tured during the collection trip on 9 October, so 

 that the total estimated population of coho salmon 

 in the stream was 24. 



During electrofishing, particular note was 

 taken of the kind of habitat in which coho, Atlantic 

 salmon, and brook trout were captured. Coho salm- 

 on were found where there was immediate or 

 nearby overhead cover in the form of overhanging 

 banks, tree roots, or fallen trees or brush, and 

 where the water current was slow ( <30 cm/s). This 

 kind of habitat was also frequently occupied by 

 brook trout. On at least one occasion, a brook trout 

 and coho salmon were captured together. Atlantic 

 salmon were scarce above the lowermost steep sec- 

 tion of the stream. However, in October and 

 November three or four Atlantic salmon were cap- 

 tured in slow water where they had never been 

 seen in summer (Symons and Harding 1974). 

 These observations suggested that summer 

 habitat requirements of coho salmon were more 

 similar to those of brook trout than of Atlantic 

 salmon, although the latter may utilize brook 

 trout-coho salmon habitat in winter. 



All captured coho salmon were retained and 

 taken to the laboratory for measuring and weigh- 

 ing. The average fork length of all coho salmon 

 captured was 89 mm, ranging from 75 to 100 mm. 

 There was no statistical difference between aver- 

 age lengths in October (89 mm) and in November 

 (91 mm). Examination of scales revealed that 

 these coho salmon were underyearlings. They 

 were considerably larger than underyearling At- 

 lantic salmon (60-70 mm fork length) and under- 

 yearling brook trout (40-60 mm) captured at the 

 same time. The coho salmon were retained for use 

 in laboratory experiments through the winter, 

 and the 1 0- 1 5 that survived were returned to Frost 

 Fish Creek the following April. 



To investigate whether coho salmon might be 

 present elsewhere, spot checks were made in 17 

 nearby locations (Figure 2) between 28 October 

 and 17 November. Spot checks consisted of 10-35 

 min of electrofishing with most effort being ex- 

 pended in parts of streams having habitat similar 

 to that in which coho salmon were caught in Frost 

 Fish Creek. No coho salmon were found at any of 

 these sites. Brook trout were caught in all 

 streams, and Atlantic salmon were caught in 

 streams where they were known to occur. Brown 

 trout, Salnjo trutta, were caught in Frost Fish 

 Creek (2 individuals), Burns Brook ( 1 ), and Sorrel 

 Ridge Brook (1), all tributaries to the Digdeguash 

 River. Brown trout were introduced to the Dig- 



deguash as early as 1921 (MacCrimmon and Mar- 

 shall 1968), and they continue to exist there in 

 small numbers. 



In sum, an estimated population of 24 under- 

 yearling coho salmon was found in Frost Fish 

 Creek in fall 1976. No coho were discovered in 

 neighboring streams during a cursory search. Al- 

 though adult coho salmon are known to spawn in 

 small, gravelly coastal streams (Scott and 

 Crossman 1973), spawning may not have occurred 

 in the creek. Atlantic salmon apparently do not 

 spawn there despite the presence of young which 

 are thought to arrive from the main Digdeguash 

 River, having descended the falls into the estuary 

 and then reentering the nearest available fresh- 

 water. The young coho salmon may have arrived 

 by the same route. Regardless of the exact location 

 in which coho salmon spawned, should they estab- 

 lish a run in the river system, it would probably be 

 revealed by continued sampling of fish in the 

 creek. 



Acknowledgments 



Constructive criticisms of an earlier draft of the 

 manuscript were made by J. W. Saunders and R. L. 

 Saunders, whom we thank. 



Literature Cited 

 MacCrimmon, H. R., and T. C. Marshall. 



1968. World distribution of brown trout, Sa/mo^rw«a. J. 

 Fish. Res. Board Can. 25:2527-2548. 



Scott, W. B., and E. J. Crossman. 



1973. Freshwater fishes of Canada. Fish. Res. Board 

 Can., Bull. 184, 966 p. 



SEBER, G. A. F., AND E. D. LE CREN. 



1967. Estimating population parameters from catches 

 large relative to the population. J. Anim. Ecol. 36:631- 

 643. 



Symons, p. E. K., and G. D. Harding. 



1974. Biomass changes of stream fishes after forest spray- 

 ing with the insecticide fenitrothion. Fish. Res. Board 

 Can., Tech. Rep. 432, 47 p. + append. 



PHILIP E. K. Symons 



Department of Fisheries and Environment 

 Fisheries and Marine Service 

 Biological Station. St. Andrews, N.B. 

 Present address: Pacific Biological Station 

 Nanaimo, B.C. V9R 5K6 



James D. Martin 



Department of Fisheries and Environment 



Fisheries and Marine Service 



Biological Station. St. Andrews, N.B. EOG 2X0 



489 



