ABUNDANCE, DISTRIBUTION, REPRODUCTION AND DIET OF NOTACANTHID FISHES FROM THE NORTHEAST ATLANTIC

Notacanthid fishes were among the 10 most abundant species sampled in research surveys using fine meshed trawls fished to depths of 3000 m i n the Rockall Trough and 4500 m in the Porcupine Seabight between 1975 and 1992. Two species, Noctacanthus bonapartei and Polyacanthonotus r issoanus, were dominant but their population structure and certain asp ects of morphometric and reproductive biology differed between the two sampling areas. In general, sex ratios were skewed in favour of femal es, size increased with depth and male and immature individuals were r estricted to shallower depth zones. Fecundity was highly correlated wi th total weight and showed a positive relationship with species' size. Ovaries contained two batches of eggs and the spawning season was pro tracted, occurring mostly over winter months. Dietary studies showed a dependence on benthic macro fauna though the two dominant species hav e different dentition and exploit different trophic niches. In the Roc kall Trough, peak abundances for N. bonapartei and P. rissoanus occurr ed in the 750 m and 1250 m zones, respectively, lying within the depth range currently exploited by commercial deep-water trawls (600-1400 m ). The probable impacts of commercial operations on notacanthid fishes are discussed. (C) 1998 The Fisheries Society of the British Isles.