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walleye express |
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 Member Posts: 2680 Location: Essexville, MI./Saginaw Bay. | Hi Everyone, Good news! The Great Lakes Fishery Commission has posted videos of most presentations made at the Upper Great Lakes Committees in Duluth last week which can be easily accessed with the following link. http://www.glfc.org/lakecom/video/2013_upper.html Pay special attention to the telementary video. http://www.youtube.com/watch?v=5oLp0VmITtU Nearly an entire day was spent discussing each of the Upper Great Lakes including Lakes Huron, Michigan and Superior. The various fisheries and food web ecology were stressed. I attended all the sessions over 3 days and the information provided insights into how and why the fisheries continue to change and I highly recommend that you review the videos. My wife Theresa also attended all the presentations and she enjoyed them very much. In addition, attached is the presentation by Jim Johnson on the native species that are recovering in Lake Huron since the alewife crashed. Included is a discussion of the role cisco may have provided in buffering the yellow perch fishery in Saginaw Bay when the walleye population was historically high. Also attached are a summary sheet and a report by Ji He on the status of lake trout in the main basin of Lake Huron. Since wild lake trout populations continue to expand throughout Lake Huron work is beginning to determine when stocking of lake trout would no longer be beneficial. More Good News! Dr. Merckel is home and doing very well. Frank Life after the Alewife collapse. [img]http://www.walleye-express.com/albums/ice/IM000875.sized.jpg[/img] I was especially flattered that they used an old Photo Gallery picture of mine in their header introduction of Johnsons report, with some perch and a walleye I caught a few years back off Ericson road. Capt. Dan. Introduction With the collapse of alewives in Lake Huron in 2003-2004 (Figure 1, Riley et al. 2008), there followed a well-documented decline in Lake Huron’s offshore fishery for Chinook salmon. Angler use fell nearly 75% after 2005 in Michigan’s Main Basin and to a lesser degree in Saginaw Bay. Prior to alewife collapse, several species were showing signs of reproductive impairment, lake trout and walleyes in particular. After the alewife collapse reproduction improved. The purpose of this report is to use trends in estimates of angler harvest, harvest rates, and effort to explore whether native species have benefited in the years following the alewife collapse. Methods Angler use has been estimated at 10 ports on the Main Basin of Lake Huron and 7 sites on Saginaw Bay since 1986. Annual surveys to make these estimates were conducted consistently across years except for 1989 and 1990 at Main Basin ports and in 1990 at Saginaw Bay ports; these years were excluded from this analysis. Since 2000, three additional ports in northern Lake Huron have been surveyed. Harvest and angler effort were estimated using angler interview data as described by Su and Clapp (2013). For summarizing catch and effort trends from 1986-2012, we used the 17 ports with most consistent coverage (index ports). For trends after 2000, we used all 20 ports. Trends in harvest of all species were summarized for Saginaw Bay, the Main Basin, and the combined lake basins. These species were grouped as either “native” or “introduced” to look at trends in native species composition of the catch. Trends in angler hours were examined with respect to catch rates and catch composition to elucidate causes for recent sharp declines in effort. For the years 2001-2012, yields and yield per angler hour were estimated. Yields were derived based on samples taken from the catch and weighed by creel survey personnel. Yield per hr of angling effort was used as an index of species abundance because this statistic is not directly related to total fishing effort, which varied widely and generally declined during the years we surveyed. Yield estimates are not influenced by the wide variation in size between species, for example yellow perch and Chinook salmon, and are thus a more stable representation of harvest composition than catch. Results Alewives collapsed during 2003-2004; most other prey species have remained in low numbers or alsodeclined (Figure 1). With little compensation by other species for the alewife collapse, the pelagic prey community reached record low biomass levels after 2004 (Riley et al. 2008). Alewives remained almost absent in prey assessments from 2005-2012 but the native bloater chub has increased in the trawl catch in recent years (Figure 1, Ed Roseman, USGS Great Lakes Science Center, unpublished data). In the Main Basin, Chinook salmon harvest and catch rates fell more than 90% and 66%, respectively, from their 1986-2004 averages during the 8 years following the alewife collapse. Angler effort followed, declining about 73% in the Main Basin. Catch and catch rates of other salmonids, such as lake trout and 4 steelhead, did not change consistently and harvest and catch rates of walleyes rose. Catch rate of walleye nearly equaled the combined catch rates of salmonids in these 10 Main Basin, traditionally salmon fishing, ports after 2009 (Figures 3). Chinook catch rate (number harvested per angling hr) explained more of the variation in fishing effort (R2 =0.36) than did total salmonid catch rates (R2 =0.07). In Saginaw Bay, where Chinook salmon were always less important, effort and harvest also declined (Figures 4 and 5), but less so than for the Main Basin. A mitigating factor was the rise in walleye (Figure 5), fueled by a surge in natural reproduction that began in 2003 (Fielder et al. 2007). Reproduction has continued to be strong in ensuing years and stocking of walleyes, which once ranged near 1 million spring fingerlings per year, has not taken place since 2006. Despite the rise in walleye, angler use declined by about 53% in the years following 2004, probably due to a long-term trend in declining yellow perch abundance. While yellow perch reproduction, measured as young-of-year in trawl catches, increased after the alewife collapse, recruitment to age-1 declined by more than 75% (M. Thomas, Lake St. Clair Fishery Research Station, unpublished data). Beginning in 2003, yellow perch became prominent in Saginaw Bay walleye diets (Figure 6); the near disappearance of alewives from the Bay probably increased exposure of yellow perch to predation. The rise in predation on yellow perch appears to explain the decline in recruitment to yearling and older ages and the failure of the perch population to recover. Yellow perch catch rates, which reached long-term low points after 2004, appear to be the leading cause of lower angler use of the Bay in recent years (angler hours as function of yellow perch catch per hour, R2 =0.53). In the Main Basin, the contribution of native species to harvest rose from 39% prior to alewife collapse to 87% after, mostly because of declines in Chinook salmon catch. While the proportion of native species in the catch rose, there was no increase in native species yield in the Main Basin after alewife collapse, because effort dropped so sharply. Yield, expressed as pounds of fish harvested per 100 hours of fishing effort (yield rate, lb/hr), is an abundance index less influenced by the effect of effort changes. Yield rate of native species more than doubled in the Main Basin, from an annual average of 48 lb/100 hr during 2001-2004 to 109 lb per 100 hr during 2005-2012. Introduced species yield rates declined from 100 to 37 lb per hour (Figure 7). In Saginaw Bay, yield rate of natives increased from 52 to 93 pounds/100 hr across the same two periods, while the introduced species almost disappeared from the catch, dropping from 15 lb/100 hr to less than 1 pound/100 hr (Figure 8). The rising contribution of native species was led by walleye, especially in Saginaw Bay because the recovery of Lake Huron’s walleye population was centered there. The Saginaw Bay walleye population migrates throughout Michigan waters of Lake Huron (Dave Fielder, MiDNR Alpena Fishery Research Station, unpublished data) and contributed to rising native fish catches in both basins (Figures 7 and 8). For the Main Basin, total yield rates did not change between the two periods; native and introduced species combined, averaged 148 lb per hr during 2001-05 and 146 lb per hour after alewife collapse (during 2005-12). In Saginaw Bay, yield rate increased from 67 lb/100 hr in the four years prior to alewife collapse to 94 lb/100 hr from 2005-2012. Discussion The Lake Huron fish community reacted sharply to alewife collapse and does not yet appear to have reached a new equilibrium. Yellow perch reproduction rose in Saginaw Bay after 2002, but yellow perch 5 also became a major prey species, having lost the predator buffering effect of a large alewife population. Recruitment of age-0 perch in the trawl to the next year’s age-1 catch dropped from 74% prior to 2003 to just 9.9% during 2003-12 (Mike Thomas, Lake St. Clair Fishery Research Station, unpublished data). Were the prey community to further diversify, yellow perch might experience a degree of relief from predation. A recent rise in consumption of gizzard shad by walleye should give perch such relief, however, gizzard shad are sensitive to hard winters and their recent rise may be short lived. The decline in alewives was followed by a rise in egg thiamine in lake trout (Riley et al. 2011) and a related rise in reproduction (Fitzsimons et al. 2010). Lake trout are continuing to undergo change, transitioning from mostly hatchery-origin fish to increasingly wild (He et al. 2012, He and Johnson 2012). As naturalized spawning populations develop, lake trout numbers (and prey consumption) should rise. Cisco (lake herring) populations and harvests are confined to Michigan’s Upper Peninsula waters of Lake Huron. Ciscoes were once very abundant in the Main Basin and Saginaw Bay (Figure 9) and they occurred at a time when commercial fisheries for both yellow perch and walleyes were at near record high levels (Figure 10). The abundance of ciscoes prior to about 1950 may have absorbed much of the predation of walleyes and lake trout, allowing the yellow perch population to thrive. If ciscoes were to recover and spread to the Lower Peninsula Main Basin and Saginaw Bay, they could again become an important nearshore and offshore prey species. Their recovery would be a test of the concept that a vibrant cisco population is a prerequisite for restoration of historical yellow perch and walleye harvest levels. They would also become an important source of large-bodied prey (a role they now play in Lake Superior) for lake trout. Yield rates are unchanged in the Main Basin and actually rose in Saginaw Bay after alewife collapse, yet angler use remains much below that of the alewife era. Low angler use is the principal reason harvestrates of both native and introduced species remain at near-record low levels in the Main Basin. In the Main Basin, the decline in effort was principally caused by low numbers of Chinook salmon. It is doubtful whether recoveries of both lake trout and walleye would be enough to stimulate the same level of angler use Chinook salmon did during the pre-alewife-collapse era. Angler use of Saginaw Bay appears to be very sensitive to yellow perch availability. Were yellow perch abundance to rise, angler use and harvest of native species would likely follow. Edited by walleye express 3/28/2013 11:13 AM Attachments ----------------  IM000875_sized.jpg (85KB - 146 downloads) | ||
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