Fisheries Research 157 (2014) 187–192 Contents lists available at ScienceDirect Fisheries Research j ourna l ho me page: www.elsevier.com/locate/fishres Green lamps as visual stimuli affect the catch efficiency of floating cod (Gadus morhua) pots in the Baltic Sea Andreas C. Bryhn ∗ , Sara J. Königson, Sven-Gunnar Lunneryd, Mikaela A.J. Bergenius Swedish University of Agricultural Sciences, Department of Aquatic Resources, Skolgatan 6, 74242 Öregrund, Sweden a r t i c l e i n f o Article history: Received 11 June 2013 Received in revised form 9 April 2014 Accepted 21 April 2014 Handling Editor Dr. P. He Available online 16 May 2014 Keywords: Atlantic cod Gadus morhua Visual stimuli Cod pot Green light a b s t r a c t This study compared catches in numbers (catch per unit effort, CPUE) and biomass (weight per unit effort, WPUE) of Atlantic cod (Gadus morhua) in two-chambered floating cod pots equipped with and without a green lamp as a form of visual stimuli in two areas. A green lamp inside the pot increased the CPUE and WPUE of cod above the maximum legal size (>38 cm) by 74 and 80%, respectively. There were no differences in CPUE and WPUE of small (<38 cm) cod caught in pots with and without a green lamp. By increasing the catch efficiency of cod green lamps could consequently be highly beneficial for the Baltic commercial cod pot fishery. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Seal-inflicted damage to fishing gear and catch losses have increased rapidly in many types of small-scale coastal fisheries along the Baltic Sea coast and have severely affected the inshore fishery (Westerberg et al., 2008; Hemmingsson et al., 2008; Bruckmeier and Höj Larsen, 2008). The gillnet fishery for Atlantic cod (Gadus morhua; hereafter simply referred to as cod) has, for instance, experienced an extensive surge in damage caused by grey seal (Halichoerus grypus) since year 2005 (Königson et al., 2009). In response to the conflict between the increasing seal population and a continued viable coastal fishery alternative, seal-safe gear, such as baited cod pots, is now under development. Pots may serve as an alternative fishing method with less seal damage and fish loss than gillnets and longlines (Königson, 2011). The Common Fisheries Policy (CFP) as well as the Helcom Baltic Sea Action Plan promote the development of an ecosystem-based management of coastal fisheries. The use of pots in the cod fish- ery would contribute towards this development. In comparison to trawls and other active fishing gears, pots cause limited harm to the marine environment (Jennings et al., 2001; Thomsen et al., 2010). Suuronen et al. (2012) included pots in a compilation of LIFE (Low Impact and Fuel Efficient) fishing gear due to their low energy use, ∗ Corresponding author. Tel.: +46 104784152. E-mail address: andreas.bryhn@slu.se (A.C. Bryhn). effective species selectivity, better protection against marine mam- mals, and low bycatch of marine mammals and seabirds, in addition to low gear construction costs. Another advantage with pots is that they can be designed to capture cod above a certain length (Königson, 2011; Ovegård et al., 2011). Another equally impor- tant reason for developing alternative fishing gear, such as pots, is that the small-scale coastal fisheries suffer from low profitability and scant addition of young fishers. A positive development such as using alternative fishing gear could include ecolabelling fish or marketing the fish as locally caught which in turn could give the fishers a higher catch value. Comparable or higher catches from an equal amount of effort provides incentives for changing from a traditional to an alternative fishery. Generally, the catch efficiency of pots has been far lower than that of other fishing gear, such as trawls (Suuronen et al., 2012). Presently there is no commercial pot fishery in the Baltic. However, experimental fishing conducted in cooperation with commercial fishermen has showed that dur- ing certain time periods pots can be as efficient as gillnet and hook fisheries in the same area (Königson and Lunneryd, 2013). The fish- ing efficiency of the pots is usually maintained by attracting fish to the pot using bait (Furevik and Løkkeborg, 1994; Løkkeborg, 1998), but discussions about how to further improve fishing efficiency are ongoing. The fishing efficiency of pots is to a great extent related to fish behaviour when compared to other types of fishing gear. Pots must have the right characteristics to lure the fish to enter the pot. Cod generally approach pots slowly (Furevik, 1994) and fish sometimes http://dx.doi.org/10.1016/j.fishres.2014.04.012 0165-7836/© 2014 Elsevier B.V. All rights reserved.