in the 1956 Cisco survey and provides additional rec- 

 ords on general geographic distribution (occurrence 

 in inner bay and outer bay) for 13 other species. 

 Three species, not listed in either table 2 or table 3, 

 are also known to inhabit, or to have inhabited, the 

 bay. Past commercial catch records show that lake 

 trout (Salvelinus namaycush ) and round whitefish 

 ( Prosopium cyllndraceum ) were both taken in Sagi- 

 naw Bay. Specimens of the sea lamprey ( Petrom y- 

 zon marinns ), a predator of considerable consequence, 

 are present in the Bureau's collection from earlier 

 studies. These various distribution records from the 

 Cisco survey, past Bureau collections, the Museum 

 of Zoology, and commercial catch statistics contri- 

 bute a total of 74 known species for Saginaw Bay. 



SEASONAL MOVEMENTS 



Alewives 



The older alewives were numerous only during 

 spawning which took place in the inner bay in late 

 July (gill net records) and early August (308 per trawl 

 tow; table 4). Adults were captured only infrequently 

 after this time in all areas. 



Approximately 97 percent of the alewives taken 

 by trawling during the season were young-of-the-year. 

 They were the most abundant species in the inner bay 

 during October (2, 549 per tow) and shallow area (2- 

 7 1/2 fathoms) of the outer bay in September and Oc- 

 tober (328 and 2, 847 per tow, respectively). The ale- 

 wife (both O group and older) was scarce in the deeper 

 portions (8-25 fathoms) of the outer bay in August (6 

 j)er tow) and October (103 per tow). 



Experimental trawling, supplemented by gill 

 net fishing, has furnished a few clues to the season- 

 al movements of the more abundant species of Sagi- 

 naw Bay. Althou^ samples are scattered and infre- 

 quent for some areas and lacking for most of the 

 year in others, certain trends are evident. The most 

 useful information comes from the trawling records. 



Five trawling stations were located in the outer 

 bay and five in the inner bay (fig. 1). In order to min- 

 imize gear bias, calculations of relative abundance 

 for the three areas - -inner bay and shallow and deep 

 waters of the outer bay --were based entirely on fish 

 taken in trawl No. 2 (table 1) in each month except 

 June (see footnote to table 4). All catches are given 

 in terms of the number of each species taken in 10 

 minutes, the usual trawling time; the actual catches 

 of tows shorter or longer than 10 minutes were ad- 

 justed accordingly. 



The older smelt were dominant in the shallow 

 inner bay during July (955 per tow), but were not 

 abundant in the same area in August and October (42 

 and 17 per tow). Most of them apparently moved to 

 the cooler, deeper water of the outer bay (and the 

 open lake) when temp>eratures of inshore areas reached 

 15°-17° C. (59°-63° F.), for the smelt was the most 

 numerous species in this area in August (471 per tow). 

 October trawling revealed the return of older smelt 

 to the shallow portion of the outer bay (937 per tow) 

 but did not take them in the deeper area. 



The O -group smelt were numerous from July to 

 October in all areas of the bay except the deeper part 

 of outer bay in August. Temperature change appears 

 to be decidedly less influential in the distribution of 

 young smelt than for the adults. 



Nylon gill nets set on the bottom at various lo- 

 cations were helpful in determining distribution and 

 species composition of the larger fish in the popu- 

 lation and provided samples in certain areas where 

 the bottom is not suitable for trawling. Many of the 

 larger fish that elude trawls axe vulnerable to giU nets; 

 thus the combination of both fishing methods in some 

 areas offered a more representative sample than could 

 be taken by either gear alone. Unfortunately, this 

 combination of fishing methods on the same date and 

 location was not possible in most areas (appendix 

 table 1). The contribution of additional data from 

 gill net catches was most valuable for adult alewives, 

 chubs, lake bening, walleyes, and white suckers. 



Yellow Perch 



Yellow perch of age -group I and older were 

 caught in all areas throughout the season. They were 

 most abundant in August in the inner bay (962 per 

 tow) and in the deep outer bay in October (1, 017 per 

 tow). They were least plentiful in the shallow outer 

 bay in October (17 per tow). 



Young-of -the -year yellow perch were taken only 

 in the inner bay. They inhabited very shallow inshore 

 areas during the summer (seining records) and were 

 numerous in the trawl catches in the inner bay in Oc- 

 tober (350 per tow). 



4 



