FISHES OF THE GULF OF MAINE 



261 



shore line, and that the growth marks on the 

 scales, in relation to the length of the fish, may 

 give a clue to the local origin of a given specimen, 

 for it seems that the rate of growth is governed 

 by the temperature of the water (p. 263). 



Habits. — Dabs are bottom fish like other flat- 

 fishes. But the}' must rise some distance from 

 the ground on occasion, and move about to a con- 

 siderable extent to account for the capture of so 

 many in gill nets (p. 264). We once caught one a 

 foot long in a tow net at least 5 to 10 fathoms 

 above the bottom off Ipswich Bay, where the 

 water was about 50 fathoms deep. 



Like some other flatfishes, they avoid rocky or 

 hard bottom, preferring a fine, sticky but gritty 

 mixture of sand and mud, such as floors much of 

 the Gulf between the hard patches, from the 20- 

 fathom contour out to the 100 fathom contour. 

 And they are also to be caught in numbers on 

 the soft oozy mud of the deeper basins in the 

 western side of the Gulf, as pointed out below 

 (p. 264). 



In one part of their range or another, they are 

 found from tide line down to as deep as about 

 390 fathoms (700 meters). 



This is an arctic-boreal species in its tempera- 

 ture relations, reaching its highest development in 

 water of 35° to 45° F.; able to live, however, in 

 the lowest polar temperatures (29° to 30°); and 

 finding the upper temperature limit to its regular 

 occurrence at about 50° to 55° F. 



In different seas it lives through a wide range 

 of salinity, from 30 per mille or lower in the Baltic 

 to upwards of 34 per mille in the open Atlantic. 

 So far as we are aware, it is never found in water 

 which could be described as brackish along the 

 coasts of New England or of the Maritime Prov- 

 inces. But R. II. Backus informs us that the 

 Blue Dolphin found it in brackish water (salinity 

 23 per mille) at the west end of Lake Melville, 

 Labrador. 



Huntsman's 84 statement that it feeds on minute 

 planktonic plants (diatoms) at first, but on cope- 

 pods as it grows larger and more active is our 

 only information as to the diet of the young fry 

 in American waters, while they are drifting near 

 the surface. When they first take to the bottom 

 they eat small shrimps and other Crustacea of 

 various sorts. But they turn (as they grow) to 



a diet consisting chiefly of sea urchins, sand dollars, 

 and brittle stars, as proved by the contents of 

 their stomachs, though they also take various 

 shrimps, hermit and spider crabs and other crus- 

 taceans, mollusks, worms and ascidians (sea 

 squirts), in fact, practically any bottom living 

 animals that are small enough for them to devour. 

 Occasionally they catch small fish. 



They do not bite a baited hook as readily as 

 various other ground fishes, partly, no doubt, 

 because they are sluggish fish, but partly, we 

 believe, because the clams, cockles, and herring 

 that are usually used for bait are not their favorite 

 food. Still, considerable numbers are caught on 

 hand and long lines. 



All the large predaceous fish that feed near 

 bottom probably prey more or less upon them, 

 and halibut no doubt destroyed great numbers 

 of them in the Gulf of Maine formerly. But the 

 adults can have no serious enemy in our Gulf 

 today except large cod and perhaps the spiny 

 dogfish. In more northern seas Greenland sharks 

 prey regularly on them. Smitt and Huntsman 

 both speak of the numbers of round worms to be 

 found in the intestines and body cavity of the 

 dab, and its gills are sometimes attacked by 

 parasitic copepods. 



While the young are drifting near the surface 

 (p. 262), they share in the same involuntary 

 journeyings as other fish fry do, that are spawned 

 at the same place and time. But it is one of the 

 more stationary fishes from the time it seeks bot- 

 tom. It has been said to work inshore more or less 

 in winter, though not on very definite evidence, and 

 it may congregate on definite grounds for spawn- 

 ing, though this is yet to be proved. But it is 

 certain that they are to be caught at any season 

 of the year wherever they are plentiful. And 

 Huntsman, 85 who has paid special attention to this 

 fish, believes that it "remains pretty much in the 

 same; place from season to season and year to 

 year. Perhaps in the course of years it may shift 

 a few miles." 



Individual females produce 30,000 to 60,000 

 eggs, according to size. The eggs are buoyant 

 and have no oil globule, but they have a trans- 

 parent (perivitelline) space around the yolk 

 so broad that they are not likely to be confused 

 with those of any other Gulf of Maine fish. 



»< Bull. Biol. Board Canada, No. 1. 1918, p. 15. 



" Bull. Biol. Board Canada, No. 1, 1918, p. 18. 



