SURFACE- CURRENT STUDIES OF SAGINAW BAY AND LAKE HURON, 1956 



It is increasingly apparent to students 

 of aquatic biology that water currents and 

 movements of large water masses play a para- 

 mount role in the life cycle of many aquatic 

 organisms. Water movements influence the 

 distribution and ultimate survival of eggs, 

 larvae, and adult aquatic organisms. The 

 relation is direct when organisms are car- 

 ried along actively by currents, and indirect 

 when currents cause changes in environmental 

 factors such as temperature, salinity, and 

 other physical and chemical conditions. 

 Although the direct effects are more obvious, 

 the indirect influences may play an impor- 

 tant role in survival and distribution of 

 aquatic life. 



At times movements of water masses can 

 alter so adversely the habitat of fishes, 

 especially those that live in a narrow 

 environmental range, that kills of catastro- 

 phic proportions occur. The disaster which 

 overtook the tilefish off the northeastern 

 coast of the United States in 1882 was due 

 to a sudden but temporary flooding of cold 

 polar water into the warmer waters normally 

 inhabited by this fish (Bigelow and Welsh 

 1925). An estimated 1 1/2 billion dead 

 fish were sighted on the surface waters 

 shortly after this calamitous event. Not 

 only was fish life affected but certain 

 invertebrates were exterminated by the cold 

 mass of water. Outbreaks of red tide off 

 the western coast of Florida are probably 

 initiated by water masses which differ in 

 salinity and chemical characteristics from 

 the normal water off the Florida coast 

 (Slobodkin 1953). Slobodkin believed that 

 prediction of red tides would depend on 

 more detailed knowledge of coastal drainage 

 and hydrography, and that prevention of red 

 tides may be possible, to some extent, by 

 altering certain coastal drainage patterns. 



The adverse effects of movements of 

 water masses upon fish populations are 

 probably matched by an equal number of 

 favorable incidents. The 1904 year class 

 of herring in the North Sea dominated the 

 commercial herring fishery in that area 

 from 1908 to 1919. This year class was 

 prominent for other species also. Evidence 

 indicated that the success of this year's 

 hatch was due to an abnormally intense 



inflow of Atlantic water into the North Sea 

 that carried with it either an abundance of 

 the actual food required by newly-hatched 

 fishes or provided certain nutrient salts 

 resulting in a high abundance of basic food 

 organisms (Tait 1952). According to Tait , 

 there seems little room for doubt that the 

 essential causes of fishery fluctuations lie 

 in hydrographic conditions and that adequate 

 observations of these conditions affords 

 the surest means of anticipating these 

 fluctuations. He perceived that the rela- 

 tionship of hydrography to fisheries is 

 analogous to that of meteorology to agricul- 

 ture. 



In recent years, certain commercial 

 fisheries of Saginaw Bay, Michigan, have 

 deteriorated at an alarming rate. The 

 annual commercial catch of the walleye 

 ( Stizostedion v. vitreum ) has decreased in 

 the last decade to such an extent that the 

 economy of this fishery has been greatly 

 weakened (Hile 1954). Many fishermen attri- 

 bute the scarcity of the walleye in the bay 

 to pollution. Production of lake herring 

 ( Leucichthys artedi ) and whitef ish ( Corego - 

 nus clupeziformis ) is also low. The yellow 

 perch (Perca f lavescens ) , on the other hand, 

 are at such a high level in numbers that 

 their growth is stunted (El-Zarka 1958). 

 A fishery survey conducted with the study 

 upon which this report is based revealed 

 an abundance of alewives (Pomolobus pseudo - 

 harengus ) and smelt ( Osmerus mordax ) but 

 there is little commercial production of 

 these species. 



The U. S. Fish md Wildlife Service 

 and the Michigan Department of Conservation 

 conducted a cooperative limnological survey 

 in Saginaw Bay and adjacent Lake Huron 

 waters in the summer and fall of 1956 (fig. 

 1). The objectives of the study were to 

 gain basic information on species composi- 

 tion and species inter- and intra- relation- 

 ships, and to develop the possible causes 

 of the fluctuations in the Saginaw Bay 

 fisheries. As part of this project drift 

 bottles were used to obtain information on 

 the current systems and to determine the 

 amount of water interchange between the bay 

 jind lake. This report analyzes the drift 

 bottle movements in Saginaw Bay and Lake 



