The American Lobster Underwater World 2

QL 626 U5313 no.18 c.2

- The American Lobster Underwater World 2

Who hasn't looked at a lobster in a fîsh or scampi. The lobster belongs to the store and wondered how such an ugly decapod or 10-legged family of crustaceans The American creature could be the epicurean's delight? which includes shrimps, prawns, crabs and At one time surplus catches of lobster crayfish. Lobs ter were used as fertilizer. Fishermen con- Lobsters have a jointed external shell, sidered them a nuisance when they became which protects and supports the body parts, entangled in their nets. while still permitting movement. The However, for qui te a number of years, lobster's body is formed mainly by the the lobster has become a highly sought after cephalothorax, or head and chest area, and creature. Gourmets the world over prize the six-jointed abdomen which is common- this crustacean as the most delectable. ly known as the tail. The claws, carried on As a result, lobsters are now trapped its first pair of legs and to which it owes unremittingly, and it appears that their much of its distinctiveness, are called the populations - at least in certain areas - pincer and the crusher according to their are threatened. Most females don't get a respective functions. Four pairs of walking chance to reproduce even once before being legs occur on its thorax, and a series of caught by the fîshing industry. swimmerets, used for carrying eggs in the Scientists are concerned, and are calling case of the female, are suspended from for stiffer contrais. Fishermen and pro- beneath the abdomen. Lobsters corne in ducers claim that the industry is already various colours - mostly colours which are severely over-regulated. In any event, there useful for camouflage purposes, but are is a need for reexamination of a manage- usually greenish when in the water, tending ment code which has evolved over the past to redden when out. 90 years. Skillful management must weigh Adult lobsters vary greatly in size among potential short-term lasses against long- localities, depending upon the age and local term gains. Ultimately, it is obvious that all growth rate, as well as the intensity of the concerns are contingent upon the protec- fîshery . In areas where the exploitation rate tion of the species. is high, the local stock of lobsters is maintained at a young average age. The average Description size is consequently smaller than it would be That most coveted of crustaceans, the if there were less fîshing pressure. The American lobster (or Homarus americanus intensively-fîshed Gulf of St. Lawrence as it is known scientifîcally), is an in- stocks have an average size of less than vertebrate crustacean. It has no immediate 400 g. Sorne lobsters can grow to a size of relatives in Canada. lt does have, however, more than 20 kg if they survive the fîshery one European brother Homarus and natural mortality. vulgaris. Also related is the Norway lobster Distribution Lobsters live along the east coast of North America from North Carolina to Labrador. They are abundant off Maine, southwest Nova Scotia, and the Gulf of St. Lawrence coastline of the Maritimes. Lobsters prefer a habitat where they can find shelter. In deep water canyons off the coast of the U .S., lobsters have been observed lodged individually in small burrows dug into the face of clay cliffs. Inshore lobster populations are found on rocky bot- toms, where a large number of individuals can obtain appropriate shelter. On sand or mud, lobsters may be found hiding under rocks of about their own size. In a number of areas lobsters tend to be larger in deeper water. There are excep- tions. For example, large egg-bearing females are found in shallow waters in the Bay of Fundy where they reproduce and moult during the summer months. Just as the emergence of droves of office workers on a sunny day in spring does not necessarily indicate that the number of office workers themselves is on the rise - soit is with lobsters. They become more active Underwater World 3

when the water begins to warm up. Thus soon after moulting, concentrating on high the catch increases and it appears that there calcium foods to encourage the rapid are more. ln fact, they are only more active. hardening of its shell. The calcium which So water temperatures, if not taken into ac- had been stored in the stomach walls is also count, can play havoc with demographic used at this time. Sometimes it may even eat surveys. its old shell. For one or two months after a moult the lobster's flesh is watery and does Life History not quite fit the shell. During this period its The Iobster begins its life as an egg, glued appetite is enormous and it is readily at- to the swirnmerets on the underside of the tracted to the bait in lobster traps. female's abdomen. The speed of matura- Growth slows down progressively as the tion at this stage may be accelerated by juvenile Iobster grows to adulthood. Since warmer water temperatures. Usually the lobsters grow faster in more temperate eggs hatch in the summer, and the newly- waters they may moult more often. In the released Iarvae float to the surface where Northumberland Strait, for example, where they feed upon smaller planktonic summer water temperatures may reach organisms and undergo three moults, each 20°C, a lobster at the current canner time growing larger, and more similar to an minimum of 63.5 mm carapace length, can adult. In three to six weeks, depending on moult twice in one year. Once a lobster has the temperature, the juvenile lobster replenished the flesh within its new shell, it descends to the sea bottom. At this stage its will be about 50 per cent heavier than total length is about 15 mm. The mortality before a moult. So in one year a lobster rate of larvae is very high, and only about from the Northumberland Strait would one per cent of the floating larvae may set- grow from 200 g to 450 g, and would moult tle on the ocean floor. twice, whereas his counterpart in a cooler Luckily, each female produces enormous habitat would average 300 g, and moult on- numbers of eggs. For example, a large ly once. "canner" with a carapace or shell length of Temperature is also a factor in the age at 78 mm releases about 7 ,500 eggs at one which a lobster attains sexual maturity. time. Even if only one per cent of these Female lobsters in the Northumberland make it to the bottom, this still means that Strait may mature at 200 g or three years of Fig. J. Egg-bearing or berried lobs ter. each female has produced at least 75 off- age, whereas their counterparts in the Bay spring that have survived. Typical large of Fundy will not mature sexually until they breeders in the Bay of Fundy release 30,000 are 700 g or eight years of age. eggs at a time, and the jumbos of more than The size at which the average female is 125 mm in length have been known to pro- mature and capable of producing eggs to duce more than 40,000 eggs. replenish the population is very important ln order to survive, small lobsters Iead a in the regulation of the fisheries harvest, Fig. 2. C/ose-upsection ofberried lobster. very secretive existence, so most of their because if females are not given the chance time is spent hiding in burrows. Through- to contribute to the reproduction of the out their lives, they prey upon correspond- species, the lobster population will obvious- ingly small individuals of high food quality, ly suffer a decline. This is the main problem such as crabs, mussels, clams, sea urchins facing the lobster population today. and starfish. There is no evidence of canna- balism in the wild. Reproduction As the growing lobster becomes too big The female is only sexually receptive for a for its shell, it sheds it for a larger one. Be- few days after moulting, while her shell is tween moults, the flesh becomes pro- still soft and flexible. When lobsters mate, gressively more densely packed inside the the male deposits sperm in the spermatheca shell. Meanwhile, a new soft shell develops between the female's last two pairs of walk- inside the old one. Calcium salts are absorb- ing legs. The sperm is then stored for as ed from the outer shell and stored in the long as a year, until the eggs are ready. At stomach wall. The lobster arches its body that time the eggs are released from the into a "V" form, folded at the junction of openings of the oviduct at the bases of the carapace and abdomen. The large flexible third pair of walking legs. As they pass old membrane stretches, then splits, and the toward the swimmerets, sperm is released to animal lies on its side and backs out of the fertilize them. The eggs are then carried on shell. Once free, the lobster flips back into the swimmerets until the following year. In the normal position and proceeds to suck in the past it was assumed that after hatching water and to puff itself up to about IO to the eggs, the female would moult and then 15 percent larger than its previous size. mate again to recommence a two-year At this stage the lobster's shell is very reproductive cycle. However, it seems that tender and the Iobster is extremely very large females are able to conserve vulnerable to predation. It begins to eat enough sperm from a single mating to fer- UnderwaWHr World 4

tilize two or even three broods of eggs. with considerable short-term local fluctua- They may spawn several times without an tions. The three Maritime provinces are intervening moult. So the energy that nor- responsible for about 80 per cent of the mally is used in increasing body size, is Canadian total. Quebec and Newfoundland directed by these prolific females solely to are responsible for most of the rest. reprod ucing. Since the 1920s, the productivity of the Another deviation from the normal two- lobster fisheries off the coast of the western year reproductive cycle is the case of Maritimes has steadily increased. In 1971 an females who moult, mate and extrude eggs offshore fishery was developing in the areas all in one season. This phenomenon seems of Browns Bank and eastern Georges Bank. to be limited to individuals reproducing for Eight large boats fish these waters and take the first lime in warmer water habitats. about 600 t of lobster per year. Grand Manan Island and southwest New Bruns- Natural Mortality wick land about 500 t. The southern Gulf of What is the natural mortality rate for St. Lawrence has produced between 5,000 t lobsters? Firstly, 99 per cent of the larvae and 9,000 t of lobster per year since 1960. do not survive. Once on the sea bottom, the Over the last 80 years the eastern Atlantic still vulnerable juveniles are so secretive coast of Nova Scotia has suffered a severe that divers cannot accurately estimate their decline in landings, mainly because most numbers. It is logical to suppose that mor- female lobsters are caught before they are tality diminishes rapidly as lobsters become able to produce eggs. larger and better able to defend themselves. The average price paid to fishermen for Fig. 3. Huge lobster from Bay of Fundy, weigh- But once lobsters reach commercial size lobsters has been increasing steadily, ing about nine kg. specifications, the rate at which they are although of late that increase has not kept harvested by the fishermen renders natural pace with increases in prices paid for most mortality figures almost insignificant by other fish and shellfish. The price varies comparison. In specific isolated cases, epi- considerably depending on the season, the demics of gaffkemia, a bacterial disease, location and the use which will be made of have decimated local populations of lob- the lobsters. sters, but these have almost always been in What happens to the lobster after it has holding facilities and not in the wild . There been caught? are few predators to which a commercial- The large lobster (81 mm or more) is sized lobster would be vulnerable. almost always sold live. Jumbos usually are shucked and sold as frozen or canned meat. The Fishery Districts in w hi ch i t is still permissible to Canada's commercial lobster fishery land lobsters as small as 63.5 mm exist in began before 1870. In the evolution of the very small numbers to supply the plants early fishery the abundance of existing large canning lobster meat, although nowadays stock was soon exhausted. During the freezing supplants canning for the most 1870s, lobsters usually averaged from part. 1-2 kg in most areas, but these larger in- A recent development is the sale of whole dividuals were fished out by 1887 when canner or "shack" lobsters frozen in brine average weights were below 500 g. By 1900, for some export markets. This eliminates average weights were often below 220 g. shucking, permitting greater profit at the Overall landings declined from 45,000 processing level. metric tons (t) in 1887 to only 12,000 t in Interestingly enough, less than 10 per Fig. 4. Young lobsters in early stages of develop- 1918. Subsequently the emphasis of the cent of the total lobster catch was consum- ment, during which they moult three fishing shifted to the smaller canning ed in Canada last year. limes. lobsters. In 1979 exports had reached 12,800 t. During the early years of this century, The European Economie Community is an areas like southwestern New Brunswick and increasingly important importer of Cana- Fig. 5. Lobsters one, two and three years old. western Nova Scotia with easy access to dian lobster products. The U .S. market lucrative live lobster markets in the U.S. declined by about 22 per cent between 1976 began to concentrate on larger lobsters to and 1979. supply these markets. The canneries shut down and the average size of lobsters in Research and Management these populations increased as a result. For the last 50 years Canadian scientists Elsewhere the heavy fishing pressure con- have been studying the lobster. Recently tinued to keep the average sizes small. Dur- that research has taken the form of lobster ing the 1920s, the emphasis in eastern Nova aquaculture. A great deal of information Scotia shifted somewhat away from can- has been obtained about dietary and habitat ning, and average sizes increased there. requirements. Through experimentation Since then, the overall average landings with temperature regime or manipulation of have been relatively stable in the long term, hormonal balance, methods have been Underwater World 5

devised to accelerate growth . Lobsters can fishing mortality). Leaving lobsters to grow be raised from larvae to adulthood within bigger before catching them should produce two years in captivity. Now it remains to be higher yields in the long run. shown that commercial scale operations can The supply of young lobsters for the be maintained on a profitable basis while fishery should be improved. lt is very im- averting the disease problems that threaten portant to note that in most stocks the pre- any mass-holding facility. Il may well be sent minimum legal sizes at which a lobster possible that financially viable operations may be captured are below the size at which will be exclusively those that do not require most females are able to produce eggs. supplementary heating of water during the Consequently, most females are notable to winter. Such operations might be located reproduce even once in their lives. The near thermal power plants in Canada, or fishing effort is very intense and only a almost anywhere in California or Florida. small rninority survive their first season in Obviously, the potential impact of such the fishery. developments on the commercial fi shery Since existing laws protect only females must be considered. Tens of thousands of bearing external eggs - females that are people in Atlantic Canada are supported by "pregnant" are not protected. This ac- the lobster industry. counted for a severe lobster harvest failure The management of the lobster fishery is in Richmond County in 1960. founded on the Lobster Fishery Regula- The desperately low level of catches tions, a complex document which has along the eastern shore of Nova Scotia to- evolved over the last 90 years of practice. day has of course led to a considerable These regulations were instituted for a decrease in fishing effort. As a result about variety of reasons, the least of which were half the new stock survive their first season. scientific. In some cases they were responses But there are very few recruits. In fact it ap- to the immediate needs or demands of pro- pears that the only way an increase could be cessors and fishermen. In many cases they attained is to increase the minimum size were based on mistaken ideas about the limit to the point where most females have biology of lobster populations and their already had at least one chance to con- reaction to fishing pressure. Modern day tribute to the reproduction of their species. research concentrates not only on obtaining In warmer waters, females who moult in- biological information, but also on to legal size during the summer extrude eggs developing the relationship between the before the fall of that same year. Conse- biology of lobster stocks and the manage- quently, when the fishery starts in the ment measures necessary to ensure a following spring these females are already health y fishery. protected. The basic tools of fishery management It is clear that in ail areas the number of are control of fishing effort and control of young lobsters could be improved and sta- the size or age at first capture. ln the case of bilized by increasing legal minimum sizes. lobster fisheries, effort is controlled There is at present a great need for through limits on the number of licences, economic research related to the lobster FEMALE TOTAL LENGTH - 38.?cm the number of traps, the dimensions of the fishery, especially concerning the possible WEIGHT -2.02Kg traps, and the length and dates of the open impact of changes to the fishery regulations fishing season. The size at first capture is based on biological arguments. For exam- Fig . 6. Underside of mature male and female protected by specifying a minimum legal ple, increased size limits would cause short lobster. size of lobsters. In addition females bearing term losses in yield . What would be the external eggs ("berried females") must be economic cost of these losses, and would returned live to the sea if captured. Lobster potential long-term gains justify them? In- management is complicated by the fact that creased size limits also would result in the Atlantic coast is divided into about higher average sizes of lobsters. What im- 25 management districts. Seasons, trap pact would such changes have on lobster limits, minimum legal sizes, and numbers of markets, in terms of demand and prices? licences vary considerably among these What would be the impact on employment districts. in the lobster processing industry? Research There is at present much discussion on these econornic questions is necessary to among fishery scientists, managers and complement the management-oriented bio- fishermen about minimum legal sizes. In logical research currently underway. both North America and Europe, scientists involved in assessing lobster populations have agreed that in most countries increases in minimum legal sizes would result in improved and more stable lobster catches. At existing size limits, growth rate is much higher than mortality rate (excluding QL 626 U5313 no.18 c.2 Underwater World Canada. Dept. of Fisheri. 6 The American lobster

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Other in this series: American Oyster American Plaice Atlantic Groundfish Atlantic Herring Atlantic Mackerel Altantic "Pelagic" Fish Atlantic Shellfish Atlantic Snow Crab Capelin Harp Seal Irish Moss Red Hake Red Tides Roundnose Grenadier Sea Scallop Spiny Dogfish Witch Flounder

Published by: Communications Branch Department of Fisheries and Oceans Fig. 7. Fishing lobster traps. Furtber Reading Ottawa, Ontario DeWolf, A . Gordon. 1976 The lobster fish- KlA 0E6 ing of the Maritime Provinces: economic Fisheries Research eff ects of regu/ations. DFQ/ 588 UW /018E Board Bull. No. 187. © Minister of Supply and Services Canada 1982 Resource prospects for Canada 's Atlantic Cat No. Fs 41-33 / 18-1982E fisheries. 1981-87. Dept. Fisheries and ISBN 0-662-12207-0 Oceans. (p. 30-35). Disponible en français Scarratt, D.J. 1982. Canadian Atlantic off- shorefisheries atlas. Cdn Special Publica- tion Fisheries and Aquatic Sciences 47 . (p. 35).

Scarratt, D .J. 1979. Life and limes of the Atlantic Lobster. Nature Canada. Vol. 8, No. 3 (p. 46-53).

Underwater World factsheels are brief il- lustrated accounts of fisheries resources and marine phenomena prepared for public information and education. They describe the life history, geographic distribution, utiliza- tion and population status of fish, shellfish and other living marine resources, and /or the nature, origin and impact of marine processes and phenomena.

Fig. 8. Removing meat from lobster in a sma/l cannery.