Management of Alewife Using Pacific Salmon in the Great Lakes: Whether to Manage for Economics or the Ecosystem?

Abstract

The combined destructive effects of overfishing, habitat destruction, and invasive species, especially alewife (Alosa pseudoharengus) and sea lamprey (Petromyzon marinus) led to the loss of the native top predator lake trout (Salvelinus namaycush) from most of the Great Lakes by 1960. Alewife populations then exploded, creating nuisance die-offs. Public demands for action, coupled with control of sea lamprey, allowed fishery managers to consider stocking Pacific salmon to control alewife and establish a recreational fishery. This effort was successful, reducing alewife numbers and creating a recreational fishery that is estimated at $7 billion annually. This fishery management regime may no longer be viable as new invasive species continue to alter the ecosystem. Fishery managers face an interesting dilemma: whether to manage in the short term for a popular and economically important sport fishery or to embrace ecosystem change and manage primarily for native fish species that appear to be better suited to ongoing ecosystem changes. Such dilemmas occur in great lakes around the world as fishery managers seek to balance economic pressure with changes in their respective ecosystems, often brought about by invasive species.

Evaluation of Lake Ontario salmonid niche space overlap using stable isotopes

“…Chinook salmon were an attractive stocking species to both fishery managers and recreational anglers as they are a large, fast-growing salmon, that could consume large numbers of alewife, and have lower hatchery production costs (Mills et al, 2003). With the establishment of an annual $7 billion dollar recreational Great Lakes salmonid fishery (Dettmers et al, 2012), fishery managers find themselves trying to maintain the balance of supporting a diversity of salmon and trout dominated by trophy-sized Chinook salmon, and protection and restoration of native species (i.e., lake trout and Atlantic salmon) (Stewart et al, 2013).…”

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

“…For the nonnative salmonines, most have been stocked since the early to mid-1900s-including Chinook Salmon (Oncorhynchus are also stocked, but naturalization of Brown Trout in the Great Lakes is extremely limited. Dettmers et al (2012) also argue, with little supporting documentation, that native fish "… may be better suited to the changing ecosystem, …" (p. 499) including the potential introduction of Asian carps to Great Lakes waters. Both native and naturalized nonnative predators are in the process of adapting to the constantly changing Great Lakes ecosystem; there is no evidence that native fish, such as coregonids and Lake Trout, are better suited to this changing system, especially given that we do not know what the future holds in terms of new perturbations.…”

“…In the section titled "Control of Sea Lamprey and Alewives," Dettmers et al (2012), intentionally or not, seem to equate these two invasive species in terms of effects, control efforts, and control success. In the case of Sea Lamprey (Petromyzon marinus), the goal of managers was elimination of this organism from the lakes, targeting the vulnerable spawning life stage.…”

“…There is little to no evidence that management solely focused on native predators will be less intensive, more certain, or better aligned with goals and objectives than that currently practiced in the majority of Great Lakes waters. Dettmers et al (2012) suggest that invasive Asian carps may drive a trend toward a benthic-dominated food web, to the benefit of native species. To suggest that an invasion of Bighead Carp (Hypopthalmichthys nobilis) and Silver Carp (H. molitrix) into the Great Lakes would benefit "coregonids and Lake Trout" via an indirect shift from a pelagic to benthic-oriented native fish community is entirely unsupported and misleading.…”

Misapplied survey data and model uncertainty result in incorrect conclusions about the role of predation on alewife population dynamics in Lake Huron: a comment on

“…Drastic recent and ongoing changes to fish populations and food webs in the Great Lakes have been well-described (Riley et al 2008;Barbiero et al 2009;Nalepa et al 2009;Fahnenstiel et al 2010;Evans et al 2011;Gobin et al 2015), and uncertainty regarding their potential effects on fisheries has caused concern among scientists and fishery managers (e.g., Dettmers et al 2012). In particular, the relative importance of "bottom-up" (e.g., lower trophic level changes) versus "top-down" (e.g., predation) factors to fish community changes in the Great Lakes have been widely debated (e.g., Barbiero et al 2011;Eshenroder and Lantry 2012;Bunnell et al 2014).…”