Aziscohos Lake Salmonid Fishery

FISHERY PROGRESS REPORT SERIES NO. 03-1

by Forrest R. Bonney

Maine Dept. Inland Fisheries & Wildlife
Fisheries and Hatcheries Division
Augusta, Maine

March, 2003

JOB NO. F-104
PROGRESS REPORT NO. 5 (2002)

Summary

Aziscohos Lake is a 6,700-acre water formed by the construction of a dam on the Magalloway River. The lake supports fisheries for both salmon and brook trout. All of the trout and most of the salmon are wild fish. Salmon stocking was suspended in 1999 due to concern about growth rates and because of the increase in the contribution of wild salmon to the fishery.

During the summer of 2002, anglers were interviewed at Aziscohos Lake to gather biological information on the quality of the salmon and brook trout fishery. This information was compared with that collected in a similar manner in 1991, 1993 1996, and 1999. The total number of angler days, which has varied from 3,703 to 6,477 in the past, was estimated to be 4,692 days in 2002. Salmon growth decreased from 1991 to 1993 but improved in 1996. Growth rates declined moderately again in 1999 and in 2002 but still exceed those of the early 1990’s when all of the tributaries were open to smelting. Furthermore, the number of salmon caught per angler has increased steadily since those tributaries were closed to smelting, despite the cessation of salmon stocking. The catch rate of legal-size brook trout has declined since 1996 because of restrictive regulations imposed that year. We will continue to monitor the Aziscohos Lake fishery by conducting a creel survey and angler count every third year.

Abstract

Aziscohos Lake is a 6,700-acre (2,714-ha) artificial impoundment located on the Magalloway River in northern Oxford County. The lake is mesotrophic, and supports populations of landlocked salmon (Salmo salar), brook trout (Salvelinus fontinalis), rainbow smelt (Osmerus mordax), suckers (Catostomidae), brown bullhead (Ameirus nebulosus), and several species of minnows (Cyprinidae). It is closed to ice fishing. Salmon were stocked at a low rate to augment natural reproduction through 1999, but the fishery is now sustained by wild fish. Systematic random creel surveys were conducted in 1991 and 1993 from ice-out to mid-July and during the entire 1986, 1996,1999 and 2002 fishing seasons. Aerial angler counts were made during all survey years except 1993. The estimated number of angler trips was 4,692 in 2002; this estimate falls within the range estimated for previous years. The estimated harvest of salmon was more than twice that estimated for the previous survey although the brook trout harvest declined, presumably in response to restrictive regulations imposed in 1996. The salmon harvest (measured in pounds/acre) increased from 0.09 in 1986 to 0.11 in 1999 and 0.27 in 2002 despite the cessation of stocking in 1999. The brook trout harvest was 0.05 lb/a in 1986 and 1999; it declined to 0.03 lb/a in 2002. Robustness (condition) of both species increased significantly from 1993 to 1996 then declined moderately in 1999 and 2002. The improved growth rate in 1996 was attributed to a increased forage abundance resulting from the closure of west-shore tributaries to smelt dipping. The majority of the legal-size salmon sampled were ages V+ and VI+, though individuals through IX+ were sampled. The brook trout harvest consisted of fish primarily of ages III+ and IV+. We will continue to monitor the Aziscohos Lake fishery routinely to determine rates of angler use, salmonid growth and harvest, and effects of the restrictive brook trout regulations.

Introduction

Aziscohos Lake is an artificial impoundment formed by the construction of a concrete dam on the Magalloway River in Lincoln Plantation. The salmon and brook trout sport fishery has been evaluated periodically (typically every third year) since the 1980’s by season-long angler counts and angler interviews. The results of clerk surveys conducted in 1991 and 1993 were reported in Progress Report No. 2. These data indicated declining salmonid growth rates, which prompted closure of the west shore tributaries to smelt dipping effective 1996 to enhance the forage base. Salmon stockings, which ranged up to 38,000 spring yearlings per year in the early 1960’s, had been gradually reduced over the years as the contribution of wild fish increased. As few as 500 spring yearling salmon were stocked in the late 1990’s when stocking was abandoned altogether (Table 1) because of the large number of wild salmon in the fishery. Results of clerk surveys conducted in 1996 and 1999 were reported in Progress Report No. 3. These data indicated an improvement in growth rates in 1996 but a slight decline in 1999, providing additional cause to terminate salmon stocking.

The Aziscohos Lake fishery is now dependent entirely on natural reproduction for both salmon and brook trout. The lake had been stocked intermittently with brook trout from 1937 to 1973 when stocking was abandoned due to poor returns of these fish to anglers.

Written by Forrest Bonney

For more information, please contact:

Forrest Bonney, Regional Fishery Biologist
689 Farmington Road
Strong, Maine 04983-9419
Telephone: (207) 778-3322 Ext. 22
Email: forrest.bonney@maine.gov