488 BULLETIN OF THE BUBEAU OF FISHERIES 



Although the plaice may be considered rather a deep-water fish compared to 

 most other flounders common in the Gulf of Maine, it spawns there chiefly in water 

 shoaler than 50 fathoms as do all its relatives except the halibut. In fact it is 

 doubtful whether plaice ever spawn deeper in the Gulf, for we have few egg records 

 from more than a mile or two outside the 50-fathom curve and these few are based 

 on only one or two eggs each. 



There is no reason to suppose that plaice gather in definite localities to spawn, 

 except that those living deepest must work up into shoaler grounds to account for 

 the concentration of our egg catches inside the 50-fathom contour. 



The temperatures and salinities in which the eggs are produced can be stated 

 with confidence for the Gulf of Maine because the plaice lies very close to, if not 

 actually on, the bottom. The earliest spawning takes place at nearly the minimum 

 temperature for the year, averaging about 37° for all the March and April stations; 

 and while the water warms to 41° to 43° by late May and early June at the depths 

 inhabited by the ripe fish we have not found its eggs where the bottom temperature 

 was higher than about 40°. Thus the optimum for breeding may be set at 37° to 

 40° for the Gulf of Maine as a whole. Plaice spawn freely in 31° to 32° off Cape 

 Breton, and even in water as cold as 29.3° to 36° in the Gulf of St. Lawrence, proving 

 that the lowest Polar temperatures are no bar to the ripening of the sexual products. 

 It is probable, however, that somewhat w r armer water is requisite for the normal 

 development of the eggs and survival of the resultant larva?, a point calling for 

 experimental investigation. 



The Gulf of Maine plaice spawn in relatively low and uniform salinities, the 

 range being only from about 31.8 per mille to 32.8 per mille at the bottom at the stations 

 where eggs were taken in any number. Although plaice, spawn so generally through- 

 out the whole area which it inhabits there is evidence that different regions differ 

 in their suitability as nurseries either for the eggs or for the newly hatched larvae. 

 The southwestern part of the Gulf of Maine must be favorable in this respect, for we 

 have taken larval plaice at 14 stations there, most of these off the Massachusetts 

 Bay region, and they have also been taken at various localities off the southeast coast 

 of Nova Scotia, on the Newfoundland Banks, and in the Gulf of St. LawTence. How- 

 ever, it seems that reproduction does not succeed in the Bay of Fundy, for neither 

 larvae nor young fry are known there in spite Of the fact that plaice spawn and 

 eggs develop at least partially. We have failed equally to find any plaice larvae 

 off the coast of Maine east of Penobscot Bay, though eggs are produced there in 

 abundance (fig. 244). The case is complicated by the strong probabihty that there 

 is a general drift from northeast to southwest along this part of the coast, and hence 

 that buoyant eggs spawned there might hatch a considerable distance west of 

 where they were produced. The influence which this drift may have on the dis- 

 tribution of larval fish in the Gulf of Maine offers a most fertile field for future 

 study. 



The plaice is a prolific fish, individual females producing 30,000 to 60,000 

 eggs, according to size. The eggs are buoyant, without oil globule, but with 

 a perivitelline space so broad that they are not apt to be confused with any other 

 species. This space forms after the eggs are shed by the entrance of water between 



