chapter 5 - fisheries145 †corresponding author: [email protected] chapter 5 ecology and...

145

†Corresponding author: [email protected]

Chapter 5

Ecology and International Governance of Lake Erie’s Percid Fisheries

Edward F. rosEman†, rogEr L. Knight, ELizabEth wright,donaLd EinhousE, KEvin KayLE, Kurt nEwman,

and ricKaLon L. hoopEs

International Governance of Fisheries Ecosystems: 145–169 © 2008 American Fisheries Society

Introduction

Walleye Sander vitreus and yellow perch Perca flavescens populations are critical components of Lake Erie’s economically and socially valuable commercial and recre-ational fisheries. These fisheries contribute billions of dollars to the economies of New York, Pennsylvania, Ohio and Michigan and the province of Ontario (Lichtkoppler 1997). Lake Erie percids support commercial and recreational fisheries in both Canada and the United States, with primarily commercial fisheries in Ontario and recreational fisheries dominating in the United States (Lloyd and Mullen 1991; Lichtkoppler 1997). Overall, lakewide walleye and yellow perch harvests have averaged about 20 million pounds an-nually since 1975 (roughly 10 million lbs per species). Percid fisheries support roughly 200 commercial operations and over a million recreational fishers each year. Commercial fisheries produce the bulk of the overall per-cid harvests, with the majority of the netting effort being directed at yellow perch. Sport fishery effort was directed primarily at wall-eye (Lichtkoppler 1997) although effort for yellow perch is increasing in recent years.

Stresses to the Lake Erie environment are well-chronicled and include impacts from eutrophication, poor land-use prac-tices, industrial pollution, effects of urban sprawl due to increasing human population growth, and overfishing (Hartman 1973; Rosa and Burns 1987; Koonce et al. 1996a). Cumulatively, these impacts have had both direct and indirect impacts on the fish com-munity and the Lake Erie ecosystem has responded to these stresses in both predict-able and unpredictable ways. For example, loss of reproductive habitat and overfishing contributed to predictable losses of sensitive percids such as sauger Sander canadensis and blue pike Sander vitreus glaucus (Regi-er and Hartman 1973; Nepszy 1977; Nepszy et al. 1991). Regulation of exploitation by interjurisdictional management programs led to the recovery and development of pres-ent-day percid fisheries (Hatch et al. 1987). In addition, increased phosphorous concen-trations led to predictable increases in nox-ious algal blooms and associated turbidity through the mid-1970s, while regulation of phosphorous loads via the Great Lakes Wa-ter Quality Agreement (GLWQA) led to pre-dictable declines in blue-green algae and de-creased turbidity in the 1980s (El-Shaarawi

146 Roseman et al.

1987; Makarewicz and Bertram 1991). Con-versely, the addition of nonnative species to the aquatic community, like dreissenid mus-sels, round gobies Apollonia melanostoma, and white perch Morone americanus, have had unpredictable influences on native bio-ta, and the effects of these introductions are still being realized (Mills et al. 1994; Jude and DeBoe 1996).

Associated with the ecological changes mentioned above, important social changes have also affected Lake Erie fisheries. Prior to 1980, U.S. fisheries on Lake Erie were dominated by commercial fishers, with only minor usage by recreational fishers (Hatch et al. 1987). Following the lake-wide clo-sure of commercial fisheries in 1970 due to mercury contamination and the subsequent recovery of percid stocks in the lake, com-mercial fishing in U.S. waters was vastly reduced and currently lucrative sport fisher-ies dominated fishing activities in the U.S. waters. Furthermore, remaining commercial fishers were restricted to using trapnets af-ter the gillnet ban in the 1980s. Meanwhile, fishing activities in Ontario waters remain dominated by commercial fishing and use of gillnets is widespread. Ontario commercial fisheries primarily target percids as well as rainbow smelt Osmerus mordax, white bass Morone chrysops, and lake whitefish Core-gonus clupeaformis, among other species. Although recreational fisheries constitute only a small fraction of the annual harvest in Ontario, walleye, yellow perch, smallmouth bass Micropterus dolomieu, and rainbow trout Oncorhynchus mykiss do support lo-cally important fisheries.

Movements of walleye and yellow perch across jurisdictional boundaries create an ecological basis for inter-jurisdictional fish-eries and habitat management programs. To better address these challenges, Great Lakes agency administrators and scientists work together as a team to compile information, solve problems, and set fisheries manage-

ment goals. In 1980 the Great Lakes Fish-ery Commission (GLFC) adopted A Joint Strategic Plan for the Management of Great Lakes Fisheries (SGLFMP; GLFC 1980). SGLFMP outlined the cooperative agree-ment between state, federal, provincial and tribal agencies to cooperatively monitor and manage Great Lakes fisheries. Coordinated management of percids in Lake Erie is ac-complished through the Lake Erie Commit-tee (LEC), a bi-national committee of state and provincial agencies, operating under the auspices of the GLFC. The resource agen-cies of the states of Michigan (MDNR), Ohio (ODNR), Pennsylvania (PAFBC), and New York (NYSDEC) and the province of Ontario (OMNR) participate in assess-ing walleye and yellow perch fisheries and populations. The LEC established technical task groups for walleye (WTG) and yellow perch (YPTG) to compile harvest data and analyze trends in population abundance. The LEC partner agencies routinely conduct independent and joint fisheries monitoring programs to better understand fish stock dynamics. Lake Erie’s Standing Technical Committee (STC) annually coordinates an array of assignments to task groups made up of agency biologists who assess data from these monitoring programs using state of the art methods and scientific knowledge. Fish population abundance models are annually updated with data from monitoring programs to determine current population sizes and to project future abundance for Lake Erie wall-eye and yellow perch populations. Annual reporting by task groups enables the LEC to establish and maintain lake-wide manage-ment initiatives and set allowable harvests.

The Lake Erie Fish Community Goals and Objectives were developed by the LEC to guide the development of strategies and management actions within a framework of sound ecological concepts and basic guiding principles (Ryan et al. 2003). The LEC sup-ports the maintenance of mesotrophic con-

147Ecology and International Governance of Lake Erie’s Percid Fisheries

ditions across much of Lake Erie, believing that the ecosystem “will provide optimal en-vironmental conditions for a more balanced, stable, and predictable fish community with maximum potential benefits for fisheries” (Ryan et al. 2003). Because the latitude, morphology, and mesotrophic conditions of Lake Erie are optimal for a percid-dominat-ed fish community, the LEC also supports balanced and harmonic percid communities in the western, central, and near-shore wa-ters of the eastern basins with walleye as the dominant predator (Ryan et al. 2003). In this chapter, we describe the history and current status of Lake Erie’s percid populations and discuss the evolution of an effective inter-national governance system for the manage-ment of Lake Erie’s percid fisheries.

Description of Lake Erie

Lake Erie is the shallowest of the Lau-rentian Great Lakes (average depth = 19 m). Its large water volume (484 km3) makes it the 11th largest freshwater lake in the world. Historically, Lake Erie has been highly productive across all trophic levels, which likely is a function of its warm temperature (>200 frost-free days), mostly agricultural

watershed (67% of total basin land, other Great Lakes range 3–44%), and short water retention time (2.6 years; Bolsenga and Her-dendorf 1993; Fuller et al. 1995). Among the Great Lakes, Lake Erie is unique in that it has three geomorphologically distinct lake basins (Figure 1). Waters west of an imagi-nary line extending from Pelee Point, On-tario, to Huron, Ohio, comprise Lake Erie’s west basin. Waters east of this line, but west of another line drawn between Long Point, Ontario and Erie, Pennsylvania, comprise the central basin. The west basin has less volume (25 km3), is shallower (mean depth = 7.4 m) and has a shorter water retention time (51 d) than the central basin (305 km3, 18.5 m, 635 d, respectively). The eastern ba-sin is deepest (27.0 m) but has a lower resi-dence time (290 d) and smaller volume (166 km3) than the central basin (Bolsenga and Herdendorf 1993; Fuller et al. 1995). Bio-logical production across all trophic levels is typically greater in the west than central and eastern basins for three reasons: (1) depth and water volume are least in the west, (2) temperature is higher in the west relative to the east, and (3) >90% of the water entering Lake Erie does so from west basin tributar-ies (i.e., Detroit, Maumee, and Sandusky

Toledo

Cleveland

ErieDetroit

Buffalo

PortDoverPort

Stanley

Wheatley

FairportHarbor

Huron

Dunkirk

East Basin

Central Basin

West Basin

Long Point

Toledo

Cleveland

ErieDetroit

BuffaloDoverPort

Stanley

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FairportHarbor

Huron

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Central Basin

West Basin

Long Point

Figure 1. Map of Lake Erie with distinct basins and jurisdictional boundaries.

148 Roseman et al.

rivers). The west basin is thought to hold the majority of fish reproductive and nursery habitat in Lake Erie, particularly for percid fishes (Goodyear et al. 1982).

Walleye

Walleye have supported important sport and commercial fisheries in Lake Erie for over 150 years (Regier et al. 1969; Knight 1997). Commercial landings of walleye var-ied in the early 1900s, peaking in 1956–1957 at more than 6,000 metric tons (Hatch et al. 1990). Catches declined dramatically in the late 1950s and early 1960s, when the popula-tion diminished due to exploitation, pollution, eutrophication, and degraded spawning habi-tat (Sweeney 1993). High levels of mercury in the tissue of walleye prompted closure of the commercial fishery in 1970, and the har-vest of Lake Erie walleye was prohibited by anglers in Ontario and Michigan (Hatch et al. 1990). Ontario fishing tackle sales declined in 1970 (Cox 1992) suggesting that, despite being allowed to fish for walleye, fewer an-glers were participating in the fishery.

Following the 1972 adoption of the Great Lakes Water Quality Agreement, basin-wide management strategies focused on reducing organic inputs to the lake in efforts to im-prove fish habitat and rehabilitate popula-tions (Burns 1985; Makarewicz and Bertram 1991). The commercial fishery for walleye was closed for three years because of mer-cury contamination and was opened only to limited harvest after 1972 when mercury levels subsided (Hatch et al. 1987). The fish-ery largely remained closed for another three years to allow the stocks to rebuild (Cowan and Paine 1997). The western basin walleye commercial fishery reopened in 1976 with a total allowable catch (TAC) agreed to, and shared by, Ohio, Ontario and Michigan, with each share determined by the proportional area of walleye habitat present in jurisdic-tional waters (Cowan and Paine 1997). Ohio

and Michigan allocated their shares of the TAC to the recreational fishery while Ontario allocated the majority of their allowable catch of walleye to the commercial fishery with the recreational fishery taking a minor share.

Lake Erie’s oligotrophic eastern basin has less favorable walleye habitat, with much lower walleye densities and smaller fisher-ies relative to those found in the western and central basins. This smaller eastern ba-sin walleye resource did not experience the sharp decline and rebound in abundance from the 1950s to the 1980s endured by the west-ern basin resource. Other notable popula-tion characteristics that differ for the eastern walleye resource are higher survival rates, more variable recruitment, and less extensive movement patterns. Long term tagging stud-ies demonstrate the range of the western basin spawning stocks extends into the eastern ba-sin, conversely tagged eastern basin walleye are seldom recovered in the lake’s central or western basins. Both eastern and western ba-sin stocks are known to contribute to eastern basin fisheries (Ryan et al. 2003). Evidence from tagging studies and seasonal fishery sta-tistics underscore that the identifiable contri-bution from western basin spawning stocks to eastern basin fisheries is the larger, older age segment of the population (Einhouse and Haas 1995; Locke et al. 2005). AAn annual description of eastern basin walleye stock status is produced by the WTG; however, at this time no formal inter-agency harvest al-locations are prepared for the much smaller eastern basin walleye resource.

Harvest of walleye from the west and central basins increased steadily from 1976 to 1988 with harvests ranging between 0.9 and 10.0 million walleye (Figure 2; WTG 2006). During this period of operation, the harvests were primarily taken by the recre-ational fisheries. Following the peak popula-tion abundance observed in 1988, the harvest of walleye fluctuated between 3.6 and 8.2 million fish (1989 to 2000) with the Ontario


commercial fishery taking the majority of fish in the mid to late 1990s.

Walleye management has changed over time, with the most notable change being the establishment of the TACs. The WTG estab-lished recommendations for allowable har-vest of walleye for the period 1993 to 2000 using a Beverton–Holt yield-per-recruit F

opt

harvest strategy (Hilborn and Walters 1992). In 2000, the LEC again decided the walleye harvest should be reduced to allow the stocks to rebuild. In 2001, the LEC agreed to the Coordinated Percid Management Strategy (CPMS), an initiative that would halt popu-lation decline, establish sustainable harvest, and promote walleye stock recovery over a three year period (2001–2003; LEC 2004). The LEC established a lower threshold level of walleye abundance equal to the estimated abundance of walleye at large in 2000. The abundance in 2000 was chosen as the base-line because the estimated size of the popu-lation did not support desirable walleye fish-eries (LEC 2004). The WTG did not use the target fishing mortality rate (F

0.1) to calculate

TAC for 2001–2003, but simplified the ap-

proach without the inclusion of long-term as-sumptions about growth or natural mortality (WTG 2001). Instead, the WTG considered recruitment, harvest, and natural mortality when formulating the recommended annual TAC of 3.4 million walleye for 2001–2003. In order to meet harvest reduction targets, the LEC jurisdictions altered bag limits, size lim-its and/or closed seasons in the recreational fisheries (all jurisdictions), and reduced the quota available to the Ontario commercial fishery, further reduced in 2004 to 2.4 million fish. Harvests remained below the allocations and fluctuated from 2.4 and 2.9 million wall-eye between 2001 and 2004 (Figure 2; WTG 2006).

At the same time as harvest reductions were being made, the walleye population abundance increased as a result of two strong year classes, one in 1999 and a second in 2003. To reflect the increase in the fishable popula-tion of walleye in 2005, TAC was increased to allow anglers and commercial fishers to benefit from the abundance of walleye in the lake. The TAC was determined following another notable change in walleye manage-

Figure 2. Harvest of walleye by sport and commercial fisheries in Lake Erie from 1976 through 2005. Source: Walleye Task Group 2006.

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1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004Year

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150 Roseman et al.

ment, the development of a decision analysis simulation model (Wright et al. 2005), the establishment of fishery objectives specific to Lake Erie walleye, and the development of a Walleye Management Plan. The LEC began to explore the use of decision analysis methods in 2002 as a way to incorporate un-certainty and transparency into the decision making process. The LEC documented fish-ery objectives, helped develop a forecasting model to better understand how factors such as harvest and natural mortality affected wall-eye abundance, and evaluated several fishing mortality options (Wright et al. 2005). The LEC agreed to manage walleye harvest using fishing mortality rates that would reduce ex-ploitation when abundance was low and pro-vide a safe TAC when abundance was high, enabling older walleye to survive and migrate eastward so that there would be a broad dis-tribution of benefits throughout the lake and achieving the related objective documented

in the Lake Erie Fish Community Goals and Objectives (Ryan et al. 2003).

Harvest allocation relies upon the esti-mates of population abundance calculated from age-class, mortality, recruitment and fishing effort data. Although accurate stock assessment is critical to fisheries manage-ment, it has long been recognized that such decisions are often made with less than per-fect information (Cowan and Paine 1997). During the period 1978 to present, the esti-mated abundance of the Lake Erie walleye stocks (age 2+ and older) in the west and cen-tral basins has fluctuated from a low of 9.7 million fish in 1978, peaking at a high of 69.5 million fish in 1988 and subsequently declin-ing in abundance into the early 2000s (WTG 2006; Figure 3).

The population age structure of walleye has also fluctuated over time (Figure 3). Ex-tremely large year classes are rare in Lake Erie and there have been only three produced

Figure 3. Annual estimated abundance of walleye in the west and central basins of Lake Erie from 1978 to 2005 (Walleye Task Group 2006).

Age

2+

wal

leye

abu

ndan

ce (m

illio

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since 1978. These were year classes spawned in 1982, 1986 and 2003 that recruited to the fishable population as age-2 walleye in 1984, 1988 and 2005, respectively.

Lake Erie walleye spawn on open lake shoals and in larger rivers systems in the western and eastern basins. Walleye begin their migration to spawning areas in the fall with males arriving ahead of females. Most spawning locations for the west and central basin population are thought to be in the west basin, although the Ontario commercial fish-ery has reported observations of spawning condition walleye in the central basin in the 1980s (Timmerman and Dunlop 1985) and in the early 2000s (L. Jackson, Ontario Com-mercial Fisheries’ Association, personal com-munication). Data from spring commercial catch samples from 1996 through 2005 show that female walleye are 50% spent by about April 17 (95% CI = April 15–18) when the temperature is 6.4°C (95% CI = 5.9–6.9°C).

Walleye length at 50% maturity data from 1989 to 2005 shows that male walleye from the west and central basins are mature at smaller lengths (367 mm) than males from the east basin (445 mm), however female walleye from the west and central basins reach 50% maturity at sizes larger than eastern basin fe-males (440 mm versus 432 mm in east basin). Differences also exist among basins in age at 50% maturity for male walleye. Male walleye achieve 50% maturity at 2.6 years in the west and central basins and 3.9 years in the east basin. Female age at maturity was 3.4 years and 3.3 years at 50% maturity in the west-central basin and east basin, respectively. Henderson and Nepszy (1994) observed that females were maturing at an older age than expected, although male maturation was not different than expected.

There is considerable uncertainty regard-ing the natural mortality of Lake Erie walleye that tag recapture data has not, as yet, been able to resolve (Wright et al. 2005). There are data to suggest that male walleye have

higher levels of mortality than do females and this may be the result of the energetic cost of male spawning behavior (Henderson and Nepszy 1994). There are some obvious concerns about what impact this might have on the Lake Erie population (e.g., if older fish are predominantly female), however, to date there is no evidence to suggest that the Lake Erie population is negatively impacted by differential mortality between male and female walleye even in the older segment of the population.

For management purposes, walleye are grouped by age with fish ages 7 and older grouped together as age 7+. Although this facilitates data analyses (by reducing the influence of small sample sizes in older age groups), the LEC recognizes that walleye older than age 7 are present in the Lake Erie populations. Recent age estimation of walleye using otoliths collected from west, central and eastern basins of Lake Erie in-dicate that walleye as old as 24 years are at large in the lake (C. Vandergoot, ODNR Sandusky Fisheries Station, personal com-munication). Additional information and research on walleye total mortality (fishing mortality and natural mortality) at the pop-ulation and stock-specific levels in Lake Erie has been identified as a research prior-ity (Locke et al. 2005).

Several independent investigations have now examined genetic stock structure for Lake Erie’s walleye resource (Stepien and Faber 1998; Gatt et al. 2003; Wilson 2003). Each of these studies documented evidence for stock structure within the Lake Erie walleye resource. Significant genetic variation was found between east and west basin spawning stocks, and was also detected among some spawning sites within a basin. Nevertheless, a recent blind experiment using genetic stock discrimina-tion techniques had only marginal success in classifying known origin of walleye cor-rectly (Johnson et al. 2005), and it remains

152 Roseman et al.

difficult to manage discrete walleye spawn-ing populations that are exploited as a mixed stock assemblage after the spawning period. Instead, Lake Erie walleye manage-ment recognizes two walleye resources that are not only somewhat genetically distin-guishable, but also inhabit different lake regions, in widely differing densities, and exhibit differing movement patterns and mortality schedules; 1) a west-central basin resource, and 2) an east basin resource.

Model analyses of long-term Lake Erie data (1978–2000) indicated that the carry-ing capacity of walleye has declined over time (Locke et al. 2005). Locke et al. pro-posed several factors that may account for the decline, including changes in phospho-rus loading, introductions of nonindigenous species, and lowered lake levels. The LEC (2004) reported that, for Lake Erie wall-eye, suitable environmental conditions ap-pear to be the limiting factor controlling recruitment (Busch et al. 1975; Roseman et al. 1999). Decision analysis model simula-tions using Lake Erie walleye data showed that the Lake Erie walleye population is in-fluenced more by variations in recruitment than it is by fluctuations in harvest (Wright et al. 2005).

Henderson and Nepszy (1994) were even more specific, stating that strong year classes have the potential to be produced if most females have sufficient surplus energy, stored during the growing period in the pre-vious year. The authors further hypothesized that, following a strong year-class, female walleye may have an energy deficit, may not be able to store surplus energy, may not al-locate sufficient energy towards ovary pro-duction, and may not spawn the next year. Parsons (1970) had previously noted that following a year with a strong year-class, there is often a year with relatively poor year-class production. There have not been enough years with strong year classes to test these hypotheses using Lake Erie wall-

eye data although Madenjian et al. (1996) showed that recruitment was best following years when age-0 gizzard shad or other for-age fish were abundant, thus supporting the Henderson and Nepszy (1994) hypothesis.

Because walleye are the dominant preda-tor in Lake Erie (Knight et al. 1984) and sup-port important sport and commercial fisher-ies, fluctuations in their population size and structure can have direct implications for the entire Lake Erie ecosystem. For example, Knight and Vondracek (1993) found that in-creases in the abundance of walleye in the late 1970s and 1980s played a major role in the decline in abundance of soft-rayed spe-cies such as emerald shiner Notropis atheri-noides, spottail shiner N. hudsonius and ale-wife Alosa pseudoharengus. They concluded that management goals focusing primarily on walleye affected not only the targeted spe-cies, but the entire fish community of western Lake Erie. Further, Nicholls (1999) hypoth-esized that the changes in the fish community documented by Knight and Vondracek (1993) were partially responsible for reductions in total phosphorous in western Lake Erie prior to the invasion of dreissenids Dreissena poly-morpha and D. bugensis. Nicholls (1999) suggests that the increase in piscivorous wall-eye reduced planktivore biomass, thereby in-creasing phytoplankton grazing by zooplank-ton allowing increased levels of phosphorous to be transferred into the foodweb.

Yellow Perch

Yellow perch have been a historically important commercial and sport fish species in Lake Erie. Like walleye, Lake Erie yel-low perch fisheries are managed under the guidance of the Great Lakes Fishery Com-mission’s Lake Erie Committee. The Yellow Perch Task Group was formed by the LEC in 1980 to determine the status of Lake Erie yel-low perch populations and to assist in quota determination. Records dating back to the


1880s show that there were commercial yel-low perch harvests in both U.S. and Canadian waters of the lake. Since the early 1900s, the yellow perch fisheries have enjoyed several peak harvest periods (Figure 4) when recruit-ment patterns showed consistently strong year classes. Wide fluctuations in harvest were seen due to highly variable recruitment pat-terns, changing lake productivity conditions, and high levels of exploitation (Leach and Nepszy 1976; YPTG 1997). Lake Erie yellow perch have shown some resilience in the light of several invasions of exotic species, includ-ing the proliferation of white perch, and the expansion of dresseinid mussels, spiny water flea Bythotrephes longimanus and the round goby. Lake Erie, unlike other Great Lakes, does not have a large population of alewife, so their deleterious effects on the yellow perch populations experienced in other Great Lakes (Eck and Wells 1987) have not been evident in Lake Erie.

Lake Erie yellow perch populations are more robust in the western and central basins

due to warmer water temperatures and bet-ter habitat. Eastern basin yellow perch stocks are mostly confined to the nearshore zone (depth <30 m) including the area in and adja-cent to Long Point Bay (MacGregor and Wit-zel 1987; YPTG 1997; OMNR 2006). The CPMS (2001–2003) recognized that a strong 1998 year-class of yellow perch was recruit-ing into the adult population and therefore cut backs to harvest were not implemented (LEC 2004). By the mid 2000s, western and central basin yellow perch populations had rebound-ed from historic lows in the 1990s, however eastern basin stocks were slow to recover. A special management plan, undertaken by the Ontario Ministry of Natural Resources, was implemented from 2000 to 2005 that insti-tuted reductions in harvest rates in an effort to rebuild stocks (OMNR 2006).

Lake Erie yellow perch inhabit a variety of areas and locations. They are commonly found in the sand and mud habitats of the western basin, and can be found from near-shore vegetated habitat to open water reefs

Figure 4. Annual lakewide harvest (commercial and sport combined) of Lake Erie yellow perch, 1915–2005. Harvest is denoted in millions of pounds on the y-axis. Data compiled from YPTG (2006), and the Great Lakes Fishery Commission database, Ann Arbor, Michigan.

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154 Roseman et al.

containing gravel, cobble and glacial boulders (Scott and Crossman 1973). In the lake’s cen-tral basin, they are generally found inshore during the spring spawning period (late April through mid to late May; water temperatures 6–10°C). Goodyear et al. (1982) found that males moved into waters 6 m or less first fol-lowed by females. However, research by the Ohio Division of Wildlife in 2006 showed that some females in the central basin spawned in waters as deep as 15 m. Their lack of specific preference or requirement for spawning sites and habitats may help yellow perch continue to thrive as conditions change the lake envi-ronment.

There is a general offshore movement of yellow perch after spawning in the summer associated with the onset of a thermocline and declining dissolved oxygen. Lake Erie yellow perch then generally move back inshore with the onset of autumn turnover and breakdown of the thermocline (Ferguson 1958; Scott and Crossman 1973; ODW 2006). Seasonal movement patterns are similar in the eastern basin; however, there is little evidence that shows movement into the deep (>30 m) hy-polimnion offshore (MacGregor et al. 1987; OMNR 2006; YPTG 2006). There is no large scale migration of adult yellow perch across Lake Erie’s basins as is seen with adult wall-eye; rather, movement is largely inshore-offshore or into adjacent waters in search of optimal temperatures (20–24°C) or preferred prey items (Collette et al. 1977; Rawson 1983). More information on the life history and habitat preferences of Lake Erie yellow perch can be found in the Yellow Perch Task Group (1997) interagency summary report.

Lake Erie yellow perch exhibit above average growth for the species in its native range (Carlander 1997). The majority of yel-low perch reach 200 mm (8 in) by age 3, with females exhibiting faster growth than the males (YPTG 2006; ODW 2006). It is not un-common to see occasional to moderate num-bers of fish 300 mm and larger in the harvest,

particularly in the central and eastern basins (YPTG 2006; ODW 2006; NYSDEC 2006). Annual growth variation can be substantial, with cohort density dependence, water tem-peratures, and growing season all playing important roles for in-season growth, condi-tion and possible future recruitment (Tyson and Knight 2001; YPTG 2006; ODW 2006). Typical Lake Erie yellow perch length-at-age going into the autumn is 60–70 mm for age 0, 125–140 mm for age 1, 160–185 mm for age 2, 185–220 mm for age 3, 205–240 mm for age 4, and 215–270 mm for age 5. There is much disparity in size by basin and sex. Many old males (>6 years of age) nev-er achieve 250 mm in length (ODW 2006; YPTG 1997; 2006).

As is the case with most Great Lakes fishes, recruitment is the driving factor in the overall numerical abundance of the Lake Erie yellow perch population. Lake Erie yellow perch are known to regularly produce cohorts at both ends of the hatch size spectrum. The relationship between the numbers of spawn-ing adults and the number of young produced is not significant. There can be large year classes and poor year classes produced by the same number of spawning adults in different years. Over the range of time Lake Erie yel-low perch have been studied and harvested, populations have not reached sufficiently low levels where a critical spawning stock biomass threshold has been passed. There is not a cyclical nature to the year-class produc-tion, either, although there were weaker year classes produced during the initial dreissenid invasion and expansion. This may have been related to declines in overall lake productiv-ity and energy flow changes at the time rather than effects by the dreissenids. Busch et al. (1975, 1978) and Koonce et al. (1977) deter-mined abiotic factors such as spring air tem-peratures, warming rates, and wind strength were significant factors in setting year-class strength. Year-class strength for Lake Erie yellow perch is generally set before the first


winter. The YPTG (2006) uses regressions that compare interagency trawl survey indices conducted in August and October for young-of year and yearling yellow perch, and resul-tant age-2 estimates from previous years, to project the abundance of incoming age-2 yel-low perch in the next year. This allows the YPTG to complete population projections and make recommendations for allowable harvest levels for the next fishing year.

Lake Erie yellow perch begin to con-tribute to the sport and commercial fisheries by age 2; however, the bulk of the fisheries are comprised of 3- to 5-year-old fish, gen-erally depending on variations in year-class strength. In the eastern basin, yellow perch age-5 and older often contribute substantially to the harvest (YPTG 1997, 2006). Harvest of young yellow perch can be problematic because female yellow perch generally do not fully mature until age 4. The majority of females are mature at age 3, but very few are mature at age 2. Nearly all yellow perch males are mature by age 2, with some preco-cious age-1 males participating in spawning (YPTG 1997; ODW 2006).

Besides fishing mortality, which can be substantial, there are a few specific sources of mortality on Lake Erie yellow perch. Natural mortality can come from a variety of preda-tors and diseases. Unlike other lake systems where yellow perch are a preferred prey spe-cies for piscivorous fish (e.g., Oneida Lake; Forney 1974), yellow perch are not a primary target prey species in Lake Erie. Species like walleye, rainbow trout, and even smallmouth bass will eat juvenile yellow perch mainly when yellow perch cohorts are large (ODW 2006) but rarely do yellow perch make up more than 10% by weight of any predatory fishes diet. The forage base in Lake Erie con-sists of healthy populations of shiners, giz-zard shad, and rainbow smelt which are more commonly found in predator’s diets. Other predators include the expanding population of double-crested cormorants, but Bur et al.

(1999) found yellow perch to be a small per-centage of cormorant diets in the western ba-sin of Lake Erie, where cormorant densities are the highest on the lake.

Yellow perch mortality due to disease has also been noted in the last several years. In spring 2006, an outbreak of Viral Hemor-rhagic Septicemia (VHS) was a complicating factor in the death of thousands of mostly juvenile and some adult yellow perch on the southern shore of Lake Erie’s central basin. The bacteria Flexibacter columnaris was found in a fish die-off that included yellow perch on the Canadian shore just south of Wheatley in 2005 (A. Cook, OMNR, person-al communication). Wounds have also been noted on yellow perch that were attributed to silver lamprey Ichthyomyzon unicuspis and sea lamprey Petromyzon marinus. While the wounds may not have caused mortality, infections may have resulted in additional stress and subsequent mortality. The overall effect of natural mortality sources has been modeled by the YPTG using the method of Pauly (1980) in the 1980s (YPTG 1986). The instantaneous natural mortality rate (M) as-signed by the task group after that analysis was 0.4. As more information is gathered about Lake Erie yellow perch, and as new techniques are used to age fish and estimate M, new estimates for Lake Erie yellow perch natural mortality will be generated.

Lake Erie is divided into four separate management units (MU) for yellow perch as-sessment, data collection, population model-ing, and quota determination (Figure 5). The western basin from the Detroit and Maumee rivers at Toledo, past the islands and Pelee Point, to Wheatley, Ontario, and Huron, Ohio, comprise MU1. The central basin is divided into MU2 and MU3 based on lake current gyres (Saylor and Miller 1987), the point of Fairport Harbor, Ohio, and the pro-jection of the Kent-Elgin counties border in Ontario. The YPTG’s MU4 is comprised of the oligotrophic eastern basin extending east

156 Roseman et al.

from Long Point, Ontario and Presque Isle, Pennsylvania, to the formation of the Niagara River at Buffalo, New York. The major bays of Sandusky, Rondeau, Presque Isle, and In-ner Long Point are not considered in the lake population and quota determination (YPTG 1987) due to the presence of geographically-isolated populations and low overall harvest in these areas. The YPTG (2006) is also as-sessing the geographic isolation of subpop-ulations in the eastern basin to determine if more finite MU4 delineations are required.

The YPTG long-term data sets comprise fishery harvest and effort, and biological data such as age and growth information. As-sessment surveys performed by all agencies gather independent information about the Lake Erie yellow perch population. Trawl and gill net surveys are performed from Au-gust through October to assess the status of adult yellow perch, while trawl surveys are used to index young-of-year and yearling abundances. All of this information enters into the process of determining the standing stock of yellow perch both numerically and in biomass. While most agencies perform the survey work annually, the OMNR has an in-teresting partnership agreement where com-mercial fishery operators are contracted to perform annual gill net surveys. The Ontario

Partnership Index Fishing Program has be-come a long-running program that provides an important data set in the YPTG assessment efforts.

One of the primary responsibilities of the YPTG is to annually determine the sta-tus, abundance and biomass of the Lake Erie yellow perch population. The YPTG has in-corporated a number of population models in that process. During the early years of the task group (YPTG 1987), the members primarily used CAGEAN (Deriso et al. 1985) for catch-at-age analysis. As newer methodologies and advances in computing were made, the YPTG shifted to ADMB (Auto Differentia-tion Model Builder; Fournier and Archibald 1982; YPTG 2002). An independent review of YPTG modeling efforts in 2001 (Myers and Bence 2001) affirmed the direction the YPTG was proceeding and recommended further steps to improve modeling efforts. ADMB is currently in use and task group ef-forts have focused on the relative weighting that fishery and survey series are assigned in the model.

Yield of Lake Erie yellow perch is deter-mined by using optimum instantaneous fish-ing rates applied to the estimated stock sizes for each year-class using Baranov’s catch equation and summing across ages. Selectiv-

Figure 5. Yellow Perch management units (MUs) used by the Lake Erie Yellow Perch Task Group. Source YPTG (2006).

MU 1

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ity and catchability are used from ADMB, and appropriate F levels are used to deter-mine F

age. Prior to the independent review

and until 2003, the task group calculated an F

opt value for each MU that was based on

the F0.1

yield strategy (Hilborn and Walters 1992). Since 2003, the YPTG (2003, 2006) has used a risk-simulation approach to deter-mine an appropriate recommended allowable harvest in each management unit. Current weight-at-age information for the population at-large and observed in the harvest allows the YPTG to convert numbers of fish to biomass and projected harvest weights. Analyses are completed, information and recommendation on TACs are presented to the LEC and stake-holders by the YPTG. After an assessment of concerns presented by stakeholders, the Lake Erie Committee determines and announc-es harvest quotas for the upcoming season by management unit. Then, MU quotas are parsed out to the agencies in each MU based on the surface water areas that each state or province has in that MU. Each agency then partitions out their portion of the quota to the significant fisheries that operate in that MU.

As Lake Erie yellow perch populations rebounded from low levels experienced in the 1990s, both harvest and effort increased. Esti-mates of yellow perch standing stock were ro-bust for all management units in 2006 (Figure 6) with abundance and biomass levels in the upper range of those observed over the last 30 years. Year classes from 1998, 1999, 2001 and 2003 are contributing to the fishery. Age esti-mates derived from otiliths have affirmed that older age groups (ages 10 and older) can con-tribute significantly to the fishery if they are not overexploited at early ages (YPTG 2006). Harvest and effort are particularly strong in the area around the MU1-MU2 border and near the major ports across the lake. The pop-ulation in MU4 has rebounded from a low in the mid-1990s, but a strong improvement to the fisheries has not taken place compared to elsewhere in the lake (Figures 6 and 7).

Survival trends for ages 2 and older have generally improved in the last fifteen years, although we have observed some re-cent erosion of gains for ages 3 and older for the last several years. More stringent quotas in the mid to late 1990s, along with mod-erate to strong cohorts in 1994, 1996 and 1998, helped rebuild the population. Recent declines in survival could be attributed to several poor year classes and increases in F associated with the risk-based yield strategy for determining the recommended allowable harvest (RAH) and subsequent TAC setting.

Economically and socially, the yellow perch sport and commercial fisheries are important drivers in the overall health of the Lake Erie area. In 2006, the YPTG and LEC established quotas in each of the four MUs that totaled almost 16.5 million pounds lakewide. In 2005, yellow perch landings in the Ontario gill net fishery was valued at 12.9 million Canadian dollars; the highest of any commercial species (OMNR 2006b). In Ohio, trap net landings of yellow perch were valued at 3.4 million U.S. dollars (ODW 2006). The recent trend of the last decade has shown an increase in the economic val-ue of these fisheries (Pennsylvania and New York have minimal commercial fisheries, and Michigan does not allow commercial harvest of yellow perch from Lake Erie). Markets for these fish are primarily in the Great Lakes region, but their popularity as a light, flaky fish certainly extends beyond the region.

The markets remain mixed for Lake Erie yellow perch as both price of fish and land-ings fluctuate from year to year (Figure 8). Its regional popularity has caused strong demand as a Great Lakes coastal restaurant menu staple. But as competing species like Eurasian perch entered the market at sig-nificantly lower prices, demand and price per pound has retreated. Yellow perch pro-duced by aquaculture methods has begun to enter the market, and market prices have

158 Roseman et al.

been affected by rising fuel and distribution costs and fluctuating U.S.-Canada exchange rate. There is more Lake Erie yellow perch product in the market stream now due to increased annual quotas, but there is not an associated surge in demand or previous un-filled demand for that product at the current prices. There are few documented efforts to develop new markets outside the Great Lakes region.

The future of Lake Erie yellow perch also remains as mixed as the markets. The Lake Erie yellow perch population will con-tinue to depend on the regular (and relatively frequent) production of strong year classes. Future management efforts will depend on strong assessment and modeling efforts to develop a long range Yellow Perch Man-agement Plan. This plan must look beyond

biological TAC strategies already in place. Besides incorporating biological data, and assessing risk, socio-economic factors will have to be evaluated in a transparent pro-cess where stakeholders can participate by providing data, direction, and desired out-comes, but not the aspects of biological and statistical analyses and management respon-sibility.

Governance Structures Affecting

Lake Erie Percid Fisheries

Governance of the Lake Erie walleye and yellow perch fisheries is complex. The pro-cess involves multiple jurisdictions, diverse stakeholders (e.g., commercial industry, rec-reational fishers, charter boat industry) with different interests (e.g., profit versus recre-

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Figure 6. Lake Erie yellow perch population estimates by management unit for age 2 (dark bars) and ages 3+ (light bars) from YPTG 2006 report.


ational benefits), varying approaches to har-vest monitoring and fishery regulation, all combined with highly variable ecological and stock conditions (Donahue 1986; Dob-son et al. 2002). The complexity of the in-teragency fishery management system mir-rors the complexity of the environmental and sociological issues on Lake Erie (Dobson et al. 2002), with further complications from in-herent uncertainties in all scientific estimates used for assessment as described in the ecol-ogy sections above.

During the early years of the 20th centu-ry, disputes arose over use and management of Great Lakes waterways. These disputes inspired the formation of the International Waterways Commission in 1905 which was an investigatory and advisory body with lim-ited authority to make decisions. Perhaps the most important outcome of this group was the 1909 Boundary Waters Treaty and the es-tablishment of the International Joint Com-mission (IJC; Donahue 1986; Sproule-Jones 2002). The IJC consists of six appointed commissioners, three each from the United States and Canada. The IJC is tasked with ap-

proving new uses and diversions of boundary waters, if these actions affect water levels or flows. The IJC also advises the government on matters referred to it for consideration. The IJC is an objective, nonpartisan author-ity that relies on the best scientific advice to make decisions. It gains power from its abil-ity to mobilize large numbers of scientific ex-perts to staff advisory committees that deal with issues pertaining to international waters. Of specific importance to the Great Lakes, the IJC has been at the forefront of interna-tional efforts to control and reduce release of contaminants and help remediate and restore environmental conditions for beneficial use.

To coordinate the maintenance of Great Lakes fisheries, the GLFC was established in 1955 by the Canadian/U.S. Convention on Great Lakes Fisheries. The 1980 Joint Stra-tegic Plan for Management of Great Lakes Fisheries, known more succinctly as the Joint Strategic Plan (JSP) was signed by each of the state, provincial, federal, and tribal nat-ural resource agencies in the Great Lakes basin (GLFC 1980). According to the JSP, the GLFC supports and facilitates five indi-

Figure 7. Spatial distribution of yellow perch total harvest (lbs.) in 2005 by 10-minute grid (YPTG 2006).

160 Roseman et al.

vidual lake committees that were identified as the “major action arms for implementing the strategic plan and developing operational procedures” (GLFC 1980). Since that time, the lake committees and the Council of Lake Committees have addressed a wide variety of issues critical to a healthy Great Lakes ecosystem. The GLFC plays a pivotal role in the implementation of the JSP through fa-cilitation of the lake committees. Without the GLFC in its facilitation role, it is highly un-likely that interjurisdictional fisheries man-agement would occur efficiently, if at all.

The Lake Erie Committee consists of se-nior staff members from the OMNR, MDNR, ODW, PAFBC, NYSDEC. The LEC’s purpos-es include: consideration of issues pertinent to, or referred by, the GLFC; consideration of issues and problems of common concern to member agencies; develop and coordinate joint programs and research projects; and

serve as a forum for state, provincial, tribal, and federal agencies (GLFC 1980; Donahue 1986; Ryan et al. 2003). Decisions made by the LEC have become part of the guiding framework for future fishery and environ-mental management in the basin.

The LEC has established a STC with several interjurisdictional technical working groups, including the YPTG and the WTG, to carry out stock assessment surveys, popu-lation modeling, and exploitation strategy modeling to provide the LEC with harvest recommendations for upcoming fishing sea-sons. Total allowable catches for Lake Erie walleye and yellow perch are determined by the LEC.

Under the JSP, the LEC makes the final decisions on yellow perch and walleye TACs in the spring of each year. As stipulated in the JSP, all decisions are consensus-based and nonbinding, yet agencies have consis-

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Figure 8. Reported Ohio commercial harvest and exvessel price per pound paid to Ohio com-mercial fishery operators (in U.S. dollars), 1986–2005, from Ohio Division of Wildlife data.


tently adhered to TAC decisions. This reflects a commitment to responsible management and a common goal of maintaining healthy fish community from which all parties can derive benefits. For the most part, committee members share a high level of trust between agencies and individuals on the committees, and also have developed a level of respect and trust with their stakeholders. A surface area sharing formula is used to determine each jurisdiction’s share of the TAC, also known as an agency quota, and each agency determines allocation of their agency quota among recreational and commercial fisher-ies. This elaborate quota system has been in place since 1976 (Hatch et al. 1987) for wall-eye fisheries, and since 1990 for yellow perch fisheries (Koonce et al. 1983, 1999). In 1984, the OMNR implemented a system of species-specific individual transferable quotas (ITQs) for the Lake Erie commercial fishing industry. These ITQs are used to distribute and control the harvest of walleye, yellow perch and lake whitefish. Similarly, the ODW implemented an ITQ system on yellow perch for commer-cial trap netters in 1996.

Over the past decade, the YPTG and WTG have significantly improved stock as-sessment and population modeling methods to the point that there is now increased confi-dence in the yellow perch and walleye popu-lation estimates and projections they gener-ate each year. Some of this improvement is attributable to the establishment of the On-tario Partnership Index Fishing Program, a long-standing cooperative assessment pro-gram in which the OMNR and the Ontario commercial fishing industry together monitor Lake Erie’s fisheries resources. Development and continuing evolution of walleye and yel-low perch management plans for Lake Erie represent dynamic responses by the LEC to integrate new science, stock assessment tech-niques, and stakeholder interests into inter-agency fisheries management plans. These developments are unique and necessary facets

of modern resource management especially in a system as complex as Lake Erie.

The LEC implemented the Coordinated Percid Management Strategy (CPMS) in March 2001, establishing a minimum lake-wide abundance target of 19.1 million wall-eye and freezing lake-wide walleye harvests at 3.45 million fish for three years, i.e., 2001, 2002 and 2003 (LEC 2004). The CPMS was developed in response to increasing con-cern by the LEC about declining abundance of Lake Erie walleye evident since the late 1980s. The objective of the CPMS was “to reverse declines and rebuild stocks of Lake Erie walleye…” (WTG 2003; LEC 2004). In 2003, however, the WTG reported relatively weak walleye year classes in 2000 and 2002, suggesting that the number of fishable (ages 2 and older) walleye would drop below the 19.1 million fish target in 2004. Subsequent-ly, the WTG recommended a harvest for 2003 below the 3.45 million fish CPMS threshold, which the LEC decided it could not imple-ment without severe economic impacts on fisheries. Instead, the LEC announced inten-tions to defer a TAC reduction of about 40–60% below the CPMS threshold until 2004, giving fishers an additional year to plan for the change. Implementation of this decision became contentious within the LEC at their next meeting (June 2003). For the better part of 2003, the LEC met monthly to try to re-solve their differences. Adding to the pres-sure, stakeholder groups on both sides of the border lobbied agency personnel to do what was necessary to meet individual jurisdiction objectives. By fall, the LEC declared an im-passe and sought GLFC assistance to enact the formal dispute resolution process to help them reach consensus on a 2004 TAC. This was only the second time that the JSP dispute resolution process was invoked by the LEC (the first occasion was in 1991, but the LEC was able to reach consensus before complet-ing the formal process). In early 2004, the GLFC assembled a Blue Ribbon Panel of

162 Roseman et al.

fishery experts to assist the LEC with their impasse. Ultimately, the LEC agencies were able to reach consensus on the 2004 walleye TAC, a testament to their commitment to the JSP, as facilitated by the GLFC.

In essence, the impasse resulted from the challenge of decision-making in the face of very low walleye abundance and associated impacts on fisheries. By late 2004, a record abundant year-class of walleye was expected to enter the upcoming fishery and the deci-sion of an appropriate TAC was once again contentious, as the jurisdictions disagreed about whether to maintain low fishing rates to conserve the stocks or to raise fishing rates to take advantage of increased walleye abun-dance. However, with renewed respect and trust among jurisdictions, and considerable scientific work by the WTG, the LEC was able to reach consensus on the 2005 walleye TAC.

Though rare over the LEC’s lengthy his-tory of successful TAC deliberations, clearly there have been episodes that have tested the strength of the JSP as an inter-jurisdictional management tool. With the professional assis-tance of the GLFC, LEC jurisdictions have re-affirmed their commitments to the JSP on each occasion. It is this commitment to a common goal of having healthy fish communities to support a broad distribution of fishery benefits that makes the JSP work for all jurisdictions.

The YPTG has changed the yellow perch exploitation strategy several times since the quota system was implemented in 1984. At the time of quota implementation, the com-mercial fishery agreed to achieve a target fishing effort of 20% of the 1984 fishing ef-fort by 1990 (YPTG 1985, 1991, 2003). In 1985–1986, the YPTG moved the exploita-tion strategy from a targeted fishing effort to an approximation of maximum sustain-able yield (MSY; YPTG 1986). In the early to mid-1990s, yellow perch biomass fell to low levels throughout Lake Erie. In 1991, the YPTG again changed the method used to de-

termine RAH levels moving from MSY to a yield per recruit (Y/R) approach, e.g., F

0.1 or

Fopt

. As yellow perch stocks recovered in the mid- to late-1990s, the YPTG again changed the methodology used to determine RAHs to a more conservative approach by altering de-tails of the F

age calculation regarding age-and

gear-specific selectivity (YPTG 1999, 2000) to parallel the technique employed by the WTG. The YPTG (2006) has also introduced another harvest strategy that incorporates bi-ological reference points, population simula-tions and assessment of risk.

Working within the harvest recommenda-tions set forth by the LEC, state and provincial agencies use restrictive fisheries regulations to achieve desired management objectives. Regulations for the sport fishery include minimum length limits, creel limits, closed seasons, and gear restrictions, although these regulations differ among jurisdictions and of-ten change from year-to-year in response to management objectives set forth by the LEC. Regulation of commercial fisheries is also set by the agencies and includes gear restric-tions, closed seasons, minimum size limits, quotas, and refuges. Fisheries regulations are enforced by law enforcement personnel in each state and provincial jurisdiction as well as by federal enforcement agencies. At a local level, some townships and municipali-ties in the Lake Erie basin have undertaken habitat restoration and management initia-tives. These include tributary and watershed improvements directed at improving water quality and fish habitat as well as providing structure to attract fish adjacent to angler ac-cess sites.

Discussion

The recovery and sustainability of wall-eye and yellow perch in Lake Erie was in part the direct result of coordinated inter-jurisdictional management and the imple-mentation of the quota management system.


Over time there have been dramatic changes in the Lake Erie ecosystem, many of which have contributed to reductions in optimal fish habitat that have translated into large fluctuations in abundance of percid popu-lations. In response to ecological changes in Lake Erie, the management framework for fisheries has evolved to include a multi-agency international cooperative that con-siders the complex desires of a broad stake-holder base and relies on the best available scientific information for decision making. Recognizing the interests and authority of five management jurisdictions and the often competing interests of sport and commercial fisheries exacerbates the complexity of man-aging percid fisheries in Lake Erie. While the effectiveness of the current cooperative interjurisdictional management structure is generally agreed to be successful, as evi-denced by the current quality and quantity of fisheries in the lake and stakeholder satis-faction, numerous factors threaten the future integrity and stability of percid fisheries and the management framework.

Perhaps the largest source of uncer-tainty affecting management of Lake Erie’s fisheries is the role of introduced organisms in the foodweb. White perch and rainbow smelt became major components of the fish community in the 1980s and, more re-cently, dreissenid mussels and round goby have flourished in Lake Erie. Examples of the impacts of these introductions are well documented; Parrish and Margraf (1990) showed competitive interactions between white perch and yellow perch; Dermott and Kerec (1997) discuss impacts of dreissenids on other benthos in the lake; and Jude and DeBoe (1996) postulate on the role and im-pacts of round goby in Great Lakes systems. While it may be impossible for scientists to predict how current and future introductions will impact fish communities, efforts should be made to prevent future introductions by managing ballast water of transoceanic

ships, the primary vector of introduced spe-cies in the Great Lakes (Mills et al. 1994).

Variability in the physical habitat of Lake Erie also presents challenges to fish-eries managers. Changes in nutrient avail-ability, particularly phosphorous, can have major influences on fish community struc-ture and production. Ludsin et al. (2001) described how phosphorus-driven reduc-tions in tolerant species abundance caused species richness to decline in the west ba-sin. In contrast, phosphorus abatement con-ceivably caused species richness to increase in the central basin by allowing a variety of species intolerant of degraded water quality to recover. In addition to changes in the nutrient loading of Lake Erie, other large-scale habitat changes have occurred including loss of wetlands; tributary chan-nelization, damming, and hydro-modifica-tion; and shoreline armouring, all of which have influenced percid habitat (Manny and Kenaga 1991; Ludsin et al. 2001; Ryan et al. 2003). Efforts to rehabilitate or reclaim habitat are planned or underway (e.g., Catta-raugus Creek and the Buffalo River in New York; dam removal on Lake Erie tributaries in Ohio; increased spawning habitat in the Grand River, Ontario; spawning habitat res-toration in the Detroit River). These types of projects are long-term initiatives that help meet the LEC’s Environmental Objectives (Davies et al. 2005) and Fish Community Goals and Objectives (Ryan et al. 2003).

Changes to agency staff and political cli-mates can be a factor in the response time and degree of cooperation among LEC and its working groups. As retirements and promo-tions happen, losses of institutional memory can occur as well as the break-up of groups of people who have successfully worked to-gether for many years. Introduction of new members to working groups can impede de-cision making as new members develop the knowledge and skills required to actively participate in the group and nurture work-

164 Roseman et al.

ing relationships with other group members, yet equally likely is the opportunity for new members to bring fresh perspective to the established group. Also to be considered in personnel rollover is the need to acquire staff members with the specific skills required to move fisheries management programs for-ward. For example, Koonce et al. (1999) discussed the need for Lake Erie fisheries managers to move from single species man-agement toward an ecosystem perspective. Toward this end, the LEC recently formed a Habitat Task Group to address rehabilitation of degraded habitat in the basin and the For-age Task Group to routinely assess the prey community of the lake. As described above, advances in statistical modeling approaches also require special training and areas of spe-cialization by scientists. These types of spe-cialization should be considered when hiring new scientists and when developing regional continuing education opportunities for exist-ing staff.

Commitments to LEC activities can place huge burdens on agency staff and travel bud-gets. Because of the interagency involvement in management planning, travel to meetings and to conduct research can limit participa-tion by some staff members, especially in years when agency budgets are constricted. Restrictions in funding can inhibit the rate at which emerging problems are addressed. Maintaining agency commitments to future funding and making staff and resources avail-able for LEC issues is important, though not due to a lack of interest by dedicated fisher-ies staff. Such commitments will assure the continuation of timely fisheries monitoring and assessment programs that provide infor-mation necessary to develop management strategies and set harvest quotas (Koonce et al. 1996b).

The shift in human population density in the U.S. is also a concern to fisheries man-agers in Lake Erie and other Great Lakes. According to recent census data, the human

population in the Great Lakes basin has de-clined in relation to increases in other parts of the U.S., primarily the southwest (U.S. Cen-sus Bureau 2006). This shift in demographics may result in loss of congressional delegates in Ohio and other Great Lakes states that can change congressional support for Great Lakes issues when alignment of congressional del-egates occurs in 2010.

The sport and commercial fisheries for percids in Lake Erie are estimated to con-tribute billions of dollars to the economies of New York, Pennsylvania, Ohio and Michi-gan and the province of Ontario (Lichtkop-pler 1997). While the level of involvement and resultant value of the Lake Erie sport fishery depends on the quality of fishing (health and abundance of fish populations) and weather conditions that allow anglers to access the fishery, value of the commercial fishery is more dependent on market condi-tions. Consumers will substitute one fish type for another, so Lake Erie fish are competing against salmon, cod, halibut, and other spe-cies depending on product price, however Lake Erie percids are a featured specialty for some restaurants around the Great Lakes. Since the early 1980s, a great interest has de-veloped in the commercial culture of percids as food fish in both the U.S. and Europe. De-velopment of percid aquaculture production facilities is driven by increasing demand and declining supplies from the wild (Malison et al. 2004). Presence of farm-raised fish on the market adds additional pressure to the mar-ket for Lake Erie fish, although the majority of Lake Erie percids are sold on local and regional markets in the Great Lakes basin (Kinnunen 2003). Fish is a high-priced com-modity and is often consumed in restaurants. These two factors make it especially sensitive to economic downturns.

Lake Erie percid fisheries rely on occa-sional strong year-classes that support harvest for several years. Managers strive to maintain a spawning stock level that will allow such


year-classes to occur when conditions permit. Recruitment of percids in Lake Erie is largely influenced by meteorological conditions that occur during reproduction (Busch et al. 1975; Henderson and Nepszy 1988; Roseman et al. 1999). Climatologists generally agree that global climate change (i.e., global warm-ing) will bring an increase in the frequency of severe meteorological phenomenon (Dotto 1988; Walther et al. 2002). Such increases are expected to cause increased variability in re-cruitment and production of freshwater fishes (Lehtonen and Lappalainen 1995; Stefan et al. 1995) and add to the uncertainty associ-ated with managing fisheries. Because large amounts of spawning habitat for walleye and, to a lesser extent, yellow perch are located in shallow waters of Lake Erie and its tribu-taries, fluctuations in water level can influ-ence the quantity and utility of shallow water spawning habitats. Cohen (1986) predicted that water levels in the Great Lakes basin will decrease due to decreased summer pre-cipitation in the basin associated with global warming, and based on trends in Great Lakes water levels since 1994 (ACE 2006), this indeed appears to be the case. Lower water levels in western Lake Erie will increase the amount of reef area exposed to strong wind-generated currents and waves increasing the susceptibility of incubating eggs to removal by these processes.

Melding the interests and desires of di-verse stakeholders from five jurisdictions to formulate common goals that match agency missions and are socially acceptable is a formidable and challenging task for percid fisheries management in Lake Erie. Quota management and the TAC system simplifies this task to some degree, but the enormous complexity and high level of uncertainty as-sociated with continued unpredictable habitat variability complicate any predictive capacity of management, and makes the development of long-term objectives more difficult. Lake Erie fisheries managers continue to rely on

innovative and up-to-date scientific informa-tion about populations and ecological inter-actions to develop cooperative interjurisdic-tional management strategies in the face of this uncertainty. The desire and ability of in-dividual agencies to comply with quotas as a guiding principle is useful and necessary for the success of percid fisheries management. By doing so, the common goal of achieving a broad distribution of fisheries benefits can be realized.

Acknowledgments

This work would not have been possible without the tireless efforts of the members of the Lake Erie Committee and Walleye and Yellow Perch Task Groups, past and present. We also acknowledge the efforts of Nancy Leonard, Lars Rudstam, Jaci Sa-vino, and Mike Thomas for comments that improved this manuscript. This is contri-bution number 1419 of the U.S.G.S. Great Lakes Science Center.

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