The dimensional units of Nephrops norvegicus (L.) distribution: from burrows to populations

Abstract

Biogeographia vol. XXV - 2004 (Printed December, 30 q' 2004) Marine Biogeography of the Mediterranean Sea: patterns and dynamics of biodiversity The dimensional units of N6]?/770105 norvegicus (L.) distribution: from burrows to populations JACOPO AGUZZI*, FRANCESC MAYNOU, JOAN BAPTISTA COMPANY, GUIOMAR ROTLLANT, FRANCESC SARDA Imtitut de Ciemie: del Mar (CS1 C), hzssezg Marz’zim de la Barceloneta 3749, 08003 Barcelona (Spain) *e—mzzz'[: jzzguzzz'@m2z'mLrz. csiaes Key words: Decapoda, Nep/Jrops rzoruegicut, burrows, patches, metapopulation, larvae. SUMMARY Nap/7211,»: noruegimt is a burrowing decapod inhabiting muddy bottoms of the continental shelves and slopes of European Atlantic and the Mediterranean seas. Several aspects concerning N uorvegim: geographical and bathyrnetric distribution are revised in relation to its biology. Burrows are considered the ultimate small-scale unity of distribution, while patches the intermediate one. Larval migration among patches determines the geographic and bathymetric distribution of populations. Ecologicil factors determining patchiness are considered along with implication for morphology and genetics of populations. Issues for further researches concerning N. narvegimt distribution and commercial exploitation are proposed. INTRODUCTION The biogeographical aspects of Nap/Jrops narvegicm (L.) distribution are intriguing for three main reasons. As a first instance, its distribution range is mainly known due to the commercial fishing fleet and to survey projects of research (see below), which identify the exploitable grounds where density meets commercial criteria required by the fishery. In this sense, for those few areas where the commercial fishery is absent, no conclusion on N norvegicus presence can be drawn. As a second instance, a two—dimensional aspect in the species distribution should be considered: the species occupies a wide geographic range (from the European Atlantic Ocean, down to the Mediterranean including Morocco), and a wide bathymetric range (spanning from the subtidal regions of the upper shelf in the Atlantic and North Sea, to the slopes of the western—central Mediterranean)