Behavior of Schools of Age Fish 

 at Outlet of Coville Lake 



Although the behavior of the juvenile sockeye 

 salmon in the interlake migrations in the Naknek sys- 

 tem were not studied in detail, incidental observations 

 of the fish involved are presented here because the 

 phenomenon of large-scale interlake migrations of 

 these presmolt fish is unique. 



Interlake migrants first appeared in the shoal waters 

 (less than 3 m) at the outlet of Coville Lake (i.e., the 

 origin of Coville River). Here the basin of the lake 

 becomes so narrow and shallow that the current is 

 readily visible. In mid-June 1962, groups of several 

 hundred age fish were frequently seen moving down- 

 stream about the same speed as the current and appar- 

 ently feeding at or near the surface — the fish were 

 breaking the surface so frequently that the movement 

 of the groups could be followed by an observer on 

 shore. These groups were not concentrated along the 

 shore or over the deepest water, but were seen at one 

 time or another over the entire outlet area. Individual 

 fish were most often facing downstream. When the 

 water depth decreased to about 1 m and the current 

 velocity had noticeably increased (and possibly when 

 the fry first made visual contact with the bottom — i.e., 

 they first "realized" they were moving downstream), 

 the fry abruptly changed their orientation. 



The visual cue as to direction or perhaps simply the 

 existence of movement seemed to halt the downstream 

 migration. All the fish of a group would suddenly turn, 

 face upstream, and move laterally across the current 

 until they were in water about 15 to 20 cm deep. They 

 then moved upstream in a narrow band until they 

 reached slower water and disappeared into deeper 

 water — that is, they appeared to return to the lake. 

 From mid-June to mid-July, during daylight, schools 

 of age sockeye salmon were frequently seen feeding 

 in shallow (1 to 2 m) water along the lake shores and 

 islands over most of Coville Lake. 



About mid-July the behavior of the age sockeye 

 salmon at the outlet of Coville Lake had noticeably 

 changed and the schools now appeared to be actively 

 migrating. They were still close to the surface, but 

 moved faster than the current (see footnote 10) and no 

 longer changed orientation when the water became 

 shoaled to about 1 m deep or moved toward shore 

 when the currently velocity increased. The orientation 

 of individuals and ultimately the entire school was 

 suddenly reversed (Hartman, Heard, and Drucker, 

 1967) as the school passed over the edge of the shoal 

 water into deeper water of the stream proper. This 

 orientation was soon reversed and the fish again 

 moved actively downstream into Grosvenor Lake and 

 deeper water. 



On one occasion after the summer outmigration of 

 age sockeye salmon was in progress, a reversal of the 

 migration was noted. At 0900 on 19 August 1962 fish 

 were seen moving upstream near the outlet of Coville 

 Lake. The characteristics of the movement, i.e.. 



speed, school compactness, size, etc., were the same 

 as for the downstream movement. In the afternoon of 

 the same day the migration had resumed its normal 

 (for that time of the summer) direction. This was the 

 only reversal of the direction of migration observed 

 here, but reversed migration has been commonly ob- 

 served in smolts in the Babine system (Groot, 1965). 



EARLY REARING AREAS OF 



SOCKEYE SALMON FRY FROM 



GROSVENOR RIVER AND HARDSCRABBLE 



CREEK 



Some stocks of sockeye salmon spawn in rivers that 

 connect lakes or connect a lake to the ocean; their 

 progeny may migrate either upstream (Andrew and 

 Geen, 1960) or downstream (most commonly) to reach 

 freshwater pelagic rearing areas. A choice of migration 

 direction is possible in three major connecting rivers in 

 the Naknek system — Brooks, Naknek. and Gros- 

 venor (Fig. 1). Fry from Brooks River move down- 

 stream into South Bay (Merrell, 1964); we assume fry 

 from Naknek River move upstream into Naknek Lake 

 rather than going directly to the ocean because adults 

 of freshwater-age are rare in the escapement. The 

 immediate destination of fry migrating from Gros- 

 venor River was unknown until 1962. 



In the spring of 1962 I studied the fry originating in 

 Grosvenor River and Hardscrabble Creek to deter- 

 mine the basin to which they first migrated. 

 Hardscrabble Creek was studied because it is close to 

 Grosvenor River and the work in the two streams 

 could be done from a single camp. Moreover, I felt 

 that information on the timing and other characteris- 

 tics of the outmigration from Hardscrabble Creek 

 might corroborate the work in Grosvenor River. Ul- 

 timately the two streams were found to be closely re- 

 lated. This work was exploratory and the results are 

 qualitative. Descriptions of the upstream migration of 

 fry in other areas indicated the upstream migration is 

 obvious — for example, Johnson ( 1956) described these 

 fry as "... a massed living band moving 

 upstream. . ."; McCart (1967) stated ". . . (upstream) 

 migrants moved in tightly knit schools at the surface, 

 close to shore, often in water only a few centimeters 

 deep." 



In Grosvenor River small fyke nets were fished 

 along each side (east and west shores) of the river 

 (usually with one wing extended to shore) near Gros- 

 venor Lake where the river first becomes less than 50 

 m wide. Initially, nets were fished to sample both the 

 upstream and downstream migrations, but most sam- 

 pling was done to catch downstream migrants. In 

 Hardscrabble Creek a fyke net was fished in fast water 

 about 0.6 m deep on the first gravelly riffle above 

 Grosvenor Lake (about 200 m from the lake at low 

 lake water level). One fyke net set was made in the 

 Savonoski River to learn if fry were produced in that 

 system above its confluence with Grosvenor River. 



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