Diel and seasonal patterns of Nephrops norvegicus (Decapoda: Nephropidae) catchability in the western Mediterranean

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 258:201-211 (2003) - doi:10.3354/meps258201 Diel and seasonal patterns of Nephrops norvegicus (Decapoda: Nephropidae) catchability in the western Mediterranean Jacopo Aguzzi*, Francesc Sardà, Pere Abelló, Joan B. Company, Guiomar Rotllant Institut de Ciències del Mar (CSIC), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain *Email: jaguzzi@icm.csic.es ABSTRACT: Catchability patterns of western Mediterranean Nephrops norvegicus were studied in relation to depth and season by sampling animals during 4 continuous 24 h cycles of trawl hauls at 100 to 110 m and 400 to 430 m in October (near the autumn equinox) and June (near the summer solstice). Bottom light intensity was recorded between consecutive catches. Catch data were transformed into density estimates of animals emerging from their burrows. Results revealed a marked emergence rhythmicity: nocturnal with crepuscular peaks on the continental shelf, and diurnal on the continental slope. On the slope, peaks of catch occurred in phase with light intensity, whereas this did not happen on the shelf. In particular, both benthic environments presented diel fluctuations in light intensity that differed within several orders of magnitude. These data indicate a differential physiological adaptation of N. norvegicus eyes to local photic conditions, implying a revision of the optimum light intensity concept, already proposed in the literature. Emergence patterns were almost identical for males, females and berried females, and these were not size-dependent. KEY WORDS: Nephrops norvegicus · Mediterranean · Catchability · Rhythms · Continental shelf · Continental slope · Light intensity Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 258. Online publication date: August 29, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.