Toxins are accumulated in the tissues of filter-feeding shellfish, such as 

 clams and mussels. In sufficient quantities they may he fatal to host 

 organisms, though certain species show high resistance to the poisons. People 

 who eat contaminated shellfish may suffer varying degrees of PSP and may die 

 from its effects. The toxins are not destroyed by cooking. 



Toxicity is 10 to 100 times greater in the cyst than in the motile organism 

 (personal communication from C. A. Mickelson, Bigelow Laboratory, West 

 Boothbay Harbor, ME; November, 1977). 



The recent history of red tides in Maine dates back to 1958. Following an 

 outbreak of shellfish poisoning in New Brunswick in 1957, Maine officials 

 initiated a sampling program in 1958. Since then, toxin G. excavata has been 

 found in shellfish each year, and closings of shellfish harvest have occurred 

 (Hurst 1975). Initially only the far eastern region of the coast, especially 

 Washington County, was affected. 



It has been suggested that since cyst beds have become established (after 

 severe blooms in 1972 and 1974) Gonyaulax will be a recurring problem along 

 the entire Maine coast. Waters near Monhegan and Matinicus Islands on the 

 Maine coast have been permanently closed to shellfish harvest because of red 

 tide. 



Management 



The monitoring scheme initially involved monthly sampling of six stations from 

 October to May, biweekly sampling until a rise in toxicity was noted (usually 

 by 15 June), and weekly sampling until 1 October (Hurst 1975). The sampling 

 program was expanded in 1975 to include 18 primary stations, and 98 secondary 

 and tertiary stations. Primary stations are sampled weekly from April to 

 October and when toxicity is first detected, secondary and tertiary stations 

 are sampled (Gilfillan et al. 1976). 



Areas are closed to shellfish harvest when the toxicity level reaches 80 yg 

 PSP/100 g shellfish. A toxicity of approximately 500 Pg PSP/100 g shellfish 

 is sufficient to cause sickness in humans (Gilfillan et al. 1976). 



RESEARCH NEEDS 



Most aspects of the role of various species in the ecosystem are unknown and 

 need to be examined. Commercial species of invertebrates should be examined 

 in relation to their role in the ecosystem, and both biotic and abiotic 

 factors should be addressed. 



Abiotic factors include temperature and salinity preferences of each species 

 at its various life stages. Movements of water masses during the time larvae 

 are in the water column should be investigated and sediment preferences of 

 settling larvae, migrating juveniles and adults should be explored. 



Biotic factors include the following: food webs in relation to each species, 

 competition between individuals of a species and between species, natural 

 mortality rates, and energy transfer between trophic levels. 



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