SEA-FISHERIES LABORATORY 



271 





March 26. 



March 27. 



March 29 





12 c.c. 



14*5 c.c. 



18-5 c.c. 



Total Diatoms = 



= 220,000 . . 



277,000 . 



326,000 



Biddulpkia mobiliensis 



.. 46,000 .. 



50,000 . 



58,000 



Chaetoceros debile 



6,000 .. 



8,000 . 



10,000 



,, decipiens 



.. 100,000 .. 



150,000 . 



160,000 



Coscinodiscus concinnus .... 



. . 64,000 . . 



67,000 . 



75,000 



Copepod nauplii 



7,000 . . 



27,000 . 



35,000 



We have only quoted those species of Diatoms which are 

 present in greatest abundance and which make up the 

 bulk of the catch. All are included in the totals given. 

 There is also an autumn maximum showing a very high 

 peak at the end of September. Omitting, however, the 

 single catch of September 30th (which is due in the main 

 to Rhizosolenia semis pina) the peak is reduced to less than 

 one-third its former height. A remarkable feature of this 

 September hump is the sudden character of its appearance 

 and disappearance and its short duration (six days). An 

 inspection of the temperature curve of the year for the 

 water of the bay (fig. 10] shows that the sudden increase 



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Fig. 10. 



in the phytoplankton coincided with the maximum in 

 temperature, and our weekly weather records at the 

 Biological Station show at that same time a week of fine 

 calm weather with easterly breezes (S.E. and E.S.E.). We 

 have noticed the same phenomenon in previous years, both 

 at Port Erin and on the west coast of Scotland, which 

 seems to indicate that if weather conditions be suitable at 



