Int roduction 



The iRV3S3tigai;ion of paralytic sbsllfish poison in the clams of 

 Sou'Hheastera Alaska condacted hy the Jish&rj Products LahoratoTy, 

 Zet'Shikan,!,' was diTidsd into threa main projects. The one with which 

 this t^por'!-. is con^tseraed '.b the geographical and seasonal distrihution of 

 th(9 taxltL in Vattes' clams, Saridonriis giganta'^is . The other two projects, 

 the study of toxin reduction "by processing methods and the study of sampling 

 aaid testing methods, are to he reported in separate papers. Batter clams 

 aae the most important ■scmmercial cleun resource in Southeastern Alaska, 

 IHherafcre, the swdies were devoted almost entirely to this species. 



InTestigations of an exploratory Qatu:re performed from 19*46 to 

 19^8 established the presence of toxin in hutter clams from many of the 

 Southeastern Ala^ska clam prod-^cing "beaches during all seasons, 



ProiE May 19^ to September 19^, inclusive, a systematic monthly 

 saTiPDling of representatiTe areas on certain eommercially exploitable clam- 

 produsing beaches was carried out. The purposes of the survey were to 

 determine the monthly fluct'iations in the toxicity of the clams from the 

 different areas and the variation in tcxicity between the siphon and the 

 body. InformatioiS. on ^-hese factors is essential for intelligent regu- 

 r.ation of this fishery and enables the processor to eliminate a major 

 so-oree of tox5.3. fr:*!!! the canned product. 



Coll ection of Glam Sa mples 



^e laboratory motor vessel Be searcher , usually operated by a 

 cr?w of three men, was tised in collecting the clam samples. Shucking of 

 the clams and preparation of the extracts were performed aboard the boat, 



A wi.de knowledge of the elam beds in Southeastern Alaska, gained 

 froas the earlier gensral survey work, made it possible to select 10 

 s-epresentativs .^iam beaches on which were laid out 22 plots. Nine of the 

 ■jeaches were knows t-5 produce clams of fairlj!" high toxicity; whereas, the 

 A-emalni-xig gzl? yielded ciams of low toxicity. Preliminary tox5.city tests 

 o^a man^' individaal clams from a single plot showed that there was con- 

 siderable ?a,riatiers. in toxicity between clams. Tb.ese tests further showed 

 that resul'.ts si^ificant wit'hia plus or minus 30 percent could be obtained from 

 a sajiiple of 25 clams. Therefore, the plots were made large enou^ to 

 supply at least 18 samples of 25 clams each. To provide a thoroughly repre- 

 ssiatati?© sample, not oT<^r 3 clams were taken from each hole dog, and the 

 holes were distributed well over the entire plot. All the study plots were 

 iatmdatsd at hi^. '^ater and comrpletely exposed only at a minus tide. The 

 c'sllections were made, weathjer permitting, during one of the minus tide 

 periods each month. 



1/ Jointly operated by vhe Alaska fisheries Experimental Commiasion and 



the U. S. Pish and Wildlife Service. 



