_ 23 — APPENDIX E: HEINOKE 



water and in the rivers, in smaller qnantities also in the "Wattenmeer". The larvse leave 

 the open sea, as a rule, before the migrating eye has reached to the ridge of the head. 



Young and older stages. 



Just as we have never found the eggs of the flounder in rivers or in brackish water, 

 we have on the other hand, never observed the first bottom-stages (about 13 to 15 mm. 

 long), and on the whole, the 0-group, except at these places; for example, on the 

 sandy beach at Twielenfleth on the Elbe a little below Hamburg, where we caught them 

 with the hand-nets in very large quantities on the 12*'^ of June 1903. How far the 

 flounder of the 0-group occur in the "Wattenmeer", has yet to be determined. P'lo under 

 of the 1- group occur together with plaice of the same size in the "Wattenmeer", and 

 occasionally also off this, as well as in the rivers and in brackish water. 



Flounder of the older years' groups are accustomed to venture considerably 

 further out to sea; we have met with them regularly, in great numbers, between the main- 

 land and Heligoland as well as close to Heligoland on the rocky ground of the island, 

 especially in autumn and winter, further, in isolated specimens as far out as the 20 m. line 

 all along the German coast. 



The flounder grows much more slowly than the plaice, and does not 

 grow to so large a size; we have taken them up to about 50 cm. only. A female 

 flounder of 42 cm. in length, caught at Heligoland in November, was at least already 8, 

 probably however 9, years old according to the rings of the otoliths and the bones; a 

 plaice of similar size is only 4 to 5, at most 6, years old. Corresponding to this, the 

 flounder reaches maturity at a smaller size. We have received spawning 

 flounder of 23 cm. and onwards; in Scotland, mature flounders have been observed at only 

 18 cm. in length. 



We have taken flounders with running spawn in the beginning of January, once 

 in great quantities off the mouth of the Weser just beyond the 20 m. line. In March, 

 we found similar flounders or specimens just spawned, further out to sea, 30 sm. N.W. 

 from Heligoland and at Borkum Reef on the 40 m. line, also in the neighbourhood of 

 Horns Reef and on the southern Mud Bank. 



The biological character of the flounder is similar to that of the plaice, 

 but it is more of a coast-fish and passes the first years of its life on the bottom, mostly 

 in brackish water and in rivers. Like the plaice, it spawns always in salt water; 

 its larvae wander from there during the metamorphosing stages towards the coast and the 

 first bottom-stages, which, like those of the plaice, are always formed perfectly symme- 

 trical, are found in quite shallow water immediately on the shore. 



3. The dab (Pleuronectes limanda) 



Eggs and larvse. 



5124 eggs and 228 larvse altogether were taken in the vertical hauls of March 1903. 

 The developmental stages of no other fish were taken m such enormous quantities. This 

 arises partly, from the fact that the spawning of this fish is at its height in March, partly 

 because the dab is certainly the commonest fish within the region investigated. 



The eggs were found in greatest numbers in the shallower parts of the southern North 

 Sea, between the 20 and 40 m. lines. The maximum, with ca. 800 eggs and larvœ per 

 square meter of surface, was met with to the north of Schiermonnikoog over 27 m. in 



