ANNUAL PRODUCTION OF FISH LARVAE AND THEIR PREY IN RELATION TO SIZE-FRACTIONATED PRIMARY PRODUCTION (SCOTIAN SHELF, NW ATLANTIC)

The annual cycles of abundance of fish larvae and their zooplankton pr ey were analysed in relation to the biomass and production of size-fra ctionated phytoplankton on the Scotian Shelf(North-west Atlantic). Out side the spring bloom of large (>5 mu m) phytoplankton (February to Ap ril), the small-sized fraction of phytoplankton (<5 mu m) contributed the bulk of total primary production. The production of copepod naupli i and copepodites was sustained throughout the year and fish larvae sp ecializing on copepod prey occurred year-round. Species feeding on a m ixed diet of copepods, cladocerans and/or appendicularians were restri cted to periods of maximum temperature in summer and early autumn, Two short trophic pathways (two links) from primary producers to fish lar vae were identified: the herbivorous food chain (large phytoplankton-- >calanoid copepods-->fish larvae) and the large-microphage shunt of th e microbial food web (small phytoplankton-->appendicularians/pteropods -->fish larvae). The year-round production of fish larvae and the fact that several of their major prey (appendicularians, thecosome pteropo ds, cladocerans, and cyclopoid copepods exploit the microbial food web , challenge the tenet that the feeding of marine fish larvae depends p rimarily on the reproduction of herbivorous calanoid copepods grazing the spring and autumn blooms of large phytoplankton.