GREAT LAKES COREGONIDS 



345 



the year round. This belief is based on the observation that eggs are found free in 

 the body cavity of an occasional specimen during the greater part of the fishing season. 

 Of course, in Lake Michigan, where some species may be spawning during every month 

 except June and July, such observations may well pertain to individuals spawning 

 normally; but in Lake Huron, where the spawning season of the four species falls 

 between August and January, some other explanation must be sought. It does not 

 follow that such specimens are spawning. In most bony fishes the eggs are formed 

 within a membranous ovisac and are carried from this to the genital opening by means 

 of an oviduct continuous with the ovisac. There are no openings connecting ovisac 

 or oviduct with the body cavity, and therefore the eggs can not get into the body 

 cavity on their way to the genital opening. 



In Coregonidse the oviduct is short and not continuous with the ovisac, so that 

 the eggs, after leaving the ovary, can get into the body cavity. It has been supposed 

 that the normal course of the eggs after leaving the ovaries was to fall into the body 

 cavity and thence to find their way out through the short oviduct. Kendall (1921) 

 has shown that the eggs probably pass along a trough formed by the mesovarium, 

 and that normally they do not escape into the body cavity. Should any eggs get 

 into the body cavity and remain there after the fish have left the spawning grounds 

 they would be noticed easily when the fish are dressed. Certain fishermen have told 

 me that they sometimes find eggs in the body cavity of the lake trout in summer. 

 Such eggs, they state, are much enlarged at this time. The retention of eggs in the 

 body cavity has been recorded at least once in literature. B. G. Smith (1916) states 

 that in many specimens of Cryptobranchus a few eggs are still to be found in the body 

 cavity after spawning. It is probable, therefore, that what the fishermen observe 

 outside of the spawning season are eggs that have been thus retained in the body 

 cavity, and there is then no evidence that the chubs deposit their eggs at irregular 

 intervals throughout the year. 



It has already been stated that four species of chubs are found in Lake Huron 

 and seven in Lake Michigan. Virtually every haul from the chub nets contains at 

 least a few representatives of each species, together with the smaller chubs and 

 bloaters that may be caught in nets with meshes of any size, even though they could 

 pass through a mesh 10 abreast. Large chubs, also, not rarely become entangled in 

 nets of mesh too coarse to gill them. Little is known concerning the proportion in 

 which the various species occur at the various locations in the lakes at different sea- 

 sons. What observations I have made will be recorded under each species concerned. 

 The fishermen themselves make no distinction between the species, and consequently 

 their records show nothing but the weight of the lift and sometimes the location of 

 the gang lifted. Some of these records show marked fluctuations in the abundance 

 of the chubs from month to month. In certain instances, with the aid of the results 

 of the examinations of the chub lifts, these fluctuations can be ascribed definitely 

 to the changes in the behavior of certain of the species of chubs. In Tables 14 and 

 15 are given statistics prepared from these records for 5 tugs from 5 ports on Lake 

 Huron and for 3 tugs from 3 ports on Lake Michigan, each of which operated large 

 chub gangs. For each tug the total and average weights of the catches are given for 

 each month as long as fishing operations were continued during the year. Such con- 



