Lobster trap detection at the Saba Bank

Abstract

According to previous studies and anecdotal evidence there are a lot of lost lobster traps at the Saba Bank. One study estimated the loss to be between 210 and 795 lobster traps per year. The Saba Bank is an approximately 2,200 km2 submerged area and spiny lobster (Panulirus argus) is one of the main fisheries with an annual economic value over USD 1 million. The traps get lost due to a combination of bad weather moving or damaging traps and marker buoy lines, ship traffic running into and cutting marker buoy lines and removal of marker buoy or theft of traps by vandals. Lost traps are a concern for the Saba Bank fisheries management, because of the potential impact of ghost fishing by lost traps and the damage to the benthic environment. IMARES was commissioned by the Ministry of Economic Affairs, Agriculture and Innovation to advise on a method to detect lost lobster traps. The objective of this desk study was to provide information for the sustainable management of the lobster fisheries and the conservation of the Saba Bank. In this report we investigate the most efficient method for the detection of lost lobster traps from a small vessel in water between 15 and 50 meter depth. We not only address methods for the location of traps, but also recommend methods for the retrieval of traps and measurement of ghost fishing. Side scan sonar in combination with a magnetometer is recommended as the best, most efficient method to locate lost lobster traps in order to retrieve them. This is not necessarily the most cost-efficient method to respond to the problem of future traps loss, as preventive measures tend to be more effective and less costly than curative measures. However, a detection survey can be used to better estimate the magnitude of the problem of already lost traps. It is not realistic that a detection survey can locate all lost traps that are present on the Saba Bank