COMM. B — DEC. 1903 — APPEND. B ( 48 ) 
The beam trawl used on one occasion by the “Huxley” has a beam of 
13 metres, and the size of the meshes is slightly smaller throughout than in the 
case of the otter-trawl. 
The Selective Power of the Nets 
“Thor” (Tables 1—3) 
The “Thor” constantly caught a smaller proportion of plaice (P. platessa) 
from 10 to 19 cm. in length, and a larger proportion of FP. platessa from 20 to 
29 cm. in length, than did the “Huxley”, the difference amounting to about 100: 
This difference appears to have been caused by the larger size of the mesh in 
the cod-end of the trawl used by the “Thor”. 
On the other hand, the “Thor” constantly caught from 4 to 9 % more 
dabs (P. limanda) of the lowest size group (0 to 9 cm.) than did the “Huxley”. 
The total numbers caught of this species both by the “Thor” and the “Huxley” 
were, however, too small to render these figures reliable. 
“Poseidon” (Tables 4 & 5) 
The results yielded by the comparative trials of the “Poseidon” and the 
“Huxley” were inconstant, both for P. platessa and P. limanda; but the selective 
action was apparently identical on the whole. 
“Wodan” (Tables 6 & 7) 
The “Wodan” usually caught a slightly smaller percentage of small P. pla- 
tessa (10 to 19 cm.) than the “Huxley”, but the average difference (2 °/o) is so low 
that it is possibly without significance, especially as it was not a constant feature. 
“Goldseeker” (Table 8) 
The trials with the “Goldseeker” were, unfortunately, limited to a single 
haul. On this occasion the “Huxley” caught six times as many small Zleuronec- 
tidae (10 to 19 cm.) as the “Goldseeker”, — a difference in efficiency which 
diminished for the larger fishes, the “Huxley” having caught only twice. as many 
Pleuronectidae at 40 to 60 cm. The catch of the two vessels as regards round. 
fish (Gadidae) was practically identical. 
Total Catching Power 
The “Thor’s” efficiency as compared with that of the “Huxley”, was less 
than one half for Plewronectidae, whether compared with the otter or beam trawl 
of the latter vessel. This difference is, of course, attributable to the much smaller 
trawl employed by the “Thor”. 
