Minimum drift times infer trajectories of ghost nets found in the Maldives

Abstract

This study explores methods to estimate minimum drift times of ghost nets found in the Maldives with the aim of identifying a putative origin. We highlight that percentage cover of biofouling organisms and capitulum length of Lepas anatifera are two methods that provide these estimates. Eight ghost nets were collected in the Maldives and estimated drift times ranged between 7.5 and 101 days. Additionally, Lagrangian simulations identified drift trajectories of 326 historical ghost nets records. Purse seine fisheries (associated with Korea, Mauritius, the Philippines, Spain, France and Seychelles) and gill nets from Sri Lanka were identified as 'high risk' fisheries with regard to likley origins of ghost nets drifting into the Maldives. These fisheries are active in areas where dense particle clusters occured (drift trajectories between 30 and 120 days). Interestingly, ghost nets drifting less than 30 days however, remained inside the exclusive economic zone of the Maldivian archipelago highlighting potential illegal, unreported and unregulated fishing activity is occuring in this area. This study therefore points to the urgent need for gear loss reporting to be undertaken, especially by purse seine and gill net fisheries in order to ascertain the source of this major threat to marine life. This should also be coupled with an improvment in the data focused on spatial distribution of the abandoned, lost or discarded fishing gear originating from both large- and small-scale fisheries.