Illumination and diel variation modify fish passage through an inclined grid

Fishing trials were carried out with a demersal trawl fitted an inclined grid in the extension. Fibre optic cables attached to allowing illumination of top and bottom halves independently. Fish that passed through half entered one codend whereas those lower another. Four lighting configurations investigated where (i) none was illuminated; (ii) bottom-half (iii) top-half (iv) all illuminated. Trials held at night during day. We demonstrate proportion fish depends on has diel variation. Most species less likely enter upper when illuminated results similar regardless whether bottom-half, top-half, or whole There also effect for haddock whiting greater flatfish than The are more subtle some cod, illuminating had no day, common dab, there but For long rough greatest effect.