Walleye in the Grand River, Ontario: an Overview of Rehabilitation Efforts, Their Effectiveness, and Implications for Eastern Lake Erie Fisheries

Home , Grand River (Ontario), Thames River (Ontario)

J. Great Lakes Res. 33 (Supplement 1):103–117 Internat. Assoc. Great Lakes Res., 2007

Thomas M. MacDougall1,*, Chris C. Wilson2, Lori M. Richardson3, Mike Lavender2, and Phil A. Ryan4 1Ontario Ministry of Natural Resources Lake Erie Management Unit P.O. Box 429, 1 Passmore St. Port Dover, Ontario N0A 1N0 2Ontario Ministry of Natural Resources Aquatic Research and Development Section Trent University, 1600 West Bank Drive Peterborough, Ontario K9J 8N8 3Grand River Conservation Authority Box 429, 400 Clyde Road Cambridge, Ontario N1R 5W6 4Villa Nova Estate Ltd. RR4 Simcoe, Ontario N3Y 4K3

ABSTRACT. Walleye (Sander vitreus) from the Grand River (Ontario) are recognized as genetically and physiologically distinct from other Lake Erie stocks. The low abundance of these walleye in the early 1980s triggered rehabilitation efforts that included intensive research, transfers of walleye from the Thames River (Ontario), supplemental stocking from local hatcheries, construction of a fishway, and cre- ation of additional spawning habitat. Walleye migrating from Lake Erie are currently hindered from reaching 90% of potential riverine spawning habitat by a dam 7 km upstream. Although increased walleye catch rates were reported following construction of a fishway in 1995, recent assessment has shown that access is still severely restrained. Catch rates of young-of-the-year walleye during fall surveys have increased notably since 1999, coincident with direct transfers of mature adults over the barrier. Recent successful year classes have contributed to a population dominated by young (< 5 y) fish. Genetic analyses show that fish culture contributed between 3% and 25% to five recent year classes of Grand River walleye. Facilitating access to spawning habitat above the Dunnville dam may be the most effective way to increase the productivity of this stock, with consequent strengthening of walleye fisheries and the fish community in the eastern basin of Lake Erie. INDEX WORDS: Walleye, Sander vitreus, migration, barriers, dams, hatchery, stocking, Lake Erie, Grand River.

INTRODUCTION a target of commercial and sport fisheries. Distinct Walleye (Sander vitreus) is an important compo- spawning groups of walleye, utilizing both lake nent of the Lake Erie fish community, both ecologi- shoals and riverine spawning habitat, contribute to cally, as a key predator and socio-economically, as the mixed-stock population of walleye within the lake as a whole (Gatt et al. 2003). *Corresponding author. E-mail: [email protected]. Within the eastern basin of the lake, the walleye

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population is composed of individuals originating from at least two known resident eastern basin stocks as well as migratory walleye from western stocks which move into the east when densities are high (Einhouse and Haas 1995). One of these resident stocks, the eastern Grand River population, is noted as being genetically distinct from all other known Lake Erie stocks (McParland et al. 1999, Schaefer and Wilson 2002, Jackson et al. 2003). The importance of the Grand River walleye is recognized in fishery management plans devised for both the river itself (OMNR and GRCA 1998) and the eastern basin of Lake Erie (OMNR 2006a). The protection and restoration of self-sustaining, stream-spawning stocks of walleye is one of the fish community objectives for Lake Erie as defined by the Lake Erie Committee of the Great Lakes Fishery Commission (Ryan et al. 2003). Recent in- vestigations have concluded that the Grand River stock of walleye is less productive than it was historically, despite a variety of attempts at rehabilitation. This paper reviews the history of the Grand River stock, provides an overview of past rehabilitation initiatives, and documents its current status and factors limiting its recovery.

BACKGROUND FIG. 1. Estimated portions of the Grand River watershed historically (pre-European settlement) Historically, the Grand River supported a spawn- accessible to migratory Lake Erie walleye. The ing run of walleye dating from pre-European settle- dark line shows otherwise accessible sections of ment. Archaeological examination of aboriginal the main river channel as well as the lower midden sites unearthed along the Grand River reaches of the Nith and Conestogo rivers. The downstream of Cambridge indicate that walleye dashed lines indicate the present location of dams was a significant component of the diet of peoples acting as barriers to upstream walleye movement. living along this lower section of the watershed; Circles indicate locations of referenced towns. walleye were the third most abundant fish species observed, after suckers and catfish (General and Warrick 2001). The seasonality of the remains sug- lumber and grist mills, which utilized dammed gests a spring fishery, implying a spawning run of water as a power source, contributed to a noticeable migratory fish. At this time, walleye migrating up- decline in water quality in adjoining sections of stream from Lake Erie would have had free access river by the 1870s (Dunnville District Heritage As- to at least 120 km of river including the main chan- sociation 1992, Barbetti 2001). Despite the dams, nel to Elora, and extensive sections of the Nith River (Fig. 1). the federal fisheries overseer was still reporting Construction of dams and locks in the lower spawning runs of walleye at the river mouth as late Grand River between 1828 and 1840 fragmented as 1890 (Goodyear et al. 1982). While many of the the lower river ecosystem and effectively isolated dams and locks have since fallen into disrepair or its upper reaches from Lake Erie (Duquemin and been removed, those barriers that remain effectively Glenney 1981). The furthest downstream dam, built subdivide the main river into the following sec- at Dunnville in 1829, blocked upstream migration tions: (1) Port Maitland to Dunnville [7 km], (2) of species such as walleye and confined them to the Dunnville to Caledonia [35 km], (3) Caledonia to first 7 km of river upstream of the river mouth at Paris including the subwatershed of the Nith River Port Maitland. Additionally, the proliferation of [48 km], and (4) upstream of Paris [50+ km]. Evaluation of Grand River Walleye Rehabilitation Efforts 105

Past Efforts to Improve Walleye Production in Hatchery Upstream Segments Since at least 1947, local Ontario Federation of Timmerman (1995) documented historic Anglers and Hunters (OFAH) conservation clubs in (1928–1952) and recent (1987–1994) efforts to en- the Dunnville area have periodically transported hance walleye angling opportunities in the two up- lake-run walleye above the Dunnville dam (OMNR, stream sections of the watershed (above Caledonia Vineland Area, unpublished data). A fish culture and Paris, respectively). Recent surveys conducted initiative, using some of these lake-run fish, was between Caledonia and Paris concluded that con- begun in 1986 and continued to the present. The siderable sections of potential walleye spawning program involves gamete collection and egg fertil- habitat exist in this section as well as in the sub- ization, and hatching and rearing the resulting prog- watershed of the Nith River (Ecologistics 1988). eny in a bell jar hatchery and pond system to the fry and/or fingerling stage. Products of the hatchery Enhancement efforts involved repeated plantings system (1,500–40,000 annually; 20-y mean = of hatchery produced eyed-eggs (as many as 20,000) were introduced into the second upstream 775,000 in the early 1930s into the Nith River) and segment of the river above Dunnville. Since 2001, fry, or by transfers of mature fish (Timmerman nonlethal tissue samples (caudal fin clips) have 1995). Records from the first half of the 1900s been taken from hatchery parent walleye and genet- were poorly documented, but there is some indica- ically characterized to enable identification of any tion that a hatchery in Collingwood, Ontario was subsequently caught offspring. the source of eyed eggs used in at least some of the transfers (Timmerman 1995). More recent efforts Thames River Transfers include the stocking of adult walleye from the Thames River (1,415 walleye to the Conestogo In the mid-1980s, perceived declines in the sub-watershed), and hatchery products of Thames spawning run (i.e., difficulty in obtaining walleye) River collections (30,000 fry in 1990) or Thames below Dunnville prompted two transfers of walleye River walleye crossed with locally-obtained (Nith from the Thames River, Ontario (Timmerman 1995; River) walleye (80,000 fry in 1990; Timmerman OMNR, Vineland Area, unpublished data). In the 1995). spring of 1989 and 1991, the Ontario Ministry of Natural Resources, in cooperation with local angling clubs, introduced 652 and 751 Thames River Past Efforts to Assist the Walleye Spawning Run walleye into the second upstream section at from Lake Erie Cayuga, mid-way between Dunnville and the next upstream dam at Caledonia (Fig. 1). Spawning Substrate A survey commissioned by the OMNR in the Fishways early 1980s mapped potential walleye spawning habitat in the first two upstream segments of river Through the first half of the last century, some (Port Maitland to Caledonia), based on substrate fishway structures were built to help upstream mov- et al. type and likelihood of siltation (Ecologistics 1982). ing fish bypass the Dunnville dam (Goodyear 1982). These structures were of step-pool design and The overall conclusion of the survey was that most would have only assisted jumping species of fish of the potential habitat in these segments occurs up- (Dunnville Heritage Association 1992). In 1994, in stream of the Dunnville dam. Area analysis of these association with upgrades and repairs to the Dun- maps provide an estimate of 245.8 ha of potentially nville dam complex, the Grand River Conservation fair to good walleye spawning habitat in the first 42 Authority (GRCA) constructed a denil-style fishway km of river upstream of the mouth (Fig. 1). Most of on a side-channel weir. This fishway was designed to this potential habitat (97%; 240 ha) occurs up- pass non-jumping fish, with walleye as the target stream of the 15 km mark; well above the Dun- species, and was located based on previously ob- nville dam (Fig. 1). Efforts to increase the area of served walleye aggregations (Nash 1999). Initial spawning substrate below Dunnville dam have in- monitoring (1995–1997) proved disappointing, with cluded modest additions of cobble and gravel by very few walleye passing through the structure (Nash OMNR and local conservation clubs in 1997, 2001, 1999). A radio telemetry study conducted in 1997 and 2002. showed that only 5 of 24 tagged walleye (21%) re- 106 MacDougall et al.

leased below Dunnville were attracted to the fishway M ΣMt, total number of fish marked during the and none were able to negotiate the upstream exit experiment (Bunt et al. 2000). A subsequent hydrologic study Ct total sample taken on day t which considered possible flow barriers within the Rt number of recaptures in the sample Ct. fishway recommended the introduction of a baffle in R ΣRt, total recaptures during the experiment order to make conditions more favorable to walleye passage (Weber 2000). The recommended changes Approximate confidence limits were estimated by were made to the fishway by the GRCA in early treating R as a Poisson variable (Ricker 1975). 2002, prior to the spawning run of most fish species. For the purposes of this exercise, only fish that The dam at Caledonia, the next upstream barrier were captured, marked, and released below the dam above Dunnville, was fitted with two fishway struc- were included in this calculation, in order to avoid tures when it was rebuilt in 1979–80. The fishways contradicting multiple census theory assumptions. are of step-pool design with wooden baffles meant In 2005 no fish were placed above the dam. Fish to assist non-jumping fish including walleye. Sub- were marked either with an individually coded jaw sequent analysis revealed that walleye were unable tag or a date-specific fin clip where fish were too to utilize either structure (Farwell 1999). small to accept jaw tags. An assumption of no jaw tag loss, over the short period of this exercise, was Current Conditions (1999–2005) made based on the findings of Isermann and Knight (2005). Spring Spawning Run Assessment Between 24 March and 2 May 2001, 20 mark and From 1999 to 2005, various population surveys recapture events took place yielding the following were directed at the spring run of walleye aggregat- results: M = 181, R = 8, N = 4,042 walleye (95% ing below the Dunnville dam. Sampling was con- Poisson range: 2,303–10,700). Between 30 March ducted using gangs of 30 m, multi-sized (32–152 and 5 May 2005, 12 mark and recapture events took mm mesh) panels of monofilament gill net, supple- place yielding the following results: M = 688, R = mented with boat electrofishing (Smith Root SR20 18, N = 14,443 walleye (95% Poisson range: electrofisher; 250–300 V, 8–12 A), from late March 9,334–23,454). until mid-May. Fishing times were adjusted in ac- cordance with catch rates to maximize capture but Fish Passage at Dunnville avoid overcrowding holding pens used prior to examination of fish. Captured fish were measured for Without facilitation, the dam at Dunnville is a length, tagged with a butt-end metal jaw tag, scales complete barrier to upstream walleye movement. were removed for ageing, and sex and spawning Between 1995 and 2005, access has been available state were noted when obvious external signs per- for some upstream migrants in the form of either mitted. When feasible, a redundant sew-on dorsal the Dunnville Fishway (1995–present) or via the di- disc tag was applied (65% of fish sampled) in order rect above-dam transfer of individuals captured as to address concerns about jaw-tag retention (New- part of spring assessment activities (2000–2004). man and Hoff 1998) and thus increase the probabil- Monitoring of walleye movements in relation to ity of recognition upon recapture. this barrier has been conducted via (1) fishway In 2001 and 2005, a series of standardized mark monitoring using a within-fishway cage trap, (2) and recapture efforts were conducted in order to fishway monitoring using radio-tagged walleye and calculate a within-year multiple census estimate of within-fishway radio-receiver antennas, (3) mobile the size of the spawning run using the formula pro- tracking of radio-tagged walleye released above and posed by Schnabel and modified by Chapman below the dam, and (4) recapture information from (Ricker 1975) as follows: tagged fish released above and below the dam. Σ Σ Σ N = (CtMt)/ ( Rt) + 1 = (CtMt)/R + 1 Fishway Cage-trap Monitoring Where: Detailed monitoring protocols are described by × × Mt total marked fish at large at the start of the Nash (1999). In brief, a cage (2 m 1 m 1.5 m; tth day, i.e. the number of previously 2.5 cm mesh) was lowered into the last section of marked less any accidentally killed at previ- the fishway channel 5 m from the upstream exit. All ous recaptures. upstream moving fish are directed into the cage Evaluation of Grand River Walleye Rehabilitation Efforts 107

For the purposes of estimating total passage each spring, it was assumed that walleye caught within the monitoring basket would have been able to negotiate final passage and exit the fishway on the upstream end. The number of walleye passing through the fishway was defined as the mean daily CPUE multiplied by the number of hours in the period between the first and last date on which walleye were observed. To acknowledge deficiencies inherent in non-continuous monitoring a second, maximum passage estimate was calculated by multiplying the mean non-zero daily CPUE by the total hours in a 60-d period (1440 h; the longest recorded annual walleye use in the 11-y monitoring period). Esti- FIG. 2. Yearly passage efficiency (mean catch- mates of the number of walleye passed each spring per-unit-effort [CPUE]; #walleye per hour) and ranged from 15 (1995 and 2001) to 404 (2003). passage estimates (# walleye passed each spring) Maximum estimates of passage ranged from 203 derived from cage monitoring efforts at the Dun- (1996) to 975 (2003) (Fig. 2). nville fishway. Error bars represent the standard error of the mean. Two passage estimates are cal- Radio-telemetry Assessment culated as: 1—mean daily CPUE × total hours between first and last seasonal observation and 2 In the spring of 2003, walleye were captured (maximum estimate)—mean non-zero daily CPUE below the Dunnville dam, surgically implanted with x total hours in a 60 day period. individually coded radio-transmitters (MCFT-3BM; Lotek Wireless Inc., Newmarket ON), and returned to the water; 14 were placed mid-way between the main dam at Dunnville and the side weir which through a 0.46 m opening and confounded from ex- contains the fishway while 15 were placed 0.5 km iting by a bottom lip and inward facing baffle pan- upstream of the main dam. Monitoring of the fish- els. The length of time the cage was submerged way was accomplished using a LOTEK SRX_400 varied in order to accommodate for larger or receiver. Antennas within the fishway were capable smaller catches. Between 1995 and 2005, yearly of detecting fish that (1) progressed 1/3 of the way total monitoring time averaged 191 h/y. Monitoring into the structure [first resting pool] and (2) passed took place during April and May and, in most the final corner and were within 5 m of the up- years, encompassed an initial period when no wall- stream exit. Continuous monitoring took place be- eye were observed followed by a peak of walleye tween 14 April and 9 June. Supplemental daily use, and a late-season absence of walleye. Daily mobile tracking was conducted in the river up- weekday monitoring occurred for, on average, 8 stream and downstream of the dam, including the h/d. While most effort occurred between 6:00 h and side channel waters of the three supplementary 18:00 h, on average 10% of each year’s effort was weirs. Mobile tracking in the lower 42 km of river directed at the period from 1800 h to 0000 h. For was conducted weekly between May and Novem- any given period, walleye catch rates were not ap- ber, 2003. preciably different between day and evening moni- Of the 14 fish released below the dam, only 12 toring. Catch per unit effort (CPUE; #walleye/total were subsequently detected within the river from hours monitored) was calculated for each monitor- Dunnville to the mouth. Within 1 week of release, ing day between the first and last walleye observa- two of the fish released above the dam were de- tion date. tected below the dam structures. Of these 14 wall- To compare changes in passage efficiency from eye, eight stayed within the side channel of Sulphur year to year, annual mean hourly CPUE was calcu- Creek, in association with strong flow over the side lated for the period from first walleye observation weirs, for approximately 10 days. During that pe- to last. Between 1995 and 2005, the annual mean riod (15–25 April), most fish detections occurred in hourly CPUE for walleye has ranged between association with areas of cobble substrate including 0.03/h (1995 and 2001) and 0.58/h (2003) (Fig. 2). locations where substrate enhancement had oc- 108 MacDougall et al.

TABLE 1. Release and recapture information for walleye tagged within the Grand River between 1991 and 2005. Location of release and recapture is noted relative to the Dunnville dam as follows: ADD— above dam, BDD—below dam. Recapture information from the sport fishery, commercial fishery, and agency fisheries assessment programs. RELEASE RECAPTURE Recaptures ADD Recaptures BDD Release # Years “at large” Total Years “at large” Total Location Released 0 1 2 3 ADD 0 1 2 3 4 5 6 7 BDD ADD 1345 33 9 5 1 48 6 12 4 2 1 1 — — 26 BDD 1927 2* — — — 2 26 19 4 4 2 5 2 1 63 Total Released 3272 Total recapture above 50 Total recapture below 89 * Caught within Dunnville fishway monitoring basket curred previously and locations identified as poten- Recapture of Tagged Fish tial spawning habitat by Ecologistics (1982). Five Records of tagged and recaptured walleye were of the eight walleye (62.5%) were detected by the examined in order to determine spawning river fi- first antenna within the fishway. This indicated that delity and movements relative to the Dunnville they had passed the first set of denils and had en- dam. In addition to walleye tagged during OMNR tered the first resting pool, 1/3 of the way into the spring assessment programs (2000–2005; 2,385 structure. Of the five fish which gained access to walleye), walleye tagged during GRCA-OMNR the fishway, two were detected by the second an- fishway monitoring (1995–2005; 203 walleye) and tenna, indicating progress to within 5 m of the up- OFAH-CFWIP hatchery fishing (1991–1999; 740 stream exit. Both of these fish were, within walleye) were also included. Several of the walleye minutes, subsequently detected at the first antenna that were originally tagged and released during indicating downstream progress and an inability to these activities were recaptured at a later date. Re- access waters upstream of the dam. Total time in- capture information came from the sport fishery, the side the fishway was 3 min for one of these fish (15 commercial fishery, and OMNR fish sampling pro- April) and 2.25 h for the second (25 April; the grams. Of the recapture records, only those in longest residency time for any of the five fish). All which more than 1 month had passed between the detections occurred between 1700 h and 0600 h. No tagging event and the recapture event were exam- radio-tagged fish were able to successfully exit the ined. This was done to allow for dispersal and upstream end of the fishway. movement especially relative to the potential bar- Radio-tagged walleye below the dam used the rier of the Dunnville dam. In total, 3,272 tagged river for much of the spring followed by movement walleye were introduced into the Grand River between 1991 and 2005. Of these, 1,345 were re- to the extreme lower reaches or were not detected leased above the dam while 1,927 were released for the summer. Radio-tagged walleye placed above below, including 110 releases in the Lake Erie the dam moved, to varying degrees, upstream as far nearshore adjacent to the river mouth. Reported re- as the next barrier (35 km; town of Caledonia) be- captures were noted as to the length of time (in fore slowly moving back downstream during late years) and relative location with respect to the Dun- spring /early summer. Five upstream fish remained nville dam between tagging and recapture. Results upstream for the entire spring and two were still up- are displayed in Table 1. The recapture rate for stream during the late fall. Six were subsequently these walleye was 4.2%. Of the fish released above detected downstream of the dam before disappear- the dam, 74 (5.5%) were recaptured; most (33) ing in late spring. Six walleye which were not de- above the dam and within the same year as release. tected for the summer, returned to the river below The longest interval between an above-dam release the dam in the fall. One of the upstream fish which and above-dam recapture was 3.2 y. Twenty-six fish was not detected after May was observed below the released above were recaptured below; most (12) in dam the following spring (2004). the year after the release. One above-dam-released Evaluation of Grand River Walleye Rehabilitation Efforts 109

Hatchery Contributions vs. Natural Reproduction The relative contributions of natural reproduction and the stocking of hatchery-produced fingerlings to YOY production were tested through genetic parentage analysis. Nonlethal finclip samples were taken from wild-captured adults that were used for gamete collection in the Dunnville OFAH-CFWIP hatchery between 2001 and 2005. Adults were mated as single pairs (one male to one female), with each fish used only once. Samples from adults were genotyped for five microsatellite DNA loci, en- abling the identification of all possible offspring genotypes based on possible combinations of parental alleles at each locus. This approach has FIG. 3. Mean catch-per-unit-effort (CPUE) of proven highly effective for tracking stocking suc- young-of-the-year (YOY) walleye caught each year cess and stock performance in other walleye popu- (Aug–Oct) during standardized electrofishing sur- lations (Eldridge et al. 2002). veys. Error bars represent standard error of the A subsample of YOY captured each year (n = 72) mean. The cumulative number of adult walleye was similarly characterized with the same mi- manually moved over the Dunnville dam each crosatellite loci and compared against the genetic spring is shown for reference. data of each parent pair from that sampling year. Fewer YOY were analyzed in 2001 and 2004 due to the limited numbers that were caught (38 and 68, fish was recaptured below, 5 years after being respectively). Parentage analysis of YOY genotypes released. was used to assign or exclude individual YOY for specific families, based on simple matching coeffi- Of the fish released below the dam, 65 (3.4%) cients for YOY versus adult genotypes from each were recaptured; mostly below the dam (63 fish). parent pair as implemented by the program Which- Two fish released below the dam were recaptured in Parents (Eichert 1999). the Dunnville fishway monitoring basket. The Assignment results from the parentage analyses greatest proportion of the below-dam-release and - showed contributions to YOY production from both recaptures occurred within the same year as release stocking and adult transfers (Fig. 4). Although con- (26 fish). The interval between release and recap- tributions from hatchery stocking were detected for ture (below dam to below dam) ranged from 0–7 y. each of the sampling years, the majority of YOY captured each year were excluded from being de- Young-of-the-year Surveys / rived from possible allelic combinations of geno- Fall Walleye Recruitment Index types from the adult pairs used for gamete collections, and were therefore considered as hav- Standardized electrofishing was conducted being wild origins (Fig. 4). Stocking contributions tween Dunnville and the river mouth each fall (Sep- varied between years, ranging from a low of 3% tember–October) between 1999 and 2005. The (2003) to 25% in 2002 (Fig. 4). As gamete collec- number of young-of-the-year (YOY) walleye cap- tions involve multiple parent pairs from the wild tured per hour of electrofishing effort was used to population (8–12 families per year between 2001 provide an index of annual walleye recruitment and 2005), stocking practices are unlikely to cause (Fig. 3). While no YOY walleye were captured in genetic erosion of the target population as has oc- 1999, subsequent years saw an increase in CPUE curred elsewhere (Gatt et al. 2002). (2000–2002) followed by a plateau at approximately 12 YOY walleye/h of electrofishing (2002- Stock and Population Demographics 2005). The increase in YOY CPUE between 1999 Changes in age structure were examined for three and 2000 is coincident with the cumulative number categories of walleye: those in the river during the of adult walleye manually moved over the dam spring spawning run, those within the river during each spring since 2000 (Fig. 3). early fall, and those occupying the eastern basin of 110 MacDougall et al.

tively mature (age-3) fish within the river. In all three surveys, the population has been getting younger from 2000 to 2005 with the proportion of the catch represented by fish aged 5 and older de- creasing over the 6-y period.

Contributions of Grand River Stock to Juvenile Population in Long Point Bay The contribution of the Grand River stock to juvenile recruitment in eastern Lake Erie was as- sessed in 2003 and 2004. Juvenile walleye caught in 2003 and 2004 by commercial fishermen and index netting in Long Point Bay were genotyped at nine microsatellite DNA loci to determine which stocks they originated from. Using genetic charac- FIG. 4. The relative contribution of natural teristics from spawning populations in the eastern reproduction and hatchery stocking to young-of- and western basins (Schaefer and Wilson 2002, the-year (YOY) walleye production in the lower Jackson et al. 2003) as baseline data, the multilocus reaches of the Grand River, 2001–2005. Non- genotype for each juvenile was assigned to its most lethal fin-clip samples taken from YOY walleye probable genetic source using a Bayesian assign- and hatchery parental broodstock in each year ment method (Piry et al. 2004). Results from the as- were genotyped with 5 microsatellite DNA loci signment tests showed that many of the young and compared. walleye originated from east-basin stocks, but that surprisingly few came from the Grand River despite its nearness to Long Point Bay (Fig. 6). New York Lake Erie during early fall. Spring and fall informa- populations made the largest contribution, followed tion for river walleye was collected during spring by those which originated from lake shoals between spawning and fall electrofish surveys as detailed the Grand River and the Niagara River (“mixed an- above. Data for eastern Lake Erie were provided by cestry”). The number of Grand River juveniles the Ontario Ministry of Natural Resources and On- caught in Lake Erie were well below what was ex- tario Commercial Fisheries Association Partnership pected, suggesting that either juveniles are remain- Index fishing program, a lake-wide annual multi- ing in the river and entering Lake Erie at a later mesh, depth stratified gillnet survey (OMNR age, or that current walleye production is severely 2006b). In all three surveys, scales from individual depressed. walleye were processed in a standardized fashion and ages were estimated based on annulus counts. A sub-set of the partnership index data was derived DISCUSSION by choosing catch information from all sites sam- The studies described here all demonstrate that pled east of the tip of Long Point. Young-of-the- walleye production in the Grand River is depressed year walleye were not included in the comparison below the watershed’s historic capacity, and point as they are not readily susceptible to capture in the to the Dunnville dam as a primary limiting factor. A gillnet survey due to methodological constraints. once continuous > 100-km stretch of river, directly The spring aggregation in the river (Fig. 5) was connected to Lake Erie, is currently divided into primarily composed of walleye aged 4 and older four segments by dams impassable to unassisted whereas most of the river fish present in the fall upstream moving walleye. Free access is restricted were aged 3 and younger. The age structure of wall- to the lower 7 km of river. The historic migratory eye caught within the eastern basin of the lake each Grand River walleye stock, cut off from its river fall was similar to the spring, river catch. The 1998, spawning habitat, may not have been able to simply 2001, and 2003 year classes made sizeable contri- switch to spawning on nearshore-lake shoals. Al- butions to the catch in all three surveys. The 2003 though Jennings et al. (1996) demonstrated herita- year class constituted 80% of the lake catch in 2005 ble preferences in spawning habitat between river- and is expected to show up in 2006 as reproduc- and shoal-spawning walleye, it is not known to Evaluation of Grand River Walleye Rehabilitation Efforts 111

FIG. 5. Walleye age distribution from the total catch of OMNR fisheries survyes conducted in the Grand River during spring and fall, and the eastern basin of Lake Erie during fall, 2000–2005. Grand River surveys were conducted by boat electrofishing while Lake Erie surveys were part of a standardized index netting program: OMNR an OCFA partnership index netting program. 112 MacDougall et al.

whether its current limitations are genetically or habitat-induced. Barriers and fragmentation of river systems sig- nificantly impact the productive capacity of fish species and stocks whose reproductive strategy involves riverine habitats for spawning or early life stages (Colby et al. 1994). With restricted movement into and within river systems, dependent stocks are limited to smaller self-sustaining sub- groups within individual river segments with signif- icantly reduced overall production. Rehabilitation efforts have focussed on either increasing production within individual segments, or increasing access, starting at the first upstream barrier, the Dunnville dam. In the early 20th century, stocking of walleye hatchery products (eyed-eggs, fry, and fingerlings) into upstream river segments resulted in uncertain success (Timmerman 1995). Despite extensive potential spawning habitat in these areas (Ecologistics 1988), small, isolated, resident populations currently only exist within the Nith River watershed and in the third upstream segment (Wright and Imhof 2001). Similarly, efforts in the late 1980s and early 1990s to introduce mature Thames River walleye to upper segments of the Grand River proved disappointing, with tagged fish mostly recaptured between the Grand River mouth and the Thames River (Timmerman 1995). This suggests that attempts to stock the Grand River with adult walleye from alternate sources will be confounded FIG. 6. Genetic origins of walleye from the east- by the natural homing instinct noted previously for ern basin of Lake Erie, representing A) the com- walleye (Einhouse and Haas 1995, Olson and Scid- mercial fishery (mean of 100 samples per year more 1962, Olson et al. 1978, and Crowe 1962). 1999–2003) and B) juvenile walleye Long Point Recent efforts at rehabilitation have focussed on Bay (pooled commercial and OMNR assessment increasing the reproductive success of walleye mi- samples from 2003 and 2004) based on individual grating into the lower river reaches from Lake Erie. assignment tests of multilocus genotypes from This has primarily been done through attempts to juvenile fish and baseline data from spawning increase access past the Dunnville dam, thereby in- populations. creasing the amount of usable river from 7 km to 42 km. Estimates of potential fair to good walleye spawning habitat below and above Dunnville are 6 ha and 240 ha, respectively (derived from Ecologis- what extent the Grand River stock is genetically tics 1982). Using an estimated spawning substrate programmed to spawn in riverine habitats. It may requirement of 20 m2/female walleye (Furlong et be that its reduced productive capacity reflects lim- al. 2006) the river below Dunnville could currently iting amounts of spawning and nursery habitat accommodate 6,000 walleye (assuming a 1:1 sex rather than an inability to reproduce (Jackson et al. ratio), well below the most recent spawning aggre- 2003). The substantial increase of young-of-the- gation estimate of 14,443. A large spawning run year fish in the upper Grand River seen with the constrained to the lower section of river will not adult transfer program (Fig. 3) suggests that facili- translate into high recruitment if spawning takes tating access to the river above the dam will greatly place over unfavourable substrate; walleye are improve the stock’s productivity, regardless of known to broadcast eggs over muck and debris Evaluation of Grand River Walleye Rehabilitation Efforts 113

when suitable substrate is not available (Johnson passage estimates were also derived, and ranged 1961). The success of spawning on the suitable sub- from 203 to 976 walleye. strate that does exist below the Dunnville dam may Comparing fishway passage and population esti- be compromised by the large numbers of benthic mates suggests that the fishway is insufficient for fish species which also aggregate in this section of allowing upstream access. Multiple-census, mark- river in the spring. This problem was identified for recapture population estimates of the spring run walleye in the Fox River, Wisconsin (Auer and below Dunnville in 2001 and 2005 were 4,042 and Auer 1987) and may negate any benefits derived 14,443 walleye, yielding passage efficiency esti- from the introduction of additional spawning sub- mates (the ratio of maximum number passed to strate below the Dunnville barrier. Radio-tagged number staging below the dam) of 0.05 and 0.03, walleye were observed utilizing areas of river respectively. Changes in mean daily fishway CPUE where substrate had been added. Regardless, even if pre- and post-2002 may be a reflection of both the additions of appropriately sized rock and cobble re- hydraulic improvements in the fishway and an in- sult in some additional production, the existing dis- crease in the number of walleye attempting up- parity (240 ha upstream) is impossible to counter stream access. However, the 2003 radio-telemetry with this method alone. work sheds doubt on the ability of cage-monitoring The Dunnville fishway, opened in 1995, was de- CPUE to predict passage as the only radio-tagged signed to provide migratory non-jumping fish such fish able to reach the section of fishway where the as walleye the ability to surmount the otherwise im- cage is situated were not able to negotiate the exit. passable Dunnville dam. Early assessments of the The low success of walleye passage through the success of this structure concluded that, despite Dunnville fishway is not unusual. Walleye are some use by walleye, passage efficiency was low known to have difficulty passing through fishways, (Nash 1999) to zero (Bunt et al. 2000). Only 21% even those designed as being walleye specific. et al. of radio-tagged walleye were able to locate the fish- Schwalme (1985) note that walleye could not navigate a Denil fishway despite expectations, and way entrance in 1997, and although they remained use of the fishway by species with poorer critical within the fishway for varying times up to 17 h, swimming speeds. Some of this difficulty might re- none were able to exit upstream (Bunt et al. 2000). sult from walleye behaviour requiring particular The radio- telemetry data reported here indicate a light regimes (Lester et al. 2004) in addition to ap- similar impediment: despite the fishway’s attraction propriate flows and temperatures. efficiency of 63%, no walleye exited upstream in- Despite ongoing poor access to upstream spawn- cluding two which were detected within 5 meters of ing habitat through the fishway, production of wall- the exit. An examination of cage monitoring-de- eye as indexed by young-of-the-year (YOY) catch rived fishway use for a longer time period rates has increased in recent years. Mean YOY (1995–2005) revealed that there was considerable CPUE increased concurrent with increasing num- annual variation in mean hourly CPUE. Structural bers of walleye manually moved from below to changes to the fishway, designed to alter the hydrol- above the Dunnville dam each spring. The largest ogy in favor of walleye passage, were completed mean YOY walleye CPUE occurred in 2002, coin- prior to the spawning run of 2002. Mean walleye cident with both a modest increase in stocking num- CPUE for the 4 years following the changes were bers, and an increase in the proportion of stocked more than double those for the 4 years prior to the fish identified in the fall YOY. Although the genetic changes, suggesting that the engineered solutions data showed that stocking events contributed to had improved attraction efficiency. Despite this, the YOY production in each of the study years, the ma- fishway was not passing even a substantial minority jority of YOY each year were produced from wild of the walleye seeking upstream passage each fish (Fig. 4). These results contrast with observa- spring. Estimates of the number of walleye passed tions by Murphy et al. (1983) in a reservoir walleye by the fishway each spring, based on mean CPUE population in Virginia, where stocking contributed and the time between first and last monitoring ob- an average of 67% to year class production versus servation, ranged from 15 to 145. In order to ac- natural reproduction. The differences between the knowledge deficiencies inherent in estimates studies may reflect the differences in available derived from non-continuous monitoring (e.g., dis- spawning habitat for natural reproduction within parities between sampling times and irregular diur- the Grand River compared with the reservoir sys- nal fish movements), more liberal maximum tem. 114 MacDougall et al.

Short of expanding capacity, there is little to sug- which are dependent on the transport of larvae to gest that further efficiencies could be found within lake-nearshore nursery habitat (Mion et al. 1998). the hatchery system to increase successful walleye Similarly, genetic examination of 1-y-old walleye, production. The size at which the CFWIP pond- present in the Long Point Bay area of Lake Erie’s reared fingerlings are typically stocked (50–80 mm) eastern basin in 2003 and 2004, found that few is within the range (25–122 mm) shown to result in could be sourced to the Grand River (Fig. 6). A high recruitment (Koppelman et al. 1992). Addi- large component were identified as originating in tionally, as gamete collections have involved multi- New York waters of the eastern basin, consistent ple parent pairs from the wild population (eight to with reports of increased recruitment of New York twelve families per year between 2001 and 2005), walleye stocks during the same years (NYSDEC stocking practices are unlikely to cause genetic ero- 2005). With the increasing age and numbers of re- sion of the target population as has occurred else- cently produced walleye within the river, the where (Gatt et al. 2002). Both stocking and adult 2002–2005 Grand River cohorts may recruit to the transfer appear to be effective in boosting walleye lake fisheries in 2006–2009. production in the Grand River, giving managers the Given the potential for increased reproduction option of pursuing either or both methods, depend- based on underutilized spawning habitat, it is prob- ing on management goals. Consultation with user able that increased access above the Dunnville dam groups should assess cost-effectiveness, socioeco- will result in further increases in production and nomic targets, and stakeholder commitment to rear- subsequently larger contributions to Lake Erie’s ing programs versus adult transfers. eastern basin walleye fisheries. Re-establishment The degree to which the fishway, in combination of open access to both the lake and river environ- with manual transfers of migratory walleye each ments should not only increase reproductive out- spring, can enable full access to the 240 ha of put, but also successful recruitment to subsequent spawning habitat in the lower 42 km of river is life stages via access to expanded and connected questionable. Telemetry studies indicate that at least habitat. The monitoring and assessment data from some of the migratory walleye which reach the sec- recent years are encouraging, and suggest that ond upstream segment remain in this section after walleye recruitment in the Grand River population the spawning season. Tag and recapture data sug- is increasing in terms of both YOY production and gest that this residence period can last up to 3 y. numbers of adults returning to the lower river. The proportion that become “resident” and the While not discounting additional limits to produc- length of time before they return downstream may tion, such as poor water and substrate quality ef- be determined by summer environmental conditions fects on egg and larval survival, increasing access and the availability of suitable temperature and/or for migratory, spawning run Grand River walleye oxygen conditions. The downstream migration of is a logical focus for rehabilitation of this stock. most upstream walleye to below the Dunnville dam Functional rehabilitation of the Grand River popu- and back to Lake Erie suggests that manual trans- lation will have been achieved once its production fers and fishway passage will probably not eventu- meets target objectives (OMNR and GRCA 1998, ally result in a permanent upstream resident OMNR 2006a). The recovery of the Grand River population that can fully utilize the upstream stock will not only provide substantial ecological spawning habitat without regular immigration each and socioeconomic benefits to the Lake Erie sys- spring (Fig. 7). tem, but will also help ensure a sustainable future Grand River walleye have been shown to con- for a unique Great Lakes stock. It will still take tribute significant numbers to both the sport and substantial amounts of time, commitment, and commercial fisheries of the eastern basin of Lake dedicated action to reach this goal, but we are al- Erie (Jackson et al. 2003; C. Wilson, OMNR Peter- ready well started. borough, unpublished data). It is possible that increased production in recent years will not be immediately reflected in either fishery. An exami- ACKNOWLEDGMENTS nation of the age structure of walleye in the river Much of this work was completed with financial provides evidence that, whereas adult walleye move support from Environment Canada (Ecosystem Re- to the lake for the summer, the lower river is being habilitation Section), provincial funds from the utilized as juvenile and YOY habitat (Fig. 7). This Canada-Ontario Agreement, OMNR Lake Erie is in contrast to other riverine walleye populations Management Program and OMNR - CFWIP, On- Evaluation of Grand River Walleye Rehabilitation Efforts 115

FIG. 7. Conceptual representation of potential life history strategies utilized by Grand River walleye including migration, reproduction, and juvenile and adult use of Lake Erie and Grand River habitat relative to the Dunnville dam (DAM). With information from fishway monitoring, spring assessment activities, and genetic analysis of walleye sampled between 2000 and 2005. Spawning habitat estimates are derived from information in Ecologistics (1982). Solid arrows represent unimpeded pathways while dashed-line arrows represent pathways potentially impeded by physical, behavioral, or habitat constraints. * Note hatchery broodstock are derived from spring lake-run aggregations below Dunnville.

tario Federation of Anglers and Hunters (OFAH), Stapanian, Patrick Kocovsky, and an anonymous re- and the Grand River Foundation. Funding for ge- viewer improved the manuscript. netic stock structure analysis was provided by the Great Lakes Recovery Fund. The work was a col- REFERENCES laboration between OMNR, GRCA, Environment Canada, and OFAH affiliated clubs, in particular the Auer, N.A., and Auer, M.T. 1987. Field evaluation of Dunnville District Hunters and Anglers, the Port barriers to walleye egg and larva survival in the lower Fox River, Wisconsin. Am. Fish. Soc. Symp. Colborne Conservation Club, and the Fort Erie 2:93–101. Conservation Club. Monitoring of the Dunnville Barbetti, F. 2001. History of Fisheries in the Lower fishway was accomplished largely through volun- Grand River. In Restoration of Healthy Ecosystem teer effort (greater than 9,000 person-hours) includ- Function in the Lower Grand River, Lake Erie Lamp ing large contributions from the three OFAH clubs Workshop, Dunnville Ontario, August 28–29, Pro- and the Dofasco Angling Club. Riverside Marina- ceedings, M. Austin ed., pp. 35–36. Environment Dunnville provided logistical support. Thanks to Canada, Burlington, ON. Warren Yerex (GRCA) and Anne Yagi (OMNR) for Bunt, C.M., Cooke, S.J., and McKinley, R.S. 2000. input and historic data. Comments by Martin Assessment of the Dunnville Fishway for Passage of 116 MacDougall et al.

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