The Niebuhr net: A net for capturing benthopelagic fish and fauna with towed camera systems.

Abstract

Historically, assessing the flora of an area of seafloor has been made by physically sampling with a trawl net, with subsequent inspection of the collected animals. This approach to sampling does not quantify well the area of seafloor to be assessed, with nets deployed blind, and these trawls may cause extensive and long-term physical impacts on habitats. These impacts may be damaging, and therefore the approach inappropriate for use in assessing vulnerable areas, such as coral reefs or other niche ecosystems. Towed camera systems, capable of filming or photographing areas of seafloor facilitates the non-invasive estimation of the abundances of animals on or near the seafloor, but does not allow the collection of physical samples. To address the drawbacks of physical net trawls and towed camera systems, the Niebuhr net has been developed. This simple device consists of a weighted net which can be mounted below a towed camera system, allowing an operator to monitor the lowering of the net to the seafloor directly, and to visually sample animals of interest. In this paper we present the design of the Niebuhr net as used by the Alfred Wegener Institute, Helmholz Centre for Polar and Marine Research, Germany, as well as results from an expedition with the research Icebreaker '<i>RV Polarstern</i>' in 2025.