Coho Salmon Studies in Southeast Alaska - arlis. COHO SALMON STUDIES IN SOUTHEAST ALASKA1 BY Artwin

  • View
    0

  • Download
    0

Embed Size (px)

Text of Coho Salmon Studies in Southeast Alaska - arlis. COHO SALMON STUDIES IN SOUTHEAST ALASKA1 BY Artwin

  • FISHERIES DATA SERIES NO. 45

    COHO SALMON STUDIES IN SOUTHEAST ALASKA1

    BY

    Artwin E. Schmidt

    Alaska Department of Fish and Game Division of Sport Fish

    Juneau, Alaska 99802

    June 1988

    1 This investigation was partially financed by the Federal Aid in Sport Fish Restoration Act (16 U.S.C. 777-777K) under Project F-10-3, Job No. S-l-4.

  • Because the Alaska Department of Fish & Game receives federal funding, all of its public programs and activities are operated free from discrimination on the basis of race, color, national origin, ageI or handicap. Any person who believes he or she has been discriminated against should write to: O.E.O., U. S. Department of the Interior, Washington, D.C. 20240.

  • TABLE OF CONTENTS

    LIST OF TABLES............................................... iii

    LIST OF FIGURES ..............................................

    LIST OF APPENDICES ...........................................

    iv

    V

    ABSTREICT .....................................................

    INTRODUCTION .................................................

    1

    2

    MATERIALS AND METHODS........................................ 4

    Adult Return............................................ 4

    Study Design ....................................... 4 Data Analysis ...................................... 4

    Adult Run Timing, Migration Routes, and Exploitation.... 5

    Study Design ....................................... 5 Data Analysis ...................................... 5

    Smolt Production and Population Estimation.............. 6

    Study Design ....................................... 6 Data Analysis ...................................... 6

    RESULTS AND DISCUSSION....................................... 7

    Adult Return............................................ 7

    Contribution to Fisheries............................... 10

    Harvest Rate............................................ 10

    Timing and Location of Harvest.......................... 10

    Smolt Production and Population Estimates............... 10

    Coho Salmon Pre-Smolt Marking in Salmon Lake ....... Coho Salmon Smolt Catch at Fyke Net Station ........ Valid Tagged Coho Salmon Emigrating from

    Salmon Lake ................................... Estimate of Coho Salmon Juvenile Population

    in the Fall ................................... Population Estimate of Coho Salmon Pre-Smolt ....... Salmon Lake Juvenile Tagging, 1987 .................

    10 18

    18

    18 18 18

  • I

    TABLE OF CONTENTS (Continued)

    Page

    LITERATURE CITED............................................. 24

    APPENDIX..................................................... 25

    ii

  • LIST OF TABLES

    Table

    1.

    2.

    3.

    4.

    5.

    6.

    7.

    8.

    Daily coho salmon escapement counts, water temperature, and stream depth at Salmon Lake weir, 1987........................................

    Number of coho salmon sampled at Salmon Lake weir by sex, tag status, and age, 1987......................

    Mean length at age (mid-eye to fork) of adult coho salmon from Salmon Lake, 1987..........................

    Age composition of adult coho salmon from Salmon Lake, 1987......................................

    Estimated commercial catch of Salmon Lake coho salmon by fishing district and time period, 1987.......

    Daily smolt catches, rainfall, water temperature, and maximum stream depth at the Salmon Lake fyke net station, 1987......................................

    Age composition of Salmon Lake coho salmon smolts, 1987...........................................

    Length composition of Salmon Lake coho salmon smelts, by age, 1987...........................................

    8

    11

    12

    13

    17

    19

    22

    23

    iii

  • LIST OF FIGURES

    Figure Paze

    1. Location of Salmon Lake research site and coho salmon index streams near Sitka, Alaska, 1987.......... 3

    2. Relative length-frequency by lo-mm size class of 318 adult male coho salmon sampled at Salmon Lake weir, 1987........................................ 14

    3. Relative length-frequency by lo-mm size class of 238 adult female coho salmon sampled at Salmon Lake weir, 1987........................................ 15

    4. Relative length-frequency by lo-mm size class of 30 jack coho salmon sampled at Salmon Lake weir, 1987.. 16

    5. Relative length-frequency by 5-mm size class of 733 coho salmon smolts sampled at Salmon Lake, 1987.... 21

    iv

  • LIST OF APPENDIX TABLES

    Appendix A Table Page

    1. Number and species of fish caught in St. Johns Creek, lo-16 July 1987........................................ 27

    2. Number and species of fish caught in Sinitsin Creek, 17-24 July 1987........................................ 28

    V

  • ABSTRACT

    A coho salmon Oncorhynchus kisutch research project was continued in 1987 to determine escapement goals, migration routes, run timing, harvest rates, and areas of harvest for the Salmon Lake system near Sitka. Coded-wire tagging of pre-smolt and smolt populations was conducted at Salmon Lake. Population sizes of these groups were estimated. The adult coho salmon escapement to Salmon Lake was estimated by weir count and foot surveys.

    The estimated coho salmon escapement to Salmon Lake was 616 adults. The contribution of this stock of coho salmon to the commercial troll fishery was 702, or 51.9 percent of the overall annual production. Contribution to the sport fishery was 29 fish and the contribution to the seine fishery was 26 fish, or 2.1 percent and 1.9 percent of annual production, respectively. Survival of tagged smolt to adult return was 9.4 percent. Nearly all returns of coded-wire tagged fish were from the outer coastal area offshore of Baranof, West Chichagof, and Yakobi Islands. Peak catch occurred during the week of 26 July through 1 August 1987.

    KEY WORDS: coho salmon, Oncorynchus kisutch, escapements, smolt, production, coded-wire tagging, weir, fyke net, harvest rates.

  • INTRODUCTION

    Coho salmon Oncorhpchus kisutch are important to commercial, recreational, and subsistence fisheries in southeast Alaska. Coho salmon harvests have re- covered from the lows during the 1960s and 1970s. The recreational angler harvest in southeast Alaska increased from 36,000 coho salmon in 1977 to 60,000 coho salmon in 1985 (Mills 1986).

    Relatively little is known about the migration routes, run timing, exploitation rates, or escapements of discrete coho salmon populations in southeast Alaska. This information is just now beginning to be collected and understood. Without such information, proper stock management cannot be accomplished.

    The Alaska Department of Fish and Game's (ADF&G) Divisions of Sport Fish and Commercial Fisheries have developed a cooperative coho salmon research program. Under this plan, Sport Fish personnel concentrate their efforts on stocks of coho salmon in and near the major urban areas (Figure 1), while Commercial Fisheries' activities focus on coho salmon in remote areas.

    The goal of this project is to acquire information needed for more precise management of southeast Alaska's coho salmon stocks. The adult coho salmon stream surveys conducted by the Division of Sport Fish in select index streams provides one of the necessary pieces of information to obtain this goal. Similar data obtained by the Division of Commercial Fisheries and companion Division of Sport Fish projects provide further information.

    The Salmon Lake project provides estimates of coho salmon adults in the escapement, and the emigrant smolt population size. Smolt from the Salmon Lake system are injected with coded-wire tags (CWT). The coded-wire tagging and subsequent recapture information provides estimates of harvest rates and the areas of harvest for this specific population. This project will document the population dynamics of coho salmon in the Salmon Lake system and will allow production estimates for other systems in the Sitka management area.

    The objectives of this study were to:

    1. Estimate the migration route, run timing, numbers caught, exploitation rate, and areas of harvest of Salmon Lake coho salmon in the various southeast Alaska fisheries.

    2. Estimate the freshwater age composition, sex composition, and mean length at age of l-ocean (.l) adult coho salmon returning to Salmon Lake in 1987.

    3. Estimate the number of coho salmon smolts emigrating from Salmon Lake between 15 April and 1 June 1987.

    4. Estimate the age composition and mean length at age of coho salmon smolts emigrating from Salmon Lake in 1987.

    2

  • Salisbury Sound

    vl \ Baranof Island KEY MAP

    Sinitsin Creek St. John Creek

    Kruzof Island

    + l-l-l

    Figure 1. Location of Salmon Lake research site and coho salmon index systems near Sitka, Alaska, 1987.

    Sitka Sound

    n N

    3

  • I

    5. Estimate the number of coho salmon juveniles greater than or equal to 85 mm fork length in Salmon Lake between 15 August and 15 September 1987.

    MATERIALS AND METHODS

    The Salmon Lake watershed was ch

Recommended

View more >