Merluccius Gayi Research Articles

Biological and Fishery Aspects of Hake (Merluccius gayi, Guichenot, 1848) Caught with Trawl Nets in the Gulf of Guayaquil, Ecuador.

Biological and Fishery Aspects of Hake (Merluccius gayi, Guichenot, 1848) Caught with Trawl Nets in the Gulf of Guayaquil, Ecuador.

Social network mechanisms of price formation in an artisanal fishing community in Chile

Local fish markets play a crucial role in meeting local and regional demand for seafood. However, the underlying social and local processes determining price formation in these markets still need to be clarified. Through ethnographic research of an artisanal fishing community in central Chile focused on the common hake catching (Merluccius gayi gayi), we found that mutual observation and negotiation are the two key social processes of the local economic order. These processes produce two local structures: (a) the fishers’ maritime cliques in the sea and (b) the chain structure in the cove, which combines commercial and community relationships to determine market prices.

Applying machine learning to predict reproductive condition in fish

Knowledge of reproductive traits in exploited marine populations is crucial for their management and conservation. The maturity status in fish is usually assigned by traditional methods such as macroscopy and histology. Macroscopic analysis is the assessing of maturity stages by naked eye and usually introduces large amount of error. In contrast, histology is the most accurate method for maturity staging but is expensive and unavailable for many stocks worldwide. Here, we use the Random Forest (RF) machine learning method for classification of reproductive condition in fish, using the extensive data from Chilean hake (Merluccius gayi gayi). Gonads randomly collected from commercial industrial and acoustic surveys were classified as immature, mature-active and mature-inactive. A classifier for these three maturity classes was fitted using RFs, with the continuous covariates total length (TL), gonadosomatic index (GSI), condition factor (Krel), latitude, longitude, and depth, along with month as a factor variable. The RF model showed high accuracy (>82%) and high proportion of agreement (>71%) compared to histology, with an OOB error rate lower than 15%. GSI and TL were the most important variables for predicting the reproductive condition in Chilean hake, and to lesser extent, depth when using survey data. The application of the RF shows a promising tool for assigning maturity stages in fishes when covariates are available, and also to improve the accuracy of maturity classification when only macroscopic staging is available.

Spatial heterogeneity of biological traits and effects on fisheries management based on the assumption of a single stock. The case of the common hake (Merluccius gayi) in Chile

Understanding the spatial structure of fishing resource stocks is a fundamental aspect for the management and development of sustainable and productive fisheries. However, this aspect is usually simplified under the assumption of a stock unit, which assumes biologically similar and spatially homogeneous individuals, regardless of the real ranges and characteristics of their distribution. The persistence of geographic patterns in the biological traits of species suggests the spatial structuring of a population, a highly relevant aspect in stock assessment, calculation of Biological Reference Points (BRP), and management of fishing resources. In this work, the spatial heterogeneity of the biological traits of common hake (Merluccius gayi) from off-central Chile is modeled. Considering four reference zones, biological data collected over 26 years of monitoring fisheries and acoustic surveys is analyzed. The findings allow to biologically differentiate these areas whose main characteristics are the increase from north to south in the condition factor, gonad weight, and size at maturity. The Spawning Potential Ratio (SPR), fishing mortality, and BRP are calculated. Exploratorily, if these areas were considered closed subpopulations, results show that overexploitation is not a characteristic of all hake fishing areas, and that not considering the heterogeneity of biological traits causes the overestimation of the population condition in the main fishing areas. The aim of this research was to understand the spatial structuring of common hake based on the heterogeneity of biological attributes and its impact for fisheries management purposes.

A Spatial-Spectral Classification Method Based on Deep Learning for Controlling Pelagic Fish Landings in Chile.

Fishing has provided mankind with a protein-rich source of food and labor, allowing for the development of an important industry, which has led to the overexploitation of most targeted fish species. The sustainable management of these natural resources requires effective control of fish landings and, therefore, an accurate calculation of fishing quotas. This work proposes a deep learning-based spatial-spectral method to classify five pelagic species of interest for the Chilean fishing industry, including the targeted Engraulis ringens, Merluccius gayi, and Strangomera bentincki and non-targeted Normanichthtys crockeri and Stromateus stellatus fish species. This proof-of-concept method is composed of two channels of a convolutional neural network (CNN) architecture that processes the Red-Green-Blue (RGB) images and the visible and near-infrared (VIS-NIR) reflectance spectra of each species. The classification results of the CNN model achieved over 94% in all performance metrics, outperforming other state-of-the-art techniques. These results support the potential use of the proposed method to automatically monitor fish landings and, therefore, ensure compliance with the established fishing quotas.

Trophic chain of the pelagic thresher, Alopias pelagicus, in the Southeastern Pacific Ocean: An approach through stable isotopes of carbon and nitrogen

The pelagic thresher, Alopias pelagicus, plays a vital role in coastal and marine ecosystems as a top predator that feeds on species from low trophic levels. It is a commercial species relevant in Ecuador. The feeding chain of A. pelagicus was analyzed through carbon and nitrogen stable isotopes in the Southeast Pacific Ocean. Considering the lack of studies regarding this topic, this would elucidate the flow of nutrients and energy from the base up to this predator. Its diet composition included 19 prey species, out of which 10 were cephalopods and nine Osteichthyes. The most relevant species were the squid Ommastrephes bartramii, Dosidicus gigas, Stenoteuthis oualaniensis, and the fish Merluccius gayi peruanus. The pelagic thresher is a carnivore predator, and its prey species belong to tertiary and quaternary trophic levels. The carbon and nitrogen male isotopic ratios were similar to those of females, as were immature and mature organisms. This suggests that this species feeds in oceanic regions of low depths and could be exploiting and sharing an area with similar feeding resources. According to the mixing models, squids were the most important prey group, in which the squid Ommastrephes bartramii contributed most to its diet. Furthermore, this shark was characterized as a specialist predator with a trophic overlap by sex and maturity stages.

Factors that affect the mean size of Chilean hake (Merluccius gayi gayi) caught with gillnets in 2001-2018 in central Chile

Chilean hake (Merluccius gayi gayi) is one of central Chile's most important demersal resources, and its fishery involves an artisanal fleet that mainly uses gillnets. In the recent history of the fishery, there has been a decrease in catch sizes and a progressive reduction in mesh sizes. This study aimed to analyze the factors that influenced the mean catch sizes of Chilean hake between 2001 and 2018 to understand this situation, correlating the response of fishermen with the capture efficiency of the nets used. Applying a generalized linear model, a significant effect of the factors year, port (zone), and mesh size were observed on the mean size of individuals caught. The model explained 85% of the deviation, the greatest relative contributions being made by the factors year (53.6%) and port (30.2%). A lower effect was estimated for the mesh size factor with 1.2% deviance. These findings suggest that the progressive reduction in mesh sizes is associated with a response to the demographic change in the stock. Differentiated management measures by zones could be considered in the fishery, given the estimated differences.

Spatio-temporal patterns of the crustacean demersal fishery discard from the south Humboldt Current System, based on scientific observer program (2014-2019).

This study summarises six years of spatio-temporal patterns of the discarded demersal community fauna recorded by onboard scientific observer program for both artisanal and industrial crustacean fisheries between 2014 and 2019, from mesophotic to aphotic depths (96 to 650 m) along the southern Humboldt Current System (28-38°S). In this period, one cold and two warm climatic events were observed during the austral summer 2014, 2015-2016 (ENSO Godzilla), and 2016-2017 (coastal ENSO), respectively. Satellite information showed that Chlorophyll-a concentration varied seasonally and latitudinally, associated with upwelling centres, while equatorial wind stress decreased southward of 36°S. Discards were composed of 108 species, dominated by finfish and molluscs. The Chilean hake Merluccius gayi was dominant and ubiquitous (occurrence, 95% of 9104 hauls), being the most vulnerable species of the bycatch. Three assemblages were identified: assemblage 1 (~200 m deep), dominated by flounders Hippoglossina macrops and lemon crabs Platymera gaudichaudii, assemblage 2 (~260 m deep), dominated by squat lobsters Pleuroncodes monodon and Cervimunida johni and assemblage 3 (~320 m depth), dominated by grenadiers Coelorinchus aconcagua and cardinalfish Epigonus crassicaudus. These assemblages were segregated by depth, and varied by year, and geographic zone. The latter represented changes in the width of the continental shelf, increasing southward of 36°S. Alpha-diversity indexes (richness, Shannon, Simpson, and Pielou) also varied with depth and latitude, with higher diversity in deeper continental waters (>300 m), between 2018-2019. Finally, at a spatial scale of tens of kilometres, and a monthly basis, interannual variations of biodiversity occurred in the demersal community. Surface sea temperature, chlorophyll-a, or wind stress did not correlate with discarded demersal fauna diversity of the crustacean fishery operating along central Chile.

Mechanism study of the gel-forming ability of heat-induced gel from Peruvian hake (Merluccius gayi peruanus) surimi

The commercial value of Peruvian hake (Merluccius gayi peruanus) meat is low because of its soft texture. This study investigated the major factor contributing to the gel-forming ability of Peruvian hake surimi by comparing the effects of endogenous protease activity and parasitic infection. Heat-induced gels could not be obtained at 50 °C–90 °C. Surimi with severe parasitic infection showed a stronger gel-forming ability. The endogenous protease activities were the main factor influencing the Peruvian hake meat proteolysis and contributed to the low gel-forming ability, rather than parasitic infection. Specifically, endogenous cysteine proteases played an essential role in protein degradation and low gel-forming ability. Moreover, endogenous transglutaminase was also shown to be involved in the gel-forming ability upon heating at 40 °C. These results suggested that Peruvian hake meat could be used as a raw material of frozen surimi for fish gel by inhibiting the activity of endogenous proteases.

Juvenile Hake Merluccius gayi Spatiotemporal Expansion and Adult-Juvenile Relationships in Chile

The abundance of juvenile fish changes due to endogenous processes, and determining the functional relationships among conspecifics is essential for fisheries’ management. The hake (Merluccius gayi) is an overexploited demersal fish widely distributed in Chile, from 23°39′ S to 47°00′ S in shallow and deep water over the continental shelf and shelf break. We studied the spatiotemporal distribution of hake juveniles (from ages 0 and 1), emphasizing endogenous relationships among juveniles and adults. The abundance per age data were obtained from bottom trawl cruises carried out in the austral winter between 1997 and 2018. Generalized additive models showed a similar spatiotemporal pattern for ages between 0 and 1, and negative effects of adult hake aged seven and older on the abundance of the young generation. Regarding the changes in juvenile abundance, the residual deviance of selected models explained 75.9% (for the age 0) and 95.3% (for the age 1) of the null deviance, revealing a significant increase in juvenile abundance from 2002 to 2007 and subsequent abundance stability at higher levels. Furthermore, the expansion in the abundance of juveniles after 2002 was favored by the low abundance of older adult hake, most which are able to cannibalize young hake. Our results highlight the importance of endogenous factors in the spatial distribution of Chilean hake juveniles to identify nurseries or juvenile areas free of potential cannibal adults.

Prevalence and molecular identification of zoonotic Anisakis and Pseudoterranova species in fish destined to human consumption in Chile

Zoonotic larvae of the family Anisakidae found in several fish species represent a serious risk in public health since they may cause food-borne anisakidosis in humans. Chile has culinary preferences including eating raw fish in many traditional preparations. In the present study, a total of 180 fish specimens representing three different fish species, i.e., Chilean hake (Merluccius gayi), snoek (Thyrsites atun), and sea bream (Brama australis), were caught at central coast of Chile. Parasitological examination was performed on musculature and abdominal cavity for subsequent extraction and quantification of anisakid larvae. Estimation of infection parameters, such as prevalence, was performed indicating 100% (CI: 0.94–1.0) prevalence of anisakid L3 in Chilean hakes and snoeks. Moreover, sea breams reached a prevalence of 35% (CI: 0.23–0.48). Prevalence of anisakid larvae in muscle was also analyzed showing values of 18.6% (CI: 0.097–0.309) in Chilean hakes, 15% (CI: 0.07–0.26) in snoeks, and 1.7% (CI: 0–0.089) in sea breams. Meanwhile, prevalence of anisakid larvae in internal organs showed highest values for peritoneum (100% and 83.3%) for snoeks and Chilean hakes, respectively, for liver (96.7%) and gonads (86.6%) in Chilean hakes, and for intestine (98.3%) in snoeks. Molecular analysis of collected anisakid L3 unveiled presence of two potentially zoonotic nematode species, i.e., Pseudoterranova cattani and Anisakis pegreffii. P. cattani was found in Chilean hakes and snoeks being the first molecular host species report for Chilean snoeks. Besides, A. pegreffii was also identified in these species being the first molecular report on this regard. These findings are relevant for better understanding of epidemiology of anisakiasis in Chilean coasts and for public health issues considering potential risk of human population due to its culinary preferences in eating raw fish.

Spatial and Temporal Variability of Parasite Communities: Implications for Fish Stock Identification

The spatial and temporal variability of parasite communities have received little attention when used as biological tags for identifying fish stocks. This study evaluated the potential spatial and temporal variability of the parasite communities affecting three marine fish species collected between 1993 and 2017. To avoid the potential effect of host age in parasite communities, individuals of similar ages were selected: 1123 Engraulis ringens (12–24 months old), 1904 Trachurus murphyi (24–36 months old), and 630 Merluccius gayi (36–48 months old). Most taxa show differences in the prevalence at the spatial and temporal scales, but the prevalence of some larval endoparasites remains constant at the temporal scale. At the spatial scale, an analysis of similarity (ANOSIM) showed differences in the parasite communities of three species; a canonical analysis of principal coordinates (CAP) showed low values of correct allocations (CA; ≈50%) and values of allocation due to chance (AdC) were lower than the CA. At the temporal scale, an ANOSIM showed differences between the three species. A CAP showed low values of CA (≈50–60%) and the AdC was always lower than CA. Samples at the spatial scale were well allocated to their localities or nearby localities, suggesting a spatial stability. Samples from different years were not well discriminated, suggesting temporal variability. Therefore, in studies regarding parasites as a tool for stock identification, temporal variability must be taken into account.

Impacts of COVID-19 on the value chain of the hake small scale fishery in northern Peru

All aspects of fish supply chains have been severely affected by the COVID-19 pandemic, with jobs, income and food security at risk. In Peru, small scale fisheries are fundamental for food security, contributing to about 2/3 of all fish consumed nationally. One of the most important resources which is more affordable for local and regional consumption is hake (Merluccius gayi peruanus). This study is a first attempt to describe the small-scale hake fishery value chain and to quantify the impact of COVID-19 from March to August 2020 in two fishing communities in northern Peru. The levels of fishing and primary buying were the most affected, and we estimate that ~ 23,000 fishing trips were not conducted, ~ 1680 t of hake was not landed (83% decrease), and 620 jobs were negatively impacted during this period. The gross income of vessel owners and primary buyers decreased by ~ $US 913,000. Marked differences were observed in the way each community responded to the pandemic and in their resilience to cope with COVID-19, despite being located less than 10 km away. In El Ñuro, which relied more heavily on the international market for hake trade, the value chain was affected for longer, while in Los Órganos which supplied national markets, the chain was restored after an initial period of adjustment. Our study suggests that government efforts should focus on facilitating a formalisation process in all levels of the chain, develop indicators to monitor the resumption of activities and the inclusion of a value chain approach to small-scale fisheries management.

Calculating the carbon footprint of the artisanal common hake fishery (Merluccius gayi gayi) in Caleta Portales, Valparaíso, Chile

Society's awareness of environmental issues increases every day. In this context, the concept of carbon footprint (CF) arises as a calculation tool that quantifies greenhouse gasses (GHG) emitted during the life cycle (LC) of a product. This calculation method is used in many productive sectors throughout the world; however, the Chilean fisheries sector has not notified the use of this tool or initiatives in that sense. This study performs a calculation of the CF of artisanal gillnet hake (Merluccius gayi gayi) fishery of the Caleta Portales, located in Valparaíso, Chile. The ISO 14040: 2006 methodology was used. The analysis was limited from the boat departure until the catch is landed, as a gate-to-gate life cycle assessment (LCA). The fuel consumption data and information related to the fleet were used as the main source of information. The Caleta Portales hake landings were 1,340.484 kg in 2011 and 703,411 kg in 2012. This fleet released into the atmosphere in 2011, 0.47 CO2 equivalent per kg of hake landed, and 0.58 kg CO2 eq, in 2012. It is the first result of CF reported in a Chilean fishery. This result can lead to an increase in the competitiveness of this hake fishery, as it can generate a positive impact on encouraging consumers to prefer the consumption from those places that have calculated the CF and are less than other food products.

A framework for assessing and intervening in markets driving unsustainable wildlife use

Understanding how markets drive unsustainable wildlife use is key for biodiversity conservation. Yet most approaches to date look at isolated components of wildlife markets, hindering our ability to intervene effectively to improve sustainability. To better assess and intervene in wildlife markets, we propose a framework that integrates three analytical levels. The first level, “actor”, assesses the underlying motivations and mechanisms that allow or constrain how actors benefit from wildlife markets. The second level, “inter-actor”, assesses the configuration of wildlife product supply-chains and the type of competition between actors participating in wildlife markets. The third level, “market”, evaluates supply-demand dynamics, quantity and price determinants, and the presence and effect of illegal products flowing into markets. We showcase the utility of the framework in a data-limited small-scale fishery case study (common hake, Merluccius gayi gayi in Chile); our mixed-method analysis provided relevant, tailored management recommendations for improving sustainability. Tackling markets driving unsustainable wildlife use needs integrated approaches that bring together the diversity of factors affecting wildlife market dynamics.

Isotopic niche and niche overlap in benthic crustacean and demersal fish associated to the bottom trawl fishing in south-central Chile

In habitats impacted by bottom trawling that influences the resilience of few and widely distributed abundant species, it is relevant to analyze how populations are structured according to their niche and niche overlap, and hence contributing to the ecosystem-based management approach. We evaluated and compared the isotopic niche width and determined the isotopic niche overlap for target and bycatch species of crustaceans and demersal fish caught with bottom trawling on the continental shelf and upper slope of the central-southern zone of Chile. Stable isotope analysis relied on carbon and nitrogen isotopes (13C and 15N) and Bayesian statistics of niche size and community metrics. Crustaceans and fish species are structured in three clusters according to the stable isotope values and the Chilean hake Merluccius gayi, which was probably clustered isolated due to its pelagic stable isotope values due to diel vertical migrations associated with feeding on euphausiids in the water column. The first group was constituted by demersal fish, that showed higher δ15N (19‰) and narrower δ13C (−16‰). The two other groups constituted a mix of crustaceans and fish, with access to different carbon sources. There were degrees of specialization for most species within the groups and overlap in the isotopic niche between populations. The benthic and demersal macrofauna species are structured by sharing resources in the habitat, probably on available sources supported by the productive pelagic system.

The recruitment dynamics of the nylon shrimp Heterocarpus reedi, effects of climate and predation off Chile

Climate variability and predation influence the fluctuations in the recruitment of exploited marine populations. This study analyses the dynamics of the recruitment of the nylon shrimp (Heterocarpus reedi Bahamonde 1955) over the period 1968 and 2015, considering the influence of climate variability and the biomass of hake (Merluccius gayi), as a proxy for predation in its distribution area. We collected the Humboldt Current Index (HCI) and Southern Oscillation Index (SOI) time series as climate variables and estimates of recruitment and spawning biomass of nylon shrimp, as well as biomass of hake. Annual deviations in nylon shrimp recruitment showed increased sensitivity to climate variability and hake biomass, expressed through a significant cumulative correlation over time. The recruitment drives the spawning biomass, implying an environmentally driven shrimp recruitment dynamic. Generalized Linear Models showed that hake biomass and climate indices affect negative and positively the shrimp recruitment during the recruitment year, respectively. A path diagram with Structural Equation Models showed that SOI impacted HCI, negatively impacting the hake stock. Hake negatively affected the shrimp stock biomass and recruitment, and SOI either directly or indirectly, through its effect on the hake. The hake impact on the shrimp's spawning stock and recruitment is due to predation under concurrent climate variability on longer-term periods.

Diet composition and feeding habits of the pelagic thresher shark Alopias pelagicus in Eastern Central Pacific Ocean, Ecuadorian waters

AbstractThe diet and feeding habits of the pelagic thresher shark Alopias pelagicus were analysed based on 104 stomachs (N = 84 females, 20 males) collected off Santa Rosa de Salinas, in the Ecuadorian Pacific. The sharks were caught between February 2008 and January 2009 in artisanal fisheries. The trophic spectrum of A. pelagicus included 19 prey items (10 cephalopods and 9 teleost fishes), the main four prey were the red flying squid Ommastrephes bartramii, jumbo squid Dosidicus gigas, the purpleback flying squid Sthenoteuthis oualaniensis and the South Pacific hake Merluccius gayi. The trophic niche was narrow (Bi = 0.2), thus the pelagic thresher could be considered a specialist predator. The analysis of dietary overlap showed high similarity between the diets of females and males (Cλ = 0.99), immature and mature females (Cλ = 0.81), immature and mature males (Cλ = 0.72), sizes of 141–230 cm TL and 231–321 cm TL (Cλ = 0.97), as well as sharks in rainy season and dry season (Cλ = 0.77). Using canonical of correspondence analysis (CCA), we found similarities in the diet for all categories recorded (sex: canonical r = 0.38, P = 0.97; sexual maturity stage: canonical r = 0.54, P = 0.31; sizes: canonical r = 0.55, P = 0.26; seasons of the year: canonical r = 0.61, P = 0.75). The trophic level estimated for A. pelagicus was 5.0, which is typical of top predators (quaternary consumers or tertiary carnivores).

Ichthyoplankton distribution and feeding habits of fish larvae at the inshore zone of northern Patagonia, Chile

The Inland Sea of Chiloe is a semi-enclosed sea of northern Patagonia characterized by freshwater inputs from a fjord in the north and high influence of offshore waters in its southern sub-basin. The zone has been referred to as an important fish nursery ground. In order to assess its relevance as a spawning ground and the strategies for temporal coexistence of larvae of fish species from diverse origins in these inshore waters, we investigated both the horizontal and vertical distributions, and the feeding habits of early stages of fish during the period of highest productivity (austral spring). Ichthyoplankton richness and abundance were higher in the northern sub-basin, dominated by the offshore midwater lightfish Maurolicus parvipinnis, and the shelf-break and demersal hake Merluccius gayi. The larvae of the coastal rockfish Sebastes oculatus and the clupeid Strangomera bentincki were more abundant in surface waters, while the larvae of Merluccius australis, M. gayi, and M. parvipinnis reached deeper waters. The co-occurring inshore larvae of M. gayi, M. parvipinnis, and S. oculatus preyed actively at day and night times on a wide spectrum of zooplankton sizes, with the small calanoid copepods being the most commonly consumed food items in the largest larvae of M. parvipinnis and M. gayi. Nauplii were frequent food items for smaller larvae of M. parvipinnis, S. oculatus, and S. bentincki. The high spring productivity and the large abundances of potential zooplanktonic prey, along with larval spatial segregation, are visualized as the main factors enabling species with different origins to co-inhabit and grow at inshore waters in northern Patagonia.

Anisakid nematodes prevalence in Chilean hake (Merluccius gayi gayi) commercialized in the city of Talca, Chile

The main objective of this work was to determine the presence of anisakid larvae in fresh Chilean hake Merluccius gayi gayi coming from the coastal area near the city of Talca, Chile, commonly commercialized by a regional fish supply center located in the same city. Flesh and viscera of 214 fish were analyzed via direct observation, and the prevalence of parasitism was calculated. The results showed a prevalence of 100% and 24.3% in viscera and flesh, respectively. Morphologic characterization of 138 randomly selected larvae was performed via diaphanization technique, observing 106 larvae of Anisakis spp., 13 larvae of Pseudoterranova spp. and 19 nematodes classified as “unidentified.” All larvae here analyzed were viable based on the spontaneous movement ability of parasites. Overall, the high prevalence of fish infected with Anisakidae larvae highlights the importance of taking early intervention actions in order to prevent the occurrence of anisakidosis in the human Chilean population; particularly critical given the current culinary preference for raw fish dishes such as ceviche and sushi, which poses a public health issue.