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Se realizó la caracterización mensual de las agregaciones de merluza de cola usando registros acústicos obtenidos por equipos SIMRAD EK60 y ES60 a bordo de tres embarcaciones multipropósito que operaron en la Unidad de Pesquería Centro-Sur durante el año 2003, para lo cual se emplearon descriptores morfológicos y batimétricos. En cuanto a su morfología, las agregaciones mostraron una amplia variabilidad, explicada por su nivel de cohesión y tendencia a formar agregaciones de gran extensión horizontal, mientras que batimétricamente se determinó que el 90% de éstas se ubicaron preferentemente entre 300 y 450 m. Existe evidencia de asociación entre diversos descriptores y estos a su vez con otros factores como talla media, temperatura del agua, latitud y mes, lo que permite describir apropiadamente la forma de las agregaciones y su ubicación en la columna de agua. Algunas relaciones relevantes corresponden a: profundidad de las agregaciones respecto a la profundidad del fondo (r = 0,55), altitud de las agregaciones respecto a la profundidad del fondo (r = 0,72), altitud de las agregaciones respecto al índice de profundidad relativa (r = -0,98) y profundidad de las agregaciones respecto a la talla media (r = 0,66).A monthly characterization of Chilean hoki aggregations was done using acoustic records ob-tained with SIMRAD EK60 and ES60 devices aboard three multipurpose vessels that operated in the central-southern fishery unit during 2003; this considered morphological and bathymetric descriptors. The wide mor-phological variation of the aggregations was explained by their cohesión level and tendency to form large horizontal aggregations whereas, bathymetrically, 90% of the aggregations were located between 300 and 450 m. Evidence of associations between various descriptors was found, and these were, in turn, associated with other factors such as mean size, water temperature, latitude, and month, allowing an adequate description of the shape of the aggregations and their location in the water column. The relevant relationships were: aggrega-tion depth with regard to bottom depth (r = 0.55), aggregation altitude with regard to bottom depth (r = 0.72), aggregation altitude with respect to the relative depth Índex (r = -0.98), and aggregation depth with respect to mean size (r = 0.66).

Delta-based estimates of longtail hake biomass off Argentina were derived from the results of summer trawl surveys carried out on an irregular basis since 1987. Annual estimates of biomass within the whole area ranged from 1.2 to 4.5 million tons, consistent with those obtained by sequential population analysis. There was no clear trend throughout the period 1987-1995, but the 1987 estimate was higher than those for the same area during the years 1992-1995, and estimates since 1997 were much higher than the mean for the four-year period 1992-1995. Since 1992 the largest concentrations of fish have been between 50 and 100 m deep. Most of those were adults, small fish being scarce. Analysis of numbers-at-age showed the dominance of 4-8 year old fish in 1987 and from 1992 to 1994 and the existence of two very strong year-classes, those of 1993 and 1995.

Patagonian grenadier migrates from the southwest Atlantic and southeast Pacific to reproduce in the northern Chilean Patagonia. Spawning occurs mainly in winter at the continental shelf break (CSB), but eggs and larvae are also collected inshore of the Chilean Patagonian Estuarine System (PES) during winter and spring. In order to evaluate whether the ontogenetic changes in distribution of early life stages was part of the reproductive strategy of Patagonian grenadier, we analyzed the distribution and transport of eggs and larvae in spring and winter in three channels of the PES (Ninualac, Darwin and Pulluche channels). Ichthyoplankton stratified sampling showed the highest abundances of eggs in the deepest strata, whereas larvae were heterogeneously distributed along the entire water column. Residual current velocities obtained from ADCP indicated seaward (westward) fluxes at the surface in all channels, except in Pulluche in winter. At depth (50–100 m) fluxes were eastward (inshore) in the northern 2 channels but seaward in the southernmost channel. These differences in residual velocities, with variations in the distribution of eggs and larvae, resulted in different landward and oceanward flows of eggs and larvae among channels and strata. Estimated net fluxes in winter suggested that eggs within the channels would either enter the PES from the continental shelf, mainly at the subsurface layer of the Darwin channel, or come from a secondary spawning within this same channel. Eggs and small larvae would be retained at the inshore zone of the Darwin channel, and the more advanced developed stages would be exported through the Pulluche channel back to the continental shelf. The inshore high abundance of eggs and larvae of M. magellanicus in winter, along with the reduced primary production and microbial-based plankton community previously reported, suggest that entering the channels in winter is not a major part of the reproductive strategy of the species. The exportation of larvae from the channels to the shelf in winter, instead, might promote better feeding conditions in offshore waters where larger zooplankton occurs. • Scarce M. magellanicus eggs and larvae occurred in spring. • Most eggs in the channels in winter come from the continental shelf. • M. magellanicus eggs and small larvae are retained at the estuarine channels. • More developed larvae of M. magellanicus are exported to the continental shelf. • Larger larvae exported to the shelf in winter could favor their feeding success. [ABSTRACT FROM AUTHOR]

Comparison of larval growth and back-calculated hatch dates on the basis of microstructure analysis of sagitta otoliths were carried out in wild-caught larvae of three commercially important gadiform fishes from Northern Patagonia, South Pacific, Chilean hake Merluccius gayi , southern hake Merluccius australis , and Patagonian grenadier Macruronus magellanicus . Because of the morphological similarities in their larval stages, we hypothesize that early life traits (ELT) will be different among the hake species in order to avoid/reduce interspecific competition. During October–November 2011, there was differences in the spatial distribution of the surviving larvae from the three species along the inner sea; while larval Chilean hake were concentrated in the warmer and fresher seawaters of the Reloncaví fjord, larval Patagonian grenadier were aggregated southward, in the Ancud Gulf, while larval southern hake were found throughout the area, but in low density. Temporal differences were evident in the back-calculated hatch days among species; larval hakes of genus Merluccius hatched during late October, while larval grenadier hatched between August and September. Estimated larval growth rates differed among hake species; larval M. magellanicus experienced the fastest growth rates (0.334 ± 0.01 mm d −1 ), while larval M. australis experienced growth rates of 0.220 ± 0.01 mm d −1 , and larval M. gayi showed the slowest growth rates (0.180 ± 0.01 mm d −1 ). Therefore, resource partitioning both in time and space are occurring among early life stages of M. gayi , M. australis and M. magellanicus during austral spring season in Northern Patagonian fjords of Chile. [ABSTRACT FROM AUTHOR]

Niklitschek, E. J., Secor, D., Toledo, P., Valenzuela, X., Cubillos, L., and Zuleta, A. 2014. Nursery systems for Patagonian grenadier off Western Patagonia: large inner sea or narrow continental shelf? – ICES Journal of Marine Science, 71: 374–390.Adjacent to Chile's long and narrow continental shelf, the Patagonian Inner Sea (PES) is among the largest and most complex estuarine systems in the world. The PES harbours high concentrations of juveniles and adults of important groundfishes, which spawn within or in near proximity to it. A dominant view is that recruitment primarily originates here rather than in adjacent coastal regions. We used otolith stable isotopes to evaluate the relative contribution of several PES and continental shelf regions to recruitment of Patagonian grenadier, one of the most abundant groundfishes in the area. Seawater chemistry confirmed that δ13C and δ18O differentiated these nursery and feeding regions. Estimated recruitments from PES nurseries to adult feeding regions were important (10–35%), but lower than dominant contributions from shelf nurseries (64–85%). Stable isotope differences within otoliths indicated, however, that most adults had previously used PES habitats as subadults. Adults exhibited stronger homing to feeding habitats in the PES than to shelf regions, suggestive of seasonal site fidelity or partial migration behaviours. The proximity of principal spawning areas to the bifurcation of the West Wind Drift Current may cause large interannual and decadal variations in larvae transport and the relative contribution of different shelf and PES nurseries to recruitment. [ABSTRACT FROM PUBLISHER]

Abstract: The aims of the present study were to investigate the protozoan and metazoan parasite fauna of hoki Macruronus magellanicus in the Southwest Atlantic and Southeast Pacific and to identify parasites of potential value as biological tags for stock identification and migrations. In 2007 a total of 76 hoki were examined from three locations, two off the coast of Chile and one off the Falkland Islands. Two further samples were taken in 2009, one of 32 hoki taken from a position off the coast of Chile between those sampled in 2007 and one of 42 juvenile hoki taken off the Falkland Islands. Seventeen different parasite taxa were recorded, including eight identified to species. Seven were new host records for hoki, and at least three, and possibly as many as five, are new species. The most promising tag parasites for hoki stock identification are the long-lived larvae of the cestodes Hepatoxylon trichiuri and Pseudophyllidea gen. sp. and of the nematode Anisakis sp. Three others – the myxosporean Myxidium baueri, the nematode Pseudascarophis sp. and the acanthocephalan Echinorhynchus longiproboscis – were identified as potentially useful for following seasonal migrations of hoki and for estimating the proportions of fish of different origin in mixed samples. [Copyright &y& Elsevier]

Abstract: Pre-spawning adult samples of long tailed hake, Macruronus magellanicus, were obtained from fisheries vessels in one location in the southeast Pacific Ocean and three in the southwest Atlantic Ocean, at different latitudes. Population structure was determined based on six nuclear hypervariable microsatellite loci and on mitochondrial DNA sequence variation at the locus COI. Paired tests of genic differentiation for microsatellite loci indicate the existence of genetic population structure for this species, where significant differences exist between some southern and northern samples. Multivariate analysis (factorial correspondence analysis) of microsatellite variation showed differentiation between the Pacific and the Atlantic populations. Analysis of the mitochondrial variation confirmed the microsatellite analysis of population structure, and revealed some additional differentiation between northern and southern Atlantic samples and exclusive haplotypes in each region. These findings suggest that the species should be managed as north–south separate stocks in the Atlantic Ocean. [Copyright &y& Elsevier]

The distribution patterns of many fishes between the three continents (Africa, Australia, and South America) in the Southern Hemisphere have been uncovered to be influenced by mostly vicariance or historical dispersal. Although some demersal fishes with intercontinental distribution are suggested to be more influenced by current/recent dispersal, few genetic studies have been made for demersal fishes so far. To provide more information for such fishes, genetic divergence was analyzed for two pairs of gadiform species and subspecies distributed around Australasia and South America: the blue grenadier, Macruronus novaezelandiae (from New Zealand) and the Patagonian grenadier, M. magellanicus (from South America) as well as two subspecies of the southern blue whiting, Micromesistius australis pallidus (from New Zealand) and M. a. australis (from South America). The sequence analyses of two mitochondrial DNA regions showed no divergence between Australasian and South American populations of the grenadiers and the southern blue whiting. The microsatellite DNA analysis also indicated significant but very minimal genetic differentiation between the two geographic populations of each pair. These results imply rather recent separation of the two geographic populations. Current/recent dispersal may be an important common factor for determining the distribution of demersal fishes in the Southern Hemisphere. Nonetheless, low but significant genetic differentiation observed requires treating the two populations of the economically important grenadiers and southern blue whiting, respectively, as different stocks for proper resource management. [ABSTRACT FROM AUTHOR]

Abstract: Changing targeting behavior of fishing fleets and zero-catch records of the target species are two characteristics common to many multi-species trawl fisheries. These features complicate analyses intended to produce indices of relative abundance from commercial catch rate data. Trawl catch rates of Patagonian grenadier caught off Southern Chile were used to calculate indices of relative abundance for this species. To allow for targeting behavior and zero catches, we first defined a subset of relevant tows combining a logistic regression on the species catch composition and knowledge about the persistence of Patagonian grenadier in the catches from the area where historically it has been more abundant. A standardization analysis was then conducted on this subset of the data using a generalized linear model (GLM) framework. Analysis of deviance tables and standard residuals GLM diagnostic plots were used for selecting the statistical models that best described the data. The candidate models tested were the delta-lognormal, delta-gamma, quasi-Poisson and compound Poisson. The models that best supported the Patagonian grenadier catch rate data were the delta-lognormal and compound Poisson models. Standardization models were then extended to generalized linear mixed models to include the vessel main effect and the significant interactions with the year effect as random effects. Estimations of the annual series of relative abundance were then obtained from the coefficients of the year effects of these models, both of which showed higher abundance for the years 2001--2008 than in previous years of the series. [ABSTRACT FROM AUTHOR]

Abstract: Trace element fingerprints of edge and core regions in otoliths from 260 specimens of Patagonian hoki, Macruronus magellanicus, were analyzed by LA-ICPMS to reveal whether this species forms one or more population units (stocks) in the Southern Oceans. Fish were caught on their spawning grounds in Chile and feeding grounds in Chile and the Falkland Islands. Univariate and multivariate analyses of trace element concentrations in the otolith edges, which relate to the adult life of fish, could not distinguish between Atlantic (Falkland) and Pacific (Chile) hoki. Cluster analyses of element concentrations in the otolith edges produced three different clusters in all sample areas indicating high mixture of the stocks. Cluster analysis of trace element concentrations in the otolith cores, relating to juvenile and larval life stages, produced two separate clusters mainly distinguished by 137Ba concentrations. The results suggest that Patagonian hoki is a highly mixed fish stock with at least two spawning grounds around South America. [Copyright &y& Elsevier]

Abstract: The ontogenetic, seasonal, bathymetric and regional variations in the feeding spectrum of 922 specimens of southern blue whiting Micromesistius australis and 512 specimens of hoki Macruronus magellanicus were studied on the Falkland Islands’ shelf (Southwest Atlantic) between November 1999 and April 2003. A total of 49 different prey items were found in the stomach contents of the two species, with the hyperiid Themisto gaudichaudii and Euphausiacea being amongst the most important prey. Although the species composition did not change over fish size, the proportions of individual prey items in their diets did, with an increase in T. gaudichaudii and Euphausiacea with increasing fish size in southern blue whiting. The opposite occurred in hoki. Seasonal variations in the diet were found to mirror the seasonal abundance of prey around the Falkland Islands for the two species. Intra-specific differences in the diet of both predators reflected the distribution of prey, which in turn was determined by the water structure in the two regions sampled, leading to very different diets. In the limited time that the two species occupied the same space there was little or no competition resulting in almost total segregation of their trophic niches in space and time. [Copyright &y& Elsevier]

A monthly characterization of Chilean hoki aggregations was done using acoustic records obtained with SIMRAD EK60 and ES60 devices aboard three multipurpose vessels that operated in the centralsouthern fishery unit during 2003; this considered morphological and bathymetric descriptors. The wide morphological variation of the aggregations was explained by their cohesion level and tendency to form large horizontal aggregations whereas, bathymetrically, 90% of the aggregations were located between 300 and 450 m. Evidence of associations between various descriptors was found, and these were, in turn, associated with other factors such as mean size, water temperature, latitude, and month, allowing an adequate description of the shape of the aggregations and their location in the water column. The relevant relationships were: aggregation depth with regard to bottom depth (r = 0.55), aggregation altitude with regard to bottom depth (r = 0.72), aggregation altitude with respect to the relative depth index (r = -0.98), and aggregation depth with respect to mean size (r = 0.66). [ABSTRACT FROM AUTHOR]

The article presents a study on the lack of divergence in the mitochondrial cytochrome b gene between the Macruronus novaezelandiae and Macruronus magellanicus grenadiers in the Southern Hemisphere. It investigates on the extent of genetic difference between the two putative species by using partial sequences of the mitochondrial deoxyribonucleic acid (DNA) cytochrome b in a phylogenetic analysis and in an analysis of molecular variance (AMOVA).

The impact of geographic heterogeneity and historical demographic factors on genetic diversity in the commercially exploited hake Macruronus magellanicus was examined applying microsatellite markers. A total of 450 fish from 6 different sites, collected in Atlantic Patagonia, were genotyped at 6 polymorphic loci. While analysis of variance-based methods ( Fst-Rst) failed to detect differentiation, the exact test for genic differentiation and factorial correspondence analysis revealed subtle differences between coastal and continental shelf edge samples. Data suggest that M. magellanicus has been subjected to a demographic expansion 2.6 to 5 times its original size thatoccurred approximately 100,000 to 200,000 years ago. Another more recent expansion seems to have occurred a few generations ago. Implications of subtle structuring and demographic instability are discussed. [ABSTRACT FROM AUTHOR]

The long-tailed hake, Macruronus magellanicus, is widely distributed in the SW Atlantic, and although it is commercially exploited, the extent of genetic structuring remains unclear. The hypothesis of a separate inshore stock as suggested by past biological data in northern Patagonia was tested with RFLP profiles of the mtDNA region ND5/6, in a total of 160 animals from eight locations. Sequence divergence between populations was nil, and all diversity is contained within populations. Despite the lack of geographic structuring in the distribution of haplotypes, the inference of population homogeneity should be taken cautiously owing to the skewed frequency distribution of haplotypes, with one allele accounting for 63% of individuals. A phylogenetic analysis of haplotypes reveals a star-shaped pattern with the presence of two lineages that may represent a population expansion. A rapid turnover of lineages, sweepstake recruitment, rapid expansion, or vulnerability to environmental conditions is not only suggested by the network pattern, but also by the departure from neutrality expectations. However, the role of selection cannot be ruled out until more loci or markers are examined. [Copyright &y& Elsevier]

Is the otolith weight (OW) of Patagonian grenadier, Macruronus magellanicus, useful for estimation of age? This question is addressed analyzing the otolith mass growth rate through both monthly otolith weight–frequency data (OWFD) and the relationship between OW and observed age. Samples were obtained from the purse-seine fishery in spring and summer of 1996 and 1997 in the central-southern area off Chile (36–40°S). We considered that a constant otolith mass growth rate among cohorts is necessary to support the hypothesis that OW is directly related to the fish age. The modal structural analysis of OWFD was done by sex using the MIX computer software. The mean OW of the identified cohorts progressed and persisted along the time axis with a constant otolith mass growth rate. This growth rate was not statistically different among cohorts, nor between sexes, and the estimate for both sexes was 32.6 mg per year. The otoliths sampled in 1996 were used to determination of age by interpretation of annuli in the surface of whole otoliths. The relationship between OW and observed age was linear and statistically significant, and the slope of regressions forced to pass through the origin were 31.8, 31.0, and 31.4 mg per year for males, females and both sexes respectively. We concluded that the results support the hypothesis that OW is related with the age of M. magellanicus. [Copyright &y& Elsevier]

SUMMARY:This paper describes a method of evaluating virtual codend selectivity with covernet selectivity when the mesh size of the covernet is not small enough to retain all the fish that enter the covernet. If the covernet mesh size is not small enough, small fish can escape through the covernet mesh after passing through the codend, and then their body length proportion retained in the codend will be overestimated. We developed a model in which covernet selectivity can be estimated at the same time as accurate codend selectivity. The validity of the method was examined with data from a covered-codend experiment on the Patagonian grenadier Macruronus magellanicus collected in the southwest Atlantic. The model fits the data well even though the plots of proportion retained were U-shaped. For both the codend and covernet selectivity estimated in the model, fish of length close to 100% selectivity had a girth close to mesh perimeter. This supported that both the codend and covernet selectivity estimated in the model were reasonable. The analysis proposed in the present study would be useful to obtain accurate estimates of codend selectivity by evaluating the effects of covernet selectivity on the data. [ABSTRACT FROM AUTHOR]

The occurrence of the merluccid Macruronus novaezelandiae from tropical waters off Bahia, eastern Brazil, is reported for the first time due to the capture of an adult of 712.3 mm standard length in May 2008, from a depth of 400 m. Until then no specimen had been reported north of 32°29′S on the South American Atlantic coast. This new record extends the species' range to about 2500 km northwards along the Brazilian coastline and is the first ever from tropical waters in the world. A comparison of the morphometric characters is provided. [ABSTRACT FROM AUTHOR]