Evidence of Walleye Spawning in Maumee Bay, Lake Erie

During the mid-1990s, anglers reported large numbers of walleye (Stizostedion vitreum) in spawning condition concentrated on shallow points adjacent to the Maumee River channel during spring. These fish had flowing eggs and semen and were suspected to be actively spawning in Maumee Bay. To investigate the potential of walleye spawning, we used a benthic pump to sample for eggs at five sites adjacent to the Maumee River channel and one site near Turtle Island in Maumee Bay on 5 April 1998, a time when walleye were actively spawning in rivers and on mid-lake reefs. We found walleye eggs at each of the six sites sampled. Relative abundance of eggs ranged from 17 to 2,105 per 2-min sample, with a mean of 459 (±232). Egg viability ranged from 33 to 54% across the sites and 10% of the viable walleye eggs were observed to be in late stages of embryonic development indicating that egg survival to hatching is likely. These results are the first documentation of walleye spawning in Maumee Bay, indicating that Maumee Bay is a viable spawning location for walleye, possibly representing an important source of recruitment for the Lake Erie stock. OHIO J SCI 102 (3):51-55, 2002 INTRODUCTION In the late 19th century, Wakeham and Rathbun (1897) referred to Maumee Bay as the most prolific spawning grounds for many important fish species in all of Lake Erie. By 1930, however, the fish spawning habitat of Maumee Bay became highly degraded due to industrial pollution, eutrophication, siltation, and associated low dissolved oxygen levels (Wright 1955). Conditions in Maumee Bay mirrored conditions in the other areas of the Lake Erie basin. The degraded habitat conditions, coupled with over-exploitation, contributed to the dramatic decline of the walleye {Stizostedion vitreum) population in the lake by the late 1950s. Discrete stocks of walleye were nearly eliminated from previously prolific spawning areas such as the Cuyahoga, Maumee, and Sandusky rivers and bays (Schneider and Leach 1977; Hatch and others 1987). The passage of the Great Lakes Water Quality Agreement in 1972 facilitated habitat rehabilitation efforts and, coupled with the closure of the walleye fishery from 1970-72, led to improved walleye recruitment and significant increases in walleye numbers (Hatch and others 1987). The formation of several strong walleye yearclasses coupled with restrictive management programs helped increase the population to more than 100 million harvestable age-2 and older fish by 1988. Current levels (2001) are estimated at approximately 40 million fish (Turner and others 2001). Reproducing stocks of walleye were flourishing again in most historic spawning locations in Lake Erie and its tributaries. Since the mid 1990s, anglers have observed large concentrations of adult fish in spawning condition in the shallow areas adjacent to the Maumee River channel 'Manuscript received 9 September 2001 and in revised form 12 November 2001 (#01-21). Corresponding address: Dominion, Inc., Millstone Power Station, PO Box 128, Waterford, CT 06385 each spring, suggesting that walleye were using these areas to spawn. Anglers reported catching large numbers of female walleye with ripe eggs and ejaculating males. These observations were similar to those made by commercial fishermen in Maumee Bay prior to 1957, but no verification of these early observations was ever made (Pinsak and Meyer 1976). In 1998, walleye anglers in Maumee Bay provided researchers at the Ohio Department of Natural Resources, Division of Wildlife, and Michigan State University with specific locations where they suspected walleye were spawning along the Maumee River channel in Maumee Bay. In this paper, we present the first documented evidence that verifies angler observations of walleye spawning in Maumee Bay. MATERIALS AND METHODS To determine if walleye were spawning in Maumee Bay, the authors sampled six potential spawning sites along the Maumee River channel (Fig. 1) during midday on 5 April 1998 using a benthic pump. We recorded depth (m), water temperature (° C), and substrate composition at each sample site to provide characteristics of the habitat (Table 1). Substrate composition was determined in three ways: surface visual analysis (Platts and others 1983); visual assessment of substrate particles collected with eggs; and surrogate estimation of particle type (that is, hard or soft bottom) by tactile probing with a pole. The benthic pump consisted of a 39 kg iron sled that was attached to a diaphragm pump at the surface by a flexible 5.0 cm diameter hose (Stauffer 1981; Roseman and others 1996). This collection method was effective for sampling demersal walleye eggs on mid-lake reefs in western Lake Erie and induced no damage or mortality to walleye eggs (Roseman and others 1996, 2001). Because walleye are known to spawn over the shallowest points on mid-lake reefs (Roseman and others 1996, 2001), we directed our sampling effort on the shallowest WALLEYE SPAWNING IN MAUMEE BAY VOL. 102 41° 45 Turtle I. MB-2 > MB-3 , ;