Monday 22 August 2005

PB1

PM0080
Characteristics of micronektonic fish layers off Peru
Cornejo Urbina, Rodolfo Martin¹, Bertrand, Arnaud², Saez, Katia³, McClatchie, Sam⁴
1 Departamento de Oceanografía, Universidad de Concepcion, Chile
2 IRD, Centre de Recherche Halieutique Méditteranéeme et Tropicalerance, Chile
3 Departamento de Estadística, Universidad de Concepción, Chile
4 South Australian Aquatic Sciences Centre, South Australia
Author email: rocornejo@udec.cl
Micronektonic fishes characteristically form dense schools (deep scattering layers) and many are strong vertical migrators. Moreover, micronektonic fishes play an important role in food webs, and biogeochemical cycles. Extensive school structures have been observed between 500 m and the surface off Peru. Dense aggregations occurred more commonly at night. The daily migration and the morphology of the schools can be classified by several biological parameters (e.g. taxonomic groups or predator-prey relationships) and as well as by abiotic factors (e.g. irradiance and oxygen) that vary by region. We studied the regional distribution, taxonomic composition, and schooling behaviour based on three trawl-acoustic surveys in 2001, 2002 and 2003. Photicthyidae and Myctophidae were the most abundant families. We classify the species that compose the deep scattering layers as Vinciguerria lucetia, non-migrating myctophids, (Lampanyctus idostigma, Lampanyctus omostigma, Triphoturus oculeus) actively migrating myctophids (Diogenicthys laternatus, Myctophum aurolaternatum, Hygophum reinhardti), planctivores (Leuroglossus urotranus, Bathylagus berycoides, Melamphaes sp.), epipelagic predators (Trachurus murphyi, Psenes sio, Scomberomorus saurus), upper mesopelagic predators (Scopelarchoides nicholsi, Nemichthys fronto, Scopelosaurus sp.) and lower mesopelagic predators (Stomias colubrinus, Idiacanthus sp., Astronesthes sp). We found regional differences in biomass and acoustic area backscattering coefficients. Multivariate statistical analyses were performed in order to compare the composition and abundance of micronektonic fishes in three zones (North, Central and South). More species and greater abundance of non-migrating myctophids were observed in the North and more Vinciguerria were found in the Central region. Greater biomass and number of species of actively migrating myctophids was found in the South.

Return to Poster Presentations