60 



Part III. — Twenty-sixth Annual Report 



basis of comparison is less extensive; the mean reduction was 11 plaice per 

 hour, and two of the stations showed an increase in the second period. 



It will be observed from the tables giving the detailed averages for 

 each of the collections that the fluctuations at any station from month to 

 month and year to year were considerable. The mean annual average 

 number of plaice per hour's fishing varied in the first period from 24 to 

 174, and in the second period from 8 to 112. In the month of June the 

 mean, for all the stations combined, fluctuated in different years from 

 10*2 to 33-4 ; in July the mean varied from 24 to 266*8 in the first 

 period and from 8*7 to 172 in the second periocl ; in August it varied 

 from 5 to 112, and in September from 22 to 54. At the individual 

 stations the fluctuations were still greater, as shown in the tables. 

 Fluctuations in quantity in this way are, of course, prominent in all fish- 

 ing operations. Thus, in the trawling experiments of the " Garland," in 

 the Firth of Forth, the fluctuations in the average catch per hour's trawl- 

 ing at the same station in the same month of different years varied for 

 plaice from 1 to 44, for dabs from 0 to 112, for haddocks from 0 to 296, 

 and for whitings from 0 to 50. But the means for all the observations in 

 a year were much less, namely, for plaice from 5 9 to 9, for dabs from 

 4'4 to 8*6, for haddocks from 3*3 to 26 '9, and for whitings from 2'2 to 

 14'4. It would be of importance to determine, if possible, whether the 

 fluctuations in the take per hour were representative of the fluctuations 

 in the natural abundance of the young plaice at the stations on the 

 various occasions when fishing was carried on. A study of the parti- 

 culars as tc the physical conditions prevailing when the collections were 

 made does not appear to show that they had much influence on the 

 averages. It might be expected that when the water was clear the 

 average would be reduced, because of the visibility of the approaching 

 push-net to many of the young plaice, but many of the best catches were 

 taken under such conditions, and the work was not prosecuted if the 

 weather was rough. It is to be noted that, as a rule, when the average 

 was high at one station or in one month it was also high at the other 

 stations and in the succeeding month. Thus the most productive year 

 in the first period was 1901, and the average in each month and for each 

 station was very high, higher than in any other year of the period, except 

 at Lochgilphead in July. In the second period the most productive 

 year was 1905, and here again the averages at each of the stations and 

 in each month were very high — the highest for any year in the period 

 except at Big Harbour in August. So also in the years of low means, 

 the averages at each of the stations and in each of the months were as a 

 rule low. This may be illustrated by contrasting the averages for 1904 

 and 1 905 as follows : — 



Lochgilp- Big 



head. Harbour. Salen. Strachur. Inveraray. Mean. 



1904— June, — 21-6 

 July, 30 10-8 

 August, 16 5 5 



1905— July, 83-0 332 0 

 August, 118-1 54-5 

 September, 99*0 97*5 



From this general uniformity at the various stations and in the 

 different months of a year, it may be concluded that the averages repre- 

 sent approximately an actual abundance or scarcity of the young plaice 

 on the beaches in Lochfyne in that year, and that they are not due to 

 accidental or temporary circumstances. 



5-6 



10-0 



2-0 



10-2 



128 



9-8 



8-4 



9-2 



8-8 



3-3 



4-4 



4-9 



230-9 



104-5 



90-7 



172 0 



252 0 



64-5 



45-6 



112-0 



18-5 



18-5 



14-5 



496 



