“…It would, however, potentially improve the interannual stability of such indices if they could be compensated for in terms of time of day, given that a basis for such corrections could be established. It would also be useful to determine whether such corrections should be based on in situ illumination rather than on time of day, because the variation in catchability is related to the fact that hake migrate diurnally (Huse et al 1998). In many fish species, the latter is, of course, itself probably related to in situ illumination (Neilson andPerry 1990, Helfman 1993).…”