Limnol. Oceanogr., 44(2), 1999, 382–392

Copepod growth rates were estimated from shipboard measurements of egg production of adult female Calanus agulhensis, Calanoides carinatus, Nannocalanus minor, and Centropages brachiatus and molting rates of juvenile stages (N6–C5) of C. agulhensis. Data were obtained during austral spring and summer of 1989–1995 in the southern Benguela upwelling system. While maximum growth rates showed less than a threefold decline over the body-size range examined (525–2,763-mm total length), probably owing to allometric considerations, mean growth rate decreased by one order of magnitude, suggesting limitation of growth rate by an environmental factor. Most of this decline in mean growth rate was attributable to food limitation of large copepods. Frequency distributions of growth rate under low food densities were severely skewed toward slow growth rate for large copepods, whereas they were more symmetric for smaller copepods. In contrast, at high food concentrations, the frequency distributions had a high degree of symmetry for all copepods. These frequency distributions were interpreted in terms of a probabilistic model describing the encounter rate of copepods with suitably sized food particles. The effect of food limitation on growth rate was evaluated by regressing the coefficient of variation of growth rate against body size. A strong positive relationship was found (r2 5 0.94, P , 0.001), indicating that small copepods were always growing well, whereas the growth rate of large copepods was more variable. It is suggested that this difference is a consequence of the ability of small copepods to consume small particles, which are present at a relatively constant background density. The two main factors controlling growth of copepods are temperature and food. The influence of temperature on growth rates in the wild has been well documented, especially in temperate seas (see McLaren et al. 1989 and references therein). Huntley and Lopez (1992) concluded that copepods grow at maximum rates in the sea, with an exponential increase in growth rate with temperature over a wide range of habitats. In contrast, growth of copepods has been found to be more related to food rather than temperature in a variety of aquatic habitats, including freshwater systems (Hart 1991; Ban 1994), tropical seas (McKinnon and Thorrold 1993; Webber and Roff 1995), some temperate coastal regions (Bautista et al. 1994; Pond et al. 1996), and in an upwelling system (Peterson and Hutchings 1995; Richardson and Verheye 1998). In the latter system, the southern Benguela, the lack of dependence of growth on temperature is attributable to slower growth at warm (18–228C) temperatures (Richardson and Verheye 1998), a consequence of very 1 Postal and correspondence address: Oceanography Department, University of Cape Town, Rondebosch 7701, Cape Town, South Africa.