170 BULLETIN OF THE BUEEATJ OF FISHERIES 



Like all sticklebacks it is distinctively a shore fish, the great majority of the 

 local stock living their whole lives in estuarine waters. Enough stray out to sea, 

 however, for it to be rather common to pick up a few here and there in the tow net, 

 right out to the center of the Gulf. On such occasions they usually hide in clumps of 

 floating eelgrass (Zostera) or rockweed (Fucus) ; indeed we have learned to expect 

 a stickleback or two whenever we dip up bunches of weeds of any size. These 

 wanderers keep to the surface except, perhaps, in very rough weather. °' 



Wherever found alongshore it is a permanent all-the-j'ear resident, merely 

 dropping down into slightly deeper water such as the bottoms of the deeper creeks 

 to pass the cold months. In such situations it probably lies in schools in a more or 

 less sluggish condition while the tem.perature is lowest.°^ It is proverbially a pug- 

 nacious fish, using its spines with good eflect as weapons of ofi'ense and defense even 

 on other fishes much larger than itself. 



Food.— This fish feeds iadiscriminately on the smaller invertebrates, on small 

 fish fry, and on fish eggs, to which it is exceedingly destructive in fresh water. It is 

 not only onmivorous but very voracious, the diet list of specimens examined by 

 Vinal Edwards at Woods Hole including copepods, of which they are often full, 

 isopods, schizapod shrimps, young squid, and some had fed on diatom.s only. 



Breeding habits. — This stickleback affords the classic instance of nest building 

 and of the care of eggs among fishes, and its nesting has been described so often in 

 popular natural histories that a bare outline will suflice here.'" The spawning time 

 is probably the same in the Gulf of Maine (May and June) as in North European 

 waters,' when the fish assume the nuptial dress described above and the males fight 

 fiercely. It is the male that biulds the nest, selecting for this purpose some sheltered 

 spot in shoal water or in some rock pool. Here he builds a barrel-shaped mass, an 

 inch or so in diameter, of bits of grass, weed, etc., cemented together with mucous 

 threads, which he spins from his kidney's, and weighed down with pebbles. To this 

 nest he escorts one or a succession of females, each of them depositing 100 to 150 

 eggs in the central cavity. The male then enters the nest to fertilize the ova, which 

 stick in clumps to each other and to the nest. Incubation occupies 6 to 10 days, 

 during which period the male guards the nest, driving away intruders large or small. 

 WTien hatching time approaches, however, he tears down the nest but continues to 

 guard the fry until these can shift for themselves. The young fish are 4.25 to 

 4.5 mm. long at hatching time. In three or four days the yolk sac is absorbed, 

 when a week old they are almost 8 mm. long, and when 6 weeks old and 14 to 16 mm. 

 long the fry are of adult form with fins and spines fully formed.^ This little fish is of 

 no commercial value in America. In Scandinavia, however, it is sometimes seined 

 in such quantities that it is worth boiling down for oil. 



•' We have taken this stickJeback on the eastern part of Georges Bank (Mar. U, 1920); over German Bank; in the western 

 basic (station 10307); off Cape Cod; near the Isles of Shoals; off Seguin; and off Matinicus; but in the Bay of Fundy it is known 

 only close to land and off the months of estuaries. 



88 Large numbers are sometimes seined in winter in Scandinavian waters. 



" Smitt (Scandinavian Fishes, 1892) and C. Tate F.egan (The fresh-water fishes of the British Isles, 1911, XXV, 287 pp.. Pis, 

 I-XXXVII) give accounts of the nest building on which the following is based. 



1 About Woods Hole it spawns from May until the last week in July. 

 Figures of stages in development of this flsh are given by Kuntz and Eadcliffe (1918, p. 131), A. Agassiz (1S82, p. 2.S8, plate 9) . 

 and by Ehrenbaum (Nordisches Plankton, Band I, 1905-1909, p. 319) 



