43 



is not known, at leaat it ia generally agreed that the quantities of starfish en- 

 countered show large variations from year to year and even from month to month 

 (Sweet, 1946). At certain times, every available craft is working at starfish 

 control , while during similar periods 

 in other years so few starfish may be 

 found that the only operations necessary 

 are periodic surveys to detect any sud- 

 den increase in population which can 

 then be checked before serious damage 

 is done. 



Unpublished work of Loosanoff sug- 

 gests that the abundance of starfish 

 for a given season can be predicted 

 with some degree of accuracy from a 

 study of larval forms in plankton samples 

 taken in the preceding months . However , 

 very little is known of the causative 

 factors in the fluctuation in abundance 

 of starfish. The opinion has been preva- 

 lent both among growers of seed oysters 

 and the State agencies of Rhode Island 

 and Massachusetts that the starfish 

 population can be materially reduced 

 for some years by intensive control 

 efforts during periods of heavy infesta- 

 tions . This theory has been the basis 

 for the limited appropriations which 

 have been made several times in recent 

 years paying a bounty on starfish caught , 

 (Barnes , 1946 and Gibbs , 1941 and 1946) . 



CLEANING MOPS ON STARFISH I NG 

 VESSEL 



On the other hand, the trend in recent years has been for biologists to at- 

 tribute more and more weight to the effects of ecological factors on the size of 

 populations. Many of these factors are still unidentified. The effect of human 

 factors, such as, hunting, sport fishing, extensive commercial fishing, trapping, 

 and even bounty payments for predators are often believed to be secondary in im- 

 portance in their effect on future abundance. 



Some of the species, the abundance of which is held to be greatly affected 

 by these ecological factors, are certain of the game birds and smaller game animals, 

 fresh-water game fish, and marine species of fish and shellfish, such as, the blue 

 crab, haddock, mackerel, menhaden, and pilchard. This does not imply that too 

 heavy hunting or fishing cannot significantly reduce a population, but in normal 

 years, it has been estimated that, for some of the marine species with a short 

 life cycle, a capture of as much as 80 percent of the population will not material- 

 ly affect future abundance. Conversely, disease, drought, abnormal rainfall, and 

 similar uncontrollable conditions may dramatically reduce a population, for many 

 years in some cases. The well-known mystery of the disappearance of smelt in 

 the Great Lakes is an illustration. 



It is not too surprising, therefore, that Burkenroad (1946) found evidence 

 of a large annual variation in his extensive, though hardly quantitative, survey 

 of starfish abundance. In the course of fluctuations of a seemingly cyclic charac- 

 ter, he estimated a decrease in the population of the order of one-twentieth of 



