Fisheries Research Report No. 1770, 1970

Michigan Department of Natural Resources
Research and Development Report No. 208
Institute for Fisheries Research Report No. 1770, 1970
Utilization of Alewives by Inshore Piscivorous Fishes in Lake Michigan

Wilbert C. Wagner

      Introduction.-The alewife (Alosa pseudoharengus) was discovered in Lake Michigan in 1949 (Miller, 1957). It soon became abundant, and by 1966 accounted for 68% of the commercial fish catch (U.S. Department of the Interior, 1968) and over 80% of the poundage in experimental trawls (Smith, 1968). During most of the year, alewives inhabit deep water. However, they spawn during May-August in inshore waters where resident warm-water fish are abundant. The effects of tremendous numbers of this exotic species on inshore fish are not known. Alewives could be quite detrimental because they may compete successfully for the zooplankton necessary to survival of young game fish. On the other hand, they may be beneficial by serving as food for game fish. In order to assess the later possibility, I examined stomachs of northern pike (Esox lucius), smallmouth bass (Micropterus dolomieui), walleye (Stizostedion vitreum vitreum), burbot (Lota lota), and bowfin (Amia calva) from Little Bay de Noc, Lake Michigan, in 1966-68.
      Little Bay de Noc is located in northern Green Bay. My study area of 9 square miles was the bay north of Gladstone, Michigan (Fig.1). Although its maximum depth is 51 feet, nearly half of the bay is less than 12 feet deep. The substrate in shallow water is predominantly sand, with rock and rubble along the north and west shores. The bottom in deep water is silt. The Whitefish River, largest of the five tributary streams, has a base flow of about 50 cubic feet per second; the other streams range from 0.4 to 4.6 cubic feet per second. The maximum surface water temperature, exclusive of shallow, sheltered bays, was 73 F.
      The fish population of Little Bay de Noc consisted predominantly of warm-water species. Northern pike, smallmouth bass and walleye were the principal predators. Smaller populations of burbot and bowfins were also present. Most of the burbot, however, apparently left the study area before the arrival of alewives in late May.
      Adult alewives were exceedingly abundant during June-August, and age-0 alewives were abundant during July-September. Yellow perch (Perca flavescens) were common throughout the bay, and large numbers spawned in the Whitefish River estuary in May. American smelt (Osmerus mordax) were very abundant during the spawning season in April, but considerably less abundant at other times. Small forage fish that were abundant included spottail shiners (Notropis hudsonius), johnny darters (Etheostoma nigrum), and trout-perch (Percopsis omiscomaycus). Other fish that were common in the bay included rock bass (Ambloplites rupestris), pumpkinseeds (Lepomis gibbosus), brown bullheads (Ictalurus nebulosus), black crappies (Pomoxis nigromaculatus), white suckers (Catostomus commersoni), and redhorse (Moxostoma spp.). Young-of-the-year largemouth bass (Micropterus salmoides) were common, but adults were rare. Brown trout (Salmo trutta) and rainbow trout (Salmo gairdneri) were present in small numbers during spawning migrations, and juvenile coho salmon (Oncorhynchus kisutch), from a plant in the Whitefish River, migrated through the bay in April-May, 1968.