The aim of this study was to analyse the general larval condition, to determine the lncidence of starvation and to investigate the effect of time of day on RNA/DNA ratios among field-caught Sardina pilchardus (L.) larvae. The larvae were collected during 4 research cruises off northern Spain, during March, April, May and June 1992. A highly sensitive fluorometric method for nucleic acid quantification was applied to larvae of S. pilchardus. The means of the RNA/DNA ratio were relat~vely high, so the larvae collected off northern Spain were generally in good condition. Low percentages of starving larvae (RNA/DNA ratio less than 1.3), ranging from 0 to 3.23%, were found over the 4 mo. The RNA/DNA ratios were significantly correlated with zooplankton biomass. Larvae collected at night revealed higher RNA/DNA ratios compared to larvae caught during the day. This seems to indicate that there is some endogenous rhythm in the production of RNA. It would then follow that, if there are die1 changes in RNA concentrations, average RNA Indices can be unrepresentative if there IS any day/night bias in sampling.

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The contribution of infauna and mussel-raft epifauna to the diet of 3 dominant species in the demersal fish community of the Ria de Arosa, N. W. Spain -Lesueurigobius friesji (Gobiidae), Callionymus lyra (Callionymidae) and Tn.sopterus luscus (Gadidae) -was determined. Intense raft mussel culture in the Ria de Arosa supports a rich epifauna which constitutes the main food resource for the fishes studied. In contrast, infauna density is low and contributes only a small proportion to fish diets. Prey consumed was similar in the 3 fish species. Gut contents consisted mainly of the small crab Pisjdja longicomis. This decapod is a dominant component of the raft epifauna, and electivity indices indicate that it is selected by the fishes. In the Ria de Pontevedra, which contains fewer mussel rafts, these flsh fed on infauna. Thus, one effect of intense mussel aquaculture has been to change the food habits of these 3 fishes from predominantly infauna to raft epifauna diet.

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Benthic samples were collected from 1982 to 1985 in two stations in La CoruAa Bay in order to study the temporal changes of two subtidal benthic assemblages: (1) a Tellina fabula -Paradoneis armata community, and (2) a Thyasirafluxuosa facies of an Abra alba community. The Tellina station is located in an area with little human disturbance, whereas the Thyasira station is located inside the organically polluted harbour area, where dredging operations took place at the beginning of this study. Temporal changes in both communities follow quite different patterns. The sedimentary environment of the Tellina station remains fairly constant through time: sediment size ranges from 2.80 to 3.85 9 , and organic matter content (loss by ignition) varies between 3.15 and 4.53%. In the Thyasira station these sedimentary variables cover a much wider range: 3.10 to 5.75 9 mean diameter and 5.19 to 17.05% organic matter.Community structure is quite stable in the Tellina station. The mean similarity of every sample with the following ones is relatively high and stable, and diversity (H') and evenness (J ') fluctuations are small. However, in the Thyasira station the community structure has changed drastically after dredging operations ended as a result of the recolonization and further stabilization of the community.At the Tellina station biomass varies between 10 and 32 g ashfree DW m-2, and it does not show a discernible temporal pattern. However, at the Thyasira station biomass increased from less than 1 g ash-free DW m-2 during the dredging period up to 16 g ash-free DW m-2 18 months after the end of dredging. In conclusion, the Tellina fabula community seems very stable through time, whereas the Thyasira flexuosa fac i e~ has wider fluctuations due to human disturbances.