In New Zealand we have several commercial fisheries that exploit fish species
that live a relatively great depths. The most notable of these species is
the orange roughy (Hoplostethus atlanticus) which is found at depths of 800
to 1500 meters. Because of the importance of population dynamics in
regulating commercial fisheries we have expended considerable effort on
determining the ages of these fish. We have 2 major pieces of evidence that
indicate that they are extremely slow growing and live to great ages. We
were able to follow the growth of very young fish by returning to the same
geographical location over several years and capturing individuals of the
same cohort. This study indicated that fish that were 1,2, and 3 years of
age averaged 3.1, 5.6 and 7.4 cm in length. Additional evidence for great
age was obtained from the determination of Pb210/Ra226 activity ratios in
calcified structures (aragonitic otoliths). These data suggested maximum
ages on the order of 200 years! We are repeating the radiometric ageing
work at another laboratory and it looks as if the results will corroborate
the earlier findings.
Further research indicates that first reproduction occurs at a mean age of
24 years. The exploited populations have mean lengths of approximately 32 cm
and weights of about 1 kg. Maximum length is less than 50 cm. All these
factors have tremondous implications regarding exploitation of the population,
life-history, and physiology. My interests are in the life-history and the
physiology of these slow growing deepwater species; however, I would like
to put the feature of extreme longevity into context with other groups in
an attempt to determine common features. Size appears to have little to do
with it since these are not large fish. They do live in a relatively dark
and cold (< 5 degrees C) environment. Also, I have estimated their mean
metabolic rate/oxygen consumption rate (VO2) to be on the order of
2.5 ul O2/g/h via a model based on oxygen and carbon stable isotope ratios
in calcified tissues.
Any information regarding long-lived animals and possible unifying
characteristics would be of interest. This could relate to physiology or
life-histories. Further discussion on age-related changes in physiology,
both qualitative and quantitative, would be valuable. For example, age
related increases in quantities of lipofuscin in neural tissue.
John Kalish Email: jmk at frc.maf.govt.nz
MAF Marine Research Tel: 64-4-386-1029
P.O. Box 297 FAX: 64-4-386-3179
Wellington
New Zealand
