Armstrong et al.: Age, growth, and reproduction of Lophius americanus 



223 



present. Small amount of spermatozoa 

 may be present in lumen. 



Developing Few primary and/or sec- 

 ondary spermatogonia visible; primary 

 and/or secondary spermatocytes and 

 spermatids present; spermatozoa pres- 

 ent in lumen. 



Ripe Few or no primary and/or second- 

 ary spermatogonia and spermatocytes 

 visible; lumen densely packed with 

 spermatozoa. 



Spent No primary and/or secondary 

 spermatogonia or spermatocytes vis- 

 ible; no spermatids present; few sper- 

 matozoa remaining in lumen. 



In all cases, maturity classifications based 



on histological examination agreed with 



visual classifications applied in the field. 



Age and growth 



Growth marks on the vertebrae of L. 

 americanus formed distinct steps on the 

 centrum surface. Under magnification in 

 reflected light, the surface texture of the 

 step appeared coarser than the rest of the 

 centrum. A narrow, dark, translucent 

 band was on the outer side of each step. 

 The step and the narrow band formed a 

 continuous ring around the centrum and 

 was considered to be the annulus. Broad- 

 er, lighter opaque bands with relatively 

 uniform surface texture were between 

 the annuli. A broad, opaque band com- 

 bined with a narrow, translucent band 

 and step was interpreted as one year's 

 growth. While these features were visible 

 on fresh vertebrae, they became much 

 more distinct when the vertebrae were 

 heated. The step became deeper and the narrow, 

 translucent band became opaque and dark relative to 

 the rest of the centrum (Fig. 7). 



Annuli were counted on vertebrae from 635 goose- 

 fish. In 200 (31.5%) cases, the first and second reading 

 did not agree and a third reading was done. In most 

 cases, the second reading differed by only one. In 25 

 (3.9%) cases, the third reading was different from both 

 the first and second; these vertebrae were considered 

 unreadable and discarded from the analysis. 



Differences between readings were due to the pres- 

 ence of false annuli or because the true annuli were not 

 distinct. False annuli appeared as dark bands but were 

 not associated with a step. Another extraneous mark 

 that sometimes occurred was a depression that formed 

 a continuous ring on the centrum but was not a defin- 



2 3 4 



Figure 7 



Vertebra from a 4-year-old Lophius americanus, after heating. Annuli are 

 indicated. 



itive step. This feature has also been found on black 

 bullhead (Lewis 1949) and northern puffer (Lyczkowski 

 1971) vertebrae. 



Annuli counts determined by the independent reader 

 agreed with the original counts in 40 (80%) cases. In 

 no case did the counts differ by more than one. 



Van Oosten (1929) established the following criteria 

 that must be met before checkmarks on scales or bones 

 can be considered annuli: (1) Scales or bones must re- 

 main constant in number and identity throughout the 

 life of the fish; (2) growth of the scale or bone must 

 be proportional to the overall growth of the fish; (8) 

 growth checkmarks must be formed at approximately 

 the same time each year; and (4) back-calculated lengths 

 should agree with empirical lengths. The first criteri- 

 on is fulfilled by using vertebrae as the aging tool. 



