Alternative low cost methods of fishing sea urchins
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Original versionNofima rapportserie. 22 p. Nofima AS, 2014
The current project intends to develop novel low cost harvesting techniques for sea urchins that may prove more economically viable due to their low cost in terms of both infrastructure (boat and associated equipment) and running costs. These novel techniques include utilising the aggregating behavior of urchins on any objects found on the sea floor (passive trapping). A series of experimental experiments were carried out to test the efficacy of three trap types, identify the optimal period of time to set the traps and also to test two bait types. The results clearly showed that the round collapsible trap design were most effective with the highest catch rates. The simple rope traps were also effective at accumulating urchins into concentrated areas which would useful for dive or ROV collection. The optimal period for setting the traps was 7 days (± 1-2 days) and this is the recommended set time for commercial operations. However, optimal catch periods may vary according to local environmental conditions (eg feed availability) and urchin abundance and commercial fishermen should take this into account. The trials clearly showed that using fish bait was more effective than using algae baits but the former attracted much higher bycatch than the algae baits. The more bait stations (of either algae or fish bait) used the greater the catch but the higher catch rates must be weighed against the increasing cost and time required to set more bait stations. A quick, easy bait station is required (eg a net pocket in the netting) that would simplify setting baits. If this can be achieved then we recommend at least two bait stations in each trap, but increasing the number of bait stations would increase the catch rates. The commercial trials undertaken as part of this study clearly show that it is absolutely essential to have some knowledge of the abundance of urchins, depth and bottom topography of an area prior to commencing fishing. This can be gained by fishing an area over a long period of time, or by undertaking rapid, relatively cheap surveys using mini ROVs as used in the salmon industry. In summary the results of this study show there is considerable potential to utilise passive trapping to develop sea urchin fisheries and possible sea urchin roe enhancement ventures throughout Norway. The results of the study will be used in follow up commercial projects with Lynsskjellan AS (Lyngen) and Capefish As (Hønningsfjord) to develop these capture techniques on a commercial scale. The former intend to supply sea urchins into the local Norwegian market and the latter intend supplying sea urchins to international markets.