Macruronus

Abstract: The food and feeding habits of hoki (Macruronus novaezelandiae), southern blue whiting (Micromesistius australis), javelin fish (Lepi‐dorhynchus denticulatus), ling (Genypterus blacodes), smooth rattail (Coelorinchus aspercephalus), silverside (Argentina elongata), and small‐scaled notothenid (Notothenia microlepidota) sampled from the Campbell Plateau in 1979 were examined. The importance of prey items in the diet has been assessed by an ‘index of relative importance’, which combines measurements of frequency of occurrence, number, and weight of prey. Hoki, southern blue whiting, and javelin fish are pelagic feeders. Hoki preyed largely on natant decapod crustaceans, amphipods, and myctophid and photichthyid fishes. The main prey of southern blue whiting were amphipods, natant decapods, and euphausiids. Javelin fish fed on natant decapods, amphipods, and small squid. Seasonal and regional differences in feeding, and dietary changes with length of fish were evident. Ling, smooth rattail, silversi...

Abstract: Scat and regurgitate samples (n = 206) from New Zealand sea lions (Phocarctos hookeri) were collected at the Auckland Islands between December 1994 and February 1997. Most (82%) samples were collected during three summer seasons while the remainder (18%) were collected during a single winter season. Thirty-three taxa were identified from 3523 prey items. The six most abundant prey species accounted for 90% of all prey items. The two most numerically abundant prey species, octopus (Enteroctopus zelandicus) and opalfish (Hemerocoetes species) made up almost 50% of total prey items. Other important prey species included lobster krill (Munida gregaria), hoki (Macruronus novaezelandiae), oblique-banded rattail (Coelorhynchus aspercephalus), and salps (Pyrosoma atlanticum). New Zealand fur seals (Arctocephalus forsteri) and seabirds were also identified in samples. New Zealand sea lions are generalist feeders utilising a wide variety of prey items, with fish comprising the most common taxa (59%) numerically and both cephalopods (21%) and crustacea (15%) forming lesser, but still important, parts of the diet. Prey taxa identified indicate that New Zealand sea lions are utilising a wide variety of benthic, demersal and pelagic species ranging from the inter-tidal zone to waters deeper than 300 m. New Zealand sea lions at the Auckland Islands target different prey species to New Zealand sea lions at other locations although they have broadly consistent prey types, with fish as the major taxa. There is only a small overlap of New Zealand sea lion prey species with commercially targeted species on the Auckland Islands Shelf in the months sampled.

Abstract: We examined the relationship between demersal fish assemblage and depth, temperature, latitude and longitude off southern New Zealand (46–54°S and 165–180°E) in water depths of 80–787 m. Catch weight data were analysed by two-way indicator analysis (TWIA), groupaverage agglomerative clustering (UPGMA) and Detrended Correspondence Analysis (DCA). The spatial pattern of demersal fish off southern New Zealand conforms to the concept of species groups or fish assemblages related to environmental gradients. Shallow-water assemblages were dominated by species from the families Gempylidae, Squalidae, Triakidae and Moridae, mainly represented by Thyrsites atun, Squalus acanthias, Galeorhinus australis, and Pseudophycis bachus. Deep water assemblages were dominated by Chimaeridae, Argentinidae, Merlucciidae and Macrouridae, mainly represented by Hydrolagus novaezelandiae, Argentina elongata, Macruronus novaezelandiae, and Lepidorhynchus denticulatus. Total catch weight was often dominated by Merlucciidae, Macrouridae and Gempylidae. Fish assemblages were related to discrete ranges of depth ( 300 m) and temperature ( 9.5°C), but the range of sediment types was too narrow to show any correlation.

Abstract: To describe the genetic relationship among regional populations of two commercially valuable species of marine fish, the orange roughy Hoplostethus atlanticus and the hoki Macruronus novaezelandiae, the mitochondrial (mt) DNA haplotypes of 59 individuals were defined by direct sequencing of the cytochrome b gene. Samples of orange roughy were collected on four fishing grounds around New Zealand, one off the west coast of Tasmania and one near South Africa from 1990–1991. Samples from hoki were collected on three fishing grounds around New Zealand and one off Tasmania during the same period. An average of 252 nucleotides were sequenced from each of 32 orange roughy and an average of 372 nucleotides from each of 27 hoki. Sequence variation allowed the definition of 9 unique orange roughy haplotypes and 5 hoki haplotypes. Genetic variation, as measured by both average sequence divergence and haplotype diversity, was high in the orange roughy (nucleotide diversity=0.590%, haplotype diversity=0.782) and low in the hoki (nucleotide diversity=0.076%, haplotype diversity=0.279) relative to a similar survey of the Atlantic cod, Gadus morhua. Differences in haplotype frequencies of orange roughy from New Zealand, Tasmania and South Africa were not significant, and the most common haplotype was found in similar frequencies in these three geographically distant regions. Differences in haplotype frequencies between the New Zealand and Tasmanian samples of hoki were significant, suggesting restricted gene flow between these two regions. The contrasting patterns of low but regionally subdivided genetic variation in the hoki versus high but geographically undifferentiated genetic variation in the orange roughy may be attributed to the low fecundity, slow maturation and long lifespan of the orange roughy relative to the hoki.