Evaluation of a Liberalized Harvest Regulation on Lake Trout in Four Western Maine Lakes

FISHERY PROGRESS REPORT SERIES NO. 02-1

By David P. Boucher and David Howatt

Maine Department of Inland Fisheries and Wildlife
Division of Fisheries and Hatcheries
Augusta, Maine

March 2002

SUMMARY

Fishery Region D, located in western Maine, supports fisheries for lake trout in 15 lakes comprising 17,434 acres. With the exception of a single population in Somerset County, lake trout were not native to this part of Maine. Their present distribution is the result of introductions made several decades ago. In a few waters lake trout quickly established themselves as self-sustaining populations, but most relied on annual stockings of hatchery fish to sustain viable fisheries.

Prior to 1982 lake trout were managed with 14 or 16-inch minimum length limits, which did not permit these slow-growing, late-maturing fish to spawn prior to harvest. The general law length limit was increased to 18 inches in 1982 as a means of increasing spawning escapement and improving size quality of harvested fish. This strategy was successful in increasing lake trout abundance and resulted in the establishment of self-sustaining populations in all but two of the Region’s lake trout lakes. Some of these new self-sustaining populations were comprised of many young fish that became "stockpiled" under the 18-inch limit. This placed considerable stress on forage populations, primarily rainbow smelts, and resulted in declines in growth rates and condition of lake trout and other predators, particularly landlocked salmon.

Several management actions were taken to reduce the impact of young lake trout on forage populations. Lake trout stockings were terminated, stocking programs for salmon were reduced or suspended, smelt harvests were reduced by closing tributary dip-net fisheries, smelt eggs were transferred to re-establish or augment forage, and in one case landlocked alewives were introduced as alternative forage. Despite this, lake trout populations remained high, sublegals continued to dominate anglers’ catches, and fish quality continued to decline.

In a further effort to reduce the impact of young lake trout, harvest regulations were liberalized in 1994 on all lake trout waters in Franklin County and on one water in Somerset County. The minimum length limit on lake trout was reduced from 18 inches to 14 inches, with one fish between 14 and 18 inches and one fish over 18 inches permitted each day. The goal of this "slot" regulation was to facilitate recovery of forage populations to levels needed to improve and maintain growth rates and condition of lake trout and salmon. Specifically, the regulation was intended to 1) direct a portion of the harvest to abundant, younger lake trout that are heavy consumers of smelt, and 2) maintain adequate spawning escapement of lake trout by reducing the harvest of mature ( → 18-inch) fish.

The slot limit succeeded in directing a portion of the winter harvest to younger, more abundant lake trout, and this may have contributed to improvements in size and condition of lake trout and salmon on some waters. However, the improvements were not dramatic. Winter anglers released large numbers of legal fish during the slot limit years, and winter fishing pressure generally declined, so the potential positive effects of the more liberal regulation were moderated.

Our results indicate that the slot limit had only a marginal effect on winter fisheries and on fish quality. Our management efforts will continue to focus on maintaining a reasonable balance between predator numbers and prey populations, so we will seek further reductions in lake trout population size and continue to strictly control salmon numbers through stocking rate manipulations. We recommend that lake trout harvest rules be further liberalized and that salmon stockings rates be maintained at low levels until predator growth rates and condition are stabilized.

Jobs F-204 and F-103

Progress Report No. 1

ABSTRACT

Fishery Region D, located in western Maine, supports principal fisheries1 for lake trout (Salvelinus namaycush) in 15 lakes comprising 17,434 acres (7,058 ha), and most are managed in conjunction with landlocked salmon (Salmo salar). Increasing the statewide general law length limit to 18 inches (457 mm) in 1982 increased lake trout abundance and established self-sustaining populations in all but two of the Region’s lake trout lakes. Some of these new self-sustaining populations were comprised of many young fish that became stockpiled under the 18-inch (457 mm) limit. This placed considerable stress on forage populations, primarily rainbow smelts (Osmerus mordax), and resulted in declines in growth rates and condition of lake trout and salmon. To reduce the impact of young lake trout, the minimum length limit was reduced to 14 inches (356 mm), with one fish between 14 inches (356 mm) and 18 inches (457 mm) and one fish over 18 inches (457 mm) permitted each day. This slot regulation was assessed on four waters by monitoring winter sport fisheries before and after its imposition. Results indicate that the slot limit had only a marginal effect on winter fisheries and on fish quality in the four study waters. Higher release rates of legal fish during the slot limit years and generally declining winter angler use moderated the positive effects of the more liberal regulation. Lake trout harvest rules will be further liberalized and salmon stockings rates will be maintained at low levels until predator growth rates and condition are stabilized.

INTRODUCTION

Fishery Region D, located in western Maine, encompasses all of Franklin County and portions of Oxford and Somerset Counties (Figure 1). The Region supports principal fisheries2 for lake trout (Salvelinus namaycush) in 15 lakes comprising 17,434 acres. Most of these lakes are small (<1,000 surface acres) and all provide excellent habitat for lake trout. Eight lakes have shorelines that have been moderately to heavily developed; most of these are located near population centers in the southern and southeastern portions of the Region. The remaining waters are located in the interior highlands and are lightly developed. Two lakes are not accessible to the general public. Winter fishing is permitted on 53% (42% of the total acres) of them, and all but four are managed in conjunction with landlocked salmon (Salmo salar).

With the exception of a West Carry Pond in Somerset County, lake trout were not native to western Maine waters. Their present distribution is the result of introductions made several decades ago, primarily during the 1930’s and 1940’s and in the 1960’s and 1970’s. In a few waters, lake trout reproduced and established self-sustaining populations, but most relied on annual stockings of hatchery fish to sustain viable fisheries.

Prior to 1982, lake trout were managed with 14 or 16-inch minimum length limits, which did not permit these slow growing, late maturing fish to spawn prior to harvest. In 1982, the statewide general law length limit was increased to 18 inches and the daily bag limit was reduced to 2 fish as means of increasing spawning escapement and improving size quality of harvested fish. This strategy was successful in increasing lake trout abundance in many Region D waters (Bonney 1988, 1989, 1993), as it was throughout Maine (Johnson 2001). Moreover, the higher length limit resulted in the establishment of self-sustaining populations in all but two of the Region’s lake trout lakes. Some of these new self-sustaining populations were comprised of many young fish that became stockpiled under the 18-inch limit. This placed considerable stress on forage populations, primarily rainbow smelts (Osmerus mordax), and resulted in declines in growth rates and condition of lake trout and other predators, particularly landlocked salmon (Bonney 1989, 1991, 1993).

Several management actions were taken to reduce the impact of young lake trout on forage populations and maintain or restore predator growth and condition. Lake trout stockings were terminated, stocking programs for salmon were reduced or suspended, smelt harvests were reduced by closing tributary dip-net fisheries, smelt eggs were transferred to re-establish or augment forage, and in one case (Wilson Pond) landlocked alewives (Alosa pseudoharengus) were introduced as alternative forage. Despite these efforts, lake trout populations remained high, sublegals continued to dominate anglers’ catches, and fish quality continued to decline on many waters.

In a further effort to reduce the impact of young lake trout, harvest regulations were liberalized in 1994 on all lake trout waters in Franklin County (six lakes, 3,192 acres) and on one water in Somerset County (762 acres). The minimum length limit on lake trout was reduced from 18 inches to 14 inches, with one fish between 14 and 18 inches and one fish over 18 inches permitted each day. The goal of this regulation was to facilitate recovery of forage populations to levels needed to improve and maintain growth rates and condition of lake trout and salmon. Specific objectives were to 1) direct a portion of the harvest to abundant, younger lake trout cohorts that are heavy consumers of smelt, and 2) maintain adequate spawning escapement of lake trout by reducing the harvest of mature ( → 18-inch) fish.

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1&2Sport fish that provide principal fisheries are those purposely fished for by anglers and comprise a significant portion of the total catch of all species in the water.

For More Information or a compete report, please contact:

Dave Boucher
Regional Fishery Biologist
Rangeley Lakes Region
689 Farmington Road
Strong, Maine 04983-9419
Tel. #207-778-3322
Dave.boucher@maine.gov