Effects of Increasing Chinook Salmon Bag Limits on Alewife Abundance: Implications for Lake Michigan Management Goals

Abstract

To predict effects of modifying the daily bag limit (DBL) on management of Chinook salmon Oncorhynchus tshawytscha and alewives Alosa pseudoharengus, we analyzed harvest and effort data collected from both charter and noncharter anglers during 1997–2005 in Michigan waters of Lake Michigan. Overall, the percent of anglers who caught the DBL of three Chinook salmon was low for charter (10.2%) and noncharter (3.3%) angler groups. However, during 1997–2005, the percent of anglers that caught their DBL increased from 3.3% to 26.5% for charter anglers and from 0.5% to 7.8% for noncharter anglers. To predict harvest under a higher DBL, we fit a discrete negative binomial distribution to the observed daily harvest distribution under the current DBL of three fish. We then used the fitted negative binomial to predict the daily harvest distribution under a DBL of five fish. Using this approach, the potential increase in the number of fish harvested with the higher DBL was minimal, but the additional harvest showed an increasing 1997–2005 trend from 315 to 7,301 fish for charter anglers and from 450 to 18,151 fish for noncharter anglers. There was a positive linear relationship between proportion of anglers harvesting the current DBL and harvest rates, which indicates that angler success is a function of Chinook salmon abundance. Using an age‐structured deterministic population model and the production‐conversion efficiency method, we estimated potential reduction in annual lakewide consumption of alewives by Chinook salmon resulting from a higher DBL. The reduction in consumption averaged 313 metric tons and increased from 28 (1997) to 935 metric tons (2005). We conclude that higher DBLs would have a relatively minor impact on lakewide forage fish abundance but would be more consistent with current management objectives.

Abiotic and biotic correlates of yellow perch recruitment to age‐2 in southern Lake Michigan, 1984–2007

“…However, the recruitment model does not provide management guidance detailing social, economic or political guidance regarding yellow perch or other recreational or commercial fishes. For example, although an alewife reduction in Lake Michigan may benefit yellow perch recruitment, this reduction would potentially alter recreational catch of salmonids (Claramunt et al. 2009) and impair Chinook salmon, Oncorhynchus tshawytscha (Walbaum) (Holey et al.…”

By-catch in the Saginaw Bay, Lake Huron commercial trap net fishery

“…Literature suggests that the negative binomial is often a reasonable probability distribution for analyzing catch data because these data often exhibit over-dispersion (Claramunt et al, 2009;Clark, 1974;Power and Moser, 1999;Pradhan and Leung, 2006;Ward and Myers, 2005). Additionally, preliminary analysis that also involved testing the Poisson and geometric distributions indicated that assuming the negative binomial probability distribution provided the best fit to the observed data.…”

Response to Dettmers et al. (2012): Great Lakes Fisheries Managers Are Pursuing Appropriate Goals

“…Dettmers et al (2012) state that "…fishery management agencies have collaboratively developed an indicator-based decision model …" (p. 497) but fail to provide citations for this management approach or for the science underlying this approach (see, for example, Claramunt et al 2008Claramunt et al , 2009Claramunt et al , 2012. They also fail to acknowledge the fact that the approach has been shared and adopted, in part or fully, across management jurisdictions and lakes; for example, this approach received recognition from the American Fisheries Society Fisheries Administrators Section as the Outstanding Sport Fish Restoration Project in 2005.…”