SEA-FISHERIES LABORATORY. 145 



Tow-nettings taken in any area at intervals 

 frequently show great changes in the pelagic organisms. 

 This is illustrated in the two tables now given, which 

 show the result from a gathering near the Liverpool N.W. 

 Lightship and one in Red Wharf Bay, on January 31st. 



N.W. Light Ship. Red Wharf Bay. 



Biddulphia — ... fr. 



Pleurobrachia r. .... — 



Sagitta c. ... ab. 



Autolytus 1 ... — 



Mitraria r. ... — 



Crab zoea r. ... — 



Copepoda c. ... v. ab. 



Calanus fr. ... c. 



Pseudocalanus fr. ... c. 



Paracalanus fr. ... c. 



Temora fr. ... c. 



Acartia clausi c. ... c. 



Oithona similis — ... c. 



Plaice eggs 1 ... — 



When these results are compared with those given 

 for January 4th, it will be seen that Diatoms and 

 Copepods were then fairly abundant in the open sea off 

 the Lightship, but in Red Wharf Bay the former were 

 absent altogether and Copepoda much scarcer. In the 

 above examples a complete reversal is shown to have taken 

 place in the course of twenty-seven days. Diatoms are 

 absent from the open sea collection, and Copepoda much 

 reduced in quantity. On the other hand, Diatoms have 

 come into Red Wharf Bay, and Copepoda become very 

 abundant. Such marked changes are often found, not 

 only after intervals of time, but frequently in a very 

 limited area, on the same day. On February 1st, four 

 tow-nettings were taken along the coast of North Wales, 

 between Red Wharf Bay and Rhyl, which show that 



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