FISHES OF THE GULF OF MAINE 



163 



form olive to bottle green, darker above, lighter 

 below, without definite markings though their 

 sides often show faint and indefinite crossbars of a 

 deeper tone of the same hue. Their fins are much 

 paler than those of males. Very young fry of 

 both sexes show dark transverse bars on the sides, 

 but these bars are lost with growth. 



Killifishes vary in shade from very pale to dark, 

 according to the color of their surroundings. And 

 recent experiments 91 have proved that their 

 ability to change from light to dark depends on the 

 sense of sight. 



Size. — The maximum length is 5 to 6 inches, 

 but adult mummichogs are seldom more than Z){ 

 to 4 inches long in the Gulf of Maine. Several 

 varieties of this species have been described, but 

 they are so closely allied that it is not necessary to 

 discuss them here. 



Habits. — The home of the mummichog is along 

 sheltered shores where the tide flows over beds of 

 eelgrass or salt hay (Sparlina), among which shoals 

 of "mummies" may often be seen moving in with 

 the flood tide. They abound in the tidal creeks 

 that cut the salt marshes, on the shores of our 

 harbors, and in the brackish water at the mouths 

 of our streams and estuaries, particularly in little 

 muddy pools, creeks, and ditches. So closely, 

 indeed, do they hug the shore that a line drawn 

 100 yards out from land would probably inclose 

 practically all the mummichogs in the Gulf of 

 Maine. Where the shore is bold and rocky, as it is 

 about the Bay of Fundy, the mummichog is 

 practically restricted to brackish water, and it 

 often goes up into fresh water. At the other 

 extreme, it is not likely that they ever descend to 

 a depth of more than a couple of fathoms in their 

 journeys in and out of the creeks or along the 

 shore. 



Mummichogs are so resistant to a lack of oxy- 

 gen, to the presence of carbon dioxide, and to un- 

 favorable surroundings generally, that they can 

 survive in very foul water. At ebb tide "mum- 

 mies" are often trapped in little pools where they 

 remain until the next tide if the water holds, often 

 huddled together in swarms. Should the pool go 

 dry, they work their way for the time being into 

 the mud, where we have often found them. 92 And 

 it is probable that they can flop overland for a few 



yards to some other drain as the striped mummi- 

 chog does. 



They winter in a more or less sluggish state on 

 the bottoms of the deeper holes or creeks, where 

 they have been found buried 6 or 8 inches deep in 

 the mud, 93 and there is no evidence that they move 

 out to sea during the cold season; in short, this is 

 one of the most stationary of fishes. 



Food. — "Mummies" are omnivorous, feeding on 

 all sorts of edible things, vegetable as well as 

 animal. They have been found full of diatoms, 

 eelgrass, and other vegetable matter; foraminif- 

 era; shrimps and other small Crustacea, also 

 small mollusks; and they sometimes have small 

 fish in their stomachs. 94 



They soon congregate about any dead fish or 

 other bit of carrion, to prey either upon it or upon 

 the amphipod scavengers that gather on such 

 dainties and they eat their own or each other's 

 eggs at spawning time. 



Spawning probably takes place at the same 

 season in the Gulf of Maine as on the southern 

 coast of New England; i. e., in June, July, and 

 early August. As sexual activity approaches, the 

 males (now brilliantly tinted) court and pursue 

 the females, rivalry among them being very keen; 

 those that are the most highly colored or most 

 excited usually driving off the others. Sometimes 

 they fight fiercely. They spawn in a few inches of 

 water, seeking shady spots. At the moment of 

 spawning the male clasps the female with his anal 

 and dorsal fins just back of her anal and dorsal, 

 usually forcing her against some stone or against 

 the bottom, the bodies of both are bent into an S 

 and their tails vibrate rapidly while the eggs and 

 the milt are extruded. 95 Occasionally, pairs clasp 

 and spawn free in the water without coming in 

 contact with any object, and sometimes a female 

 is seen to pursue and court a male. 



The eggs, which are about 2 mm. in diameter, 

 colorless or pale yellowish and surrounded by a 

 firm capsule, sink and become so sticky on contact 

 with the water that they mass together in clumps, 

 or stick fast to sand grains or to anything else 

 they chance to rest upon. Incubation occupies 

 from 9 to 18 days, the exact duration probably 



81 Parker and Lanchner, Amcr. Jour, of Physiol., vol. 61, 1922, p. 548. 

 " This habit Is described by Mast (Jour, of Animal Behavior, vol. 5, No. 5, 

 1915, p. 381). 



•» Chichester, Amer. Naturalist, vol. 54, 1920, p. 551. 



" Lists of stomach contents arc given by Field (Rept. U. S. Coram. Fish., 

 fl906) 1907, p. 29). 



•« Newman (Biol. Bull., vol. 12, No. 5, April 1907, p. 315) gives an Interest- 

 ing account of the courtship and spawning, from which the preceding Is 

 condensed. 



