Ag. Hirst et Rs. Lampitt, TOWARDS A GLOBAL-MODEL OF IN-SITU WEIGHT-SPECIFIC GROWTH IN MARINE PLANKTONIC COPEPODS, Marine Biology, 132(2), 1998, pp. 247-257
The dependency of in situ weight-specific fecundity of adult females l
as egg production) and growth of juveniles las somatic production) upo
n individual body weight in marine planktonic copepods was examined. A
compilation was made of results where wild-caught individuals were in
cubated in natural seawater (often pre-screened to remove large organi
sms), at near in situ temperatures, over short periods of the order of
24 h. The results demonstrate that for the adult broadcast-spawning g
roup weight-specific fecundity rates are dependent upon body weight, b
ut independent of temperature. We postulate this may be the result of
global patterns in available phytoplankton. Weight-specific growth rat
es are dependent upon individual temperature and body weight in juveni
le broadcast-spawners, with rates declining as body weight increases.
Sac-spawners have growth/fecundity rates that are independent of body
weight in adults, juveniles, and both combined, but which ape temperat
ure-dependent. Globally applicable equations are derived which may be
used to predict growth and production of marine copepods using easily
quantifiable parameters, namely size-distributed biomass and temperatu
re. Some of the variability in growth which remained unaccounted for i
s the result of variations in food quantity and quality in the natural
environment. Comparisons of the rates compiled here over the temperat
ure range 10 to 20 degrees C with previously compiled food-saturated r
ates over the same temperature interval, revealed that in situ rates a
re typically suboptimal. Adults appear to be more food-limited than ju
veniles, adult rates in situ being 32 and 40% of those under food satu
ration in broadcasters and sac-spawners, respectively, while juvenile
in situ rates are on average similar to 70% of those at food saturatio
n in both broadcasters and sac-spawners.