222 



Part III. — Seventeenth Annual Report 



The temperature changes are practically similar in St. Andrews Bay, 

 but they differ in the outer parts of the Moray Firth and in the Clyde, 

 although the observations in these areas are neither so numerous nor so 

 extensive. At the inshore stations in the Moray Firth (I. -VI.) the 

 changes in the abundance of gurnards in the various months resemble 

 those occuring in the inner parts of the Firth of Forth, except that in 

 October they are more abundant in the northern waters. When the 

 temperature observations are calculated, it is found that they agree fairly 

 well with this result. The means for the various months in which 

 observations were taken and hauls made at these stations are as follows : — 



May. June. July. August. September. October. November. 



48-1° 50-5° 52-3° 54-2° 52-8° 52-3° 47-6° 



The corresponding temperatures for the Firth of Forth stations are given 

 in Tables III. and IV., and it will be seen that the temperature in 

 October is about 1 deg. F. less. At the outer offshore stations in the 

 Moray Firth the temperature observations are not so complete, but they 

 show that the bottom water in October and especially in November is 

 still warmer, and this is related to the greater abundance of gurnards in 

 these months. (See p. 215). The mean temperatures are as follows : — 



May. June. July. August. October. November. 



45-5 deg. 477 deg. 50*2 deg. 52"1 deg. 52-6 deg. 49 -4 deg. 

 There are unfortunately no records for January, February, March, April, 

 and December. 



Similarly, the presence of gurnards in the Clyde area in January and 

 December, and their abundance in October and November, are explained 

 by reference to the higher temperature of the bottom water in that area. 

 The observations in the Clyde are not very numerous, but they show that 

 in January the temperature at the deeper stations where the gurnards 

 were chiefly caught ranges from 47 deg. F. to over 48 deg. F., or about 

 5 deg. or 6 deg. higher than in the Firth of Forth, where the same 

 bottom temperature exists in the latter part of June. In March, at the 

 Clyde stations, the bottom temperature is about 3 deg. higher than in the 

 Firth of Forth; in October, at the outer stations, it is about 1 deg. higher; 

 in November it is about 2*5 deg. higher, and in December the difference 

 may amount to over 6 deg. F., the temperature corresponding then to the 

 bottom temperature in the Firth of Forth at the end of July. 



The Relation of the Migratory Movement to Reproduction. 



The gurnard begins to spawn in April, and the spawning period extends 

 until the latter part of August, in some cases into September. Spawning 

 reaches its height in the early part of June, when the percentage of ripe 

 fish is greatest. The curve, based on the percentage of ripe fish among 

 those examined, is shown in the diagram (Fig. 2). The period over which 

 spawning occurs is therefore extensive, more prolonged indeed than in 

 most sea fishes.* Another feature in the reproduction of the gurnard, first 

 established by the investigations of the " Garland," is that the spawning 

 fish frequent the inshore waters, and shed their eggs there, within the 

 Firth of Forth, as well as in the waters a little further off. In this 

 respect the gurnard differs from most other fishes, and especially round- 

 fishes. Most other adult fishes, such as the cod, haddock, plaice, lemon 

 sole, &c, leave the shallower inshore waters at the spawniug period, and 

 shed their eggs offshore. The gurnard, on the other hand, approaches 



* Fulton — "The Spawning and Spawning Places of Marine Food Fishes." Eighth 

 Annual Report Fishery Board for Scotland, Part III., p. 257. Tenth Annual Report, 

 Part TIT., p. 232. 



