Prøvehøsting av stortare i Nord-Trøndelag – Gjenvekstundersøkelser 2010–2014

Abstract

The Institute of Marine Research monitored the kelp (Laminaria hyperborea) vegetation and sea urchin populations in Nord-Trøndelag in 2014. The survey included previously kelp harvested areas and nearby reference areas, and was performed by underwater video. In addition, kelp plants were collected from areas harvested four years earlier, for measurements of plant size, age and epiphytes. Observations in harvested areas revealed that although kelp rapidly re-monopolizes the substratum (< 2 years), plant sizes and epiphytes are still below pre-harvesting levels 4 years later. Age structure of plants collected in areas harvested in 2010, suggests that kelp recruits present as understory vegetation prior to harvesting, contribute substantially to the restocking of kelp on trawlfields. The understory density of new kelp recruits 4 years after harvesting was significantly lower than it was prior to harvesting. The density of sea urchins was generally low and grazing effects on recovering kelp plants appeared negligible