Zooplankton biomass estimation from digitized images: a comparison between subtropical and Antarctic organisms

The measurement of mesozooplankton biomass in the ocean requires the use of analytical procedures that destroy the samples. Alternatively, the development of methods to estimate biomass from optical systems and appropriate conversion factors could be a compromise between the accuracy of analytical methods and the need to preserve the samples for further taxonomic studies. The conversion of the body area recorded by an optical counter or a camera, by converting the digitized area of an organism into individual biomass, was suggested as a suitable method to estimate total biomass. In this study, crustacean mesozooplankton from subtropical waters were analyzed, and individual dry weight and body area were compared. The obtained relationships agreed with other measurements of biomass obtained from a previous study in Antarctic waters. Gelatinous mesozooplankton from subtropical and Antarctic waters were also sampled and processed for body area and biomass. As expected, differences between crustacean and gelatinous plankton were highly significant. Transparent gelatinous organisms have a lower dry weight per unit area. Therefore, to estimate biomass from digitized images, pattern recognition discerning, at least, between crustaceans and gelatinous forms is required.

Epi- and mesopelagic fishes, acoustic data, and SST images collected off Lanzarote, Fuerteventura, and Gran Canaria, Canary Islands, during cruise "La Bocaina 04-97"

[ES]Durante la campaña La Bocaina 0497 se llevaron a cabo una serie de 14 lances con una red de arrastre pelágico de tipo comercial entre 20 y 700 m. de profundidad y una porspección acústica con una ecosonda SIMRAD EK-500 en aguas neríticas y oceánicas adyacentes a Lanzarote, Fuerteventura y Gran Canaria. Además se obtuvieron imágenes SST para obtener información de las condiciones hidrológicas en el área de estudio. Los resultados mostraron que la caballa Scomber japonicus presentaba gran variabilidad espacial en biomasa entre las diferentes localidades muestreadas.