Population monitoring for Government Regulation and for fishing efficiency in Iceland

A dredge survey was conducted by Thorisholmi and Marine Research Institute in September 13-18, 2015. The aim was to provide the first assessment of green sea urchin resources in southern Breidifjördur by a dredge and an underwater camera. The ski-dredge used is the same as the one that is used for commercial fishing, a modified scallop dredge of 250 cm width and a bag of 150 cm length.  The mesh size of the bag is 100mm. The whole area investigated was 9.7 km² and was divided into seven separate fishing areas of different sizes, depths (8-60m) bottom types and quality. Sea urchins of good quality (roe filling >10%) were observed in 45% of the whole area investigated. The maximum densities observed in an area were 0.12 kg/m² or 1.5 indiv/m². Information on population structure and roe yield was also investigated and these differed between areas. The size range was 17-85mm but over 50% of the urchins were in the size class 55-65mm. The relationship between size (diameter) and wet weight was good, especially at the stations where a few small individuals were sampled. The efficiency and selectivity of the dredge is unknown but will be assessed when results from the bottom photographs become available.