Future Declines of the Binational Laurentian Great Lakes Fisheries : the Importance of Environmental and Cultural Change

It is increasingly clear that future long-term environmental challenges (eg climate change) are being driven by economic and cultural choices, as well as by physical and biological mechanisms. We looked at the extent to which these apply to potential future changes in fisheries in the Laurentian Great Lakes. These fisheries rank among the most valuable freshwater fisheries in the world, but have declined markedly in recent decades. To investigate how these fisheries might develop in the future, we elicited projections from experts in fisheries and related fields. Experts provided assessments on variables relating to US and Canadian commercial (pounds landed) and sport (participation and expenditures) fisheries for the years 2006 and 2025. We measured each expert's ability to quantify their uncertainty, producing performance-weighted combinations of expert estimates. All experts expected commercial fisheries to decline from 2006 to 2025, with greater declines in the US (25%) than in Canada (9%). Expectations for sport fishing differed more between lakes and less between countries, with median expected declines ranging from 1% to 13%. Experts attributed expected declines primarily to changes in economic market demands and shifts in societal interests. Increased attention to social and economic trends could aid Laurentian Great Lakes fishery policy and management.


Future declines of the binational Laurentian
John D Rothlisberger1*, David M Lodge1, Roger M Cooke2, and David C Finnoff3 It is increasingly clear that future long-term environmental challenges (eg climate change) are being driven by economic and cultural choices, as well as by physical and biological mechanisms.We looked at the extent to which these apply to potential future changes in fisheries in the Laurentian Great Lakes.These fisheries rank among the most valuable freshwater fisheries in the world, but have declined markedly in recent decades.To investigate how these fisheries might develop in the future, we elicited projections from experts in fisheries and related fields.Experts provided assessments on variables relating to US and Canadian com mercial (pounds landed) and sport (participation and expenditures) fisheries for the years 2006 and 2025.We measured each expert's ability to quantify their uncertainty, producing performance-weighted combinations of expert estimates.All experts expected commercial fisheries to decline from 2006 to 2025, with greater declines in the US (25%) than in Canada (9%).Expectations for sport fishing differed more between lakes and less between countries, with median expected declines ranging from 1% to 13%.Experts attributed expected declines primarily to changes in economic market demands and shifts in societal interests.Increased atten tion to social and economic trends could aid Laurentian Great Lakes fishery policy and management.A typical pair of questions took the following form: How many total pounds of commercial fish were landed from the US waters of Lake Erie in 2006?

5%_ 50%_ 95%_
How many total pounds of commercial fish WILL BE landed from the US waters of Lake Erie in 2025?

5%_ 50%_ 95%_
Following each such pair of questions, we asked the experts to provide their rationale for the predicted changes in the variable between 2006 and 2025, identify ing if possible the most important expected driver of change.We made notes and audio recordings of these responses.

Analysis, combination, and reporting of results
We report the experts' answers as individual assessments (WebFigures 1, 2, and 3) and as combined assessments for each variable (Figures 1 and 2).We combined expert assessments in two ways: (1) equal weight given to each expert and (2) expert weight based on calibration vari able performance (Cooke 1991).
For each variable, we calculated the expected percent change between 2006 and 2025, and the associated uncertainty range.To make this calculation, we assumed independence of all variables and used a convolution algorithm to obtain the distribution of the differences between the 2006 and 2025 performance-based combina tion (PBC) distributions.We then divided the 5th, 50th, and 95 th percentiles of this distribution of differences by the appropriate 2006 median assessment and multiplied by 100 ([(2025 -2006)5th,50th,or95thpercentik)/200650th]*100) to find expert-expected percent change.We extracted from the experts' rationales the driver of change each one identified as being most important to the future condition of GL fisheries.We also tabulated how many experts mentioned each driver of change (Figure 3).

Results
Equal weighting and PBC of expert assessments produced roughly similar median results.However, the equal weight combination was statistically inaccurate, whereas the PBC variables were statistically accurate (WebTable 1).Furthermore, the PBC allowed us to weight experts according to the precision and accuracy of their assess ments (WebTable 1; WebFigures 1 and 2).We therefore report here only the results of the PBC.In our figures, we provide PBC uncertainty ranges (Figure 1) and probabil ity distributions (Figure 2).In the text, we focus on median values, because these reflect the outcomes experts saw as most likely, and experts' rationales for their predic tions correspond to these medians.Moreover, because we assumed independence between 2006 and 2025 when calculating projected percent changes, the ranges of these projections (Figures 1 and 2) are overly broad relative to the experts' narrative descriptions of how GL fisheries might change between 2006 and 2025.

US commercial fishery
The actual 2006 commercial catch data are enclosed in the PBC 90% uncertainty estimates in all cases (Figure 1; WebTable 1).The PBC projected 19-31% decreases in commercial catches in 2025 for Lakes Superior, Michigan, Huron, and Erie (Figure 2).Six of the nine experts (67%) indicated that the most important reason for predicted declines in commercial fishing was the decreasing eco nomic viability of the fishery, resulting from a combina tion of cheaper supplies of fish entering the marketplace (eg aquaculture) and sport fishing continuing to receive political preference (eg higher allocation of total allow able catch quotas).The other experts gave invasive species impacts (one expert), climate change (one expert), and limitations on ecosystem productivity (one expert) as the primary causes of declines.The most com monly mentioned reasons for decline were invasive species, economic markets, and fishery policy (Figure 3).

Canadian commercial fishery
Historical data on individual lakes were not available for the Canadian commercial fishery; experts were therefore asked for estimates on landings aggregated from all Canadian waters of the GL.The PBC assessments accu rately predicted the 2006 Canadian commercial catch (Figure 1 ) and forecast that Canadian commercial land ings will decline 9% by 2025 (Figure 2).Five of the nine experts (56%) cited failing economic viability of the fish ery as the main reason for the predicted declines.Of the remaining experts, one attributed expected declines pri marily to food-web disruptions by invasive species.Three others predicted stability or even a slight increase in the Canadian commercial catch by 2025, owing largely to strong political support for commercial fishing in Canada.Invasive species and changing economic markets were the most commonly mentioned factors driving declines or limiting growth (Figure 3).

US sport fishery
The PBC estimates were not as accurate for 2006 sport effort as for commercial landings, but the actual data for 2006 fell within the 90% uncertainty range for four of the five lakes (Figure 1).For four lakes, the PBC pro jected 9-13% declines in fishing effort in 2025 relative to that in 2006.In contrast, the PBC predicted that effort will increase 1% in Lake Huron (Figure 2); several experts attributed this projected increase to 2006 being a particularly bad year for Lake Huron because of food-web disruptions involving alewife (Alosa pseudoharengus) pop ulation declines.Six out of the nine experts (67%) gave as their primary reason for expected declines in angling effort reduced cultural interest in consumptive outdoor recreation (eg fishing) and, for the population segment still interested in angling, a preference for inland water ways over the GL.These experts attributed the shifting preference away from the GL to the rising costs of partic ipation in GL fishing, as nearshore fisheries decline and as costs climb for equipment and fuel to participate in off shore fishing.Of the remaining experts, one believed that invasive species will be the primary reason for declines by 2025, one expected stability in angler participation, and one did not identify a primary cause for declines.Invasive species were the most commonly mentioned secondary driver of declines (Figure 3).

Canadian sport fishery
The PBC forecast that effort in Canadian sport fisheries will decline 1-12% by 2025 (Figures 1 and 2).
Most experts (six out of the nine) expressed greater uncertainty in their predictions for Canadian sport fisheries than for their US counter parts, partially because of their cur rent small size, possibly causing volatility.Five experts indicated changing trends in pastimes would be the primary driver of declines, but two said invasive species impacts would be the main driver of declines.On the other hand, one expert expected stability in the fishery and one expected a slight increase in angler effort.Shifts away from fishing as a pastime and harm caused by inva sive species were mentioned most often as drivers of declines for the Canadian sport fishery (Figure 3).

Drivers of change in GL fisheries
According to experts, the projected declines in fisheries in the US and Canadian waters of the GL (Figure 2) will largely be a function of social trends, economic conditions, and political decisions (Figure 3).Thus, when considering the future of fisheries in the GL, a comprehensive view of societal dynamics and interactions between biological and economic systems must be taken into account.This is espe cially the case for the economically valuable sport fisheries (GLFC 1988), on which we focus our discussion here.The importance of biological and cultural factors on GL fisheries is clear when considering the rehabilitation of self-sustaining populations of native species in the GL.Lake trout (Salvelinus namaycush) rehabilitation is a major emphasis in GL fishery management, particularly for US federal agencies (Holey et al 1995;Knuth et al 1995).Using Lake Superior as a case study, Kitchell et al (2000) point out that the ecological turnover rate of the historical fish community in the upper GL consisting of lake trout and lake herring (Coregonus artedii) as primary of lean lake trout stocks, which is currently specified as one of the major management goals in Lake Superior (GLFC 2003), will be extremely challenging.In fact, Lake Superior may be as close to a restored state in this regard as possible; hence, any continued efforts to enhance lean lake trout populations in Lake Superior may unintentionally force declines in Pacific salmon, a valuable component of the sport fishery, possibly reducing angler participation and, consequently, economic benefits (Kitchell et al. 2000).This apparent conflict in objectives in Lake Superior, however, may be a false dilemma, as may be the case with other similar situations across the GL, because cultural trends may now be more important drivers of fishery partici pation levels than are stock sizes.Even as managers actively try to balance recreational fishery (Pacific salmon) enhance ment with native fish community (lake trout) restoration, experts expressed considerable uncertainty regarding the value of these efforts for improving fisheries, mainly because of doubts as to whether angler effort will increase in response to these management efforts.Of course, management deci sions regarding the restoration of native communities and the enhancement of particular fish stocks are complex issues, the goals of which certainly extend beyond creating success ful fisheries (eg intrinsic value of native species).Our focus here, however, is on expectations for GL fisheries and their expected drivers of change.Therefore, increased consideration of the response of anglers to changes in fish stocks relative to cultural change could help to inform fishery policy and manage ment.For example, if the deci sion were made to try to increase participation levels in GL sport fisheries in the coming years, it would be valuable to know the tradeoffs between investing in programs to improve sport fish stocks versus efforts to recruit more anglers to the fishery through advertising and educa tional programs.According to our experts, the latter would probably be a more effective tool in growing or maintaining the fishery.This is because, as long as the target species are not ex tremely scarce, most of the pro jected declines in sport fishing on the GL will occur as a result

Front
Ecol Environ 2010; 8(5): 239-244, doi: 10.1890/090002 (published online 2 Dec 2009) 239 Recent Intergovernmental Panel on Climate Change .reports indicate that future climate will, in part, be a function of human choices regarding cultural and eco nomic priorities (Parry et al 2007).Recent experience with marine and freshwater fisheries in many countries also demonstrates the importance of the interaction of cultural practices and economic policies with fish popula tion dynamics in determining the current status of fish stocks (Hilborn et al. 2003).Here, we apply this perspec tive of co-determination the two-way interactions between human and natural systems (Crocker and Tschirhart 1992; Knowler and Barbier 2001) by using structured expert judgment (SEJ) to estimate the future magnitude of fisheries-derived ecosystem services in the Laurentian Great Lakes (GL).The commercial and sport fisheries of the GL are valu able natural resources that have been exploited exten sively since European colonization, but have changed substantially in recent decades as a result of various fac tors, including water-quality regulation, increased soci etal interest in recreational as opposed to commercial fishing, and invasions by non-indigenous species (Figure 1).Beginning in the early 1800s, humans have extracted fishery resources from the GL at a rapid and sometimes Center for Aquatic Conservation and Department of Biological Sciences, University of Notre Dame, Notre Dame, IN *(jrothlis@ gmail.com);2Resources for the Future, Washington, DC, and Tech nical University of Delft, Delft, Netherlands; department of Economics and Finance, University of Wyoming, Ear amie, WY unsustainable pace (Bogue 2000).Growing human popu lations and increasing prosperity brought more resource extraction, more intensive agriculture, and the develop ment of various industries, including a wide variety of GL-based recreational activities.However, erosion and water pollution byproducts of agriculture and industry modified the GL environment, often to the detriment of fish populations that had been instrumental in promoting economic growth (Beeton 1969 Figure 1* Historical and projected commercial and recreational fisheries in the US and Canadian waters of the Great Lakes (GL).Angler effort in recreational fisheries is shown as insets in the upper right of each panel.Vertical range bars are performance-based combinations of expert assessments (WebTable I ) where lower and upper limits show, respectively, 5th and 95th percentiles of the combined expert subjective probability distributions.Filled circles depict the 50th percentile of each distribution.Note different vertical scales across countries, lakes, and fishery types.Canadian commercial catch (panel i) is for all Canadian waters of the GL.In the past decade, 75% of Canadian commercial catch has come from Lake Erie.Historical recreational fisheries data are from USFWS (2007).Commercial catch data dating back to 1971 were obtained for the US from the US Geological Survey (USGS) Great Lakes Science Center and for Canada from Fisheries and Oceans Canada.naturaland anthropogenic stresses such as future biologi cal invasions, regional climate change, economic market changes, and developing trends in pastime activitiesexperts provided rationales, explaining the reasoning

Figure 2 *
Figure 2* Probability density functions of PBC-projected percent change between 2006 and 2025 in US and Canadian commercial fish landings (pounds landed), and sport fishing effort (angler-days) and expenditures (2007 LJS$).Vertical black lines show median of each distribution.Vertical dotted lines provide a reference to zero percent change.Note that, even though most distributions extend to the left of -100%, the value of these variables in 2025 cannot be less than zero, na = not applicable.
The PBC performed well in pre dicting 2006 angler expenditures aggregated over all lakes (WebFigure 3), which are expected to fall by 24% (or about US$330 million, expressed in 2007 US$) by 2025 (USFWS 2007; Figure 2).

Figure 3 *
Figure 3* Number of experts that mentioned various potential drivers of change in explaining their expectations for declines in US and Canadian commercial and sport fisheries between 2006 and 2025.
of dwindling societal interest in the pastime, driven by less dis cretionary free time and the pur suit of other pastimes, not by declining abundance of target species.This is counter to some reports that fishing pres sure has previously responded to shifts in abundance of popular species in the GL (eg the spike in Ohio fishing license sales in the 1980s in response to walleye recovery in Lake Erie [Hatch et al 1987], the drop in Lake and human society in the GL region could never be tested directly with standard research methods, even if an enormous budget were avail able to support such research.SEJ provides a tool to over come this obstacle and to predict future states of the GL fisheries, with explicit attention given to the substantial uncertainties involved.Results that suggest the impor tance of social and cultural factors in the future of GL ecosystem services do not in any way diminish the well known importance of environmental degradation and unsustainable harvest practices that have led to past stock collapses and production declines in many of the world's most important marine (Pauly et al 2002; Hilborn et al 2003) and freshwater (Allan et al 2005) fisheries.Indeed, the importance of cultural factors relative to environ mental ones (Figure 3) may be of greater magnitude for the GL than for other major fisheries because of the grow ing primacy of sport fishing in the lakes.Our study under scores the continued and increasing relevance of cultural factors, including economic considerations, when design ing plans and setting objectives for fishery management, particularly in the North American GL.Specifically, fur ther research on the drivers of change in GL fisheries especially sport fisheries is needed to support scientifi cally sound and socially beneficial fishery policy and management.The primary drivers of change that experts identified point the way for future inquiries, particularly into the causes and consequences of people spending less time fishing recreationally on the GL. ).