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Tarakihi (Nemadactylus macropterus) is a demersal fish that supports valuable commercial, recreational, and customary fisheries in New Zealand. However, little is known about its stock structure. T...

Cheilodactylus rubrolabiatus collected from the south and lower west coasts of Western Australia were used to investigate the influence of habitat and environmental conditions on the biology of this species. A lack of difference in the growth C. rubrolabiatus from cool south coast and warmer lower west coast waters in Western Australia and the greater maximum ages attained by fish on the latter coast, both run contrary to premises of the metabolic theory of ecology (MTE). Although the greater size (L 50 ) and age (A 50 ) at maturity of C. rubrolabiatus on the south coast is consistent with MTE, this may reflect higher densities of fish on discontinuous shoreline rocky reefs on this coast and thus the need for fish, particularly males, to attain a larger size to successfully defend habitat and mates during spawning. Members of the closely related Cheiodactylidae and Latridae vary in maximum fork length (L Fmax 280–950 mm) and age (19–97 years) and display a range of growth patterns. While the L 50 of cheilodactylid and latrid species increased with increasing asymptotic lengths (L ∞ ), their maximum ages did not necessary reflect the A 50 (i.e., mature early, but live long). The M (natural mortality): k (von Bertalanffy growth parameter) ratios indicate that Cheilodactylus and Nemadactylus species exhibit a type II life-history strategy, typified by initial rapid growth, L 50 close to their L ∞ and little or no growth during an extended adult phase. A lack of distinct difference in the biological characteristics of the Cheilodactylidae and latrids may assist in resolving uncertainty regarding the taxonomy of these families.

The influence of ‘no take’ Marine Protected Areas (MPAs) on abundance and size of fishes varies considerably and the likely benefits are still debated. Meta-analyses reveal findings are biased towards studies in shallower depths suitable for diving surveys. Empirical comparisons in deeper waters, including among areas with differing spatial management, further contribute to understanding of MPA benefits and constraints. We compare length and abundance of commercially and recreationally targeted fishes (and bycatch) among management types within and adjacent to the Solitary Islands Marine Park (SIMP), Australia. Sampling was done on reefs between 25 and 40 m depth in ‘no-take’ and fished ‘partially protected’ areas within the marine park and fished areas outside the SIMP, using stereo- Baited Remote Underwater Videos (stereo-BRUVs) at eight, nine, thirteen and fourteen years after these ‘no take’ areas were established. Four species targeted by fishers: snapper Chrysophrys auratus, grey morwong Nemadactylus douglasi, pearl perch Glaucosoma scapulare, and venus-tuskfish Choerodon venustus, were more abundant and larger in ‘no take’ zones overall and showed an increase through time in ‘no take’ relative to both types of fished area. In contrast, there was no distinct pattern of four bycatch species increasing in abundance in ‘no-take’ areas. Abundances of fish in partially protected areas were similar to fished areas outside the MPA. This study adds empirical evidence to the assertion that ‘no take’ areas in particular, can contribute to both marine conservation and natural resource management.

Breakdown of trimethylamine oxide (TMAO) during post-harvest storage contributes significantly to loss of seafood quality. We surveyed 51 New Zealand commercial fish species and determined white muscle tissue concentrations of TMAO and the TMAO-derived spoilage indices: trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N). There were significant differences in the TMAO concentrations between fish of various genus and species. Values ranged between 8 and 789 mg/100 g for ray-finned fishes (Actinopterygii), and 262 and 789 mg/100 g for cartilaginous fishes. The distribution of TMAO was similar to that of Northern Hemisphere fish species. Deep water species had the highest concentrations of TMAO. Seasonal effects in tarakihi (Nemadactylus macropterus) and red gurnard (Chelidonichthys kumu) were studied and TMAO declined significantly over the summer months. TMA-N was typically below 2 mg/100 g and TVB-N concentrations did not exceed the limits set by the European Community (EC) C...

Three dominant recruitment patterns were identified across 30 stocks from Australia, New Zealand, Chile, South Africa, and the Falkland Islands using data from 1980 to 2010. Cluster and dynamic factor analysis provided similar groupings. Stocks exhibited a detectable degree of synchrony among species, in particular the hakes and lings from Australia, New Zealand, Chile, and South Africa. We tested three climate indices, the Interdecadal Pacific Oscillation (IPO), Southern Annular Mode (SAM), and Southern Oscillation Index (SOI), to explore their relationship with fish stock recruitment patterns. The time series of IPO and SOI showed the strongest correlation with New Zealand hoki (blue grenadier, Macruronus novaezelandiae) and Australian jackass morwong (Nemadactylus macropterus) (r = 0.50 and r = –0.50), and SAM was positively related to Australian Macquarie Island Patagonian toothfish (Dissostichus eleginoides) (r = 0.49). Potential linkages in recruitment patterns at sub-basin, basin, and multibasin scales and regional and global climate indices do account for some of the variation, playing an important role for several key Southern Hemisphere species.

Many fished stocks show long-term reductions in adult body size. Such changes could lead to new feeding interactions and alter stock productivity, introducing new levels of uncertainty in fisheries management. We use a marine ecosystem model parameterized for Southeast Australia to explore how reductions (up to 6% in 50 years) in size-at-age of fished species affect stock recovery after an implementation of a fishing moratorium. We show that reduction in body size can greatly elevate predation mortality and lower the post-fishing biomass of affected species. In our simulations, the recovery period after the fishing moratorium was characterized by two phases. In the initial readjustment phase, the ecosystem dynamics was largely determined by the rapid changes in the biomasses of recovering species and changes in body size had negligible effects. In contrast, fish body sizes had the major impact on the biomasses in the second, semi-equilibrium state and the final biomasses were generally not affected by the harvest rate during the fishing period. When reduced size-at-age elevated predation mortality in most age groups of a species (tiger flathead Platycephalus richardsoni or silver warehou Seriolella punctata in our simulations), the species' equilibrium biomass was considerably lower compared with the scenarios of no change in body size. For other species (pink ling Genypterus blacodes and jackass morwong Nemadactylus macropterus), a predation increase in some age groups was balanced by the decrease in others. The latter reduction in predation mortality occurred when major predators of species with reducing size-at-age were decreasing in size themselves, or when cannibalism was an important source of juvenile mortality (in blue grenadier Macruronus novaezelandiae). We suggest that decreased size-at-age will be most detrimental to stock recovery when the main predators of the stock are not affected by the drivers causing changes in body size.

Fishery responses to climate change are occurring on time-scales relevant to the provision of short-term management advice. This is especially the case in climate change ‘hotspots’ such as south-eastern Australia, where the rate of ocean-warming is 3–4 times the global average. The application of harvest strategies utilizing biological reference points that do not take into account the effect of the changing environment on fish productivity may lead to unsustainable catch recommendations. Jackass morwong (Nemadactylus macropterus) is a moderately long-lived demersal species inhabiting continental shelf waters of the southern hemisphere. The most recent Stock Synthesis assessment for the species suggests that this stock has recently declined in abundance off south-eastern Australia. The stock assessment attributes the decline to mostly below average recruitment since 1985, but the recommended catch levels are based on an assumption of average recruitment from a stationary stock–recruitment relationship. The ability of Stock Synthesis to include an environmental variable to adjust the stock–recruitment relationship is used to model a regime shift on the average level of recruitment. Management strategy evaluation (MSE) is then used to examine the consequences of using the wrong recruitment assumption in the assessment used in the harvest strategy for setting the catches. The MSE shows that the consequences of mis-specifying the assessment model are greater if the assessment continues to assume that no shift in recruitment has occurred. Thus the more precautionary approach for management wishing to meet all the aims of the Australian government Harvest Strategy Policy is to assume that a shift in recruitment has occurred. A possible mechanism for how observed oceanic changes could be impacting jackass morwong recruitment is presented.

The trophic structure of organisms is an important aspect of the ecosystem as it describes how energy is transferred between different trophic levels. Here, we studied the diet and foraging ecology of 144 individuals belonging to five abundant fish species of subtidal habitats at Isla Robinson Crusoe. Sampling was conducted during the austral spring and summer of 2007 and 2008, respectively. The shallow subtidal habitat is mainly characterized by the abundance of two types of habitat: foliose algae and encrusting invertebrates. Diet and trophic characteristic of fishes were obtained by volumetric contribution and frequency of occurrence of each prey item. Of the five species studied, one is herbivorous (juvenile Scorpis chilensis), four are omnivores (Nemadactylus gayi, Malapterus reticulatus, Pseudocaranx chilensis and Scorpis chilensis adult), and one carnivore (Hypoplectrodes semicinctum). The dietary diversity index was relatively low compared to other temperate reef systems, which could indicate a low availability of prey items for coastal fishes. The morphological parameters indicated that cranial structures and pairs of pectoral fins influence the foraging behaviour. Differences in fin aspect ratio among species provided insight about fish depth distribution and feeding behaviour. These results suggest important adaptive changes in the depth gradient of fishes in the subtidal environments of this island. According to our records, this is the first attempt to characterize the trophic ecology of the subtidal fish assemblages at Juan Fernandez Archipelago, revealing the need for testing hypotheses related to selective traits that may enhance species coexistence in oceanic islands.

Para contribuir al conocimiento de la explotación de peces asociada a la pesquería de langosta de Juan Fernández, se monitorearon 157 salidas de pesca durante la temporada 2010-2011. Se capturaron 10.462 ejemplares correspondientes a 19 especies de peces, tres de las cuales concentraron el 94% de la captura en número: jurel de Juan Fernández (Pseudocaranx chilensis) (45%), breca (Nemadactylus gayi) (41%) y anguila morena (Gymnothoraxporphyreus) (8%). Las capturas totales estimadas fueron 40, 24 y 13 ton de breca, jurel de Juan Fernández y anguila morena, respectivamente. El 97% de los ejemplares de peces capturados fueron utilizados como carnada de peces o langosta.

The distribution of morwong larvae in the southwestern Tasman Sea was investigated during autumn/early winter over three consecutive years (1992-1994). Larvae were confined to surface tows and large numbers (6-30 mm in length) were captured up to 250 km east of Tasmania (the limit of sampling). The jackass morwong (Nemadactylus macropterus) dominated samples, although larvae of the banded morwong (Cheilodactylus spectabilis) were also recorded. N. macropterus larvae were found within water masses derived from the East Australian Current (EAC) and Sub-tropical Convergence Zone (STCZ). Back-calculated spawning dates, significant differences in otolith microstructure, and inferred current patterns suggest that larvae from within each water mass originate from different spawning regions: a northern one (probably southern New South Wales and eastern Victoria) and a southern one (probably western and southern Tasmania). There was a significant positive relationship between larval age and distance offshore. Seasonal movements of the major water masses provide mechanisms that may facilitate regionally self-sustaining populations in northern and southern regions with an area of recruitment derived from both regions covering eastern Tasmania and Bass Strait. Larval distribution and advection processes suggest spatially variable levels of mixing between spawning regions. These data provide an explanation for both the lack of previously detected population sub-structuring from genetics studies and the multiple spawning population scenario suggested by otolith microchemistry studies.

The biogeographic history of three cirrhitoid species pairs with east–west allopatric distributions across southern Australia was examined by determining levels of mitochondrial DNA sequence divergence and applying molecular clock calibrations. Similar levels of genetic divergence were observed for Aplodactylus Valenciennes and Goniistius Gill species pairs, but these were more than twice that observed for a Nemadactylus Richardson pair. Molecular clock calibrations suggested divergences occurred during the late Miocene and mid Pliocene, respectively. Given evidence of high dispersal capabilities, the habitat and climatic barriers of the Australian south coast appear too small to have facilitated speciation of the cirrhitoids examined. A mechanism is proposed by which ancestral cirrhitoids were vicariantly isolated into east and west coast populations during periods of climate change. Although Aplodactylus and Goniistius divergences occurred during the same period, separate vicariant events across the Australian north and south coasts are invoked.

The prevalence, intensity, abundance, and density of Anisakis larval infection of four species of New Zealand fish and one species of squid were determined. In order of intensity of infection these were: barracouta (Thyristes atun), tarakihi (Nemadactylus macropterus), red cod (Pseudophycis bachus), red gurnard (Chelidonichthys kumu), and arrow squid (Nototodarus solanii). Some data on infections in monkfish (Kathetostoma giganteum) are also presented. There was no evidence of postmortem migration of larvae in red cod, red gurnard, or barracouta. The larvae did excapsulate postmortem and the excapsulation was less in fish kept on ice. The majority of larvae were associated with the visceral organs and membranes (98.5% or more of the total worm burden). However, a proportion of all fish species examined had small numbers of larvae in the fillets and these may pose a risk to human health.

The use of otolith chemistry as a tool for analysing the biology of fishes assumes that the procedures used to collect and prepare otoliths for analysis do not alter their composition. With otoliths of Nemadactylus macropterus, Hoplostethus atlanticus, and Rhombosolea tapirina, we show that this assumption is not valid for the elements that can be detected using electron-probe microanalysers (those present at concentrations greater than ≃100 parts per million): all six elements routinely measured using these techniques were affected by at least one post-mortem procedure tested. Measured concentrations of calcium and strontium were relatively insensitive to most procedures tested, whereas concentrations of sodium, potassium, sulphur and chlorine were affected substantially by many commonly used procedures. The ease with which otolith composition could be modified post-mortem suggests that apparent geographic, habitat-specific or ontogenetic differences in otolith composition should be interpreted with extreme caution because of easily induced artefacts and the problem of pseudo-replication associated with the ways otoliths are sampled and prepared for analysis.

Specimens of king tarakihi from northern New Zealand were shown to differ from specimens of tarakihi, using two genetic methods: allozymes and random amplified polymorphic DNA (RAPD). Allozyme techniques revealed fixed differences between tarakihi and king tarakihi at one locus and very different electromorph frequencies at a further three loci. There was a genetic distance of 0.35–0.39 between the two morphs. RAPD markers were generated with 10‐base oligonucleotide primers. Three out of 9 primers produced different DNA fragments in tarakihi and king tarakihi collected on the same longline, indicating that the morphs are discrete species. The two morphs could not be distinguished by conventional isoelectric focusing of muscle proteins. We conclude that the king tarakihi is a previously undescribed species found in subtropical waters of northern New Zealand.

The carcass and gut contents of 10 species of fish caught along the eastern coast of Australia were analysed by gas chromatography-multiple ion detection-mass spectrometry for a range of bromophenols including 2- and 4-bromophenol, 2,4- and 2,6-dibromophenol and 2,4,6-tribromophenol. These bromophenols, the cause of iodoform-like off-flavours in seafoods, were found in eight of the above species; the largest total concentrations of bromophenols occurred in the commercially important species Nemadactylus douglasii (40 ng/g). The concentrations of bromophenols in another three species Branchiostegus wardi, Rhabdosargus sarba, and Girella tricuspidata, were found to exceed 10 ng/g while in a further four species their concentrations varied between 3 and 8 ng/g. However, these compounds were not identified in the remaining two species at a detection limit of 0.05 ng/g. The variations among fish diets suggest that the bromophenol content of individual fish can be explained by the relative contribution of benthic organisms and marine algae to the fish diet. Bromophenols were found in all of the benthic carnivores and diverse omnivores examined but were not detected in pelagic carnivorous fish.

Relationships between the anatomy of the endolymphatic sac, sac otoconia, sagitta and astericus of Nemadactylus macropterus (Cheilodactylidae: Teleostei) are described and the variation in opaque and hyaline zones, sulcal checks, and daily microincrement widths along different growth axes of the otolith measured. The quantitative morphology of the otolith is used to compare the different age estimation techniques for N. macropterus that are based on opaque and hyaline zones, sulcal checks, and daily microincrements. Comparison of the different methods shows that at the present state of knowledge daily microincrements present the most credible age estimation method for N. macropterus.

The jackass morwong (Nemadactylus macropterus), a commercially valuable marine fish in the Australian–New Zealand region, was surveyed for genetic variation as part of a larger project aimed at clarifying its stock structure. Mitochondrial DNA variation in 166 jackass morwong from seven southern Australian localities was examined using nine restriction enzymes. The 28 haplotypes identified gave an overall nucleon diversity of 0.671. Mean nucleotide diversity per sample was 0.458%, with a (corrected) nucleotide divergence among samples of 0.001%. There was no significant spatial patterning. Five hundred individuals from eight southern Australian localities and one New Zealand locality were examined using three restriction enzymes detecting polymorphic cut sites. The 33 haplotypes identified gave an overall nucleon diversity of 0.635. Mean nucleotide diversity per sample was 1.247%, with a (corrected) nucleotide divergence among samples of 0.002%. No differentiation was detected among the Australian localities. The New Zealand sample showed weak but significant divergence from the Australian samples. These results were similar to those from a concurrent allozyme analysis, and we conclude that there is appreciable nuclear and mitochondrial DNA gene flow among Australian localities, while the Tasman Sea separating Australia from New Zealand acts as a partial barrier.

The short-scale temporal repeatability in the structure and composition of parasite communities of Nemadactylus bergi were analyzed by comparing population and infracommunity descriptors in five samples caught off Mar del Plata, Argentina (38o 27′ S, 57o 90′ W) at intervals of 20 days. This is the first study aiming to detect relevant local or short-term processes in an area where larval endohelminths dominate the parasite assemblages and are expected to provide predictability to the communities they belong. The parasite fauna of this host species was composed by 18 species, 16 of them being endoparasites, among which larval stages accounted for most of both the number of parasite individuals found and the highest percentages of average similarity among infracommunities. The structure of parasite communities of N. bergi was, as predicted, repeatable across samples at short spatial and temporal scales and, as expected, this predictability was mainly provided by larval stages, namely Corynosoma australe and Grillotia carvajalregorum. These results imply that a single sample of N. bergi from this locality will be enough to catch the structure and intrinsic variability of their component communities in further studies aiming to compare parasite assemblages at larger spatial scales. These studies should, however, take into account the heterogeneity in the size of fish among samples, which proved to be an important confounding factor in comparisons among samples by affecting their similarity.

Rubberlip morwong Nemadactylus douglasii are important members of temperate reef communities off south-eastern Australia where they are targeted by offshore commercial and recreational fisheries. Macroscopic gonad staging and gonadosomatic indices demonstrated that N. douglasii have a distinct autumn/winter spawning period. Males and females attained sexual maturity at approximately 24 cm fork length, corresponding to an age of approximately 3 years old. During the spawning period male gonadosomatic index values were of an order of magnitude smaller than those for females, suggesting that N. douglasii may belong to the group of cheilodactylids that are not group spawners. The method of counting opaque zones in sectioned otoliths to estimate age was validated using marginal increment analysis. The results showed that opaque zones in the otoliths of N. douglasii were similar to other cheilodactylids in this region and formed once each year during spring/early summer. Males grew at a similar rate to females until approximately 2 years of age, after which males grew faster and attained larger sizes. The longest and oldest fish observed during the study were 52.4 cm fork length and 22 years, respectively. N. douglasii were fully recruited to the commercial fishery by 4 years of age and the fishery was dominated (>93%) by fish between 3 and 15 years of age. The age composition in landings showed evidence of variable recruitment through time. The total instantaneous mortality rate was estimated using catch curve analysis and ranged between 0.27 and 0.37 yr−1. Natural mortality was estimated as 0.14 yr−1 based on the maximum observed age. Steady declines during the past three decades in the quantities and average sizes of N. douglasii in landings suggest that the stock has been substantially depleted.

The species of Nemadactylus and Acantholatris are perciform fishes with representatives in each ocean of the Southern Hemisphere. Mitochondrial DNA sequences were obtained from all five species of Nemadactylus, two of the three Acantholatris species, and several outgroup taxa. Analysis of cytochrome b sequences placed A. monodactylus and A. gayi within an otherwise entirely Nemadactylus clade, suggesting that these genera are synonymous. The Acantholatris sequences were also very similar to those from three of the Nemadactylus species, despite their geographic separation. Analysis of D-loop sequences paralleled the cytochrome b results, but provided greater resolution of species relationships. Nemadactylus sp. and A. gayi are transoceanic sister taxa. Polytypic clades observed for N. macropterus and A. monodactylus most likely reflect incomplete sorting of mitochondrial DNA lineages. It is proposed that this group dispersed and radiated during the last 0.6–2.6 million years, and the possible mechanisms of this process are discussed.

Instituto de Investigaciones Oceanologicas,FAREMAR, Universidad de Antofagasta, CasillaPostal 170, Antofagasta, Chile *Departamento deParasitologia Animal, Universidade Federal Rural doRio de Janeiro, Caixa Postal 74508, 23851-970Seropedica, RJ, BrasilKey words: monogenea - marine fishes - ecology -habitat segregation

Per-haul records of catches by steam trawlers on the south-eastern Australian continental shelf from 1918 to 1957 were examined for the main commercial species tiger flathead (Neoplatycephalus richardsoni), jackass morwong (Nemadactylus macropterus), redfish (Centroberyx affinis), latchet (Pterygotrigla polyommata) and chinaman leatherjacket (Nelusetta ayraudi). Catch rates in weight per haul per species were standardised to annual indices of abundance using a log-linear model. Standardised annual index trends for flathead, latchet and leatherjacket indicate a strong to severe decline during the period covered by the data. All species showed seasonal patterns, but the peak season varied depending on the species. The distribution of standardised catch rate by area also differed greatly by species, and no single area showed consistent differences across all species. Day trawls caught more flathead, redfish and latchet, while night trawls caught more morwong and leatherjacket. Moon phase had less influence on catch rates than other factors. The correlation of annual index trends to a number of annual mean environmental factors was examined and no strong correlations were found.

In situ examination of the behaviour of fish was undertaken with underwater cameras positioned on demersal trawl gear used by Australia’s South East Trawl Fishery. Blue grenadier (Macruronus novaezelandiae), pink ling (Genypterus blacodes) and whiptails (Coelorinchus spp.) swam in an anguilliform mode whereas other species displayed a carangiform swimming mode. Tiger flathead (Neoplatycephalus richardsoni) and ocean perch (Heliocolenus spp.) were active in response to the approaching trawl net compared with the generally passive activity of whiptails, New Zealand dory (Cyttus novaezelandiae), and jackass morwong (Nemadactylus macropterus). However, when in the body of the trawl, gemfish were active while ocean perch, whiptails and New Zealand dory were generally passive. Some blue grenadier, ocean perch and whiptails escaped capture by passing through open meshes in the trawl mouth, whereas tiger flathead passed under the ground gear. In the trawl body, small numbers of blue grenadier passed through open meshes in the top panel whereas numerous spotted warehou swam faster than the towing speed, presumably escaping capture by swimming forwards and out of the trawl. Interspecific behavioural variation in escape response could be utilised to design more efficient trawl gears.

Depth-stratified random demersal trawl surveys of the shelf of southern and eastern Tasmania from summer 1993 to summer 1995 showed seasonal variations in abundance of N. macropterus in all depth strata, although the trend varied between years, with abundance peaking in summer 1993 and winter 1994. This variation is attributed to the seasonal movement of fish from south-eastern Tasmanian shelf waters, although some seasonal change in size composition is also evident. Catch rates were highest on the outer shelf and lowest on the inner shelf, reflecting the distinct size-structuring, with juveniles concentrated on the inner and mid shelf and mature fish on the outer shelf. Size compositions differed among shelf regions, with few mature fish on the mid shelf of Storm Bay compared with the same stratum on the east coast, indicating that the bay is primarily a nursery area for the species. Settlement from the pelagic post-larval phase occurred in spring and early summer at 7–9 cm, with evidence of movement between inner-and mid-shelf strata by autumn. Abundance of 0+ fish was highest in 1993 and 1994 and a considerable decrease in the abundance in both regions in 1995. The influences of local hydrography and the large size at settlement are discussed.

Haul-by-haul steam trawler catch and effort data for 1918–23, 1937–43 and 1952–57, which cover a large portion of the history of steam trawling in the Australian South East Fishery, were examined in detail for the first time. There were 64371 haul records in total. The catch-rate for all retained catch combined shows a strong decline overall, with a brief recovery during World War II, probably due to increased retention of previously discarded species. The fishing fleet moved to more distant fishing grounds and deeper waters as the catch-rate declined. The catch-rates of the main commercial species followed a similar pattern in a number of regions within the fishery. The catch-rate of the primary target species – tiger flathead (Neoplatycephalus richardsoni) – dropped considerably from the early, very high, catch-rates. Chinaman leatherjacket (Nelusetta ayraudi) and latchet (Pterygotrigla polyommata) – species that were apparently abundant in the early years of the fishery, virtually disappeared from catches in later years. The appearance of greater catches of jackass morwong (Nemadactylus macropterus), redfish (Centroberyx affinis) and shark/skate during the war and afterwards was probably due to increased retention of catches of these species. The disappearance of certain species from the catch may be due to high fishing pressure alone, or to a combination of fishing pressure, changes in the shelf habitat possibly caused by the trawl gear, and environmental fluctuations.

Transverse sections of sagittae were examined. The first and second annual increments were defined by examination of the progression of otolith radius and length of the 0+ and 1+ cohorts. Growth in both sexes is rapid until ~5 years old (32–35 cm), and then slows appreciably. There was a broad range of lengths within individual age-classes, with a maximum of 12 age-classes present in a 1 cm length-class. Maximum ages of males and females were 41 and 30 years, respectively, which is considerably higher than previously estimated from whole otoliths. There was no significant difference in the growth curves between males and females, although this is influenced by the large number of juveniles and by the examination of relatively few large, older fish. The sex-specific von Bertalanffy growth parameters are: L∞ 38.4 cm FL, t0 –0.07 years, K 0.36 year–1 for females and L∞ 36.2 cm FL, t0 0.15 years, K 0.42 year–1 for males. The age composition was dominated by 4–7 year olds but showed evidence of considerable recruitment variability, particularly in the strong 1988 year-class. The relationship between the life-history strategy of N. macropterus and recruitment variability is discussed.

Nemadactylus macropterus was sampled from eight localities around southern Australia, ranging from Western Australia to New South Wales, and from one area off the western coast of New Zealand. Thirty-three enzyme loci were analysed by gel electrophoresis. Average heterozygosity per locus per sample was 10.1 %, ranging from 8.4% to 11.I% per sample. Although no significant differentiation was observed among the Australian samples, there was significant differentiation between the Australian and New Zealand samples. This was primarily attributable to variation at the sAAT-I * locus, where the common allele had a frequency of around 0.80 in Australian samples and around 0.94 in the New Zealand sample (P

Various brining times in saturated salt solution and various drying temperatures were used to produce dried Nemadactylus macropterus fillets. The quality of the products was assessed visually before and after reconstitution and also by scanning electron microscopy and isoelectric focusing of the water-soluble proteins. Product quality deteriorated when brining times exceeded 24 h and also as drying temperatures rose. This was evidenced by poor appearance and reconstitution behaviour, disruption of surface and deep tissue and changes in soluble protein components. An acceptable product was obtained by brining for 8h followed by drying at 50°C. The composition of this product was comparable with that of some commercial dried fish products from South-east Asia.

The catch-curve method was used to estimate the instantaneous rate of total mortality (Z) of jackass morwong (Nemadactylus macropterus) in south-east Australian waters. Age-frequency distributions were obtained for fish collected from eastern Bass Strait during the 3 years. March 1982–February 1985. Fish were obtained from: (1) demersal research fishing surveys stratified by depth; (2) commercial landings from eastern Bass Strait; (3) commercial landings from the adjacent New South Wales fishery. Jackass morwong were found in water 65–299-m deep, and almost half the biomass was in water 90–179-m deep. Our estimate of the total biomass (from the survey results) of the part of the population in eastern Bass Strait was 15 700 t. The oldest male morwong caught was 11 years old, the oldest female 13 years old. From the survey data, total mortality (Z) was estimated as 0.45 for males, which is equivalent to an annual survival rate (S) of 0.64, and as 0.47 for females, equivalent to an S of 0.63. There was substantial annual variation in estimates of Z. For the survey results, the annual mortality rate estimated for males was significantly different from that for females. The instantaneous rate of fishing mortality (F) estimated from population biomass and mean commercial landings was very low (about 0.024; sensitivity analysis indicated a possible range of 0.012–0.072), and indicated that about 2% (by number; range 1–6%) of the part of the population in eastern Bass Strait was harvested annually. Z values estimated from samples of commercial landings were consistently larger than Z estimated from the survey samples. Using estimates of Z from commercial landings data resulted in high values of M (the instantaneous rate of natural mortality), which were inconsistent with the longevity of the species and the proportion of older fish found in the population. We believe this to be due to bias in the way commercial landings sample the population, and to be an inherent bias in the use of age-frequency data from commercial landings unless some correction for size-selectivity due to commercial fishing gear and fishing behaviour can be made.

A new genus and species of the Hatschekiidae, Laminohatschekia synaphobranchi, is described from an eel caught off New Caledonia. It is characterised by its long ribbon-like trunk and by the possession of three pairs of biramous legs. The pennellid Sarcotretes scopeli is redescribed from a macrourid also taken off New Caledonia. Sarcotretes lobatus is recognised as a synonym of S. scopeli. Phrixocephalus carcellesi is described in detail for the first time, from the stomach contents of a King Shag caught in the Falkland Islands. A wide range of individual variability in holdfast structure was noted in P. carcellesi. A new species, Peniculisa bellwoodi, is described from Pomacentrus amboiensis collected at Lizard Island on the Great Barrier Reef. The sphyriid Lophoura cornuta is redescribed from a synaphobranchid eel caught off New Caledonia and both sexes of a lernanthropid, Aethon morelandi, are redescribed from Nemadactylus macropterus in southern Australia.

Combinations of potassium sorbate and polyphosphate, in conjunction with vacuum or modified atmosphere packaging, were assessed for their preservative effects on morwong fillets (pH 6.75) stored at 4°C. Vacuum packaged and/or frozen fillets were used as comparisons for microbiological and taste panel analysis. A combination of potassium sorbate, polyphosphate and 100% CO2 was the most effective packaging regime. Potassium sorbate on vacuum packaged fish was more effective than a 100% CO2 atmosphere alone. Polyphosphate had no apparent additional effect on fillets stored under vacuum with or without potassium sorbate.

The postlarval metamorphosis of the tarakihi Cheilodactylus macropterus (Bloch and Schneider) takes place in New Zealand waters in spring or early summer (October‐December), when the fish are 70–90 mm long and 9–12 months old. For the scales below the lateral line, the growth pattern changes during the post‐larval metamorphosis, and the boundary between the central shield and remainder in these scales is formed during this event. Three types of hyaline rings occur in otoliths of postlarvae and/or juveniles: ring type A, with a diameter of 0.1–0.3 mm, possibly formed during the first winter or the larval metamorphosis; ring type B, with a diameter of 0.8–1.2 mm, formed during the postlarval metamorphosis; and ring type C, with a diameter of 1.5–1.6 mm, formed during the second winter. The early life histories of related species and the general absence of records of postlarval tarakihi from trawl catches suggest that they may be pelagic and may occur in offshore waters, and that small tarakihi assu...

The total mercury content of six species of Australian commercial fish (John dory. Zeus faber: mirror dory. Zenopsis nebulosus; tiger flathead, Neoplatycephalus richardsoni; rubberlip morwong, Nemadactylus douglasii; jackass morwong, Nemadactylus macroprerus; and sand whiting, Sillago ciliata) is reported. Total mercury content is regressed against fish length and the resultant equations and correlation coefficients are presented for each species. A length-frequency histogram derived from the Sydney Fish Market data and a length-mercury content curve are plotted as an overlay for each of the six species. The integrated average mercury content (mg/kg) has been calculated for each species and these are as follows: sand whiting, 0.08; rubberlip morwong, 0.13; tiger flathead, 0.14; John dory, 0.14; mirror dory, 0.15; and jackass morwong, 0.16. The graphical method adequately demonstrates the relationship between mercury levels and the commercial size range of particular species.

Catch curves were analysed to estimate the annual total mortality of jackass morwong landed at the port of Eden between July 1976 and June 1979. The annual total mortality of females was lower in 1978-1979 than in the previous 2 years, reflecting the expansion of the trawl fishery in New South Wales to include previously unexploited deepwater grounds. Males were fully recruited to the commercially exploited population at an earlier age than females. It is suggested that the increased mortality in older males is due to an increase in natural mortality.

N. macropterus, landed at the port of Eden, were sampled from July 1976 to June 1979. Saggital otoliths were used for age determination. A hyaline and an opaque ring were found to be formed during winter and summer. respectively. The growth of adult N. macropterus was adequately described by the von Bertalanffy growth curve. Females (K = 0.13, L∞ = 51.13) were found to grow faster, and to a greater age, than males (K = 0.17. L∞ = 45.50). No significant difference between sexes was apparent in the length-weight relationships.