FISHERY BULLETIN: VOL 82. NO. 2 



The sample site was 48 km SSE of Shinnecock 

 Inlet, Long Island, N.Y., at lat. 40°21'N, long. 

 72°24'W, and 53 m deep. This location contained 

 high densities and a wide size range of ocean 

 quahogs and had a low probability of being dis- 

 turbed by the fishery: criteria important for suc- 

 cess in the marking experiment (Murawski et al. 

 1982). The wide size range of ocean quahogs found 

 at and near the site included more small individu- 

 als for a study of maturity than elsewhere in the 

 Middle Atlantic Bight. 



Small quahogs ( ^ 65 mm shell length) were 

 sorted from the catch during the marking opera- 

 tion, and the soft bodies were immediately re- 

 moved from the shells for preservation in Bouin's 

 fixative; shells were saved and coded for reference 

 to corresponding tissues. Slides of the gonadal tis- 

 sues were prepared for microscopic examination 

 using standard histological techniques. The clam 

 bodies were cut dorsoventrally through the mid- 

 section, and the anterior and posterior pieces of 

 each clam were embedded to produce two sections 

 for examination. The 6 /xm thick sections were 

 stained in Harris' hematoxylin and eosin. Recog- 

 nition of gametogenic stages was based on previ- 

 ous studies of bivalve reproduction by Loosanoff 

 ( 1953 ); Ropes and Stickney ( 1965 ); Ropes ( 1968a, b; 

 1971; 1979a ); Thompson et al. ( 1980b ); Jones ( 1981 1; 

 and Mann (1982). 



The shells were processed for observation of 

 internal age/growth lines in acetate peels by 

 methods similar to those reported in Thompson et 

 al. 1 1980a, b) and reported more fully by Ropes 

 (1982) 3 . A radial section was made from the umbo 

 to ventral margin of left valves, since these contain 

 a single prominent tooth that Thompson et al. 

 ( 1980a, b) found had growth lines corresponding in 

 number to those in the valve. Proper orientation of 

 the valve for sectioning to retain the umbonal por- 

 tion and broadest tooth surface in the anterior 

 portion of the valve was a critical procedural step. 

 The sections were made on a low-speed saw and by 

 a 10.2 cm diameter by 0.03 cm thick diamond wa- 

 tering blade. The cut edges were hand polished on 

 wetable carborundum paper (240, 400, and 600 

 grits) to remove saw marks, polished to a high 

 luster on a vibrating lap machine charged with 

 aluminum oxide, then etched in a \ c /< HC1 solution 

 for one min. Peels were produced by flooding the 



;) Ropes, J. W. 1982. Procedures for preparing acetate peels 

 of embedded valves of Arctica islandica for ageing. Woods Hole 

 Lab. Ref. Doc. 82-18, 8 p. Northeast Fisheries (inter Woods 

 Hole Laboratory, National Marine Fisheries Service. NOAA, 

 Woods Hole, MA 02543 



etched surfaces with acetone and applying 0.127 

 mm thick acetate film. After a 15-min drying 

 period, the film was peeled off and sandwiched 

 between glass slides. Peel images were enlarged 

 on a microprojector to 40 x . Age/growth lines were 

 counted and the exit location of each at the exter- 

 nal edge was marked on the peel for a comparison 

 with the external bands by placing the anterior 

 valve portion on the peel image. This procedure 

 clearly demonstrated correspondence between the 

 number and location of internal lines and external 

 bands. It also delimited sequential increments be- 

 tween external bands for measurement to the 

 nearest 0.1 mm with calipers. 



Periodic age/growth phenomena in the shells of 

 ocean quahogs have been called "bands" for incre- 

 ments of darker periostracum deposits on the ex- 

 ternal shell surfaces and "lines" for those accreted 

 in the shells. The latter have been identified as 

 prismatic microstructures that demark bound- 

 aries of growth increments (Ropes et al. in press); 

 the external pigmented bands varied in intensity 

 and width (from to -2 mm). A slight concentric 

 depression often outlined the shell shape in the 

 bands and corresponded to the location of internal 

 lines. This and the method of marking the acetate 

 peel aided in measuring increments of growth. 



After completing the study of the gonadal tis- 

 sues of small ocean quahogs, it was evident that 

 the sex ratio of larger clams from the same area 

 should be examined. Therefore, squashes of 

 thawed gonadal tissues from 199 marked clams 

 57-103 mm shell length recaptured in August 1980 

 were examined microscopically at the laboratory 

 for determination of sex. 



RESULTS 



Observations of Age 



The shells and acetate peels of 137 clams were 

 examined. Bands on the external shell surfaces 

 were not equally distinct for all clams in the sam- 

 ple. The bands were widely separated for small 

 clams, but crowded together at the ventral margin 

 for large clams. A few shells had poorly defined 

 bands, but lines in the peels aided in locating 

 them. Age annuli formed during the earliest on- 

 togeny of ocean quahogs are difficult to detect on 

 the valve surface and must be carefully exposed in 

 the sectioned shell. A quahog 20.0 mm in shell 

 length had three barely detectable bands on the 

 surface of its valves; the two most recent annuli in 

 peels of the valve and hinge tooth were most obvi- 



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