40 Fishery Board for Scotland. 



tlie coast. On the European side of the Atlantic, the known spawning range 

 extends from the Mediterranean to the northern North Sea. The extension of the 

 limits of spawning towards the north depends on the physical conditions in the 

 Atlantic at the time of spawning. The frequency of spawning in the northern 

 portion of the North Sea, which is under influences fromi the Atlantic, is dependent 

 on these conditions. Spawning begins earliest in the Mediterranean, probably- in 

 the winter months, but at least as early as January ; the spawning is later further 

 north in the Atlantic ; in the northern North Sea, spawning may begin as early as 

 March, and it extends to the end of July. 



The method of deposition of the eggs in long extended bands of mucus, and the 

 characteristic development of post-larval adaptations secure for the species a very 

 prolonged pelagic life, and during this early period the young forms may be carried 

 very considerable distances from the original spav/ning grounds by the prevailing 

 currents. Even when the larvae are hatched from the eggs, they may be detained 

 for some time in the gelatinous matrix which tends to keep the larvae in the upper 

 water layers until post-larval structures are developed. The appearance of the 

 larvae and post-larvae is very unlike that of the ty]>ical bottom form. In the pelagic 

 stages, the body and head are laterally compressed, and the eyes are situated on 

 each side of the head. The young forms svv^im upright in the water. From the 

 earliest stages, the embryonic fin is especially broad, and it is very persistent, 

 traces remaining even in the older post-larval stages. As the post-larvae grow, 

 the embryonic fin is replaced by the development of the unpaired fins, and the 

 enormous development of the membrane between the rays of these fins adds greatly 

 to the depth of the fish, thus giving stability to the pelagic form. The paired fins 

 are extremely well adapted for pelagic life. The pectoral fins, as ]ierfect balancing 

 organs, are large and fan-shaped, attached high up on the body just behind the 

 gill-openings, whose surface is in a plane parallel to the plane of symmetry. The 

 pelvic fins — enormously developed — extend far beyond the body, and the fila- 

 mentous tips of the rays grow to an extraordinary length. When expanded, 

 these fins have an enormous surface in comparison to the size of the small fish, 

 and attached far forward on the ventral surface of the fish their rapid up-and-down 

 motion keeps the young fish in the upper water layers. The pelagic life may last 

 many months, and the young form appears to be more than nine months old before 

 it takes to a bottom habitat. During the pelagic period, the young forms may be 

 drifted far from the spawning area. In the North Sea, sheets of spawn may be 

 drifted south from the deeper northern area and may be ultimately stranded on 

 the east coast of Britain. In the Atlantic, the prevailing current carries the young 

 pelagic forms northwards and eastwards ; some may be carried towards Iceland, 

 for isolated specimens have been taken over waters of great depths to the south of 

 Iceland ; others may be carried up over the Faeroe-Shetland Channel, whilst a 

 number may enter the North Sea by the channels betvv^een Scotland and Shetland. 

 The magnitude of the northerly immigration at this stage will depend largely on 

 the prevailing conditions iu the Atlantic. In the Mediterranean, spawning does 

 not occur in the coastal water, but the sheets of spawn may be drifted into shallow 

 areas, such as the Gulf of Naples, from the near deep water areas. Spawning 

 does not occur in the shallow inner region of the Adriatic, and the post-larval forms 

 are late in arriving there, as the area is far removed from the deep water of the 

 Mediterranean. On the American side of the Atlantic, the deep water is adjacent 

 to the coast, and therefore the sheets of spawn and the larval forms have been fre- 

 quently met with in the coastal area at such places as Newport and in Massachusetts 



Bay. 



The prolonged pelagic life therefore secures a wide distribution for the growing 

 forms. The extension of the distribution area does not stop at the completion of 

 the pelagic life. The change from the typical pelagic form to the bottom form is 

 progressive but slow, and the young fish may take to a bottom habitat long before 

 these changes are complete. In the North Sea area, although the larger forms are 

 common, the very small bottom forms are extremely rare ; few are found less than 

 200 mm. in length. The Angler does not appear in the North Sea in numbers until 

 it is at least one year and a half old, and even then the smaller ones are relatively 

 in greater proportion in the northern and deeper parts of the North Sea. Although 

 the North Sea thus depends on its supply of Anglers from areas beyond its own 



