MOSHER: SCALE FEATURES OF SOCKEYE SALMON 



appearance of the Bristol Bay scales. An area 

 of wider spaced circuli may often be found at 

 any position in the first ocean zone, but usually 

 it is near the middle of the zone or the following 

 winter zone. Plus growth is sometimes pre- 

 sent. 



Scales of many fish from Lake Blizhnee are 

 distinctive. They have a very small freshwater 

 zone with few circuli in each year's growth. 

 Circuli are irregular and the zone is difficult to 

 interpret because of the broken and closely 

 spaced circuli. The first ocean zone is similar 

 to that of the other Asian fish of the Ozernaya, 

 Bolshaya, and Kamchatka Rivers. 



Scales from Lake Dalnee fish have large to 

 very large freshwater zones. The freshwater 

 growth makes up a larger portion of these scales 

 than those from any other locality over the 

 range of the species. The circuli of both the 

 freshwater and ocean zones are usually regular 

 and well marked. Sometimes there are fewer 

 circuli in the first ocean zone than on scales from 

 other Asian areas. Scales of fish of this fresh- 

 water age can be easily identified as being from 

 Lake Dalnee when they are encountered in sam- 

 ples of fish taken from the North Pacific and 

 Bering Sea because of the unusually large fresh- 

 water zone (Mosher et al., 1961). 



AGE 2., NORTH AMERICA 

 Bristol Bay (Plate 11; Tables 6 and 7) 



The number of fish of this freshwater age 

 varies from year to year in the diff'erent rivers, 

 but few are ever found in the Nushagak and 

 Togiak areas. In some years of large production 

 in Bristol Bay most of the fish are of age group 

 2.2. 



As was true of age 1. fish from Bristol Bay 

 (Plate 4), most scales from these fish, including 

 Bear River, do not differ much between streams. 

 Freshwater and ocean circuli are regular and 

 clear cut. The freshwater zone is moderately 

 large to large, and well marked; the circuli are 

 generally well separated, and plus growth is 

 often present. There are relatively few, well- 

 separated circuli in the first ocean zone. In most 

 cases the winter marks are distinct. Usually the 

 widest circuli are near the freshwater zone. Be- 



cause the first 5 or 10 circuli of each ocean growth 

 zone usually are widely separated and the winter 

 marks are well marked and compact, the scales 

 have a more open appearance than scales of fish 

 from other geographical areas. Taken as a 

 whole, scales from Bristol Bay fish are easier 

 to interpret than sockeye scales from other geo- 

 graphical areas. 



Aleutian Islands to Cook Inlet 

 (Plate 12; Tables 6 and 7) 



Fish of age 2. are usually abundant in this 

 area. Diverse types are present. Aleutian 

 Islands (typified by Attn Island) and Chignik 

 River fish have a small freshwater zone with ir- 

 regular circuli much like the Asian sockeye salm- 

 on. Fish from Unalaska Island (not pictured). 

 Red River (Kodiak Island) , and Cook Inlet have 

 moderate-sized freshwater zones with more ir- 

 regular and broken circuli on their scales than 

 Bristol Bay fish, but fewer than the Asian fish. 

 Adak Island and Karluk River (Kodiak Island) 

 fish have large, usually clear-cut, freshwater 

 zones on their scales, also with more irregular 

 circuli than those from Bristol Bay, 



As is true with the age 1. fish, Adak Island 

 sockeye salmon have the fewest circuli in the 

 first ocean zone of their scales; those from Una- 

 laska Island have about the same distribution 

 of circuli as the Bristol Bay fish ; and those from 

 Attu Island and from the Alaska Peninsula to 

 Cook Inlet have somewhat more circuli than fish 

 from Bristol Bay. The circuli in the first ocean 

 zone are generally closer together than on scales 

 from Bristol Bay fish. The area of widest circuli, 

 if present, may occur at any position within the 

 growth zone, but it is often near the following 

 winter ring, such as occurs with many Asian 

 fish. Many of the scales from this area, espe- 

 cially from the Aleutian Islands and Chignik, 

 are difficult to interpret with confidence. 



Copper River to Columbia River 

 (Plate 13; Tables 6 and 7) 



In this large area relatively few age 2. sockeye 

 salmon are produced. In fact only in some years 

 in the Nass River are there substantial numbers. 



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