32 
Proceedings of Royal Society of Edinburgh. [sess. 
( 24! lbs. : 37f": clean: 6 : 14th Nov. 1902 : Westshot, Linn of 
No. 8882 < Campsie. 
i 22| lbs. : 40" : clean : 13th Feb. 1903 : Flookie, in tidal water. 
! 7f lbs. : 27" : unspawned grilse : $ : 22nd Nov. 1902 : Almond- 
mouth. 
12 lbs. : 31|" : clean : 13th Aug. 1903 : Needle station. 
No 9402 I : 2 ^ ,r : g r il se kelt: $ : 5th Feb. 1903: Logierait, Upper Tay. 
1 10! lbs. : 30 : clean : 31st July 1903 : Flookie station. 
The intervals of time are, in order, 556 days, 447 days, 191 
days, 91 days, 295, and 176 days. In other words, we have one 
recapture after 18 months, and, at the other extreme, a recapture 
after only 3 months, but this latter is peculiar, since the fish was. 
clean run when marked. It is just possible that this fish, No. 
8882, may have been descending (without having spawned) when 
recaptured. The loss of weight is significant. 
I have already noticed that the gill maggots are commonly 
found on kelts. Lerneopoda salmonea is usually believed to be 
exclusively a fresh- water parasite. My attention was first called 
to the fact that this may not be the case in the results obtained 
by the marking of salmon which has been conducted by the 
Fishery Board for Scotland during recent years. A grilse kelt, 
marked in the Deveron on 11th March 1901 by a silver label 
numbered 6508, was recaptured on 11th July of the same year, 
at Cove, just south of Aberdeen. To have travelled in four 
months round the coast, passing, as it had done, the mouths of the 
rivers Ugie, Ythan, Don, and Dee, is sufficient to show that the 
fish must have been some time in salt water, and between marking 
and recapture it had gained 2f lbs. in weight, yet quite a number 
of maggots were still attached to the gills when I received the 
fish. This induced a more careful examination of the gills of fish 
ascending rivers from the sea, and during the continuance of 
salmon marking, Mr H. W. Johnston, who kindly associates himself 
with me in all the Tay markings, has noted, as I also have noted, 
many autumu fish with a few maggots in their gills — indeed, late- 
running fish are very commonly found with maggots. In salmon 
and grilse proper the maggots are never so numerous as in ‘ bull 
trout,’ or fish with certain bull trout markings, but I regard it 
as most significant that fish fresh from the tide-way in the lower 
Tay should be so found. Our marking experiments have shown 
