PAUL and FEDER: LITTLENECK CLAM IN GALENA BAY 



a greater density of young littleneck clams per 

 unit area on the latter site. On the other hand, 

 a comparison of the average number of older 

 P. stamiuea per 0.25-m2 station along these 

 same transects reveals 55 littleneck clams per 

 station on Eater Beach and 25 per station 

 on the mud flat. 



The intertidal distribution of P. stamiuea 

 is influenced by tidal height; Figure 9 pro- 

 vides a general picture of the intertidal distri- 

 bution of two size groups of P. staminea in 

 Galena Bay. The distribution and frequency 

 of age classes 0^ through 6 for different tidal 

 heights along one transect on Eater Beach are 

 shown in Figure 10. 



The intertidal distribution of P. staminea 

 in Galena Bay in 1971 was similar to that 

 reported for pre-earthquake Kodiak Island 

 (Nybakken, 1969) and pre-earthquake Olsen 



^ The term age group refers to those individuals 

 of the setthng year class that have undergone only one 

 growing season (5 to 6 mo) before forming their first 

 winter annulus. Thus, individuals referred to as 1 yr 

 of age are actually 17 or 18 mo old and have lived 

 through two growing seasons. 



I70| 



-• Clom Length >20mm 

 -o Clam Length <20rnm 



073 055 043 027015 00-015-030-043-052-064-076 



Tidal Height (Meters) 

 2 4 18 14 9 05 00-0 5 -10 -14 -17 -2 1 -2 5 



Tidal Height (Feet) 



Figure 9. — An example of the typical intertidal distribu- 

 tion of Protothaca staminea as observed in Galena Bay. 

 Data plotted here is from Eater Beach. Clams less than 

 20 mm in length are primarily ages 0-7; those larger 

 than 20 mm in length are mainly ages 8-12. 



073m 



T 



! 



055m 



T 





3 





is 



-076m 



MM 



Number of clams 



I I I M I ! M I I 

 5/0 



iH 





D 



2 3 



Age Code 



I ^ 



Figure 10. — The horizontal distribution of Protothaca 

 staminea, age groups 0-6, grouped according to tidal 

 height. Specimens were collected on Eater Beach, Galena 

 Bay. Numbers above each plot refer to tidal height. 



Bay (Hubbard, 1971), with the upper and lower 

 extremes of this distribution occurring between 

 the tidal heights of + 0.73 and -0.76 m, respec- 

 tively. On the three study beaches the maximum 

 density for clams larger than 20 mm in length, 

 primarily individuals 8 to 12 yr of age, occurred 

 between the tidal heights of +0.43 and -0.43 m, 

 while the greatest density for smaller indi- 

 viduals occurred between -0.43 and -0.64 m 

 (Figure 9). 



The maximum depth in the sediment at 

 which P. staminea was observed in Galena Bay 

 was 8 cm. Clams of ages through 7 con- 

 sistently occurred in the upper 2 cm with most 

 individuals of all age groups within 4 cm of the 

 surface. Clams as large as 10 mm in length 

 were often clearly visible between or just 

 under small rocks. There was no apparent 

 difference in vertical distribution of P. staminea 

 on the gravel beaches or the mud flat. 



DISCUSSION 



Aging 



Aging by the annular method is a time- 

 consuming process best accomplished with a 



673 



