BIOLOGY AND METHODS OF CONTROLLING THE STARFISH, Asterias forbesi {DESOR}

By Victor L. Loosanoff Biological Laboratory Bureau of Commercial Fisheries U. S. Fish and Wildlife Service Milford, Connecticut

CONTENTS

Page

Introduction...... 1 Distribution and occurrence...... 2 Food and feeding ...... 3 Methods of controL...... 5 Mechanical methods : Starfish mop...... 5 Oyster dredge...... 5 Suction dredge...... 5 Underwater plow ...... 6 Chemical methods ...... 6 Quicklime...... 7 Salt solution...... 8 Organic chemicals...... 9 Utilization of starfish...... 11 References...... 11

INTRODUCTION Even in the old days, when the purchas­ ing power of the dollar was much higher, The starfish has long been regarded as the direct damage caused by starfish to one of the most destructive enemies of shell­ the Connecticut oyster industry was as­ fish on the Atlantic coast of North America. sum.ed to be $463,000 in 1887; $631,000 in The greatest part of the loss caused by 1888; and $412,000 in 1889. Now, according these pests is borne by the oystermen, to the estimates of. biologists and practical WJ"lO often find their stock depleted or oystermen, the value of oysters destroyed entirely destroyed. Beds populated with by starfish in Long Island Sound alone may young oysters are especially vulnerable. reach several million dollars in some years.

UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE BUREAU OF COMMERCIAL FISHERIES

Fishery Leaflet 520 Washington 25, D.C. July 1961 (Revised) For example, in 1958 starfish almost en­ these animals live near the shore in com­ tirely destroyed one of the h eaviest oyster paratively shallow water. A. vulgaris is sets in the history of shellfish cultivation found from Labrador, Canada, to Cape in Connecticut. The monetary loss that year Hatteras, North Carolina, and from the was considered to be between $10,·000,000 shoreline to a depth of 170 fathoms. This and $15,000,000 and, perhaps, even greater species, however, is most com.m.on in because of the present high price of oysters. water of moderate depth, preferring deeper and cooler water than A. forbesi and, con­ Starfish also kill large quantities of sequently, is rarely found in shallow places oysters in the States of New York, Rhode where oysters are grown. Only A. forbesi, Island, and Massachusetts . Scallop beds, the species causing the most damage to as in Buzzards Bay, are often invade d and oyster beds, is discussed in this article. their population partially or completely destroyed by starfish. One phase of depreda­ Surveys ' by the U.S. Fish and Wildlife tion, the extent of which is very difficult to Service have disclosed great concentrations estimate, is the heavy destruction of oyster of starfish in Buzzards Bay, Mass.; Nar­ spat caused by newly set starfish. In re­ ragansett Bay, R. I.; in the waters of Long gions where heavy setting of these pests Island Sound; and, at times, in Chesapeake im.m.ediately precedes or coincides with Bay. In all cases the majority of the animals setting of oysters, the latter may be de­ were found to live in comparatively shallow voured in a short time. water not deeper than 40 feet, their number decreasing with increasing depths. Usually, DISTRIBUTION AND OCCURRENCE large concentrations were found near the shore where natural and cultivated oyster Of the several species of starfish found beds are located. Starfish appeared to be on oyster beds only two are serious preda­ equally abundant on hard and soft bottoms, tors of commercial mollusks. These are wherever food was available. In Chesapeake Asterias forbesi (Desor), the com.m.on star­ Bay they were concentrated chiefly in fish (fig. 1), and Asterias vulgaris (Verrill), areas where an abundant supply of the small known as the purple starfish. The range of clam, Mulinia lateralis, was found. distribution of the first species extends from Maine to Florida and to the Gulf of It has been reliably established by semi­ Mexico. This form, h owever, is most abun­ annual surveys that the number of starfish dant between Cape Cod and Virginia. It is in Long Island Sound varies tremendously found at all depths ranging from the low in different years. Although there are no water mark to 250 feet, but the majority of definite cycles in its population density,

...... -: ------

Figure l..--Common starfish. Asterias forbes;, moving on b:lnolIl,

2 there are periods when starfish are ex­ Laboratory observations also showed that tremely numerous and. also. periods when movements of starfish are irregular and they are' comparatively scarce. For ex­ quite slow, usually not exceeding a few ample. pronounced increases in the starfish inches per minute. In the winter, when population were observed during the years the temperature of the water is near the of 1934-35. 1939. 1948-50 and. especially. freezing point, locomotion is slowed con­ in the fall of 1957. The starfish set of siderably or ceases entirely. However, 1957. although not unusually heavy. sur­ severe storms or hurricanes, which cause vived well. increasing the number of star­ strong movements of water near the bottom, fish in Long Island Sound about tenfold. may carry masses of starfish from one area Since then. because of the preponderance to another over considerable distances in of starfish and the difficulty of combatting a short time. them. many sections of Long Island Sound that were formerly very productive as FOOD AND FEEDING oyster grounds have been completely aban­ doned. The heavy damage to the shellfish in­ dustry from starfish predation has caused It is important to recognize thaOt in 1957 great interest in the method employed by a comparatively good setting of starfish starfish to open shells of bivalve mollusks. occurred although the population of adult In general. all the suggestions offered in starfish. at that time. was one of the the past may be reduced to two probable lowest recorded since systematic surveys alternatives. One of these is a "toxin" of their occurrence and distribution were theory. It proposes that starfish release a begun in the middle 1930's. This and similar chemical substance which produces relaxa­ observations clearly demonstrated that in tion of the adductor muscles of the bivalves. the case of starfish there is no direct The second. the so-called "mechanical" correlation between the numbers of parents theory, maintains that starfish are able to and the intensity of setting. pull ope n the valves of molluscan shells by means of their tube feet. At presen t . Starfish cannot exist in water containing the second or "mechanical" theory is ac­ l ess than 1.8 percent of salt. However, they cepted by most biologists. There is evi­ are capable of withstanding. without serious dence that the opening of the valves is a injury. sharp reductions in salinity provided rapid process involving overwhelming, dis­ that the low salinity periods are of short continuous f orc es . In experiments with duration. Prolonged exposures eventually mollusks i t was found that the tube feet r esult in death of the starfish. Because of did pull the valves open. and forc es of over the inability of these animals to adjust 3,000 grams were recorded. themselves to water of low salinity they do not penetrate far into harbors and bays In addition to bivalves. such as clams, where the water is too brackish. oysters, and mussels. the food of sta rfish also consists of sea snails. small cru s ta­ Surveys on the occurrence and distribu­ ceans, worms, and various dead marine tion of starfish conducted semi-annually in animals. However, the small s i ze of the Long Island Sound during the last 22 years starfish mouth, which in adult a nimals is f ail to support the opinion prevalent among only about one-fourth of an inch in d i ameter, oystermen that seasonal migration. occurs does not permit taking in large pi eces of regularly from shallow to deep water. and food. To compensate for thi s handicap, vice versa. Results of these surveys in­ nature provided starfish with a very unique dicate that the distribution of these animals method of feeding. After the shells of the in relation to depth is fairly constant and attached mollusk are open, the s t a rfish that in many instances large groups of extrudes its stomach, insert s it bet we en starfish found in inshore areas remain the shells, and digests the soft meat of its there for a period of several years. Studies prey in situ. As soon as the mollusk is of movements of starfish. stained blue with eaten, the stomach of the starfish i s with­ the harmless dye. Nile Blue Sulphate. and drawn. It has been found that a single, then released at a definite point in Long medium-sized starfish may destroy as many Island Sound showed that the greatest dis­ as five I-year old oysters per day (fig. 2) . tance any of the animals traveled in 10 Older and stronger mollusks are better months was about 5.000 feet. The stained equipped to withstand the attack. However, starfish dispersed in all d ire c t ion s. even large oysters, if in a weakened

3 Figure 2.--Starfish feeding on young oysters. Two oysters recently opened and eaten by starfish can be seen in upper left hand corner. condition, become easy prey to star­ period may v ary in different localities . fish. It usually begins soon after the water tem­ perature reaches 600 F. and continues The starfish of Long Island Sound mani­ throughout the summer, ending some time fest decided seasonal differences in their late in September. Recent experiments feeding habits . Indifference to food is shown conducted with starfish of Long Island throughout the pre-spawning period, extend­ Sound have shown that in adult A. [orbesi ing from the end of May until July. Active sex reversal from male to female may feeding begins again after spawning, and occur. starfish become voracious eaters during the period from August to December. The Fertilized starfish eggs develop into low temperature of the water during winter very small, delicate, free-swimming or­ and early spring alInost entirely suppresses ganisms called larvae, which subsist upon their feeding activities. algae and other microscopic forms. The change from larval to juvenile stage occurs REPRODUCTION 2 or 3 weeks after fertilization, depending upon the water temperature and food supply. The sexes of starfish are separate. If The young starfish, about four one-hun­ the animals spent their first y ear in a dredths of an inch in diameter, sets on the favorable environment, they are able to bottom where it begins to feed upon small breed when only 1 year old. They become oysters, clams, and other animals. In Long ripe during late spring, and in the summer Island Sound setting of starfish occurs at the sexual products of males and females all depths, from the mean low water mark are discharged into the water, where fer­ to 100 feet, being Illost intense in water tilization Qf eggs occurs. The spawning less than 40 feet deep. Setting may begin

4 late in June and continues until late Sep­ 16 light chains, and attached to each light tember or even early October. chain i s a large bundle, about 5 feet long, of rope yarn. A boat usually carries two If food is abundant, young starfish may mops which are raised and lowered from grow very rapidly reaching the size of 3 the side of the deck. As the mops are inches by the end of November. Generally, dragged over the oyster beds, the starfish, however, the rate of growth is slower. Old, the bodies of which are covered with nu­ fully grown starfish are known to reach the merous spines, are entangled in the yarn size of 11 inches in diameter. and brought to the deck, where the mops are dipped into wooden vats of hot water. METHODS OF CONTROL After the starfish are killed and removed from the mops the latter are again lowered Eradication of starfish on oyster bottoms overboard and the process repeated. has been practiced ever since cultivation of oysters was begun. Various methods of Oyster dredge.--During the regular cleaning oyster beds of starfish are now dredging for oysters many starfish are also employed by oystermen but the following caught and later destroyed. In some in­ are most conunonly used: stances oystermen prefer to use dredges instead of mops (fig. 4). Mechanical Methods Suction dredge. - -The suction dredge is Starfish mop.--At present the most com­ a comparatively new implement placed in mon device for destroying starfish is the operation about 20 years ago. The dredge mop (fig. 3). It consists of an iron bar is designed on the principal of the ordinary 8 to 10 feet long to which are tied 12 to suction vacuum cleaner. Starfish and other

Figure 3• .l-Starfisb mop about to be lowered into vat of boiling water.

5 Figure 4.--Oyster dredge. which sometimes is used to catch starfish, being hoisted from the water. materials are drawn from the bottom by unable to escape and s o on d i s integrate and means of a suction pump, carried through die. These obser v ations l ed to the devel op­ a flexible pipe and finally forced into an ment of a n ew mecha nical met hod, whi ch enclosed rotating drum made of wire mesh is I s till in t he process of being evaluated. of differe nt sizes. Small objects pass It appear s to be extremely promi sing in through the m e sh and drop to the sedime nt the c ont r ol of several species of drills , tank the contents of which, including small starfish and, perhaps, m us s e 1 s and starfish, are later taken ashore. L a r ge Crepidula. Basi cally, the method consists objects are dropped on th e conveyor, where of using a somewhat modified agricultural the adult starfish are p i cked off by hand disc plow on oyster beds where the ground and killed, while oysters and other material is soft enough to be turned over by the are returned to the beds. The effici ency blades (fig. 5). Oyster enemies are covered of the dredge is high a n d the catch is much in this way by a· layer of bottom deposit, greater than that of a regular starfish boat. are unable to emerge, and eventually perish. It is unfortunate, in view of the great The method may be especially valuable in efficienc y of suction dredges, that they are preparation of oyster grounds either for not more widely used. planting of cultch to collect new set or for cleaning grounds prior to transplanting of Underwater plow--Recently, Service bi­ seed oysters. ologists at Milford Laboratory demonstrated that the majority of oyster drills buried Chemical Methods under a comparatively thin layer of bottom soil cannot emerge, and perish; Further Since the mechanical control of starfish experiments have shown that starfish cov­ over oyster beds is expensive and only ered by a layer of mud or sand also are partially effective, attempts to discover 6 Figure 5.--Underwater plow, used in control of oyster enemies and competitors, ready to be lowered.

some cheaper and more efficient means direct contact with its body. Such a method of destroying starfish have led to con­ was found by using calcium oxide, com­ sideration of the use of certain chemicals monly called quicklime, which has the which might cause their death. Among the important property of causing an almost substances tried were different concentra­ immediate effect upon the starfish body. tions of copper sulphate and its mixture Moreover, because of its low solubility, with nitre cake. The use of these sub­ a comparatively small quantity of quick­ stances, however, proved impracticable lime, in powdered or granular form, is for beds of any size since only a small sufficient to cover a relatively large area percentage of starfish was killed, while the of oyster beds. When quicklime is spread others were driven to adjacent bottoms. over the oyster beds, its particles would In addition, in a few instances the shells fall and imbed in the upper surface of the of the mollusks of the treated area became starfish. This surface is covered .with a discolored and the oysters were found to delicate membrane which acts as the res­ be unfavorably affected. Since introduction piratory organ. The caustic action of lime of metal salts over oyster bottoms may causes surface lesions which quickly deepen result in an accumulation which may even­ and after a few days may penetrate through­ tually prove dangerous to aquatic animals out the bodywall of the starfish exposing and plants, this method was not recom­ the internal organs and finally causing mended for the control of starfish. death (fig. 6).

Quicklime.--Better results can be ex­ Once spread on the bottom, the lime pected from a method based on the use of retains its effectiveness for some time. insoluble, or only slightly soluble material Starfish which are not directly hit by t he which is harmful to the starfish when in falling particles will eventually corne in ) 7 Figure 6.--Starfish injured by particles of lime which either fall on their surfaces or over which they crawl. contact with them while crawling on the tried on the cultivated beds of Long Islafld bottom. Thus, in the course of time the Sound. Whenever lime is used the direction lower surfaces of the starfish also become and speed of the tidal currents should be affected and disintegration of their bodies taken into consideration. If properly applied, begins. Starfish weakened by the wounds even small quantities of lime (500 to 750 are attacked and eaten by crabs and other lbs. per acre) will be sufficient to destroy animals, a circumstance which adds to the the majority of the starfish present. Some­ number of starfish eventually killed. times, however, larger quantities may be needed. Fortunately, the concentrations of Lime is also used when oyster set is quicklime required to kill sta,rfish do not transplanted. By spreading several hand­ seriously affect many other commercially fuls of powdered quicklime over each important forms of marine life. When used dredgeload the majority of the starfish in the concentrations employed in these found among the oyster s will be killed. experiments, lime does not kill nor notice­ This method prevents transplanting star­ ably injure oysters, clams, or other mol­ fish from one area to another. lusks commonly found on cultivated bottoms.

To cause injury to starfish it is necessary Salt solution. - -Recently another ex­ to create actual contact of particles of tremely simple method was developed to quicklime with the bodies of these pests. kill starfish during transplanting of oyster s Therefore, the efficiency of the method from one area to another. The method depends primarily upon the uniform dis­ consists of dipping dredgeloads of oysters, tribution- of the lime over the area treated, together with their enemies, in saturated and also upon the quantities used. An or strong solutions of common salt. This apparatus insuring uniform distributi on of simple method is extremely effective in kill­ lime has been devised by biologists of the ing small and l arge starfish, boring sponges, Fish and Wildlife Service and successfully tunicates, hydroids, Crepidula, etc.,

8 without c au sin g serious injuries to groups of e n emi es. The treated s and can be oysters. used as a barrier t o s urround the h e lli18 h beds, thus p r event ing the e ntrance of ene ­ mies (fig . 7 ), o r i t may b e spread o ver The advantage of this method over some infest ed areas, killin g the enemies and , others, such as spraying loads of oysters under c ertain conditi on s, preventing even with certain solutions or small particle s of thei r pelagic l a rvae from re-invading the lime, is that all starfish, even those hidden beds (fig . 8). Under experimental conditions in such places as empty conch shells, will chemical barrie rs only a few inche s wid e be reached when dipped in the salt brine. stopped starfi s h . How ever, i n p r actice, to Starfish that are immersed in a saturated compensate for th e fact that starfi s h may salt solution for only 30 seconds and then sometimes be c a r r i e d by curren ts for long returned immediately to sea water usually distances, the b arrier shoul d b e consid­ die . One minute of immersion, especially erably wider . if the starfish are afterwards kept on deck for some time before being returned to sea The first sign of d i stress shown b y water, causes 100 percent mortality, re­ starfish that c orne into contac t w ith a gardless of the size of the starfish. chemical b a r r i e r i s usu ally a curling of the rays (fig. 9) . Often a starfish acquired Organic chemicals. - -Several year s ago it an arched position sta nding on the tips of its was discovered by Milford biologi sts that rays . In e xtreme cases, when the chemical many enemies of oysters and clams, in­ f ormula i s especially strong, the starfish cluding starfish, can be contr olled by the may roll into a ball. After r e lative ly short use of c ertain organic chemica ls. These p e riods of contact with the b arrier, the chemi cals are mixed w ith dry sand , o r bodies of starfish b egin to disintegrate and other inert carriers, to hold them on shell­ the pests soon d i e . The m ethod, although fish beds. The potency can be cons iderably extremely promising, is still under study increased by incorporating ot h e r che micals °t o determine its safety to bivalves and to that may be especially selected f o r specific humans.

Figure 7.--Experimeotal chemical barrier constructed in intertidal zone in Milford Harbor. Strings over the bottom were needed to keep sea gulls away from the animals planted inside the barrier.

9 Figure 8.--Method of lrutlng shellfish ms Invaded by sur(ls 11 CIOIU\Sts truted sand by means of a r ary spreader. Experiments a re sull In pr r delernu ne formula to be used and quantity of m.1tenal per acre ( nom needed ellnunau sur(ls

Figure 9.--Starfish curling their rays and some diSintegrating at centers soon after contact with chemical barrier.

10 UTll..IZATION OF STARFISH GALTSOFF, P. S., and V. L. LOOSANOFF. 1939. Natural history and method of Many attempts have been made to utilize controlling the s tar f ish (Asterias starfish as fertilizer or chicken feed. forbesi, Desor). Bulletin of the U. S. Technological studies of this nature con­ Bureau of Fisheries, vol. 49, no. 31 , ducted in the pAst by the U. S. Fish and p. 75-132. Wildlife Service led to the conclusion that production of starfish meal was not practical LAVOIE, M. E. bec:ause the oyster industry did not provide 1956. Technological studies of the star­ a reliable source of this material and be­ fish. U. S. Fish and Wildlife Service, cause a separate fishery for starfish could Fishery Leaflet 391, p . 1-47. not operate to yield raw material at a cost consistent with its value as a feed stock or as fertilizer. Furthermore, extreme fluc ­ LEVIN, E., N. T. RAND, J. D. MOSSER, tuations in the abundance of starfish prom­ D. S. VERNER, and V. K. COLLINS. ised a very poor source of supply of raw 1960. Defatted starfish meal as source material. Finally, starfish meal had a low of nutrients in poultry rations. Poul­ nitrogen content and high ash content and, try Science, vol. 39, no. 3, p. 646- therefore, was less desirable. 654.

More recent studies have demonstrated, nevertheless, that protein concentrates pre­ LOOSANOFF, V. L. 1937. Use of Nile Blue Sulfate in mark­ pared from starfish, either by pancreatic ing starfish. Science, vol. 85, no. digestion or by washing with hydrochloric 2208, p. 412. acid, have high protein-quality values that are comparable to good-quality fish meals. 1945. Effects of sea water of reduced Defatted starfish meal was also shown to be approximately equal to fish meal, on a salinities upon starfish, A. forbesi, of Long Island Sound. Transactions protein basis, when added at levels of 3 to of the Connecticut Academy of Arts 6 percent to purified or practical diets, and Sciences, vol. 36, p . 813-835. while maintaining the same dietary calcium level. In general, these studies suggested 1958. Oysters. U. S. Fish and Wildlife that defatted starfish can compete nutri­ Service, Com m ercial Fisheries Re­ tionally and economically with fish meal as view, Sep. No. 506, p . 45-47. a source of protein, calcium, and unidenti­ fied growth factors in poultry ration. Thus, modern techniques of processing showed LOOSANOFF, V. L., and J. B. ENGLE. new means of utilizing sea products, such 1942. Use of lime in controlling star­ as starfish, which until recently were fish. U. S. Fish and Wildlife Service, c onsidered virtually valueless. Because Research Report No.2, p. 1-29. of the unreliable nature of the supply, however, it is doubtful that utilization of LOOSANOFF, V. L., C. L. MacKENZIE, Jr., starfish meal offers much promise of aid and L. W. SHEARER. to the oyster industry. 1960. Use of chemicals to control shell­ fish predators. Science, vol. 131, REFERENCES no. 3412, p. 1522-1523. CHRISTENSEN, A. M. 1957. The feeding behavior of the sea star, LOOSANOFF, V. L., and C. A. NOMEJKO. Evasterias troschelii S tim p son. 1958. Burial as a method for control of Limnology and Oceanography, vol. 2, the conunon oyster drill, Urosalpinx no. 3, p. 180-197. Cinerea, of Long Island Sound. Pro­ ceedings of the National Shellfisher­ CLARK, A. H. ies Association, vol. 48, p. 83-89. 1956. Starfish. Encyclopaedia Britannica, vol. 21, p. 333. MEAD, A. D. COE, W. R. 1899. The natural history of the starfish 1912. Enchinoderms of Connecticut. Con­ (Asterias forbesi). Bulletin of the necticut. Geological and Natural His­ U. S. Fish Commission for 1899 tory Survey, Bulletin No. 19, 152 p. (1901), vol. 19, p. 203-224.

11 MS #1047

GPO 915515