Energetics of growth and reproduction in cockles (Cerastoderma edule): Seasonal and age-dependent variations

Abstract

Abstract. Seasonal patterns of growth were compared interannually between 1983 and 1985 for different ageclasses of an intertidal population of cockles, Cerastoderma edule L., in the Mundaka Estuary (Basque Country, North Spain). Growth data and simultaneous determinations of respiratory metabolism were integrated over defined periods of time in order to compute assimilation and net growth efficiency. Consistent differences between the exponents that scale both assimilation and metabolism to body size led to growth efficiency values that were a decreasing function of age. Total growth was partitioned into three components: somatic growth, reproductive output and reserve storage, and the corresponding effort indexes were calculated. Despite important differences in total growth, reproductive output was constant between years, indicating a higher reproductive effort under poorer growth conditions. Increased costs of reproduction that appeared to be associated with this higher reproductive effort did not affect somatic maintenance, since previously stored carbohydrate reserves were primarily used to fuel gametogenesis.

Annual cockle Cerastoderma edule production in the Wadden Sea usually fails to sustain both wintering birds and a commercial fishery

“…Such negative annual production values in old cockles also occurred in a Spanish cockle population, as can be inferred from Fig. 2 of Iglesias & Navarro (1991). Negative annual production estimates obtained by the weight-increment method appear to be rare for entire populations, but are certainly possible, viz.…”

“…Results of such incomplete studies are almost certainly biased. Some examples of full annual curves of annual weights that can be adequately used for production estimates are those by Wolff & De Wolf (1977), Ivell (1981), and Iglesias & Navarro (1991).…”

“…Iglesias & Navarro (1991) estimated gamete production over 2 yr in a Spanish cockle population and found values of ~10 and 20% of the total production that was accomplished in the first half of the year (the 2 values are for a year with low and high growth rates, respectively). If we assume that such proportions were also applicable for Balgzand, this would result in a mean gamete production of 1 to ~2 g AFDW m -2 yr -1 that should be added to our somatic-production estimates.…”

Growth, metabolism and lipid peroxidation in Mytilus edulis: age and size effects

“…These changes comprised a decrease in citrate synthase activity or in the concentrations of high-energy phosphates, as well as a lowering of intracellular pH. An exponential decrease in K 2 with increasing age is well documented for bivalves (Fuji & Hashizume 1974, Alimov 1981, Shafee & Conan 1984, Iglesias & Navarro 1991, Urrutia et al 1999. In some cases (Rodhouse 1978, Vahl 1981) K 2 declines rapidly until maturity is reached and then tends to level off.…”

Seasonal changes in C, N and P budgets of green-lipped mussels Perna viridis and removal of nutrients from fish farming in Hong Kong

“…Significant correlations between oxygen consumption and reproductive activity have widely been reported (e.g. Iglesias & Navarro 1991). The minimum oxygen demand in December and February coincided with the reproductive resting period during winter, and the abruptly increased metabolic rate (in terms of oxygen consumption) from April onwards might be driven by the nutritional requirement of gametogenesis or spawning after gonadal development in late spring (Lee 1988).…”