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



219 



and sandbar sharks Carcharinus plumbeus. These 

 halves were then heated in an oven at 200 °C for about 

 3 hours. Larger vertebra required one-half to 1 hour 

 further heating. This heating made the alternating 

 opaque and translucent bands of the vertebral centra 

 more distinct. 



Annuli were counted on the posterior face of the 

 centrum. This was generally more concave than the 

 anterior face, thus allowing greater separation of the 

 rings. Each vertebra was read twice at an interval of 

 at least one month to insure independence of readings. 

 If they disagreed, a third reading was done. Agreement 

 between any two readings was considered as the true 

 count. If all three readings differed, the vertebra was 

 considered unreadable and not used in the analysis. A 

 random sample of fifty vertebrae was selected for 

 verification by an independent reader. 



Measurements of the vertebral rings and radius were 

 made from the apex of the posterior and anterior faces 

 of the centrum along an oblique line that followed the 

 midline of the posterior centrum. All measurements 

 and counts were made with a binocular dissecting 

 microscope equipped with an ocular micrometer at 10 x 

 magnification using reflected light. 



Regression analyses of vertebral radius on total 

 length and weight on total length were calculated by 

 the method of least squares. Length-at-age was back- 

 calculated by the Lee method (Lagler 1956): 



L' = C + S' (L-C)/S 



where L' = total length of the fish at time of annulus 

 formation, 

 L = total length of fish at time of capture, 

 S' = measurement to the annulus. 



S = vertebral radius at time of capture, 

 C = correction factor; y-axis intercept of the 



regression of total length on vertebral 



radius. 



Computation of the von Bertalanffy growth equations 

 followed Ricker (1975). 



Results 



Reproduction 



External sexual dimorphism was not apparent in L. 

 americanus. Caruso (1975) noted sexual differences in 

 nostril morphology, but this was not a useable field 

 character. Sex was easily determined in mature in- 

 dividuals by examination of the gonads, which are 

 markedly different in appearance. Gonads from small 

 juveniles (<160-180mmTL) were indistinguishable 

 macroscopically. Both testes and ovaries from these 

 juveniles were small, translucent, and string-like. 



In females larger than ~180mmTL the ovaries were 

 long, wide, and ribbon-like. They were greatly coiled 

 in the abdomen and supported by an extensive meso- 

 varium. The two ovaries were fused at their posterior 

 ends, forming a single, confluent organ. Dimensions 

 of the ovary varied greatly depending on the stage of 

 sexual development. 



The testes were solid, sausage-like organs. A groove 

 was present along the medial aspect of each testis. This 

 groove contained blood vessels and served as the site 

 of attachment for mesentary connective tissue. 



A physical description of the gonads in the five 

 developmental stages (immature, resting, developing, 

 ripe, and spent) is presented in Table 1. 



Stage 



Table 1 



Description of gonads at five maturity stages assigned to Lophius americanus, based on macroscopic examination. 

 Description 



Ovaries 



Immature 

 Resting 

 Developing 

 Ripe 



Spent 



Testes 



Immature 

 Resting 

 Developing 

 Ripe 



Spent 



Grayish-pink, relatively small, ribbon-like, appear almost empty, no vascularization. 



Orangish-pink, contain material but no ova visible, larger than immature, little vascularization. 



Pink, ova discernible by eye, abdominal cavity slightly bulging, highly vascular. 



Straw-colored to almost clear as ovary approaches spawning, distinct ova present, abdominal cavity greatly bulging, 



highly vascular. 

 Gray, extremely flaccid, appear almost empty, atretic ova appear as black or white dots, moderately vascular. 



White to tan, similar in shape as mature testes but very small, medial groove less distinct. 



White to tan, much larger than immature, medial groove distinct, small amount of milt sometimes present when dissected. 



Blotchy cream to tan, moderate to large amount of milt produced when dissected, very firm in texture. 



Blotchy cream to tan with areas of pink, extremely firm in texture, milt produced from genital pore when pressure 



is applied on abdomen, copious amounts present when dissected. 

 Grayish-tan, edges appear translucent, extremely flaccid, small amount of milt sometimes present when dissected. 



