Genypterus Blacodes Research Articles

The impacts of fish body size changes on stock recovery: a case study using an Australian marine ecosystem model

Abstract 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.

DNA Barcoding identification of commercialized seafood in South Brazil: A governmental regulatory forensic program

Here we report a governmental initiative to enforce a regulatory program based on DNA Barcode identification of mislabeled seafood products commercialized in Southern Brazil marketplaces, resulting in financial penalties to retailers. The Brazilian Governmental Regulatory Agency (PROCON) confiscated 30 seafood samples from fishmongers, supermarkets and restaurants of commercially important species such as cod, flounder, grouper, tuna and pink cusk-eel. Using the standard DNA Barcode methodology (i.e. 650bp of the mitochondrial gene COI), we identified all the 30 samples of fresh, frozen, cooked and fried seafood to the species level. Cases of mislabeling were found in 24% of samples obtained. We found that highly priced species (flounder, pink cusk-eel and cod) were substituted for cheaper species (basa and Alaska pollock). Establishments involved in cases of mislabeling were officially notified by the Governmental Regulatory Agency and financial penalties were applied. The implementation of such regulatory programs using innovative technologies, such as DNA based identification methods, may discourage deliberate replacement in the seafood market and lead to a significant reduction in seafood mislabeling.

Use of a negative binomial distribution to describe the presence of Sphyrion laevigatum in Genypterus blacodes

This paper describes the frequency and number of Sphyrion laevigatum in the skin of Genypterus blacodes, an important economic resource in Chile. The analysis of a spatial distribution model indicated that the parasites tended to cluster. Variations in the number of parasites per host could be described by a negative binomial distribution. The maximum number of parasites observed per host was two.

Reproductive ecology of the female pink cusk-eel (Genypterus blacodes): evaluating differences between fishery management zones in the Chilean austral zone

The pink cusk-eel (Genypterus blacodes), a benthic-demersal fish confined to the southern hemisphere, supports an important commercial fishery in Chile where it is exploited over an extensive geographic area. Although the fishery was originally divided into a northern (41o28′–47o00′S) and southern (47o00′–57o00′S) zone for the purposes of fisheries management, recent studies have reported significant differences in life history parameters between these zones. Individuals from the southern zone reached larger asymptotic sizes and possessed higher survival rates compared to the northern zone. We estimate and compare the gonadosomatic index (GSI), shape of the maturity ogive, and length at 50 % maturity (L50%) of female G. blacodes between management zones and across time using biological data collected from the industrial fleet between 1985 and 2009. Females in the northern zone had higher monthly mean GSI than females in the southern zone. Our analyses also revealed L50% to be significantly higher in the southern zone than in the northern zone from 1985 to 2009. The significant differences in life-history traits between fishery management zones agree with the trade-offs predicted by Charnov’s life history theory. Together these results provide additional support for the hypothesis that two separate stocks exist and suggest that females from the northern zone have developed a life-history strategy, which favours early maturation and a proportionally greater investment in reproduction than females from the southern zone.

Survey into the seafood consumption preferences and patterns in the portuguese population. Gender and regional variability

With the purpose of achieving a deeper knowledge of one of the most important seafood markets in Europe, a survey into the seafood consumption preferences and patterns in the Portuguese population was carried out. A thorough, comprehensive, and simple questionnaire was developed. Consumers were asked to state their preferences towards fish products, their consumption frequencies, the average meal portion, and the usual culinary treatments. Respondents provided personal data: gender, age, geographical location, education level, weight, height, and health condition. This paper presents the first part of the study’s results, focusing mainly on the gender and regional variables. Portuguese consumers prefer wild to cultured fish as well as fat to lean fish. Chilled fish is preferred over frozen, salted/dried, canned, and smoked fish, being the latter the least preferred. Soaked cod, hake, and canned tuna are the most eaten seafood products. Men prefer to a greater extent wild and smoked fish. Men consume more cephalopods and sardine and women eat more frequently hake, pink cusk-eel, and redfish. Coastal populations prefer wild fish. Algarve (southern Portugal) consumers exhibit a stronger tendency to wild and whole fish and consume more sardine and sole. Madeira archipelago consumers are particularly fond of black scabbard fish.

Aporocotyle mariachristinaen. sp., andA. YmakaraVillalba & Fernández, 1986 (Digenea: Aporocotylidae) of the pink cusk-eel,Genypterus blacodes(Ophidiiformes: Ophidiidae) from Patagonia, Argentina

Aporocotyle mariachristinae n. sp. and A. ymakara Villalba & Fernández, 1986 were collected from the bulbus arteriosus and ventral aorta of pink cusk-eels, Genypterus blacodes (Forster, 1801) from Patagonia, Argentina. A. mariachristinae n. sp. can be distinguished from all the species of Aporocotyle by the asymmetrical extension of posterior caeca (right posterior caecum longer, terminating at the area between mid-level of ovary and posterior body end; left posterior caecum shorter, terminating at the area between mid-level of cirrus sac and posterior to reproductive organs), the distribution of spines along the ventro-lateral body margins and the number of testes. The new species clearly differs from A. ymakara, from the same host species, in the esophagus / body length ratio, the absence of distal loops at caeca, the anterior caeca / posterior caeca length ratio, and the number of testes. Additionally, in A. ymakara the left posterior caecum may be longer than right posterior caecum, while in the new species left posterior caecum is always shorter. The specimen of A. ymakara collected from Argentina is also described. We also provide observations of the distribution of spines in different species of Aporocotyle, including new specimens of A. argentinensis Smith, 1969 from Merluccius hubbsi Marini, 1933. Molecular sequence data obtained from partial 18S and 28S rDNA regions were compared between the new species and other two species of Aporocotyle (A. argentinensis and A. spinosicanalis Williams, 1958). This is a new locality record for A. ymakara, extending the known geographical distribution for this species from Chile to Argentina, and the first report of two species of Aporocotyle in the same host species and locality.

Lectin histochemical aspects of the ovarian lamellae epithelium of Genypterus blacodes (Schneider, 1801)

The composition and distribution of the glycoconjugates (GCs) secreted by the epithelium of ovarian lamellae with reference to the reproductive biology of Genypterus blacodes (Schneider, 1801) through lectin hi stochemistry is here discussed. In this species, the epithelial cells that line the ovarian cavity presented sharp morphological variations along the reproductive cycle related to the mucus secretion that accompanies oocyte ma turation. During sp awning season, residues of mannose and N-acetylglucosamine were detected in the glycocalyx of those cells using lectinhistochemistry. N- acetylgalactosamine and fucose were also observed in the same zone. The greatest variations in the lectinhistochemical pattern were found in the apical cytoplasm composition in comparison to the basal zone of the cells. The results of the present study were discussed by comparing their possible functional implications.

The economic cost of seabird bycatch in Argentinean longline fisheries

SummarySeabird mortality in longline fisheries is believed to be an important cause of the reductions in many seabird populations worldwide, and results in reduced fishing efficiency and economic losses for fishing companies. We estimated the economic cost of not using seabird bycatch deterrents in Argentinean longline fisheries, with the intention of encouraging adoption of mitigation measures in those fisheries. We conducted the study in the Argentine ling Genypterus blacodes and Patagonian toothfish Dissostichus eleginoides fisheries from 2001 to 2006 on three fishing vessels. Data on the incidence of seabird bycatch were collected by seabird observers specially trained in seabird identification and data on the catch rates of target species, cost of bait and fish were provided by the fishing company, supervised by Federal Inspectors from the Provincial Fisheries Agency. To estimate the bait loss, we set lines both with and without the use of deterrents (streamer lines, night setting and strategic discharge of offal) in both fisheries. Seabird bycatch varies temporally and geographically, so to estimate economic losses using deterrents in each fishery, we used different bycatch rates/1000 hooks registered for different periods and fishing areas. Bycatch rates in the absence of deterrents were two birds/1000 hooks and 1.53 birds/1000 hooks for the Patagonian toothfish and ling fisheries, respectively. These rates equate to the loss of more than 1.5 and 2 million dollars over a 10 year period for each fishery. When estimations are made with lower mortality rates, economic losses declined abruptly and were in the order of hundreds of dollars/fishing trip, for the same period of time. Results show that using deterrents, long term profits for the fishing company increase at a considerably high rate (the decrease in monetary loss is an order of magnitude), and the mortality of seabirds decreases by the same proportion (CPUE of seabirds decreases from tens of thousands to a few hundred). In these fisheries, the use of mitigation measures that reduce bait loss and seabird mortality represents a win-win situation with benefits to conservation and fishing companies.

Estimación de mortalidad natural e incertidumbre para congrio dorado (Genypterus blacodes Schneider, 1801) en la zona sur-austral de Chile

Pink cusk-eel (Genypterus blacodes) is a demersal fish of high economic importance for the multi-species and multi-fleet fishery operating off far-southern Chile (41°28'-57°00'S). Since the early 1990s, the existence of a single stock was assumed for purposes of stock assessments. However, several attributes related with life history and demography led to the designation, as of 2005, of two administrative stocks of this species, a northern-austral stock stock (41°28'-47°00S) and a southern-austral stock (47°00-57°00S). The division of these stocks has produced a demand for updating life history parameters, including natural mortality (M). In the present work, we used empirical methods to estimate M for pink cusk-eel by zone and sex. The uncertainty in M was incorporated through Monte Carlo resampling considering two sources of error: one from the life history parameters that feed the empirical models and the other from the coefficients that define them. The average M obtained by the different methods showed important differences between sexes for a given zone and between combined sexes between the different fishing zones. The M for individuals from the northern-austral zone was higher than that for those from the southern-austral zone. The coefficients of variation by method were highly dependent on the type of error incorporated. Pauly's (1980) method seems to be the most appropriate for pink cusk-eel, providing M values for the combined sexes of 0.27 year -1 (IC: 0.13- 0.47) for the northern-austral zone and 0.23 year -1 (IC: 0.11-0.40) for the southern-austral zone.

Thermal Transition Properties of Hoki (Macruronus novaezelandiae) and Ling (Genypterus blacodes) Skin Collagens: Implications for Processing

Hoki (Macruronus novaezelandiae) and ling (Genypterus blacodes) are cold-water fish caught in New Zealand waters. Their skins are a major component of the post-processing waste stream. Valuable products could be developed from the skins, as they are primarily composed of collagen, which has many commercial applications. We prepared acid soluble collagens (ASC) from hoki and ling skins, and analyzed their thermal denaturation properties using a Rapid Visco™ Analyzer. At slower heating rates the denaturation temperature (TD) of hoki and ling collagens decreased. This result is consistent with the model of irreversible rate kinetics for the denaturation of collagen. We determined the effects of solvents that disrupt hydrogen bonding on ASC stability. Increasing concentrations of urea from 0.1 M to 1.0 M and acetic acid from 0.1 M to 0.5 M decreased TD. This resulted from the effects of these reagents on the hydrogen bonds that stabilize the collagen triple helix.

Distribution of trace metals in a ling ( Genypterus blacodes) fish fillet

The distribution of trace metals in a ling ( Genypterus blacodes) fish fillet was determined from ICP-MS measurements of digests prepared using nitric acid and hydrogen peroxide, followed by microwave digestion. Most trace elements were inhomogeneously distributed in the muscle tissue of the ling with a non-linear increase in concentration towards the tail end of the fillet. This distribution pattern may be connected to the size variation of the individual muscle cells or the change in the ratio of connective tissue to muscle tissue, suggesting that the observed inhomogeneity of muscle elemental distribution may be inherent to all fish species. The concentration of an element in a sample of fish muscle tissue thus depends on the physical location within the fish from which the sample was dissected. Significant differences in trace element concentrations were also detected between the red and white muscle fibres of ling, as well as between the belly flap and the rest of the musculature.

Population structure and demographic history of Genypterus blacodes using microsatellite loci

Three loci microsatellites were used to determine genetic variability and population structure at 15 locations within three zones where Genypterus blacodes is being fully exploited in Chilean waters. A total of 209 individuals were used: 77 from Cuadra Meulin (CM), 65 from the northern Magellan Strait (NMS), and 67 from the southern Magellan Strait (SMS). The genetic variability found, measured as observed heterozygosity, was Ho = 0.841 ± 0.016. The levels of population subdivision found were F st = 0.0032 ( p = 0.687 ± 0.004) and R st = 0.0059 ( p = 0.160 ± 0.003). Both the F st and R st values were near zero, with non-significant probability values, indicating that the three studied zones were not significantly different. The demographic history analyses did not exhibit significant differences between the observed and expected diversity, under a scenario of reduced effective population size. Therefore, the results obtained in the present study show that there was no population level genetic differentiation of G. blacodes between the analyzed zones in austral Chilean waters (between 41 and 57° S), confirming the presence of a single genetic stock. This result should be included in the management strategy by which harvest quotas are set, and used to improve the application of government management policies, with the aim of increasing the sustainability of this important fishery resource.

Demographical analysis of the pink ling Genypterus blacodes (Schneider 1801) in the austral demersal fishery: A matrix approach evaluating harvest and non-harvest states

In this work we model the population dynamics of Genypterus blacodes of the demersal fishery on Chilean southern-austral region, using stage structured matrices, from a 17-year time-series of annual age-specific female abundances. For the parameterized matrices obtained, we calculated population growth rates with confidence intervals, net reproductive rate, reproductive value, stable stage structure, and we performed a sensitivity analysis. We also generated and analyzed an analogous stage structured matrix model for the same population assuming no harvesting. The main results are (1) a negative growth rate for the observed population data; (2) a positive growth rate for the population without the capture effect which is significantly different from the growth rate of the harvested population; (3) the sensitivity analysis revealed that λ is more sensitive to variations in adult survival in the age class 7–10 years; (4) the observed population exhibits a stable stage structure.

Morphological and histochemical characteristics of the epithelium of ovarian lamellae of Genypterus blacodes (Schneider, 1801)

The physiological significance of the glycoproteins (GPs) secreted by the epithelium of ovarian lamellae is discussed in reference to the reproductive biology of G. blacodes. Histochemical procedures for localising and characterising GPs were used to determine the cytoplasmic components of cells of the epithelium that covers the ovarian lamellae of pink cuskeel, Genypterus blacodes (Schneider, 1801) (Pisces, Ophidiidae), during spawning. This species is one of the most valuable demersal fish resources in the Argentine Sea, mainly due its large size and flesh quality. GPs with oxidizable vicinal diol groups, sialic acid with or without O-acyl substituents, O-acyl sugars, neutral sugars and GPs with carboxyl and sulphate groups were detected. Light microscope examination showed morphological changes in the epithelium of ovarian lamellae during the spawning season, associated with a secretory activity of mucus. Optical density studies revealed the presence of polyploid cells encompassing those morphological changes. Results of the present study suggest that the epithelium of ovarian lamellae of G. blacodes performs a secretory role, which is intensified during ovarian maturity, suggesting that G. blacodes could release masses of eggs enveloped in mucus.

Morphological characteristics of five bycatch sharks caught by southern Chilean demersal longline fisheries

The by-catch of sharks in artisanal demersal pink cusk-eel (Genypterus blacodes) and yellownose skate (Dipturus chilensis) fisheries is frequent within their fishing effort. Nevertheless, there is no registry of landings, which could help to control this problem. This is particularly evident for endemic species, which includes most coastal and deep water Chilean sharks. The main systematic characteristic of these Chondrichthyan species is the external morphology of the neurocraneum. The form and arrangement of the teeth and dermal denticles allow specific differences to be identified. The objective of this paper is to contribute to the biology and systematic knowledge of demersal shark species, teeth and dermal denticle morphology and neurocraneum morphometrics of two species of Scyliorhinids, the redspotted catshark (Schroederichthys chilensis) and the dusky catshark (Halaelurus canescens), as well as three Squaliforms, the granular dogfish (Centroscyllium granulatum), the birdbeak dogfish (Deania calcea) and the spiny dogfish (Squalus acanthias).

Observer effect on fisher bycatch reports in the New Zealand ling (Genypterus blacodes) bottom longlining fishery

Reports by commercial fishers in New Zealand's ling (Genypterus blacodes) bottom longline fishery were analysed to identify the influence of official fishery observers on reported weights of bycatch. Observer data show that on every day ling were taken by bottom longline, both individual transferable quota (ITQ) and nonquota (non‐ITQ) bycatch were reported. However, commercial fishers reported ITQ bycatch on 82% of days fished, and non‐ITQ bycatch on only 50% of days fished. Frequencies of reported bycatch were compared for fishers’ data with and without an observer aboard for the Chatham Rise, Campbell Plateau, and Bounty Plateau areas. Significant underreporting of bycatch was indicated for some bycatch fish species in several areas in the absence of an observer. A sample selection model of reported spiny dogfish (Squalus acanthias) bycatch was used to model the effects of observers on whether spiny dogfish bycatch was reported at all, and the effects of observer presence and other independent variables on the quantity of spiny dogfish bycatch reported. The evidence reported here illustrates that misreporting of bycatch is common and can introduce significant errors into total catch estimation that can have serious implications for fishery sustainability.

Age and growth in pink cusk-eel (Genypterus blacodes) off the Chilean austral zone: evaluating differences between management fishing zones

Summary The von Bertalanffy (vB) growth parameters for pink cusk-eel (Genypterus blacodes) were estimated for the Chilean austral-zone (41°28′–57°00′S) by gender and management fishing zones. A total of 47 026 samples were collected between March 1982 and May 2004, with total length ranging from 19 to 154 cm. Age determinations, based on the reading of saggital otoliths, were between 1 and 14 years in males and between 1 and 16 years in females. Statistical differences in growth were found between the sexes and management fishing zones. For the combined sexes the vB growth parameters for the northern-austral zone (41°28′–47°00′S) were: l∞=111.452 cm, k = 0.186 year−1, t0 = −0.912 year; and for the southern-austral zone (47°00′–57°00′S): l∞ = 123.447 cm, k = 0.147 year−1, t0 = −1.779 year.

Stable isotope analysis reveals pelagic foraging by the Southern sea lion in central Chile

The diet of Southern sea lion Otaria flavescens is poorly known along the coast of central Chile (32°–39°S), where a population of about 17,300 individuals occurs, in an ecosystem that sustains one of the world's most important fishing industries. The primary objective of this study was to reconstruct the diet and estimate Trophic Positions (TPs) of sea lions and their prey off central Chile using stable isotopes ( δ 13C and δ 15N). Our results showed that the diet of sea lions is primarily composed of pelagic prey, with the jack mackerel Trachurus murphyi as the principal prey item in the diet of sea lion (1–99th percentile: 20–66%), while demersal prey accounted for only 0–2.8%. We also found regional differences on the relative contribution of prey to the diet of sea lions. Animals that were sampled close to major fishing areas showed an increase in the relative contribution of jack mackerel to the diet as opposed to animals sampled away from these areas that displayed a relatively more heterogeneous diet. Trophic Positions (TPs) of sea lions prey items ranged between 3.39 for jack mackerel and 4.48 for pink cusk-eel ( Genypterus blacodes). The TP for sea lions was 4.57. Hence, our results showed a community composed by at least 5 trophic levels, with sea lion as the top predator. In summary, our study demonstrates that the Southern sea lion is displaying pelagic foraging off central Chile. We highlight the necessity of conducting further research on the trophic ecology and diving behavior of Southern sea lion to obtain a better understanding of their role as top predator.

Effect of longline configuration on seabird mortality in the Argentine semi-pelagic Kingclip Genypterus blacodes fishery

Incidental mortality of seabirds caused by longline fisheries in the south-western Atlantic Ocean has been assessed only with reference to the number of birds caught, not taking into account how the configuration of the gear affects mortality. We provide the first direct estimates of the impact on seabirds of the semi-pelagic fishing gear used in the Argentine Kingclip Genypterus blacodes fishery. The gear included weights and buoys, sequentially spaced along the lines, which enabled fishing to occur at different depths. During a fishing trip onboard the F/V Argenova XII in the austral summer of 2005, 74 birds were captured, comprising 56 White-chinned petrels Procellaria aequinoctialis and 18 Black-browed albatrosses Thalassarche melanophrys. More than half of the hooked birds were caught in the first third of the lines being set, and almost all White-chinned petrels (96%) and Black-browed albatrosses (83%) were caught within 30 m (i.e. 24 hooks) of buoys. The floats used in semi-pelagic longlines are likely to decrease the sinking rates of baited hooks near them, buoying up the lines near the surface and increasing the likelihood of seabird interactions. Although we lack information on the distribution of captured fish along these longlines, the most feasible methods to reduce seabird bycatch in the Argentine semi-pelagic longline fishery would be (1) to deploy lines without hooks near line floats (the removal of 24 hooks either side of each float should substantially reduce seabird interactions with gear) or (2) to use long snoods between the mainline and the floats, allowing the baited hooks to quickly sink beyond the reach of seabirds.

Fast sinking (integrated weight) longlines reduce mortality of white-chinned petrels ( Procellaria aequinoctialis) and sooty shearwaters ( Puffinus griseus) in demersal longline fisheries

Longline fisheries have been responsible for the deaths of large numbers of seabirds worldwide. Two of the most difficult seabird species to deter from baited hooks are the white-chinned petrel ( Procellaria aequinoctialis) and sooty shearwater ( Puffinus griseus). Longlines with integrated weight (IW) sink faster than normal, unweighted (UW), longlines and have the potential to reduce the numbers of these species killed. The relative differences in the number of white-chinned petrels and sooty shearwaters killed on UW longlines and IW longlines containing 50 g/m beaded lead core were investigated in 2002 and 2003 in the New Zealand ling ( Genypterus blacodes) autoline fishery. Effects on catch rates of target and non-target fish species, and operational aspects of the use of IW gear, were also assessed. A single bird scaring streamer line was deployed on all sets of longlines. In 2002 and 2003, compared to UW lines IW lines reduced mortality of white-chinned petrels by 98.7% and 93.5%, respectively. In 2003 IW lines reduced sooty shearwater mortality by 60.5%. Catch rates of white-chinned petrels (including on sets when no fatalities were recorded) by IW gear were low: 0.005/1000 hooks (UW: 0.4) and 0.01/1000 hooks (UW: 0.17) in 2002 and 2003, respectively. Equivalent rates for sooty shearwaters in 2003 were 0.06/1000 hooks by IW and 0.13/1000 hooks by UW. No albatrosses were caught on either line type in 2002; in 2003 a single Salvin’s albatross ( Thalassarche salvini) was caught on UW gear. Both the number of ling and the mean masses of ling caught in 2003 by IW (mass: 189.3; CL 95% 162.7–220.3 kg/1000 hooks) and UW (200.6; CL 95% 178.2–225.9 kg/1000 hooks) longlines were similar statistically. Use of IW longlines and streamer lines in autoline fisheries should yield major conservation benefits to seabirds interacting with these fisheries worldwide.