Search

Continuous video recordings of entries and exits from blue cod Parapercis colias pots in central New Zealand showed that less than 8% of approaches to pot entrances during 30 min sets led to pot entries. Thirty-four percent of the blue cod that did enter exited before the pot was hauled. Time-courses of approaches were relatively steady throughout 30 min, though the greatest number of approaches occurred during the first 10 min of sets. A more limited dataset of 60 min sets found that the number of blue cod contained in pots changed little after 30 min, indicating that maximal catch per unit effort would be derived from sets of about 30 min duration. Local topography appeared to constrain pot entries in some situations. A spreadsheet model of catch per time as a function of number of pots, set durations, haul time and catch handling time indicated that 30–40 min sets were optimal for the range of variables we considered. It is clear that efficiency of capture might be greatly improved. [Copyright &y& Elsevier]

Lebensspuren ('life traces') are biologically formed physical imprints or structures left behind in sediments, the origins of which are often unknown or speculative. During a biodiversity survey on Chatham Rise (a deepsea submarine ridge off SE Aotearoa New Zealand) in winter 2013, distinctive 'iron-shaped' lebensspuren, often with a central 'bitemark' where a plug of sediment had apparently been removed, were observed during towed camera transects at depths of 450–562 m. We link these impressions in soft deep-sea sediments to the head shape of grenadiers, and infer they resulted from grenadiers foraging on benthic prey. The imprints varied in shape, depth, and clarity. Two very clearly defined impressions were matched to Coelorinchus aspercephalus and C. biclinozonalis using ventral head profiles, and the size of the fish estimated. Grenadier foraging marks were frequently seen but their occurrence and densities have not yet been mapped. • Iron-shaped impressions are found in deepsea soft sediments off New Zealand. • Impressions were matched to head shapes of deep-sea fish (grenadiers). • Impressions are likely life traces ('lebensspuren') of benthic foraging grenadiers. [ABSTRACT FROM AUTHOR]