Lake Trout Ecosystems in a Changing Environment - Chapter 11 ppsx

Harvest is controlled by applying such methods as 1 limiting fishing opportunitiesmanipulating season length and regulating physical access; 2 using size-based regula-tions to exert biol

section III

Biological effects and management reactions

chapter eleven

The control of harvest in lake trout

sport fisheries on Precambrian

Despite increasingly comprehensive and complex legislation intended to regulate

exploi-tation, it is the most critical stress affecting the lake trout Salvelinus namaycush across the

Precambrian Shield The two main contributing factors are the lake trout’s innate ability to exploitation and the rapid growth of recreational fishing following the end ofWorld War II For instance, angling almost quadrupled in Ontario between 1950 and the

vulner-early 1970s (Ontario Ministry of Natural Resources and Environment Canada, 1976) Withthe development and expansion of highways and forest access roads, the advent of thesnow machine and the all-terrain vehicle, and the ready availability of aircraft, few laketrout lakes are inaccessible to anglers.

The sensitivity of lake trout to exploitation has been described by several authors (see,for example, Fry, 1949; Daley et al., 1965; Martin and Olver, 1980) Lake trout are easilycaught by angling, so stocks can be depleted with only a moderate amount of fishingpressure (MacKay, 1956; Eschmeyer, 1964) Certain biological characteristics of the species(slow growth, late maturity, and low reproductive potential) and the unproductive nature

of the waters it inhabits (low nutrient levels, cold temperatures) also contribute to thevulnerability of lake trout to exploitation As a result of these limiting factors, lake troutoccur in a small number of Precambrian Shield lakes, where they form sparse populationswith low annual sustainable yields

The main purpose of angling regulations is to ensure the perpetuation of fish stocksthrough regulation of the harvest Simply stated, it is the kill of fish that needs to becontrolled Within this context, the intent of the regulations is to provide a continuingsupply of fishing opportunities and to distribute the catch fairly among the participants.Regulations also prescribe the “rules of the game” and impart a sense of ethics by empha-sizing the sporting aspects of angling

Christie (1978) observed that short of closing lakes to fishing it is difficult to controlangling effort given the open access, common property nature of resource management(e.g., Hardin, 1968) This is also true of lakes where stocks have been depressed becauseresidual pressure may be sufficient to prevent their recovery In open access fisheries,Christie also noted that traditional harvest control regulations (e.g., seasons, daily catchlimits) work well until their effectiveness is undermined by large increases in the demandfor recreational fishing Anglers also often fail to appreciate the significance of their catchrelative to the total harvest (Christie, 1978)

The growth of sport fishing for lake trout, and for many other species, has exceededthe ability of most agencies to be proactive Attempts by managers to control exploitationpressures by introducing almost annual revisions to the angling regulations have resulted

in a loss of credibility with anglers, who have become somewhat suspicious of managers’motives Anglers usually see proposals for harvest reduction mainly in terms of a loss offishing opportunities, whereas to the manager these proposals are seen as necessary tomaintain the resource (Ontario Ministry of Natural Resources, 1978a)

Harvest is controlled by applying such methods as (1) limiting fishing opportunities(manipulating season length and regulating physical access); (2) using size-based regula-tions to exert biological control of the harvest; (3) applying daily catch limits to apportionthe catch; (4) implementing quota controls to match actual harvest with maximum equi-librium yields; and (5) imposing gear restrictions to make anglers less efficient or toincrease the survival of released fish These measures are reviewed and directions forexperimental management proposed

Angling seasons

The establishment of a fishing season with fixed opening and closing dates is a commonregulatory measure for most sport fish, including the lake trout Ideally, the length of afishing season indicates how intensively a species should be managed It also reflects thesocial values and traditions that have developed for a particular sport species and itsfishery Seasons may be closed because a species may be especially vulnerable to exploi-tation at certain times of the year (such as the ice-out period for lake trout) or to protectmature fish during their spawning season

In Manitoba and Saskatchewan, lake trout fishing is generally closed for only a shortperiod of time in April or May (Table 11.1) Long seasons are also the norm in Ontario,where winter fishing is permitted in 30 of 35 fishing divisions However, winter fishingfor lake trout is not permitted in Quebec (with few exceptions), is confined to certain areas

in Minnesota, and is confined to specified waters in New York Lakes closed to late fallfishing are usually closed by or before September 30 Presumably the closing date selected

is designed to protect lake trout from exploitation just prior to and during the spawningseason

In an attempt to reduce catch by about 30%, a number of measures were applied tofree-access lake trout waters in southern Quebec in 1989 These are waters in which noaccess provisions apply, and no daily or annual fees other than a provincial fishing licenseare required to fish legally These measures included closing the winter season, openingthe summer season on June 1 (a loss of about 5 weeks of ice-free fishing), and loweringthe daily catch limit to two fish Season reductions were expected to have the most effect

A creel census was conducted on two lakes in 1991 to measure the changes in the fisheries

In Lac Matapédia there was no winter fishery, while in Lac des Trente et un Milles therewere both winter and open-water fisheries Changes in fishing effort (angler-hours), CUE(catch-per-unit-effort), and estimated harvest (number) were observed as follows:

Table 11.1 General Summary of Open Seasons for Lake Trout Angling in the Precambrian Shield Area of North Americaa

Saskatchewan May 16–March 31 Central zone

May 25–March 31 Northern zoneManitoba May 16–April 30 North-central and northwest divisions

Generally all year Northeast divisionOntario January 1–September 30 Most common, but 12 different seasons, 4 split

seasons (closed in late winter, reopened in spring)

5 divisionwide winter closures, approximately 50+ lakes elsewhere with specific winter closuresQuebec April 25–September 1, 7,

14, or 30

Seasons may vary slightly in wildlife reserves and ZECs

Minnesota May 9–September 30 Lakes both inside and outside and partly outside

Boundary Waters Canoe Area adjacent to Ontario border have winter seasons

New York April 1–October 15 All year in Finger Lakes, Lake Champlain

Ice fishing permitted in designated trout waters

Note: ZECs, Zones d’Exploitation Controlée.

a Regulations pertaining to Great Lakes waters are not included These regulations may have changed in recent years Check with your local management agencies for updates.

In Lac Matapédia, despite the loss of 5 weeks of spring fishing, effort, fishing success,and harvest all increased substantially In Lac des Trente et un Milles, although the winterfishery was closed and total fishing effort decreased substantially, a large increase in fishingsuccess in summer resulted in an overall increase in total harvest These examples showthat anglers can quickly adapt to changes in season regulations, and that exploitation canstill be quite high even when seasons are reduced.

A different approach to harvest control than in-year season changes has been theclosure of lakes to fishing in alternate years This system was instituted on a number of

lake trout and brook trout Salvelinus fontinalis lakes in Algonquin Park, Ontario, in

response to concerns that the large catches of mature fish in some of these lakes mightadversely affect production and recruitment Spawning escapement was not measurablyenhanced because there was little difference in the size of year-classes produced in openand closed years (Martin and Baldwin, 1953) The quality of lake trout angling in lakessubject to alternate-year closure was also similar to that experienced in lakes open tofishing each year A later study by Martin (1966) produced the same results He suggestedthat a system of alternate-year closure might be most beneficial in intensively fished lakesthat have fast growing fish and stable year-class production He also noted that in lakesopen for 2 consecutive years then closed for 1 year, the angling quality declined substan-tially in the second open year

Winter fishing

One of the contentious issues of lake trout management is that of winter fishing In theearly 1950s, Fenderson (1953) noted that the effects of ice fishing on trout and salmonhave been controversial for a long time in Maine Concerns about the effect of ice fishing

on lake trout stocks in Ontario arose shortly after winter open seasons for lake trout wereestablished in inland lakes in 1957 (Armstrong, 1961) Hughson (1961) reported that inthe Sudbury area, fishery managers were concerned with the large increase in winter

fishing in recent years (primarily for lake trout and walleye, Stizostedion vitreum vitreum)

and with the poor-quality angling occasionally experienced for these species during thesummer Ryder (1957), on the basis of a winter creel survey of 19 lakes in 1957, suggestedthat winter fishing did not overexploit lake trout populations in the Thunder Bay, Ontario,area as winter harvests were only about a tenth of those experienced during open water.However, some 15 years later the impact of winter fishing had changed dramatically.Ryder and Johnson (1972), citing just one example, estimated that 2 to 4 years of annuallake trout production was removed from one such Thunder Bay area lake by ice fishermen

in 1 day

The impact that winter angling can have on a small Precambrian Shield lake troutlake is shown in Figure 11.1 A similar exploitation pattern occurred in 1980 in NelsonLake, a 308-ha rehabilitated lake trout lake also near Sudbury, Ontario (Gunn et al., 1988).Winter effort, harvest, and yield were estimated at 28,137 angler hour, 2132 fish, and 3.26

kg ha−1, respectively Catch rates (number/angler hour), mean fork length (FL), and meanweight of fish sampled generally declined monthly from January through March Theauthorities responded by closing the lake to winter fishing The closure is still in effect,and the lake is heavily fished in the spring The rapid response of anglers and the resultant

“high grading” that occurs when a closed lake is opened to uncontrolled fishing (by eithernew access or removal of sanctuary status) is a familiar pattern It was also a commonoccurrence, at least in Ontario throughout the 1960s, because lake trout regulations wereliberalized and the use of mechanized forms of winter travel allowed anglers access topreviously inaccessible lakes

One of the earliest studies comparing winter and open-water lake trout fisheriesoccurred on Algonquin Park lakes in the late 1940s and early 1950s Martin (1954) foundthat in lakes where lake trout mature at a young age (5 years) and a small size (28 to 30.5-

cm FL), as in Canisbay and Louisa Lakes, a summer fishery leaves a greater proportion

of the mature fish to spawn each year than the winter fishery In these lakes, harvestswere generally greater in the winter The catches sampled in the winter were made up ofsmaller trout and had a larger proportion of immature fish than in the summer fisheries.For example, in Canisbay and Louisa Lakes 60 and 50%, respectively, of the lake troutcaught in winter had fork lengths less than 30 cm compared to 15 and 10%, respectively,

in the summer fishery These results in part contributed to the closure of Algonquin Parklakes to winter fishing after 1955

Martin (1954) found that plankton feeding was generally at a low level during thewinter, and with the absence of thermal barriers the smaller and more numerous plank-tivorous lake trout were able to feed on minnows more frequently These fish are especiallyvulnerable to capture by anglers using bait fish Lakes with an abundance of small laketrout (usually the smaller lakes) may attract more anglers and have greater effort on aper-unit-area basis than other lakes because the higher catch rates on such lakes providethe angler with “lots of action” and increase the likelihood of limit catches The high

Figure 11.1 Impact of winter anglers on a remote lake trout lake near Sudbury, Ontario MichaudLake is a 148-ha lake accessible by a 26-km forestry road (12 km are used as a snowmobile trail inthe winter) The lake was closed to angling for 7 years (1991–1997) to allow the lake trout population

to be rehabilitated by hatchery stocking The lake opened to fishing (without any public notice) onJanuary 1, 1998, under the standard regulations for this area (unlimited access and entry, three fishper person daily catch [bag] limit) Catch rates were very high the first week of January (0.4fish/angler-hour), but declined rapidly as more and more people (>90 people the 4th week) learnedabout the fishing in the lake In spite of poor fishing late in the winter season, anglers continued tofish the lake until ice breakup occurred They then returned for one last try in early spring Catchrates were initially high in early spring (0.17 fish/angler-hour the first week of May), but declinedagain to zero by the third week of May A creel survey was conducted every weekend day and ontwo random weekdays per week A total of 384 harvested lake trout (2.6 kg/ha) were observed bythe creel survey crew By extrapolation, the estimated total harvest was 515 fish (3.8 kg/ha) Based

on a marking program conducted in fall 1997 (220 fish marked and released), the adult populationwas reduced by about 72% (from 765 to 210) by anglers in the first few months that the lake wasopen (Modified from Gunn and Sein, 2003; See Gunn and Sein, Chapter 14, this volume.)

harvests in some lakes during the winter may also be taken into account by the observation

of Ryder and Johnson (1972) that “lake trout tend to form close schools in the winter,which, once located, can be harvested at will.” This supports Martin’s (1954) observationthat the winter catch of lake trout in large lakes may be lower in part because of thedifficulty in locating the fish

An assessment of winter and summer lake trout fisheries was done by Schumacher(1961) on four lakes in Minnesota In the lake with the longest time series (9 years) hefound that both winter angling pressure and catchability were twice that of summer andresulted in the capture of five times the number of fish Winter anglers took smaller trout,and nearly two-thirds of the fish caught were immature Winter anglers were also the first

to exploit each new year-class entering the fishery Schumacher concluded that these lakeswere overexploited

Many other authors have observed that effort, fishing success, and catch tend to behigher in winter fisheries than in open-water fisheries and that winter catches containhigher proportions of small, young, and immature fish Goddard et al (1987) found thatfishing effort is the most important factor affecting lake trout harvest in Ontario lakes,accounting for 73% of the annual variation in angler catch among lakes Evans et al (1991),

in their review of Ontario lake trout sport fisheries, found that a disproportionate amount

of annual effort occurred in winter because effort on lake trout was about 25% greater inwinter than in spring and summer combined

Lake trout are also very vulnerable to angling when the ice fishing season first opens,which is usually in January A disproportionate amount of effort and harvest in winterlake trout fisheries has been observed in that month In four Ontario lakes, for example,about one-half of the effort and one-half to two-thirds of the harvest occurred in the firstmonth of the season (Vozeh, 1965; Samis, 1968; Purych, 1975; Bernier, 1977) Correspondingcatch rates were from one-third to three times higher in January than in February or March

in three of the four lakes A similar pattern was observed in Michaud Lake (Figure 11.1).Catch rates and harvests may be lower in February and March simply because fewer fishare available for capture If the season was not open until February or March, initial catchrates and harvests might also be as high as in January, although the cumulative harvestmight be less because of a shorter season

A high proportion of lake trout caught in winter angling fisheries are also immature.For example, Purych (1975) found that 80.7% of the lake trout sampled from the angler’scatch at Summers Lake, Ontario were immature, and Walker (1978) reported that 77% ofthe lake trout caught at Lake Manitou, Ontario were immature This could have a majoreffect on recruitment, as Martin and Fry (1973) have shown that in Lake Opeongo year-class strength is significantly related to spawning escapement, which is in turn largelygoverned by exploitation

There is little doubt that winter fishing for lake trout has been harmful to many laketrout stocks Evans et al (1991) concluded that yields of lake trout in many Ontario lakes,especially for winter fisheries and small lakes, appear to be well above self-sustaininglimits As Schumacher (1961) pointed out, the winter angler is the first to catch each newyear-class as it becomes vulnerable to fishing, and thus the winter fishery may have thedominating effect on the summer fishery as well as the total fishery

Allocating the resource among winter and summer anglers is a social, not a biological,issue As Christie (1978) noted, it makes little difference what time of year a fish isharvested as the same loss to the spawning population occurs whether it is caught manymonths before or just prior to the spawning season DeRoche (1973) contended that winterfishermen have as much “right” to the resource as summer (open-water) anglers Ingeneral, in winter most anglers tend to be local residents Larger economic benefits mayaccrue in summer fisheries that attract a larger proportion of tourists Social and economic

interests may not be compatible with biological concerns, and compromises are inevitable.Managers must balance the demands of anglers with the demands of those who have aneconomic interest in the fisheries However, more than 40 years ago, Weir and Martin(1961) noted that if the issues associated with winter fishing for lake trout are to beresolved, biological considerations should take precedence over nonbiological concerns.There is justification for curtailing winter fishing in some manner because of thepotential biological impact on lake trout stocks This does not mean that winter fishingfor lake trout should be eliminated across all lakes Nevertheless, a reduction in the length

of the winter fishing season in areas or on small lakes where exploitation is excessive, oreven winter closures on individual lakes, may be an effective harvest control mechanism

In Ontario, for example, a review of lake trout management strategies (Olver et al., 1991)recommended that winter lake trout seasons be reduced to 1 month (February 15 to March15) on all lake trout lakes less than 1000 ha, and that lake trout lakes less than 100 ha beclosed to winter fishing These recommendations have not been implemented

One method to reduce harvest has been to delay the “traditional” opening date ofJanuary 1 to sometime in February or March and continue the season uninterruptedthrough to the fall However, shortening the winter season from a few months to a fewweeks might cause anglers to compress a similar amount of effort observed in a longseason into a shortened season if opportunities to fish nearby open lake trout lakes arenot available Local conditions (sufficient ice cover, snow conditions, weather conditions)may also vary considerably from month to month, year to year, and lake to lake withinthe same fishing division, thereby making it difficult to establish regulations that areeffective or suitable over broad areas

Another option is to have a split season in which the season is closed for a period oftime prior to the spring breakup of ice and then is reopened some time after the ice goesout This approach deserves closer scrutiny, as the intent is to reduce harvest during aperiod when the lake trout appear to be especially vulnerable to angling Regardless ofwhether season adjustments are applied across a fishing division or to individual lakes,the fine tuning of seasons by manipulating the opening and closing dates is a viable option

to control harvest

Access control

Access controls, in addition to fishing regulations, can be used to control harvest Thesetypes of measures are usually designed to limit or to impede access to water bodies, restrictaccess of certain user groups, and limit development in remote areas or lakes The tradi-tional means of access control have been restrictions on travel by motorized road vehicles,road closures, and the siting of access roads away from relatively unexploited lakes Accesscontrols that may be used to lower fishing pressure include controls on the use of snowmachines and power boats, the establishment of daily travel quotas at access points, thecontrol of boats cached on public land, the allocation of fish in remote lakes or areas tospecific outfitters, and the limitation of development or accommodation at outpost camps.Access controls are used in Quebec, but they are part of the quota management strategyused there and are discussed in that context

Use of publicly owned access roads is usually permitted, although travel on suchroads may be closed for various reasons On private access roads, such as those owned

by logging companies, public travel can be denied or negotiated between a private pany and a government agency or potential local users Road closures, however, oftenhave not come into effect until after overexploitation has already occurred Also, locatingforest access roads away from lakes containing lake trout, as well as other species, is nolonger an effective deterrent to exploitation in Ontario (Ontario Ministry of Natural

com-Resources, 1982) because of the ready availability of motorized vehicles that do not requireroads for travel.

Regulations have also been enacted in some parks (such as Algonquin Park, Ontario),which prohibit the operation of snow machines and power boats or limit the horsepower

of motor boats on certain lakes or to specified times of the year The last restriction, forexample, while primarily intended to separate canoe trippers and outboard motor users,also limits the ability of anglers to troll for lake trout on some of the larger lakes in thepark In Quetico Park, Ontario, which is much further from major population centers thanAlgonquin Park, access controls have also apparently had a strong influence on exploita-tion Maher (1985) noted that in Quetico Park, the prohibition on power boats and snowmachines reduced fishing pressure to a noncritical level In Algonquin Park, quotas havealso been established that limit the number of canoeing/camping parties entering the parkinterior from designated access points on any day at certain times of the year The closure

of Algonquin Park to winter fishing in 1955 and the use of access controls in more recentyears are probably the major factors contributing to the retention of quality fishing in thatpark, as overexploitation of lake trout is largely confined to lakes adjacent to road access.Limiting the numbers and locations of boats cached or left unattended on public lands

is another form of access control that could also act as a harvest control mechanism onlakes where fishing pressure by anglers using such boats has contributed to the overex-ploitation of fishery resources This idea has been used since the early 1980s in thenorthwestern part of Ontario (Ontario Ministry of Natural Resources, 1996), where allboats cached on public land must be authorized and identified by means of a validationdecal On some lakes boat caches may not be permitted, while on other lakes the number

of boats and the conditions of use may be regulated

Outpost camps on remote lakes may be allocated to specific tourist outfitters Thebasic intent is to support the tourist industry by limiting competition and to preventoverexploitation Agreements between government agencies and the tourist industry mayalso result in limits on the number of overnight accommodation units at these outpostcamps This in effect places a quota on the number of anglers who have access to thesefacilities The intent is to maintain high-quality fishing by keeping projected harvestsbelow annual production

In summary, fishing pressure and ultimately harvest depend, in part, on accessibility.Hence, access controls to curb overexploitation offer a viable alternative to additional ormore stringent angling regulations They may also be used to complement existing anglingregulations to effect the same result Many types of access control have evolved in response

to “local” problems Consequently, they often lack a sense of perspective and can erate independently of one another and therefore have not been used to their full potential(Ontario Ministry of Natural Resources, 1982) A study of the role of these controls relative

prolif-to the harvest of fishery resources would be both appropriate and timely

Size limits

Size limit regulations have important management implications, because the size and age

of recruitment and the entry of year-classes into a fishery can be determined and thusmanipulated Size-based regulations infer the release of live fish Their use to achieve aparticular social or biological goal is based on the assumption that the survival rate ofreleased fish is sufficient to ensure sustainability of wild fish

Although studies that test that assumption are not reviewed in detail, a few commentsare presented to show the importance of hooking mortality to size-based regulations.Studies in large lakes during spring and summer have shown hooking mortality rates inthe range of 7.0% (Great Bear and Great Slave Lakes, Northwest Territories; Falk et al.,

1974) to 14.9% (Lakes Huron, Michigan, and Superior; Loftus et al., 1988) UnpublishedQuebec and Ontario studies on smaller lakes of the Precambrian Shield have shown similar

or slightly higher mortality rates The higher mortality in some of the Ontario lakes wasattributed to prolonged handling times, poor handling practices, and entanglement prob-lems with tethering gear used to retain lake trout for assessment of delayed hookingmortality In addition to hooking mortality, Lee and Bergersen (1996) noted that the releaseand subsequent high mortality of lake trout in late summer in lakes with inadequatethermal and dissolved oxygen refugia may nullify the intended benefit of size-basedregulations

Hooking mortality of lake trout during the winter may be higher than during theopen-water period, especially when set-lining (i.e., still fishing) using a bait (usually

cyprinids, dead rainbow smelt Osmerus mordax, or lake herring Coregonus artedi) In

Gun-flint Lake, Minnesota (Persons and Hirsch, 1994) the observed mortality rate using thismethod was 32.0%, and fish were still dying at the end of the 6-day holding period Incontrast, jigging caused a mortality rate of only 9% Jigging is a more active method thanstill fishing, the line is closely tended, and the fish has less chance or time to deeply ingestthe bait (as it must strike a moving target) before the hook is set With still fishing, thefish generally swallows the bait before the hook is set, and the bait tends to be deeplyingested and may be difficult to remove without causing further injury or death As noted,anglers tend to catch smaller lake trout in the winter than in open-water even in the samelake The mortality rate of released small fish is generally considered greater than that forlarger fish Additional studies of winter lake trout hooking mortality are required Hookplacement (i.e., location) and hook size are important aspects of hooking mortality andneed to be studied further

It would seem prudent for anglers to leave deeply imbedded hooks in any fish theyintend to release (at any time of the year) because removal is likely to induce bleeding orcause further injury or death Lake trout that are bleeding should not be released unlessrequired by a size-based regulation The importance of effective techniques for hookremoval, handling, and release of fish should be promoted through public educationprograms

The general purpose of minimum length limits, in which all fish below some nated size must be released, is to permit fish to mature and spawn at least once beforereaching legal size In theory, some of the released sublegal fish will be harvested whenthey attain legal size or will increase catches by contributing to future spawning stocks.These length limits are generally applied in fisheries where growth is good and recruitmenthas been reduced because of high exploitation

desig-Maximum size limits, in which all fish above a specified size must be released, areused to protect brood stock or to counter a decline in age and size of spawning stock.They are applied to stocks for which growth potential is large, but high exploitation hasresulted in a low density of mature fish and limited recruitment Conversely, these limitsmay be used to maintain the population structure of unexploited stocks, especially in largelakes where large body size can be attained

A combination of minimum and maximum size limits is the slot limit A size range

in which anglers may only keep fish below or above specified lengths is called a protected

slot All fish within the protected slot must be released The intent is to protect the brood

stock while still allowing anglers access to the more numerous, smaller fish and the lessabundant large or trophy-size fish The capture of fish below the slot should, in theory,reduce density, increase growth, and allow escapement into the protected slot size Repro-duction of adults in the slot should increase recruitment A harvested slot in which onlyfish between a specified minimum and maximum size may be kept has not, to ourknowledge, been applied to lake trout

Minimum length limits have generally been avoided for lake trout throughout most

of the Precambrian Shield except in New York, which has statewide and lake-specificminimum size limits (Table 11.2) Most authors reporting on the utility of size limits haveindicated that the existing minimum length limits were too small to ensure sufficientspawning escapement

Webster et al (1959) reported that the 38-cm FL size limit in Cayuga Lake, New York,was ineffective as few trout smaller than this size were taken by anglers Seamans (1960)noted that a 38-cm total length (TL) size limit was ineffective in controlling exploitation

in New Hampshire lakes as few lake trout were mature below 46 cm long He reportedthat the size limit of 38 cm in Newfound Lake, New Hampshire, was arbitrary and denoted

a “desirable” keeper, and suggested that the limit be increased to 46 or 48 cm or abandonedentirely It is still in effect on that lake today AuClair (1976) reported that the size limit

on lake trout in Moosehead Lake, Maine, was increased from 38 to 46 cm in 1972 to increasenatural reproduction

A minimum size limit has been in effect for lake trout for many years in Raquette Lake,New York Overharvest was thought to be the major reason for the population decline(Shupp, 1973) He recommended an increase in the minimum size limit (TL) from 38 to 53

cm, as 90% of female trout were mature at lengths greater than 51 cm Barnhart andEngstrom-Heg (1984) noted several changes in the lake trout population at Raquette Lakefollowing an increase in the minimum size limit from 38 to 53 cm in 1973 There was athreefold increase in the spawning stock within 2 years, and the catch rate of fish retainedincreased from 0.03 lake trout h−1 in 1968 to 0.08 during 1973–1978 Natural reproductionincreased substantially because about 75% of the juvenile lake trout by 1978 were wild fish,whereas at the time of the change in the size limit, they were almost entirely hatchery fish

Table 11.2 Size Limit Regulations for Lake Trout in Small, Forested Precambrian Shield Lakes

In catch-and-release one lakes, only one of two may be larger than 65 cm

In catch-and-release two and three lakes, none may be larger than 65 cm

lakesMaximum size 38 cm in 4 lakesLake-specific one over certain size (40, 56, 65,

70 cm) in approximately 20 lakes

not apply to parks, wildlife reserves, and ZECs

38 cm Finger Lakes, Lake Champlain

Note: TL, total length; ZECs, Zones d’Exploitation Controlée.

a Regulations pertaining to Great Lakes waters are not included Regulations in some jurisdictions may have changed in recent years.

Genetic and environmentally induced variability in lake trout growth makes it tical to set a single minimum legal length to protect immature fish over a broad geographicarea Across the total range of the lake trout, first maturity has been reached at lengthsfrom 18 cm (FL) in stunted populations in national parks in western Canada (Donald andAlger, 1986) to 66–76 cm (TL) in fast-growing lake trout in Seneca Lake, New York (Royce,1951) Even in a relatively small area such as Algonquin Park, Ontario, size at first maturityvaried from 28 to 48 cm (FL) (Martin, 1966) The selection of a single minimum size limitover any large area to allow part of the stock to spawn at least once before legal harvestingwould be difficult to determine and would result in lake trout that were almost entirelyunavailable to anglers in many lakes (Martin, 1966) This would be true of any regionwhere there is a large concentration of lake trout lakes, particularly with a mix of plank-tivorous and piscivorous stocks that vary considerably in their age, size, and maturitystructure The practicality of minimum size limits is further complicated by the fact that

imprac-in the same lake, the wimprac-inter fishery tends to catch smaller trout than the summer fishery(Martin, 1954; Schumacher, 1961) Martin (1966) noted that summer fishing with wire lineand large spoons serves as a self-regulating control on the size of fish caught MacCrimmonand Skobe (1970) concluded that a length limit was unnecessary for lake trout in LakeSimcoe because the selective trout baits usually catch the larger fish This self-regulatingeffect may explain why minimum size limits are not common in many areas

Work by Trippel (1993) on low- (<40 µS/cm) and high-conductivity (>77 µS/cm) lakes

in northwestern Ontario suggested that managers may need to restrict the harvest offemales larger than 55 cm (FL) in low-conductivity lakes and of females larger than 60 cm(FL) in high-conductivity lakes Lake trout in the former lakes had slower growth, matured

at an older age, attained maturity at similar or smaller body sizes, and were less fecundthan lake trout in high-conductivity lakes Simple possession limits are not sensitive tointerlake differences in lake trout population structure (growth, maturation, fecundity)

To regulate the harvest of large adults, Trippel proposed that depending on lake tivity, the daily catch or possession limit be changed so that anglers are allowed to keeponly one fish larger than 55 or 60 cm Alternatively, a maximum size in effect at thesesizes could be employed

conduc-A maximum size limit requires anglers to release all fish above a specified size It mayalso be used in combination with a daily catch limit to control the harvest of large ortrophy-size fish The daily catch limit may remain unchanged, but only one fish above alarge maximum size may be kept In Manitoba, the general regulation is that only onelake trout larger than 65 cm (TL) may be kept However, a maximum size limit (65-cmTL) is in effect across one fishing division and in designated high-quality lakes in anotherfishing division (Table 11.2) In these lakes, all lake trout larger than 65 cm (TL) must bereleased Limiting the catch of large lake trout may be a useful regulatory device whereanglers target on large lake trout or where the establishment of a trophy fishery is amanagement objective Although a maximum size is usually imposed to limit the harvest

of large, trophy-size fish, a maximum size of 38 cm (TL) is in effect on four south-centralOntario lakes as a means of protecting the unique genetic structure of these stocks

A protected slot limit of 40 to 56 cm (TL) was placed on seven Highway 60 corridorlakes in Algonquin Park, Ontario in 1989 Even though these lakes are closed to winterangling, some were overexploited during the open-water fishery On one lake studied(Smoke Lake), initial results in 1992 were promising (Hicks, 1994) Effort continued todecline, possibly in response to previous overharvest and because anglers tend to fishelsewhere when more restrictive regulations are first imposed Harvest declined by 38%,catch rates improved, and fall spawning assessment studies showed that more fish in thelength range from 40 to 60 cm were appearing on the spawning shoals and that totalabundance of lake trout on the spawning shoals had increased

Beginning in 1996, protected slot limits were also used to regulate harvest in othersouth-central Ontario lakes south of Algonquin Park About 88 lakes now have a slot limit

of 40–55 cm (TL), and a slot limit of 33–40 cm (TL) has been placed on 13 lakes withpolyphagous lake trout stocks Of the 101 lakes in both slot ranges, 20 have been closed

to winter fishing and in the other 81 slot limit lakes where winter fishing is allowed, 70lakes have had the number of lines allowed when fishing through the ice reduced fromtwo to one Anglers have been slow to accept these changes and have complained aboutwhat they perceive to be unnecessary restrictions and are concerned about the mortality

of fish released within the slot ranges Government response has been to reduce thenumber of lakes regulated by slot limits

In 1993 Quebec imposed a 35- to 50-cm (FL) protected slot in southern areas of theprovince except in Zones d’Exploitation Controlée (ZECs; literally, a zone where exploi-tation is controlled), parks, and wildlife reserves, and in those areas where outfittingoperations have exclusive fishing rights Angling is managed by a quota system in theseareas The regulation was imposed after an evaluation of the status of lake trout stocks,the high survival of released fish, and the receptivity of anglers to the regulation (Ministère

du Loisir de la Chasse et de la Pêche, 1991) To keep the system manageable, a singleprotected slot size was applied to more than 300 lakes in which many lake trout stockshave different growth rates and age and length at first maturity

Lake trout lakes were grouped into three categories according to growth rate (slow,medium, fast) Size limit options (minimum, maximum, protected slot) were evaluatedfor each growth category using Ontario’s Lake Trout Management Support System(LTMSS) age-structured population model (Korver, 1992) A single minimum size limitwas not effective across such a broad range of biological variability in growth Onlyprotected slot size limits offered the needed reduction in catch across all growth categories.For the fastest growing fish the protected slot acts as a minimum size limit, while for fishwith the slowest growth rates it acts as a maximum size limit

Modeling showed that the 35- to 50-cm (FL) slot, by protecting a significant portion

of the brood stock, should permit higher recruitment and higher population densities Inturn, release of part of the catch by anglers should translate into high catch rates (the total

of released and kept fish) than historically observed in these fisheries According to thesimulation model, the slot regulation should be effective for an angling effort up to 12angler hours/ha In 1993, angling effort was on the order of 8 angler hours/ha

Results of creel surveys conducted in 1993–1994 on two lakes to evaluate the tiveness of the 35- to 50-cm (FL) protected slot are shown below (Legault, 1994; Nadeau, D.,unpublished data) Results are in accordance with model simulations for harvest reductionand the proportion of fish released The biological objectives of the regulation change wereachieved

effec-A phone survey of 318 lake trout anglers conducted 1 year after the regulation wasintroduced indicated that 61% of the anglers interviewed agreed with the slot size regu-lation, 30% disagreed, and 9% had no opinion (Montminy, 1994) The level of acceptance

of the measure indicates that the social objectives were also met

Lac des Trente