Effects of Experimental Otter Trawling on Surficial Sediment Properties of a Sandy‐Bottom Ecosystem on the Grand Banks of Newfoundland

• Published in: Conservation Biology
• Main Authors: Schwinghamer, Peter, Gordon, Donald C., Rowell, Terence W., Prena, Jens, McKeown, David L., Sonnichsen, G., Guigné, J. Y.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1998
• Subjects: Nature and Landscape Conservation; Ecology; Ecology, Evolution, Behavior and Systematics; Newfoundland; Terranova
• Online Access: http://dx.doi.org/10.1046/j.1523-1739.1998.0120061215.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1523-1739.1998.0120061215.x; http://onlinelibrary.wiley.com/wol1/doi/10.1046/j.1523-1739.1998.0120061215.x/fullpdf

We conducted a 3‐year experiment on the effects of otter trawling on benthic habitat and communities on a sandy‐bottom ecosystem of the Grand Banks of Newfoundland that has supported commercial fisheries. Each year, three 13‐km‐long corridors were trawled 12 times with an Engel 145 otter trawl, creating a disturbance zone 120–250 m wide. Using a variety of oceanographic instruments, measurements were made before and after trawling to document effects. Trawling had no detectable effect on sediment grain size. Tracks made by trawl doors were readily visible on the sea floor immediately after trawling and 10 weeks later; in some cases they were still faintly visible after 1 year. Acoustic data indicated that trawling increased the topographic relief or roughness of surficial sediments and changed small‐scale biogenic sediment structures down to depths of 4.5 cm. Video observations in trawled corridors revealed that organisms and shells tended to be organized into linear features parallel to the corridor axis. They also demonstrated that trawling reduces both surficial biogenic sediment structure and the abundance of flocculated organic matter; untrawled sediments had a hummocky, mottled appearance, whereas trawled sediments were smoother and cleaner. These changes combined to give the trawled corridors a lighter appearance in color. It appears that the physical effects of otter trawling observed in this experiment are moderate and that recovery occurs in about a year. The biological effects of this experimental trawling have yet to be examined. Efectos del Arrastre Experimental en las Propiedades de Sedimentos Superficiales de un Ecosistema de Fondo Arenoso de los Grande Bancos de Terranova Un experimento de tres años sobre los efectos del arrastre en hábitat bentónico y sus comunidades fue realizado en un ecosistema arenoso que soporta pesquerías comerciales de los Grandes Bancos de Terranova. Cada año, tres corredores de 13 km de largo fueron arrastrados 12 veces con una red de arrastre Engel, creando una zona de ...