VARIABILITY IN PINK SALMON ESCAPEMENTS 

 ESTIMATED FROM SURVEYS ON FOOT 



by 



William L. Sheridan 



Senior Fisheries Biologist 



Fisheries Research Institute 



University of Washington 



Seattle, Washington 



ABSTRACT 



Spawning pink salmon were enunnerated in five study streanns in the Hollis 

 area of Southeastern Alaska. One stream was logged, two were being logged, 

 and two were unlogged. Because enumeration required the ground survey as 

 well as other methods, tests were made to assess variability in estimates of 

 pink salmon abundance from surveys on foot between different observers and between 

 successive counts by the same observer. Variability was lower when observers 

 counted spawning salmon in well-defined riffle areas than when they counted in both 

 pools and riffles. A method is proposed for obtaining more reliable indices of 

 abundance from routine foot surveys. 



INTRODUCTION 



Because of increased logging in South- 

 eastern Alaska, a need arose to evaluate 

 the effects of logging on salmon. To satisfy 

 this need the Alaska Forest Research Center 

 began a study of physical changes in logged 

 and unlogged streams in 1949, and the Fish- 

 eries Research Institute started biological in- 

 vestigations in 1956 under a contract awarded 

 by the U.S. Fish and Wildlife Service utilizing 

 Saltonstall-Kennedy funds. 



The Hollis area of Kasaan Bay in South- 

 eastern Alaska was the principal location for 

 the Institute's research (fig. 1). Study streams 

 were Harris River and Twelvemile Creek, 

 which are being logged; Maybeso Creek, which 

 had been logged; and Indian and Old Tom 

 Creeks, which are unlogged and were used 

 as control streams. 



One of the factors studied was the size of 

 yearly escapements of spawning salmon. This 

 information was needed to define levels and 

 patterns of escapements before and after 

 logging so that postlogging changes might be 

 detected. The abundance of spawners was 

 assessed by various methods, such as sur- 

 veys from the air and on foot, counting from 

 towers, and nnark and recovery techniques. 



Surveys on foot have been used extensively 

 to determine abundance of salmon in streams 



in Alaska and other West Coast States for 

 many years. Although it has been recognized 

 that variability existed in estimates made on 

 such surveys, seldom has this variability 

 been evaluated quantitatively. 



Since we were using foot surveys as one of 

 our methods, we tested variability in esti- 

 mates of pink salmon (Oncorhynchus gorbuscha) 

 made on foot surveys by different observers 

 under different conditions. 



GENERAL DESCRIPTION OF STREAMS 



Streamflow in all five of the streams studied 

 is subject to wide and rapid variation because 

 of precipitation, which is usually heavy in 

 October and November. In all but Old Tom 

 Creek most pink salmon spawn in intertidal 

 zones, and chum (0. keta) and coho (0. kisutch) 

 salmon usually spawn above tidal influence. 



Harris River, the largest of the five streams 

 is 40 to 150 feet wide and has a watershed of 

 32 square miles. About 8 miles of the stream 

 is used by salmon. Average gradient for the 

 first 3.3 miles is 0.30 percent (James, 1956). 



Indian Creek, 15 to 50 feet wide, is con- 

 fluent with the Harris River at approximately 

 the 12-foot tide level. It has a watershed of 9 

 square miles and an average gradient of 1.0 

 percent for 1.8 miles (James, 1956). Only 



Note. --The author is presently with the Alaska Department of Fish and Game, Kodiak. 



