Assessing variables that affect catch efficiency of king scallops ( Pecten maximus ) in illuminated pots

Abstract

Fishing pots illuminated with light-emitting diodes (LEDs) could offer a lower-impact alternative to dredges for capturing European king scallops (Pecten maximus; hereafter ‘scallops’). However, low catch efficiency of pots could be a barrier to uptake and constrain the potential for any environmental gain. In this study, we sought to identify pot configurations that maximize scallop catch efficiency within illuminated pots, and to evaluate how these modifications influence catch efficiencies of two other target species: brown crab (Cancer pagurus), and European lobster (Homarus gammarus; hereafter ‘lobsters’). We investigated (i) LED colour, (ii) number of LEDs, (iii) pot base type, and (iv) pot entrance (hereafter ‘eye’) design across four spatially discrete experiments (69 fishing trips; 186 hauls; 3 559 pots). In total, 17 742 individuals from 48 species were caught, with 57% of catches comprising brown crabs (n = 6 612; 37%), scallops (n = 2 435; 14%), and lobsters (n = 1 025; 6%). Of the scallops captured, 99% (n = 2 407) were caught in illuminated pots. Catch efficiency of scallops was maximized using a standard metal-based pot fitted with a single white LED and elongated soft-eyes or ScallopEyes, particularly when deployed on scallop grounds. Neither blue LEDs, multiple white LEDs, nor rubber pot bases increased scallop catch efficiency relative to this configuration. In contrast, eye modifications designed to enhance scallop entry reduced brown crab catch efficiency, highlighting species-specific, spatially and seasonally targeted potting strategies could be more appropriate than a multi-species approach. If appropriately regulated alongside existing crustacean fisheries, scallop potting with LEDs could support sustainable diversification, not necessarily augmenting crustacean catches within pots, but increasing fishing options. These findings will contribute to broader conservation and climate objectives while enhancing the resilience of small-scale coastal fleets reliant on declining brown crab and lobster stocks.