23 



APPENDIX H: GARSTANü 



Gram 

 ISOO 



1400 



1100 

 IDOO 

 300 

 »00 

 700 

 600 

 500 

 400 



m 



wo 

 m 



«5 20 22i 25 275 30 22;> 3S ili 40 «5 45 475 



lipon tlie charts on the present occasion. In tlie accompanj'ing diagram, Pig. 10, however, 

 tlie average weiglit per flsli for hauls of plaice of different average size has been graphicallj' re- 

 presented. The figures at- 

 tached to the individual 

 points upon the black curve 

 of observed data represent 

 the number of hauls from 

 whicli the averages have 

 been derived. On the same 

 diagram a curve' is shown 

 wliich represents the nor- 

 mal increase of weiglit for 

 individual fishes of suc- 

 cessively greater size. It 

 will be observed that in 

 the case of hauls in which 

 the average size of plaice 

 is less than 30 cm., the 

 average weight per fish 

 corresponds very closely 

 with tlie normal weight of 

 individual fishes of corre- 

 sponding size. But from 

 30 cm. upwards the ave- 

 rage weight of the fishes 

 at eacli successive average 

 size tends to exceed appreciably tlie normal weight of individual fishes at the same size. This 

 phenomenen is easily intelligible owing to the fact that the weiglit of the fish increases pro- 



' A single average c\ii"vo, Kcioi'i^lb' apiilicable over the whole North Sea area, appears to be impossible 

 of attainniciit in the case of the smaller tishos, which show marked local as well as seasonal ilitlerences. 

 The curve here presented is the mathematical curve, varying as the cube of the length, and based on the 

 assumed datum that plaice of 20 cm. length possess an average Weight of 90 grams. It corresponds with 

 the observed data that have been published by Fulton (XII"' Report Scottish Fishery Board, pp. 141—205) 

 and Meek (Rejiort of the Noi'thumborland Soa Fisheries Committee for the year 190n, pp. 40, 41) as regards 

 the weight of tlie larger fishes, but somewhat exceeds tlio average woi.i:;hts given by these observers for plaice 

 of less than ?>0 cm. L'ngtli. The difference is slight by eomparisou with Meek's data (about 5 per cent.), 

 but somewhat greater by comparison with Fulton's (about 10 jier cent.). The excess is greatest of all 

 (about 20 per cent.) by comparison with Archer's data concerning fish from the Sylt and Horn Reef (îroiiiuls 

 (Report from the Select Committee of tlio House of Lords on the Sea Fisheries Bill, together with minutes 

 of evidence. London 1004, p. 80). 



These local deviations from the ideal curve in the case of small fishes present a problem for further in- 

 vestigation. Although other factors are doubtless concerned, it appears probable that the exiihination is to 

 be sought chiefly in the bibornatiug habits of small plaice in winter, winch aro thenisolvos dependent on 

 the minimum temperature and its duration. During this period the fish do not feed, and conscipiently 

 lose weiubt. The hydrographie investigations of the last two years (cf Bulletins for February Tt'M'-) and 

 1904) show that the winter temperatures are much lower on the Eastern grounds than elsewbere in the 



Fig. 10. Diagram, showing the relation between Average Size (cm.) of 



Plaice and Average Weight per fish (gr.) for the number of hauls of the 



trawl enumerated (Dutch and English observations). The curve without 



figures shows the normal relation for indiviilnal fishes. 



