Radtke and Hourigan: Age and growth of Nototheniops nudifrons 



569 



Table 4 



Parameter estimates derived from the Von Bertalanffy growth equation (L^ constrained to 160 mm 

 SL), natural mortality rates, and associated parameters for Nototheniops nudifroiis collected from 

 the Antarctic Peninsula. 



Parameter 



SL vs. age in days 



SL vs. age in years 



Estimate 



Confidence limits 



Estimate 



Confidence limits 



K 



K 



From otoliths (A^ = 32) 



0.0005 0.00049-0.00061 0.200 



2.20 -158.10-162.50 0.006 



From predicted ages (N = 194) 



0.00048 0.00047-0.00050 0.175 



-40.848 -94.681-12.986 0.112 



0.000-0.223 

 -0.434-0.445 



0.172-0.183 

 -0.259-0.036 



Lr 



k 

 Z 



Mortality estimates (Beverton and Holt 1956) 



All Male Female 



101 91 101 



113.1 106.6 112.5 



0.175 0.175 0.175 



0.678 0.599 0.73 



From estimated ages where the mortality rate Z is the slope of the log-survivorship curve (Ricker 1975) 



Z 0.894 0.807 1.26 



sampling caught significantly more females than males 

 (x^, p<0.05), and the modal size of males was smaller. 

 This might mean that there are fewer large males in 

 this population. Alternatively, larger males may be less 

 subject to capture in spring, perhaps because of dif- 

 ferent habitat preferences of nesting males. This would 

 skew mortality estimates upwards. 



The life history of A'^. nudifrons is characterized by 

 slow growth and a relatively long life for a small fish. 

 Age at sexual maturity is late (4-5 years), and fecun- 

 dity is low (Hourigan and Radtke 1989). Eggs take 

 several months to hatch, followed by a pelagic larval 

 stage of several months duration (Kellermann 1986, 

 Hourigan and Radtke 1989). It has become clear that 

 these life-history traits are the norm for Antarctic 

 fishes (Daniels 1983, Kock et al. 1985). They combine 

 to produce species that are vulnerable to overfishing 

 and that recover slowly when stocks are depleted. In- 

 deed, catches of both Notothenia rossii and A^. gib- 

 berifrons on the shelves of certain islands of the Scotia 

 Sea decreased drastically after several years of fishing 

 (Kock et al. 1985). The methods used in the present 

 study may provide more accurate estimates of the ages 

 of Antarctic fishes, and facilitate management of Ant- 

 arctic fisheries. 



Acknowledgments 



We would like to thank the staff of Palmer Station, 

 Antarctica, in particular the winter 1985 scientists and 

 support personnel, without whose assistance this re- 

 search would not have been possible. J. Archie, J. Bell, 

 S. Folsom and T. Telecky provided valuable assistance. 

 Editorial assistance was given by P. Lenz and B. Tilley. 

 The manuscript has benefited from the comments of 

 A. Kellermann, P. Lenz, S. Ralston, and two anony- 

 mous reviewers. This research was supported by NSF 

 Grants OCE 84-15968, OCE 88-00686, DPP 85-21017, 

 and DPP 88-16521. 



Citations 



Beverton. R.J.H., and S.J. Holt 



1956 A review of methods for estimating mortality rates in 

 fish populations, with special reference to source of bias in catch 

 sampling. Rapp. P.-V. R^un. Cons. Perm. Int. Explor. Mer 

 140:67-83. 

 Boehlert, G.W. 



1985 Using objective criteria and multiple regression models 

 for age determination in fishes. Fish. Bull.. U.S. 28:103-117. 

 Burchett, M.S., A. DeVries, and A.J. Briggs 



1984 Age determination and growth oi Di^sostwkvs mawsoni 

 (Norman, 1937) (Pisces, Nototheniidae) from McMurdo Sound 

 (Antarctica). Cybium 8:27-31. 



