From May to November, inclusive, the kiyis of southern Lake Michigan (north to and including localities off Kewaunee, Wisconsin, and Frankfort, Michigan) characteristically inhabit depths of more than 50 fathoms, although small numbers commonly are taken in shallower water (as shallow as 20 29 fathoms). There is evidence that the occasional penetration of relatively large numbers of kiyis into depths of less than 50 fathoms in this area is the result of exceptional hydrographic conditions involving the disturbance of considerable masses of water.

In northern Lake Michigan the scattered lifts made in the region south of Manistique, Michigan, from June to September indicated kiyis to be abundant at depths from 40 to 69 fathoms (no lifts from shallower or deeper water). In northeastern Lake Michigan (Manitou, Fox, and Beaver Islands and the region between these islands and the east shore) kiyis were lacking in all lifts from 20–39 fathoms and were scarce at greater depths (three to four times as abundant, however, at 50–69 fathoms as at 40–49 fathoms).

The consistency with which kiyis remain in water deeper than 40 or 50 fathoms is difficult to explain on the basis of a preference for cold water (about 4°C.). Water of temperatures only a fraction of a degree warmer than that in the region occupied by most kiyis extended up to depths of less than 30 fathoms. Possibly the bathymetric distribution of the kiyi is related to that of its principal food organisms. It was suggested also that the deeper-water habitat may enable the kiyi to avoid strong currents and that an aversion for currents may account for the scarcity of the species in the hydro-graphically complex northeastern area. Other possible factors are chemical conditions of the water or a preference of kiyis for great pressure and darkness.

The abundance of kiyis appeared to be more or less uniform throughout the great central basins of Lake Michigan, except as related to depths of water. The scarcity of this species in the island region of northeastern Lake Michigan provided the only certain example of a regional difference in abundance.

The survey of 1930–1932 yielded 89 new locality records for the kiyi in Lake Michigan. These localities, together with those reported previously by Koelz (1929), have been charted in Figure 1.

Although the gonads of certain apparently aberrant individuals may ripen as early as mid-July and considerable pre-spawning development of the organs may occur in August, there is no evidence of significant spawning activities of kiyis in southern Lake Michigan before the latter part of September. Spawning continues through at least the first week or two in November and possibly longer. The peak of spawning activity seems to occur in the latter half of October and in early November.

The depth of water on known spawning grounds (all in southern Lake Michigan) was 57.5 to 84 fathoms. There is evidence that the kiyi may spawn in more than 90 fathoms. Spawning appears to be widespread throughout waters of suitable depth.