8 Proceedings of the Biological Society of Washington. 



LIST OF SPECIES. 



*Petromyzon marinus *Perca flavescens 



Ictalurus furcatus *Stizostedion vitreum 

 *Carpiodes cyprinus Roccus lineatus 



*Enmyzon sucetta oblongus *Morone americana 

 Alosa sapidissima 



Restriction of Fishes to Certain Parts of Our Area. 



The brook trout is confined to Difficult Run, probably because 

 that stream was the first resort found in the down-stream 

 journey by some pioneers or wait's from the normal mountain 

 home of the species. Campostoma anomalum and Hyhognathus 

 nuchalis have so far been collected only in Turkey Run; both 

 should be found elsewhere. Boleosoma effidgens has been found 

 at Little Falls; if it occurs in the upper part of these rapids it 

 may fairly be considered as a species of our area. Percopsis 

 omiscomaycus has been collected only in Cabin John Run; and 

 Exoglossum maxillingua and Etheostoma flabellare shared by this 

 stream and Rock Run have not been found elsewhere. The 

 pickerel { Esox reticulatus) has been taken only in the canal. The 

 river alone harbors the shad, and the striped bass, and has 

 yielded the only specimens so far caught of the sea lamprey, 

 forked-tailed catfish, and pike-perch. The carp sucker {Carpiodes 

 cyprinus), chub sucker {Erimyzon sncetta oblongus), the yellow 

 perch, and white perch, have been taken in both the canal and 

 river but nowhere else, and the mud-shad (Dorosoma) has been 

 collected only in the channel behind Plummers Island and in 

 the canal. 



Ecology of Some of the Fishes. 



Some of the above-mentioned restrictions in distribution are 

 no doubt due to ecological conditions; others can not be so 

 explained. A fact impressed upon one when seining the various 

 brooks is the extent to which the upper courses of the creeks are 

 monopolized by the fall fish iSemotilus atromaculatus) and the 

 black-nosed dace (Rhinichthys atronasus). These fishes are of 

 general distribution but it is evident that they are expert climbers. 

 They do not ascend streams merely to spawn for the upper 

 reaches of the brooks always have a certain population of these 

 two species, Etheostoma flabellare was found only in shallow 



