HERRING SPAWNING SURVEYS IN SOUTHEASTERN ALASKA 



by 



Bernard Einar Skud 

 U. S. Fish and Wildlife Service 

 Galveston, Texas 



ABSTRACT 



Aerial surveys to observe milt 

 herring in Southeastern Alaska waters ho 

 assessing the extent of spawn deposition 

 altitudes of 500 to 700 feet and at crui 

 mileage of beach utilized for spawning i 

 of navigation charts. The surveys have 

 80 previously unreported spawning beache 

 preliminary flights have also added valu 

 of spawning and the physical characteris 



clouds produced by spawning 

 Id promise as a method for 



Flights are conducted at 

 sing speeds of 120 knots. The 

 s recorded on reduced prints 

 resulted in the discovery of 

 s. Observations during these 

 able information on the time 

 tics of the beaches. 



INTRODUCTION 



Biological studies of Pacific herring, 

 Clupea harengus pallasi , in Alaska have 

 provided valuable information regarding the 

 life history and behavior of this species 

 (Rounsefell, 1930), but violent fluctua- 

 tions in catches have not been adequately 

 explained. Catch statistics suggest that 

 changes in abundance are responsible for 

 the fluctuations, but other evidence sug- 

 gests that availability of herring to the 

 fishing gear may vary considerably. 



To resolve this difference, abundance 

 estimates based on other than catch-effort 

 data were considered. Canadian biologists 

 had developed one such method by appraising 

 egg deposition at time of spawning. Ground 

 surveys measuring egg density and length 

 and width of areas utilized for spawning 

 afford a measure of total mileage of deposi- 

 tion, which is used as a comparative index 

 of abundance (Taylor, 1955). In Southeast- 

 ern Alaska spawning areas are so widespread 

 that intensive ground surveys to assess 

 spawn deposition are not feasible. There- 

 fore, a method of aerial assessment was 

 developed through the collaboration of L. N. 



Kolloen 1/ f G. W. Hilsinger, and C. H. 

 Elling of the Bureau of Commercial Fisher- 

 ies, and J. C. Stevenson of the Fisheries 

 Research Board of Canada. In the spring of 

 1953 a systematic aerial survey was made in 

 British Columbia and Southeastern Alaska. 

 The success of this initial survey encour- 

 aged further investigation, and somewhat 

 more refined surveys have continued in 

 Southeastern Alaska. 



The prime objective of aerial surveys 

 is to determine the mileage of beach used 

 for spawning in a given area. The extent 

 of spawn deposition is assumed to indicate 

 size of spawning population. In addition 

 to comparison of annual changes in actual 

 mileage utilized, changes in areas used for 

 spawning can be studied and may help to 

 determine environmental requirements for 



1/ The author especially wishes to acknowl- 

 edge the late L. N. Kolloen who initi- 

 ated this research and who unfortunately 

 died in a plane crash while on official 

 business in Southeastern Alaska on Sep- 

 tember 1, 1954. 



