SEA-FISHERIES LABORATORY. 227 



fathom or two below the surface — it is almost invariably 

 found that the weighted net, with its wider range through 

 the deeper layers of waters, gave a larger, and sometimes 

 a much larger, quantity of organisms. The only 

 exceptions to this rule are on some occasions in April, 

 when the sea was full of Diatoms and the surface nets 

 gave very large hauls, equal to or even exceeding the 

 deeper ones. But even during the Diatom maximum in 

 April some days showed more in the weighted than in the 

 surface nets. For example, on April 10th, at along-shore 

 station III (Form 22), the surface gave 11*5 and the net 

 at one fathom 19'5 c.c, and the total Diatoms were 27,000 

 in the former and 188,000 in the latter (see also Form 19, 

 same date, above). 



Such numbers as 18, 18, 29 ; 3, 3, 6'5 ; 15-5, 16, 23'5 ; 

 9-5, 9-5, 19-5 ; and 9, 11, 18 are frequent. On April 25th, 

 the numbers are 5*5, 4'5 at the surface and 20 in the 

 deeper net. In some cases the difference is even more 

 marked, as, for example, on August 24th, at off-shore 

 station II, when the surface nets gave respectively 2 and 

 1'5 c.c, while the weighted net gave 16 c.c. The increase 

 in this case was due to Copepoda being more abundant in 

 the lower zone, especially Acartia clausi (23,000), Oithona 

 similis (1,500), and Copepod nauplii (70,000). Other 

 similar results were obtained at the same locality on 

 neighbouring days. 



Here is a haul (Form 38) ten miles off shore, in April, 

 where the two surface nets gave very different results and 

 the weighted net did not exceed them in quantity. The 

 bulk of the catch in all three nets was Copepoda both 

 young and old. Oikojrteura is rather evenly distributed 

 in these nets, there being roughly 3,000 in each. The 

 shear-net haul was taken on the way in, half-way between 

 the Calf Island and Port Erin, and shows an extraordinary 



