorable localities now. It is supposed that lobsters do not travel much along the coast, though they probably change their grounds from time to time in search of food. On some portions of the coast the fishermen claim to have good evidence of the schooling of lobsters, and state that the schools appear and disappear suddenly, indicating the possession of certain migratory habits, but there is no proof that their migrations extend far, and they are very different in character from those of the true fishes. We have no evidence to prove that any one region has been directly benefited by large accessions from an adjoining region, and the extent to which some districts have been depleted by overfishing without subsequent recovery indicates that the supplies of one region are but little dependent upon those of another, at least not for immediate relief. The Cape Cod lobster fishery has been at a low standing for many years, and although but few men have engaged in the fishery of that region for a long time, there are, as yet, no signs of improvement. SPAWNING SEASON AND HABITS, DEVELOPMENT AND RATE OF GROWTH. Lobsters are found with spawn attached to the abdomen during the entire year. This fact is recorded of both the American and the European species, but the length of time they are carried before hatching and the limits of the hatching season are not precisely known. As regards the European crayfish, a freshwater crustacean closely related to the lobster, Professor Huxley states: "The process of development is very slow, as it occupies the whole winter. In late springtime or early summer, the young burst the thin shell of the egg, and, when they are hatched, present a general resemblance to their parents. This is very unlike what takes place in crabs and lobsters, in which the young -------------------------------------------------------------------------------------- Page 28 BULLETIN OF THE UNITED STATES FISH COMMISSION. leave the egg in a condition very different from the parent, and undergo a remarkable metamorphosis before they attain their proper form." The smackmen of the southern New England coast claim that the eggs hatch in the wells of their smacks in the greatest abundance, from some time in May until late in July, but that at other seasons they have never seen any embryo lobsters; although the smack trade in lobsters is kept up during nearly the entire year. During the season mentioned, the surface of the water in the wells of the smacks often becomes per- fectly alive with the young, and they may be scooped up by the hundreds of thousands. This evidence is tolerably conclusive as to the duration of the principal hatching season, and determines the period when experimental work in artificial propagation can best be under taken. The fact that a few of the eggs contained in the jars at the Wood's Holl station of the Fish Commission hatched during November of this year indicates, however, that some hatching may take place at other seasons, as the conditions under which the eggs were kept were perfectly normal, the water being of about the same temperature as that of the harbor outside. Hatching is supposed to begin somewhat later farther north. The writer was, at first, inclined to believe that the hatching continued to a considerable extent through the entire year, basing his conclusions upon the fact that, during the months of August and September last, eggs were found in various stages of development, from the freshly laid and totally opaque ones to others in which the dark greenish yolk sack occupied scarcely more than one-half of the area of the egg, the remainder being transparent and clearly showing the structure of the embryo. Some of these eggs, preserved in the hatching jars, were carefully examined from day to day, and, although they exhibited a certain amount of progress, development was slow. It finally became evident that the development of the eggs was being retarded by some cause, presumably the lower temperature of the water, and this result, coupled with the statements of the fishermen, that embryos are seen only in May, June, and July, makes it probable that the hatching of lobster eggs at other seasons is only an accidental or occasional occurrence. It is also not at all improbable that the young hatched during cold weather perish soon after they leave the egg, as they did at Wood's Holl in November last. The hardy character of the lobster eggs, before referred to, favors the idea of a long period of development, and they appear to be well adapted to endure the hardships of a long winter. The rough handling to which they were sometimes subjected, in connection with the experiments of last summer, did not seem to harm them in the least. It is also probable, from this quality of the eggs, that they are not destroyed to any extent in nature, unless actually eaten from the swimmerets of the parent by predaceous fishes, and that the chief assistance which artificial culture can give, in an attempt to increase the supply, must be directed toward protecting the embryos from the period of hatching. ---------------------------------------------------------------------------------- BULLETIN OF THE UNITED STATES FISH COMMISSION. Page 29 Embryo lobsters are seldom seen at the surface in the open waters about our coast and have rarely been taken in the towing net. Prof. S. I. Smith, who has studied the younger stages, obtained his specimens during July; mainly in Vineyard Sound, near Wood's Holl, Mass. Nothing positive is known respecting the habits of lobsters during the spawning season. It has been stated with reference to lobsters marketed in Boston, that berried lobsters are seldom seen measuring less than about 10 and one half inches in length, and it is probable that they rarely begin to spawn before attaining that size. However, a few smaller ones were observed at Wood's Holl during the summer of 1885. In a lot of fifty-two berried lobsters, examined at that place in September, three measured loss than 10 inches, the smallest having been 9 one half inches long; eight were between 10 and 10 and one half inches; ten between 10 and 11 inches; fifteen between 11 and 12 inches; eleven between 12 and 13 inches, and five between 13 and 14 inches. The measurements were made from the tip of the rostrum to the end of the telson, not including the hairs. The development of the younger stages of lobsters has been studied by Prof. S. I. Smith, for the American species, and by Prof. G. O. Sars, for the European. The eggs, when first emitted, are entirely opaque and of a dark green color, sometimes almost black. Professor Smith examined the well advanced eggs at Wood's Holl, in May. They were not perfectly round, measuring a trifle more than two millimeters (about one-twelfth of an inch) in their longest diameter. One side was still dark, due to the unabsorbed yolk mass, and the other more or less transparent, showing the eyes as two large black spots, and the outlines of the carapag and legs. All of these features are readily made out under a low-power objective. Soon after hatching they measure about one third of an inch in length, and resemble in appearance and structure a low group of shrimps, called the Schizopods, which are common on some portions of our coast. The eyes are bright blue, while portions of the body and its appendages are marked with orange of different intensities, rendering them very conspicuous objects. The swimmerets are not yet developed. In the second stage, which resembles the first, they have increased somewhat in size, and have obtained the rudiments of a portion of the swimmerets. In the third stage they measure about half an inch loug, and the shell has become firmer than before. In the next and last stage observed, the embryo is about three-fifths of an inch long; it has lost all of the characters in which it resembles the Schizopods, and has assumed the more important features of the adult. It still retains the free-swimming habit and is very active in its movements, frequently jumping out of the water by means of its caudal appendages. This stage was frequently taken from the 8th to the 20th of July, and Professor Smith thinks that the larva passes through all of these stages in the course of a single season. The stages immediately following the above were not observed. ------------------------------------------------------------------------------------------- Page 30 BULLETIN OF THE UNITED STATES FISH COMMISSION. The young, like the adult lobster and the crabs, increase in size by molting, or casting off the shell covering the body, a new shell rapidly forming in place of the old one. During the first season, as above described, the molts are frequent, and the embryos remain at the surface of the water as free swimmers, but how long the young, after reaching the lobster-like form, retain this free-swimming habit was not ascertained. As the lobsters increase in size, it is evident that molting occurs less frequently, and in the adults probably only once a year. . The rate of growth of lobsters has not been determined, and at present we have no means of telling the age of a lobster measuring 10 inches in length. A few measurements have been made showing the amount of increase at certain molts, but it is not always constant, even for lobsters of the same size, and not knowing the frequency of molting or shedding, we have no way of computing the rate of increase. One lobster measuring 8 inches before shedding was said to measure 10 Inches after shedding; another, 10 inches before and 12 inches after shedding; a third, 10 and one half inches before and 11 three forths inches after shedding; a fourth, 10 and one half inches before and 12 inches after shedding. Ten-inch lobsters are probably at least five or six years old, but such estimates are only the result of guesswork, and may be very far out of the way. EXPERIMENTS PREVIOUSLY MADE IN LOBSTER CULTURE. In the United States the only practical attempts that have yet been made toward the artificial propagation of lobsters have been in connec- tion with the so-called "parking" of lobsters-that is to say, their pro-' tection in large inclosed natural basins, primarily for the purpose of perfecting them for market, and of retaining conveniently at hand at all seasons a large reserve stock. In these parks the young lobsters taken by the fishermen are allowed to attain the adult size, the soft- shelled individuals to become hardened, and injuries to be repaired. Under such natural conditions, it is reasonable to suppose that the breeding habits would continue normal, and that large quantities of spawn would be hatched; but whether the young would survive and increase in sufficient numbers to render the scheme profitable, if carried on for this purpose alone, has not been determined, though none of the projects had been continued long enough to give satisfactory results, at last accounts. Two such parks in the United States have been specially called to our attention. The first was established on the coast of Massachusetts in 1872, and was afterwards abandoned, though for what reasons we do not know. The second was started in 1879 or 1880, on the coast of Maine, and is, we believe, still in operation. The latter is a small inclosed bay, with a narrow entrance, through which the passage of all objects above a very small size is prevented by a screen of wire netting. This bay had previously furnished good lobster fishing, and was much resorted to by fishermen. It contains an ------------------------------------------------------------------------------------------- BULLETIN OF THE UNITED STATES FISH COMMISSION. Page 31 abundance of food suitable for lobsters, and toward the center has a sffiucient depth of water, with soft bottom, to afford some protection to the lobsters during the colder part of the year. Into this park large quantities of soft-shelled lobsters, of lobsters minus one or both claws, as well as of young individuals under the legal size of 10 or 10 and one half inches, have been placed for growth and repair, and it is claimed that the results have been very satisfactory in that particular. At the beginning of cold weather the lobsters retire to the deeper parts of the bay, and at times, when the water has been calm and clear, they have been observed almost completely buried in the mud, with only their feelers, eyes, and a small portion of the front of the carapax exposed. Many of the injured lobsters first placed in the park were females with spawn, and since then berried lobsters have been purposely added from time to time. Young individuals of different sizes were said to have been abundant at last accounts, but in an experiment of this character a cunsiderable lapse of time is required to test its merits. As such parks do not depend for their practical success solely upon the rearing of the young, but rather upon the perfecting of market supplies, which come from the traps in poor condition, it is possible that they may be made to pay if carried on economically. Their effect upon a general increase of supplies would probably never be very great. So far as we are aware, experiments upon the propagation of lobsters in Europe have been confined mainly to Norway, and were commenced there in 1873. The first report upon this subject was published in 1875. The berried lobsters were kept in boxes, constructed so as to retain the embryos after hatching. The young remained alive for several weeks, and their habits and the causes of their destruction were carefully studied. The results of these experiments will be of great service in the treatment of the young at the Wood's Holl Station next summer. Mr. Dannevig's more recent investigations in the same line have been noticed above. TRANSPLANTING OF LOBSTERS. Of great interest in connection with the artificial propagation of lobsters, and bearing upon the same subject, is the question as to whether lobsters can be successfully transplanted from one region to another. This experiment has already been tried two or three times, but so far without success. The transportation of live lobsters long distances, even by railroads, has been accomplished, and they have also been carried from this country to England. Mr. Livingston Stone made three attempts to introduce the East Coast lobster on the coast of California, and on the last trial succeeded in planting a number of living individuals near the mouth of San Francisco Bay. As full accounts of these experiments have already been published by the Fish Commission,* we do not need to repeat them here. *Report U. S. Com. of Fish and Fisheries, Part III, pp. 259-265,1873-175 (1876); Part VII, pp. 637-644,1879 (1882). ------------------------------------------------------------------------------------------- Page 32 BULLETIN OF UNITED STATES FISH COMMISSION. The successful transplanting of lobsters must depend upon the new region affording conditions sufficiently like those of the old to favor the growth and reproduction of the species; but the relative conditions of different regions have never been carefully studied with this object in view, and we are to-day unable to state precisely in what mauner the Pacific coast waters agree with, or differ from, those of the Atlantic coast. Neither the temperatures nor the specific gravity of the waters of the two coasts have been compared, and it is only through incidental experiments that the fact has been ascertained that a few species from each coast are able to live and thrive upon the other. The conditions that are essential to, or control the existence of a species in a new region undoubtedly vary more or less according to its organization, and the effects of changes of location upon the higher crustacea have been but little studied, if at all. Above all the new-comer must have the power to sustain itself in the struggle for existence with those forms which already occupy the ground, and have been accustomed to it from long habit. Careful studies and experiments in this line of research, with reference to marine forms, would be of great practical benefit to the aims of the Fish Commission, and would probably lead to the .trans- planting of many kinds of marine products to regions which are now poorly supplied with edible forms. A sort of transplanting of young lobsters has been going on along the New England coast, and especially the southern portion of it, ever since the well-smack lobster trade began. The fact was mentioned above that immense quantities of embryo lobsters appear at the surface of the wells in the carrier smacks during the hatching season, and as the smacks journey along they work out through the holes in the bottom of the well, and are thus constantly adding to the supply of the regions through which the smacks pass. It is unquestionable that the abundance of lobsters on the southern New England coast has been partly kept up, and probably increased at times in the past, by this transplanting of the young, and this fact was noticed and referred to over thirty years ago. The fishermen have the greatest respect for the embryo lobsters that appear in the wells of their smacks, and take great pains that no harm shall come to them. Numerous accounts have appeared in the newspapers, from time to time, since this transplanting occurred, to the effect that many young lobsters, supposed to be the progeny of those brought over by Mr. Stone, had been taken by the fishermen in the vicinity of San Francisco. Careful investigation, however, has failed to substantiate these reports, and the few small lobsters, so-called, that have been referred to naturalists, have proved to belong to another related genus, quite common on the California coast, but the species of which never grow to a length of more than 3 or 4 inches. WASHINGTON, D. C., December 16, 1885. END
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