Peter Mcmillan

Genetic and meristic variation in black and smooth oreos in the New Zealand Exclusive Economic Zone

Abstract Meristic and genetic methods were used to determine the stock relationships of black Allocytus niger (James, Inada & Nakamura, 1988) and smooth oreo Pseudocyttus maculatus (Gilchrist, 1906) in the New Zealand Exclusive Economic Zone (EEZ). Samples were collected from four management areas—OEO 1 (south‐west), OEO 3A (Chatham Rise west), OEO 4 (Chatham Rise east), and OEO 6 (subantarctic) during the 1998 October‐December spawning period. Lateral line scale counts and pyloric caeca counts revealed differences between black oreo samples from OEO 6 and the other three OEO management areas. Lateral line scale counts in smooth oreo showed no significant differences between areas. Genetic analyses of four non‐coding regions of nuclear DNA and mitochondrial (mt) DNA haplotypes in black oreo showed no significant differentiation among the four management areas. Likewise for smooth oreo, genetic analyses of five non‐coding regions of nuclear DNA and mtDNA haplotypes showed no overall regional differentiation, although there was weak evidence at one locus for a difference between OEO 3A and OEO 6. The data do not reject the null hypothesis of a single genetic stock in New Zealand waters, and are typical of marine species with long pelagic juvenile stages.

Diversity, relative abundance, new locality records, and updated fish fauna of the Ross Sea region

Abstract Two surveys were carried out in the Ross Sea region during February and March 2004 and 2008 from the New Zealand RV Tangaroa. Fishes were sampled on the continental shelf and slope of the Ross Sea, and on adjacent seamounts to the north, mainly using a large demersal fish trawl and a large mesopelagic fish trawl. Parts of the shelf and slope were stratified by depth and at least three random demersal trawls were completed in each stratum, enabling biomass estimates of demersal fish to be calculated. Fish distribution data from these two surveys were supplemented by collections made by observers from the toothfish fishery. A diverse collection of over 2500 fish specimens was obtained from the two surveys representing 110 species in 21 families. When combined with previous documented material this gave a total species list of 175, of which 135 were from the Ross Sea shelf and slope (to the 2000 m isobath). Demersal species-richness, diversity and evenness indices all decreased going from the shelf to the slope and the seamounts. In contrast, indices for pelagic species were similar for the slope and seamounts/abyss but were much lower for the shelf.

Latitudinal variation of demersal fish assemblages in the western Ross Sea

Abstract Demersal fishes were sampled using a large fish trawl during two surveys carried out in February and March 2004 and 2008 in the Ross Sea, and around seamounts and islands just to the north at 66°S. The distribution and abundance of 65 species collected in these surveys were examined to determine if demersal fish communities varied throughout the area, and what environmental factors might influence this. Species accumulation with sample frequency did not reach an asymptote, but the rate of new species was low suggesting data were adequate for describing the main components of the communities. Three broad assemblages were identified, in the southern Ross Sea (south of 74°S), central–northern Ross Sea (between latitudes 71°–74°S), and the seamounts further north (65°–68°S) where some species more typical of sub-Antarctic latitudes were observed. Multivariate analyses indicated that environmental factors of seafloor rugosity (roughness), temperature, depth, and current speed were the main variables determining patterns in demersal fish communities.

Age verification, growth and life history of rubyfish Plagiogeneion rubiginosum

Abstract Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (14C) and stable isotope (δ18O and δ13C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core 14C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the 14C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ18O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ13C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns.

DNA barcoding of morid cods reveals deep divergence in the antitropical Halargyreus johnsoni but little distinction between Antimora rostrata and Antimora microlepis

Background and aims: DNA barcoding strongly suggests that specimens of the slender codling (Halargyreus johnsonii) from New Zealand and Tasmania belong to a different species to H. johnsonii reported from other areas. Results: Sequence divergence between the two groups averaged 3.95%, much higher than within-group divergences of 0.03 and 0.02% for specimens, respectively, from New Zealand–Tasmania and from the North Pacific, Atlantic Ocean, and Southern Ocean. Conclusion: Meristic data for specimens from New Zealand and from the Southern Ocean north of the Ross Sea support the conclusion of two species. DNA barcodes for two sister taxa, Antimora rostrata and Antimora microlepis, show low intra-species (0.3–0.06%) and inter-species (0.23%) divergence.

A NEW GRENADIER, GENUS CAELORINCHUS, FROM AUSTRALIA AND NEW ZEALAND (PISCES, GADIFORMES, MACROURIDAE)

Abstract A new species, Caelorinchus trachycarus, is described from continental slope depths of 622–1350 m off New Zealand, southern Australia, and the Norfolk Ridge south of New Caledonia. The modified scales of head ridges is especially spiny, more so than in any other member of the genus. The blackish fins, dark overall coloration, prominent free neuromasts on the head, and the numerous parallel rows of spinules on body scales distinguish the new species from the closely similar and sympatric C. acanthiger. It differs from C. parallelus and C. kermadecus by its naked nasal fossa, snout length, and scale spinulation, among other characters.

Age and life histories of black and smooth oreos inferred using bomb radiocarbon dating and stable isotope analysis

ABSTRACT Black oreo (Allocyttus niger) and smooth oreo (Pseudocyttus maculatus) are commercially exploited deepwater fishes in New Zealand. They are considered to be long-lived with unvalidated maximum otolith growth zone counts of 153 years and 86 years, respectively. Bomb radiocarbon dating results supported the otolith age estimates for A. niger, but those for P. maculatus provided only partial support. Oxygen isotope (δ18O) results for A. niger otoliths suggested that juveniles were in near-surface waters and adults in depths of 700–1300 m. In contrast, P. maculatus otoliths suggested a variable depth history (500 to at least 1500 m) throughout life. Carbon isotope (δ13C) results showed a steady enrichment from core values to c. 20 years for both species, owing to changes in diet and metabolic rate from the juvenile to the adult fish, associated with a depth increase. Von Bertalanffy growth parameters are provided for both species.