102 



Part III. — Seventeenth Annual Report 



here compared is quite an arbitrary one, and is only used in order to 

 show the relation between the numbers of eggs just spawned and the 

 numbers of eggs present in the waters at certain dates. It simply 

 indicates increase or decrease in a, In a single week after each of these 

 dates it is quite possible that the ratio might have very materially 

 altered. While we are dealing with the sum of the eggs of all species, 

 the change from a minimum to a maximum spawning season for any 

 individual species must also be taken into account. The large increase 

 in the ratio of newly spawned eggs at any period is mainly due to the 

 fact that a number of species begin spawning then. For example, in 

 March the ratio of a to x is equal 1 *2. In February seven species were 

 spawning, and in March other eight species commenced to spawn. 

 At the same time two species, haddock and bib, had reached 

 their greatest spawning period ; but the numbers of their eggs are so 

 small as not to affect the main result. At the height of the spawning 

 period of a fish the number of eggs in each of the stages ought to be 

 very nearly equal, or at least ought to show a greater tendency towards 

 equality than they would do in early or late portions of said period. 



In April six species commenced spawning, and for eight species this 

 month was the main spawning time. We find, then, that the ratio of 

 a to x is diminished by one-fourth — viz., to 75. 



Twenty-one species were spawning in May, but none of these was 

 at its maximum; three species commenced spawning. The ratio has 

 increased, and now equals 1. The ratio decreases again in June — viz., 

 to *68. During this month seven species are at their main spawning 

 period, and four species commenced spawning. In July the ratio is 

 again increased — viz., to *9. Twenty-two species are still spawning; 

 five species have left off spawning. 



The five stations vary as regards the numbers of eggs in Stage a. 

 The presence of large numbers of eggs in the first stage of development 

 in any area may be taken as prima facie evidence that they were 

 spawned somewhere in the neighbourhood, since, on an average, such eggs 

 are not more than two days old. By the data supplied by the Table an 

 attempt might be made to infer the location of the principal spawning 

 places. It must, however, be borne in mind that the transport of 

 floating eggs from one place to another may take place with considerable 

 rapidity, especially in cases where the surface water is acted upon for any 

 length of time by the wind blowing in one direction, or when the tidal 

 movement is great. (See p. 119.) 



The proportion of eggs in each stage is shown diagrammatically in 

 Plate III. A circle is used to represent 3600 eggs, and a segment of the 

 circle proportional in size to their number is given to the eggs of each 

 stage. The segments are contrasted by difference in shading. Fig. 1 

 gives the key to the shading adopted, segment I. referring to Stage a, 

 II. to Stage ft III. to Stage y, IV. to Stage 8, and V. to Stage e. It is 

 at once seen from an examination of the plate that spawning appears to 

 take place chiefly in the vicinity of Station V., at the very head of the 

 loch. In April and May especially the proportion of early eggs was 

 very great ; and in March also they exceeded the sum of the eggs of 

 later development. Stations II. and III. are also probably closely 

 associated with spawning places. 



The eggs have so far been discussed without regard to species. Tables 

 XIII. aud XIV. give analyses of the eggs of the more important species 

 with respect to the stage of development. Cod and haddock have been 

 grouped together, as also h?ve whiting and saithe. 



