Daily carbon, nitrogen and phosphorus budgets for the Mediterranean planktivorous damselfish Chromis chromis

The planktivorous damselfish Chromis chromis is one of the most numerous fish species in the Mediterranean rocky littoral, yet the role this species plays in the overall functioning of the ecosystem is poorly understood. In this study nitrogen, carbon and phosphorus budgets were constructed for C. chromis from the Bay of Calvi, Corsica and an attempt was made to resolve the possible fates of these nutrients from ingested materials, to somatic growth (Ps), reproductive tissues (Pr), respiration (R), assimilation (A′), faeces (F) and dissolved wastes (U). C. chromis were estimated to consume on average 4.7% of their own body mass of zooplankton per day, in two separate feeding episodes — at dawn and at dusk. This is equivalent to 8288 individual copepods or 42.1 mg carbon, 9.7 mg nitrogen, 0.8 g phosphorus. 44% of all phosphorus ingested was shown to be excreted as dissolved waste, and 46% as faeces; this may be of considerable importance in the Mediterranean, where littoral macrophytes are often severely phosphorus-limited. 85% of all nitrogen was excreted as dissolved waste (mostly ammonia) and local nutrient enrichment may enhance littoral primary productivity, particularly around C. chromis night-shelters.