Her data were presented in a table which I have 

 incorporated into a growth curve (fig. 5). It 

 seems reasonable to consider the spiny dogfish a 

 long-lived species in view of the evidence of tagged 

 dogfish at liberty for up to 10 years. 



. KAGANOVSKAIA (19531 

 i QONHAM tf ol (1949) 



AGE IN YEARS 



Figure 5. — Two growth rates for the spiny dogfish, based 

 on interpretation of spine markings. 



Using the Russian method, Bonham et al. ( 1949) 

 examined the spines from 215 dogfish collected in 

 State of Washington waters. The fish were 34—127 

 cm. long and 1-29 years old, and although there is 

 variation in the Washington data, the trend is 

 similar to that in the Russian paper. To prepare 

 the spines for reading, Bonham (personal com- 

 munication) removed them by slicing down along 

 the bases of the spines into the back of the dogfish 

 and freeing the spines from the skin or muscle. 

 The spines were not treated; and low magnifica- 

 tion (5X) or none at all was used in actual 

 examination. 



Only about 20 percent of the spines (215 out of 

 1,100) had markings that were sufficiently dis- 

 tinct to be readable without appreciable disagree- 

 ment by different observers (Bonham, personal 

 communication). In the report (Bonham et al., 

 1949) the authors cautioned, "It must be under- 

 stood that rejection of unclear or doubtful spines 

 would probably eliminate from consideration most 

 of the old dogfish, whose spines usually are broken, 

 badly eroded, and have the annulations closely 

 crowded near the bases of the spines." 



A recent study by Holden and Meadows (1962) 

 supports the hypothesis of annual zone formation 



in dogfish spines. The authors examined the 

 spines from dogfish landed by trawlers that fished 

 the grounds around the north and west coasts of 

 Scotland. A total of 317 males (41.3-82.5 cm. 

 long) and 445 females (39.6-97.5 cm. long) were 

 examined. The ages determined were 1-19 years 

 for males and 1-21 years for females. The rate 

 of growth for both sexes was about the same up 

 to the time of sexual maturity (at an age of about 

 9 years). After the fish became mature, the fe- 

 males grew faster than the males. 



Comparisons between dogfish growth calculated 

 from spine readings or length frequencies, and 

 growth observed in tagged dogfish indicate that 

 the growth of the tagged individuals is often half, 

 or less, of the calculated values. Bonham et al. 

 (1949) report that on the basis of a study of eggs 

 and embryos, the suggested rate of growth is 7 cm. 

 in 2 years or about 3.5 cm. per year. The rate cal- 

 culated from spine readings is 3.1 cm. per year, and 

 from length frequencies 3.3 cm. per year, but from 

 tagging studies the rate is only 1.4 cm. per year. 



In the above example, the spine readings were 

 from fish 40-100 cm. long (2.5-21 years, indicated 

 age). An examination of Kaganovskaia's (1933) 

 data for fish of similar lengths and indicated ages 

 suggests a growth of 3.5 cm. per year. Temple- 

 man (1944) calculated ". . . approximately U/fc 

 cm. as the average growth per year for all mature 

 females and 1.6 cm. for the first mature year . . ." 

 However, a tagged dogfish at liberty for 10 years 

 grew only about 8.1 cm. in that time (Templeman, 

 1958), but he concludes the fish was in worse con- 

 dition when recaptured than when tagged, hence 

 the poor growth rate. Kauffman (1955) reports 

 the growth of two tagged spiny dogfish from the 

 Pacific Coast as 14 cm. after 8V2 years at liberty 

 (2.3 cm./year). A dogfish tagged in British 

 Columbia waters and at liberty almost 8 years 

 grew 5% inches (Fisheries Research Board of 

 Canada, 1952), or about 14.1 cm. (1.8 cm./year). 

 My own experience with the growth of tagged dog- 

 fish is limited to one specimen at liberty nearly 1 

 year during which time it grew only 0.7 cm. 



At the present time there is no way to resolve the 

 differences reported for the annual growth of the 

 spiny dogfish. No doubt it is a long-lived species, 

 attaining a maximum age of 25-30 years. The 

 lengthy time interval between tagging and recap- 

 ture, up to 10 years for certain individuals, is 



LIFE HISTORY OF SPINY DOGFISH 



537 



