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The Chilean jack mackerel (Trachurus murphyi) is a predominantly Southeast Pacific Ocean species. It is relatively difficult to determine its age, and multiple studies of its growth off South America have produced markedly different sets of von Bertalanffy parameters. T. murphyi was first identified from New Zealand waters in the mid‐1980s and has comprised part of the commercial landings of Trachurus species (along with Trachurus declivis and Trachurus novaezelandiae) since then. Results from 13 years of age determination of New Zealand samples using sectioned otoliths indicate that a partially validated age determination method has been developed, with a precision level (average percentage error) of 4.6%. The best available von Bertalanffy growth parameters for the New Zealand population (sexes combined) are as follows: L∞, 51.9 cm fork length; K, 0.223 per year; t0, −0.5 year. Analyses by sex showed that males have a significantly larger L∞ than females. Estimated annual catch‐at‐length and catch‐at‐age distributions from the fishery are presented for 2007–2019. There have been at least two episodes of immigration of T. murphyi from international waters, but little evidence of spawning success to maintain the New Zealand population. [ABSTRACT FROM AUTHOR]

To investigate whether wild fish populations are food limited, this study explored whether the provision of supplementary food had a positive effect on the abundance, condition and growth characteristics of estuarine fish assemblages in New Zealand. Feed (7690 kg) was delivered from an anthropogenic feeding station over a 60‐week period to a naturally occurring assemblage of wild fish. Yellow‐eyed mullet (Aldrichetta forsteri) of juvenile, sub‐adult and newly matured size classes were the dominant species actively foraging at the feeding station throughout its operation, whereas larger piscivorous species visited and foraged from the feed station over the summer period only. Other species were present in the wider area of Nelson Haven, but not at the feed station. No obvious changes in the condition factor of yellow‐eyed mullet were observed across the period of monitoring, and no changes in their catchability were detected – although marked seasonal variation in catch rates was observed. Results from tag‐recapture data identify that the length‐based growth rates of yellow‐eyed mullet recaptured near the feed station were higher than those of tagged individuals recaptured at a nearby comparison site, and were higher than the growth rates observed in natural populations of yellow‐eyed mullet in the wider region. Shifts in the median size of fish, as observed by acoustic observations, agreed with the tag‐recapture data. Although some of the results identified were not amenable to statistical analyses, the attendance of yellow‐eyed mullet at the feeding station, in combination with the improved estimates of growth by most of the techniques employed, indicates that yellow‐eyed mullet are food limited in their natural environment and that the growth performance of these fish can be positively affected by the increased availability of food. [ABSTRACT FROM AUTHOR]

The diet of the alfonsino Beryx splendens was determined from examination of stomach contents of 287 specimens of 17 to 48 cm fork length ( LF) sampled by bottom trawl on the Chatham Rise to the east of New Zealand. Prey items were predominantly crustaceans and mesopelagic fishes. The most important prey species by mass was Sergestes spp. prawns, followed by the myctophid Lampanyctodes hectoris, and then Pasiphaea spp. prawns. Multivariate analyses indicated that small crustaceans (euphausiids and amphipods) were most important in the diet of smaller B. splendens (100-424 g, 17-26·5 cm), with larger prawn species and mesopelagic fishes most important for larger fish (425-2070 g, 27-46 cm). Moon phase and bottom temperature also explained some of the variability in diet, but the moon phase effect was difficult to explain, and the bottom temperature effect may have been confounded, to some extent, with LF. The results indicated that B. splendens were moderately selective feeders that foraged primarily in the mesopelagic layers. The diet of New Zealand B. splendens is generally similar to those reported from other areas, i.e. dominated by mesopelagic crustaceans and fishes, and with a transition from small crustaceans to fishes with increasing predator size. [ABSTRACT FROM AUTHOR]

The effects of surface type and slope on fish passage over artificial ramps were evaluated for two small diadromous fish species native to New Zealand: the redfin bully Gobiomorphus huttoni and adult and juvenile inanga Galaxias maculatus. Surfaces tested include smooth plastic, sand, gravel (limestone chips 5-20 mm), nylon brush and two plastic moulded cores of ground drainage products Cordrain® and Miradrain®. Slopes of 15° (1:3.7), 30° (1:1.7) and 45° (1:1) were assessed. Slope was the greatest factor influencing successful passage, with the lowest gradient tested (15°) providing the highest passage for both fish species. Most ramps at 45° only allowed the passage of redfin bullies, these fish being capable of 'climbing' the wetted margin of the ramps. Because of this climbing ability, redfin bullies were not as affected by the ramp surface, as inanga. Nevertheless, the smooth plastic surface, which resulted in the highest water velocities over the ramps, was un-passable by either species at slopes >15°. Gravel, the nylon brush and the two plastic moulds provided high passage rates for inanga at gradients of 15 and 30°. At a slope of 45°, Miradrain® was the only surface inanga could pass. Overall, Miradrain® produced the most successful passage for both inanga and redfin bullies, but to maximize passage, slope should not be >15° and a wetted margin is essential for climbing species. [ABSTRACT FROM AUTHOR]