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Background: Functional resistance training is frequently applied to rehabilitate individuals with neuromusculoskeletal injuries. It is performed by applying resistance in conjunction with a task-specific training, such as walking. However, the benefits of this training may be limited by motor slacking, a phenomenon in which the human body attempts to reduce muscle activation levels or movement excursions to minimize metabolic- or movement-related costs. While kinematic feedback could reduce one's tendency to minimize effort during training, this has not been verified experimentally.Research Question: Does functional resistance training during walking lead to motor slacking, and can techniques such as visual feedback be used to reduce these effects?Methods: Fourteen able-bodied individuals participated in this experiment. Participants were trained by walking on a treadmill while a bidirectional resistance was applied to the knee using a robotic knee exoskeleton. During training, participants were either instructed to walk in a manner that felt natural or were provided real-time visual feedback of their kinematics. Electromyography and knee kinematics were measured to determine if adding resistance to the limb induced slacking and if feedback could reduce slacking behavior. Kinematic aftereffects were measured after training bouts to gauge adaptation.Results: Functional resistance training without feedback significantly reduced knee flexion when compared to baseline walking, indicating that participants were slacking. This reduction in knee flexion did not improve with continued training. Providing visual feedback of knee joint kinematics during training significantly increased knee muscle activation and kinematic aftereffects.Significance: The findings indicate that individuals are susceptible to motor slacking during functional resistance training, which could affect outcomes of this training. However, motor slacking can be reduced if training is provided in conjunction with a feedback paradigm. This finding underscores the importance of using additional methods that externally motivate motor adaptation when the body is not intrinsically motivated to do so. [ABSTRACT FROM AUTHOR]

A key factor in population models, the temporal scale, should both reflect intra-annual biological processes and avoid over-parameterization. We applied the separability assumption to model recruitment process error as additive effects of random annual deviates and quarterly fixed effects (QFEM) to improve our understanding of intra-annual recruitment patterns and, at the same time, minimize the impact of over-parameterization. We formulated a length-based model with a quarter-year temporal resolution and applied it to the anchovy (Engraulis ringens) fishery off northern Chile and southern Peru, using data from 1984 to 2015. Model performance was compared to that of a larger model in which the process error is treated as an interaction of quarter-year effects (QYIM). QFEM proved to be most adequate only when the variability of population processes and the fishery are determined by a clear seasonal pattern. In those cases, QFEM characterized recruitment seasonality as well as inter-annual trends. Under these conditions, the separability hypothesis of recruitment process error substantially reduced the number of parameters in the stock assessment model, the bias of estimated population variables, and uncertainty when the most recent data were incomplete or non-informative. QFEM provides an alternative way to improve assessments and fishery management for fast-growing and short-lived species such as small pelagic fish. [ABSTRACT FROM AUTHOR]

Intense fishing mortality generates changes in marine populations and ecosystems, and an increase in the sensitivity to environmental changes. Fishery-induced demographic changes are the main mechanisms involved due to truncation of age structure of a population trough selective removal of larger and older fish from a population. As a consequence, changes in the seasonal spawning pattern can occur because larger and older fish tend to have a longer and more extensive reproductive activity than smaller and first-time spawners. This is the case of a small pelagic fish, known as the common sardine Strangomera bentincki, which supports an important fish activity off central southern Chile (33°S-41°30? S). In this paper, fishery-induced changes on the seasonal reproductive cycle of common sardine were simulated through an age-structured population dynamics on a monthly basis. The fishery is dependent on the annual pulse of recruitment and fishing efforts are applied intensively on the juvenile fraction during the first half of each year. Thus, fishing mortality removes fast growing fish or fish recruiting earlier, and thereafter the age structure tends to be truncated, and as a consequence, slow-growing fish or late-recruiting fish could be selected in the population. A delayed peak in the reproductive cycle was observed in the gonadosomatic index during the period 2000-2010, as compared with the period 1993-1999. In addition, a change in the length composition of the catches was observed, supporting the results obtained with simulations. The fishery-induced changes on the reproductive cycle of common sardine can increase the sensitivity of the population to climate variability either matching or mismatching the reproductive cycle with favorable/unfavorable environmental variables for recruitment. [ABSTRACT FROM AUTHOR]

In Chile, anchovy (Engraulis ringens) and common sardine (Strangomera bentincki) are two commercially important small pelagic fish. In southern Chile (32-41° S), both species coexist and inhabit the coastal zone. In northern Chile (18-25° S), only anchovy is present in the coastal zone. The determine onset, peak, end, and duration of the spawning periods in these small pelagic fish are key factors in population studies and of great interest for fisheries management. The objective of this study is to determine the temporal trends of spawning in these two species. A quantitative method was developed to obtain objective indicators of the spawning periods and the method is a useful tool for comparative studies between populations as well as to study the relationship of spawning periods with other demographic variables affected by fishing or environmental variability. Peak spawning in the three populations was consistent through time but showed changes in the duration of the maximum reproductive period. Anchovy and common sardine of the southern zone show synchrony and a shortening of the duration of spawning periods, probably in response to environmental fluctuations. Anchovy in northern Chile have shown an increase in duration from 1986 that is coincidental with the regime shift reported for the Humboldt Current Ecosystem in the mid-1980s. [ABSTRACT FROM AUTHOR]

Abstract: The recruitment rate of anchovy in the Peru–Chile upwelling system was studied by testing sensitive to environmental variability when the spawning stock is low in abundance. Times series of sea surface temperature, salinity, depth of the 15°C isotherm, the upper limit of the oxygen minimum zone, upwelling indices, the Southern Oscillation Index, and indices El Niño 1+2 and El Niño 3.4 were summarized trough Principal Component Analysis (PCA). The first PCA (PC-I) explained 57% of variance and was related to interannual variability driven by the El Niño-Southern Oscillation. The second Principal Component explained 15% of variance and was linked to upwelling indices. Anchovy recruitment rate anomalies were correlated with PC-I scores on the basis of a 6-year-moving-window and accumulated correlation as time progressed. Significant correlation coefficients were found when the spawning stock biomass was low in abundance before 1990. Once sufficient spawning biomass was accumulated (after 1990), the stock was less sensitive to environmental variability. Thus, sensitivity to environmental changes in anchovy, and probably in other small pelagic fishes, is stock-size dependent. This is a key aspect to be considered in the management of transboundary fish stock shared between Chile and Peru, upon current efforts to develop an ecosystem approach to fisheries management. [Copyright &y& Elsevier]

Abstract: The inter-cohort variability in the von Bertalanffy (VB) growth parameters of common sardine (Strangomera bentincki) was analyzed for the period between 1990 and 2007. Time series of monthly length–frequency data were used to study the growth of the species. The MIX software was used to separate normal components and modal progression analysis was used to identify cohorts that have recruited each year. The VB growth parameters were estimated using nonlinear mixed-effects model (NLME) by considering that the population growth parameters have a common distribution, and that cohort-specific parameters can be treated as random effects. A model that considered L ∞ (asymptotic length) and K (growth coefficient) as random effects was the best in explaining inter-cohort changes in body growth. The growth rate during the first fast-growing period of sardine cohorts exhibited a significant change after 1998. Cohorts recruited between 1990 and 1997 showed higher growth rates than cohorts recruited from 1999 to 2006. This significant change is coincident with a colder period established in the area after 1998, and with a significant increment in the Ekman transport. Sea surface temperature anomalies explained 46.2% of the variability observed in the early growth rate of the cohorts. It is concluded that environmental conditions encountered by the cohorts during the spawning period could modulate the growth rate of common sardine year to year, but the possibility of further intrinsic factors affecting the growth dynamics of common sardine could be also important and deserve to be considered in future studies. [ABSTRACT FROM AUTHOR]

The management of small pelagic fisheries is a complex task due to its large variability of both environmental and biological processes. This high variability can impact the reliability of stock assessment models and fishery management recommendations. When this occurs, management decisions should explore alternative control rules based on empirical abundance indices or pragmatic management procedures. In this paper, we examined the performance of a harvest control rule (HCR) for the Chilean fleet in the shared Chile-Peru anchovy (Engraulis ringens) fishery (16°S–24°S), which is one of the most important stocks in the Humboldt marine ecosystem in the Southeast Pacific. The HCR uses the annual changes in spawning biomass estimated by Daily Egg Production Method (DEPM) surveys in the waters off northern Chile. Analyzes are carried out through operating models simulating population regime shifts under different uncertainty sources. The results show that despite the latent risk of overfishing caused both by recruitment variability and the lack of fisheries management coordination between two jurisdictions, the control of one of the parties' fishing mortality can enable the sustainability of the entire stock, provided the fishing effort of the other jurisdiction be remained at similar levels as in the last decade. The use of an HCR would avoid increases in fishing mortality and would facilitate B MSY -based management goals. This research determined conditions under which the shared Chile-Peru anchovy fishery can be sustainable considering different sources of uncertainty of the biological-fishing system. [ABSTRACT FROM AUTHOR]

Abstract: The jack mackerel population has a widespread oceanic spawning habitat off central Chile, extending more than one thousand nautical miles offshore. In this paper, the spatial structure of jack mackerel eggs density is analyzed on the basis of four surveys carried out in oceanic waters (32°S–39°S, 75°W–92°W), from 1998 to 2001. In each survey, a grid of plankton stations was sampled through vertical hauls with WP2 plankton nets by using several purse-seine fishing ships sampling simultaneously along the E–W transects. With the aim of finding the bulk of the egg distribution within the surveyed area, an exploratory analysis between jack mackerel egg densities, latitude, longitude, and sea surface temperature (SST) was carried out. The spatial structure of the egg distribution was studied using geostatistical techniques. The bulk of the jack mackerel spawning tends to occur offshore between 80°W and 92°W, is maximal at 35°S and associated to SST warmer than 15–16°C. All of the variograms showed clear spatial autocorrelations without anisotropy, with the range fluctuating between 125 and 252 nautical miles. The range of variograms suggests that the spawning of jack mackerel is a large scale process, probably reflected in the adult behavior of the spawning by favoring a high dispersion of eggs and/or associated with sea surface temperature characterizing the subtropical frontal zone (16–18°C) off central Chile. [Copyright &y& Elsevier]

Abstract: In this paper, the first daily egg production method (DEPM) parameters were estimated for anchovy and common sardine stocks distributed in the central-south area off Chile (33–40°S). The study area was stratified according to the topography, shape and orientation of the coastal line, and the survey was carried out on the continental shelf during the main spawning peak (August–September, 2002). The bulk of the spawning of both species was successfully covered, which was characterized by a coastal distribution within the first 20 nautical miles, and following the inner zone associated with the 100m bottom depth. The coastal distribution of the spawning can be related to the oceanographic conditions occurring during the transition from winter to spring (southern Hemisphere), which are characterized by the alternation between northerly and southerly winds. Probably, these factors are interacting to produce enrichment, concentration and retention of egg in coastal zones in the study area. The daily egg production rate (P 0) was estimated for two geographic strata, and was different in each region. Also, the length frequency and adult reproductive parameters were different between geographic strata, specially the daily spawning fraction. For anchovy, the P 0 was lower in comparison with available estimates for the same species in Peru and in the north area off Chile. Also, the relative fecundity of anchovy was lower, probably because anchovy in the study area have bigger eggs as compared with the anchovy in Northern Chile. The DEPM parameters estimated for common sardine in the investigated area were similar to the range of existing values for the Engraulis genus in other upwelling areas. The stratified spawning stock biomass estimate was 133,031t (CV=44%) for anchovy and 706,792t (CV=68%) for common sardine. Probably, daily egg production and adult reproductive parameters of both species are highly variables and further research is suggested for improvements future DEPM application for the species. [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]

Abundance, biomass, recruitment and fishing mortality of common sardine, Strangomera bentincki, and anchovy, Engraulis ringens, are estimated for stocks distributed in the central-southern area (34–40°S) off Chile. Monthly length–frequency data, from July 1990 to November 1999, were used to identify cohorts, to analyze growth, and to determine the monthly age composition of the catches. The abundance of cohorts was estimated using cohort analysis on a monthly time-scale that is sufficiently small for capturing the rapid seasonal changes that characterize both resources. An ADAPT approach was used to estimate the unknown parameters by using catch per unit effort (CPUE) data as auxiliary information. Growth was a regular process for different cohorts of both species, and a seasonal oscillating growth curve was fitted. The parameters of the seasonal von Bertalanffy growth function were: L∞=17.7 cm, K=0.79 yr−1, t0=−0.347 yr, C=0.996, and winter point (WP)=0.373 (r2=0.930, n=207, P<0.05) for common sardine; L∞=20.8 cm, K=0.444 yr−1, t0=−0.392 yr, C=0.849, and WP=0.310 (r2=0.906, n=203, P<0.05) for anchovy. The growth rates were slowest between April and May, before the spawning season. Recruitment of common sardine occurred in November, while recruitment of anchovy tended to occur in January. The yearly pulse of recruitment dominates the population dynamics of both species, and it was observed that the recruitment of the two species varies inversely. The 1997 cohort of common sardine was the lowest in the 1990s, but recruitment of anchovy was higher, probably as a consequence of the 1997–1998 El Nin˜o event. The biomass of the common sardine stock declined from 1997 to 1999, while fishing effort was growing. On the contrary, the biomass of anchovy was higher in 1998 and 1999 due to the stronger cohorts of 1996 and 1997. Evidence for density-dependent catchability was found for sardine, but not for anchovy. At present, both species can be considered as overfished because a growing trend in fishing effort is not compensated by the productivity of the stocks. [Copyright &y& Elsevier]

The Territorial Use Rights for Fisheries (TURF) system are a kind of marine property where user rights are assiged to collective entities of artisanal fishers' organizations. But their effectivity continues to be limited, which demands a comprehensive evaluation of their social, economic, and ecological performance. Consequently, the practical integration and application of these aspects continue to be a significant challenge for their management. The "RAPFISH" multidimensional scaling technique was applied to assess the sustainability status of 19 TURFs of the Biobio Region (Chile), using 51 transdisciplinary attributes relating to ecological, economic, social, among other dimensions. The results obtained in the two-dimensional arrangement presented a sustainability gradient, due to the marked variations among the different TURFs, and only four cases had very weak sustainability scores. Broadly speaking, this study determined that the social dimension (score: 61.37%) had a "high" influence on the best performance of the TURF system, while the ecological, ethical, and institutional dimensions were rated from 'regular' to 'bad'. Overall, results indicate an average performance in the "medium" sustainability range (score: 54.68%), and these results generated questions about the TURFs' viability, mainly in those that have not reached their sustainability objectives. Therefore, more local studies are needed on the social dimension of this system, in order to define the effective participatory tools and social management plans in TURFs, which will contribute to improve their performance. • The performance of the TURFs system in the Biobio region. • The transdisciplinary analysis on selected TURFs achieved an average sustainability (<70%). • Fishers identified various attributes influencing the sustainability status of local TURFs. • Strong bio-ecological and human relationships were inherent in responsible practices on TURFs. • Ensuring new conceptual tools should be allocated to improve participation among stakeholders. [ABSTRACT FROM AUTHOR]

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. • A few abundant and widely distributed populations may be resilient to bottom trawl fishing, which are usually structured by abundance and distribution. • Isotopic niche and niche overlap of benthic crustacean and demersal fish were studied. • Benthic crustacean and demersal fish were grouped into three assemblies composited with similar small and overlapped isotopic niches. • Chilean hake is isolated due to access to pelagic sources (zooplankton). • Stable isotopes of C and N allow grouping of functional species with similar isotopic niches, which can contribute to an ecosystem-based management approach. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The upwelling ecosystem of central southern Chile sustains the pelagic common sardine and anchovy fisheries, which are managed by setting a global quota allocated to small-scale (artisanal) and industrial fishers. A prearranged spatial allocation of quotas for small-scale fishers is based on historical landings rather than the current spatial distribution of the target species. Artisanal fishers can only fish in their original Spatial Administrative Units (SAUs) according to fishing rights. Marked environmental variability, such as that caused by ENSO events, trigger changes in the local availability of resources. Thereafter, artisanal and industrial fishers compensate for low yields by transferring their fishing quota to quota holders (artisanal-artisanal, industrial-artisanal, artisanal-industrial) from other SAUs. The legal procedure for transferring quotas among users is efficient to harvest the total allowable catch. This procedure favors the quota holders but is detrimental to the crew of vessels that transfer quotas to other fishers. A mechanism is recommended to distribute the profits obtained by quota transfers between ship owners and crews to avoid this negative effect. [ABSTRACT FROM AUTHOR]

• We analyzed spawning markers to estimate daily spawning fraction. • Gamma probability distribution was fitted to spawning markers fraction per hour. • Daily spawning fraction in anchovy is 25% on average. • Spawning fraction depend on body weight, time of capture and temperature. • An advance arising from methodological advances concerning fish reproductive biology. The procedures used to estimate the daily spawning fraction of northern Chile anchovy (Engraulis ringens) have been revised based on information from 17 Daily Egg Production Method (DEPM) survey estimates of the anchovy spawning biomass. The most commonly used spawning marker is postovulatory follicles (POFs). POFs are transitory remnants of the ovulated follicles that remain within the ovary after spawning, until they are fully resorbed. As the process of Postovulatory Follicles (POF) degeneration is continuous, the assignment of POF stages to daily cohorts of spawners can be imprecise. Therefore, the main objective of this paper is to review the criteria used to assign females to daily spawning cohorts in anchovy (Engraulis ringens) located off northern Chile. For our first step, we review the peak spawning time using recently fertilized eggs. To study the POF duration, we divided the POF degenerative process into seven stages and then fitted a gamma probability distribution to the hourly POF stage fractions in a daily cycle. This approach is a quantitative, objective way to define the range of time during which the POF stages are present in the samples, as well as the overlap between daily cycles. The hourly distribution of recently fertilized eggs (Stage 1) indicated a strong daily spawning time synchrony that peaked at 4:00 GMT (00:00 local time). We found that the class Day 1 cohort (females that spawn on the night before their capture) belongs primarily to POF Stages 1 to 3, with some proportions belonging to POF Stages 4 and 5 according to the capture time. The migratory nucleus (MN) and hydrated (H) phases correspond to the cohort that spawns on the night of capture. The daily spawning fraction estimates the based on the POF or MN and H phases did not show significant differences. Our results indicated an average spawning frequency of four days (S = 0.27 day−1). The prevalence of POFs according to female size follow an asymptotic model of the von Bertalanffy type, indicating an asymptote around 0.27 day−1. The POF presence was higher during cold periods, probably due to a longer period of decay. A general linear model analysis showed that body weight, time of catch and mean temperature significantly influenced the spawning fraction. [ABSTRACT FROM AUTHOR]

Abstract: The yellownose skate (Dipturus chilensis) is one of the most important component of the commercial elasmobranch fishery off Chile with an extensive distribution range from 36°44′S−55°13′S. Nevertheless, fishery management for this species does not extend beyond the central zone off Chile (36°44′−41°28′S), leaving the southern zone (41°28′S−55°13′S) without a proper fishing effort regulation. As a result, fishing pressure has increased dramatically in the southern zone, with unknown potential consequences for this elasmobranch population. In the absence of rigorous fishery-biological data, we used a matrix population model to assess yellownose skate demographic traits under different fishing mortality levels. A Leslie matrix model was implemented, where changes in age classes are defined in terms of of life history parameters. Uncertainty was incorporated by applying a Monte Carlo method to survival, age at maturity, and fecundity. Three scenarios were evaluated based on different assumptions about survival, fishing mortality rates, and age at 50% of vulnerability. These scenarios showed a slow growth rate for population abundance (3–15% per year) with no fishing exploitation. The population reaches equilibrium at low mortality levels (0.31yr−1), which is consistent with estimates reported for other rajidae skates. The elasticity analysis indicates that juvenile survival contributes the most to variations in the population growth rate. The sustainable mortality rate has a positive, non-linear relationship with age at 50% of vulnerability. Projections using different selectivity patterns showed that the population abundance is stable only when age-dependent fishing mortality removes individuals of older ages. We concluded that yellownose skate is extremely vulnerable to fishing exploitation and it is remarkably sensitive to juvenile and early life stages survival, implying that management actions are needed to ensure a sustainable exploitation. [Copyright &y& Elsevier]

Abstract: We incorporated predation equations from the multispecies virtual population analysis model MSVPA into an age-structured model for the Chilean hake (Merluccius gayi gayi) to estimate cannibalism. Two models, model I with constant natural mortality and the MSM, were fitted to the total annual catch, spawning biomass from acoustic surveys and length composition data from fishery and acoustic surveys. Model I fitted the data better than MSM. The majority of the MSM estimates of adult population and spawning biomass were larger than the model I estimates; probably due to the choice of residual mortality M1. High estimates of predation mortality were observed for age-0 hake. In spite of a decreasing fishing mortality, the spawning biomass decreased in the last years. Preliminary MSM results suggest that this might be due to an increase in cannibalism. A sensitivity analysis suggested all response variables were not sensible to the “other food” parameter but sensible to M1 and the predator annual ration. MSM is a promising approach that introduces the predation mortality equations into a statistical framework, allowing the incorporation of the uncertainty in the estimation of the parameters and the use of standard statistical tools in a multispecies context. This approach will contribute to provide useful information on the indirect effects of fishing on non-target species to fisheries managers. [Copyright &y& Elsevier]

Trophic interactions and community structure of commercial fishery species off Central Chile (33°–39°S) were analyzed and compared for 1992 and 1998 by ecotrophic modelling, using the Ecopath modelling software. The model encompasses the fishery, pinnipeds (sea lions), small pelagic fish (anchovy, pilchard), medium-sized pelagic fish (horse mackerel), demersal fish (e.g. Chilean hake, black conger), benthic invertebrates (carrot prawn, yellow prawn), and other groups such as zooplankton, phytoplankton, and detritus. Input information for the model was gathered from published and unpublished reports and our own estimates. Also, the effects of fishing and predation on fishery resources and on the most important components of the system were investigated, within an ecotrophic framework.Predators consumed the greater part of the production of the most important fishery resources, particularly juvenile stages, and the fishery removed a large fraction of adult production. Mortality by predation is an important component of natural mortality, especially in recruit and prerecruit groups. Analysis of direct and indirect trophic impact shows that adult Chilean hake have a negative impact on juvenile Chilean hake through cannibalism, and on pilchard, anchovy, and carrot prawn through predation. Also, fishing has a strong impact on fishery resources, such as Chilean hake, pilchard, and anchovy. Total biomass in 1998 was 1.5 times higher than in 1992. However, total catches in 1998 were about 80% of those in 1992. Changes in biomass and total yields of the system between 1992 and 1998 can be observed in such properties as total flows, consumption, respiration, and production. It is concluded that ecotrophic modelling is an useful tool for fishery management, since it can improve our understanding of the predator–prey interactions among the exploited (fishery resources) and unexploited but potential fishery resources of the system. [Copyright &y& Elsevier]

Abstract Common sardine, Strangomera bentincki , support an important artisanal fishery along the Chilean coast; however, there is lack of knowledge of the early life history traits of this species. Using satellite-derived environmental conditions (sea surface temperature, SST, and chlorophyll- a), and otolith microstructure analysis of larval stages collected in coastal waters of central Chile, larval age, growth rates, and back-calculated yolk-sac absorption date patterns were analyzed for 2010–2013. SST varied from 11 to 20 °C and showed the highest values during austral summer 2013, whereas Chl- a varied between 0.2 and 66 mg m−3. The abundance of larval S. bentincki was similar during 2010 and 2011, decreased in 2012 but increased again in 2013 to similar densities of 2010 to 2011. Similarly, larvae collected during 2012 had the largest otoliths (radius, perimeter, area). Larval growth rates did not vary significantly among years and ranged between 0.32 and 0.42 mm day−1. From 2010 to 2011, a significant decrease occurred in the size-at-age of larval S. bentincki , and then, size-at-age was maintained until 2013. Back-calculated yolk-sac absorption dates differed among years and were delayed from winter to spring during 2012. The latter occurred in a period with significantly warmer waters. Additionally, SST and Chl- a concentration were not linearly related to the mean growth rates of larval S. bentincki. Highlights • Larval growth rates did not vary significantly among years • Larvae collected during 2012 had the largest otoliths (radius, perimeter, area) • From 2010 to 2011, a significant decrease occurred in the size-at-age of larvae • Yolk-sac absorption dates were delayed from winter to spring during 2012 • SST and Chl-a concentration were not linearly related to the mean growth rates [ABSTRACT FROM AUTHOR]

Abstract: The Chilean hake (Merluccius gayi gayi) is one of the most important demersal resources fished in Chile since the early 1940s. Since 1993, an acoustic survey program was established to assess the abundance of this resource. A sudden decrease in abundance was observed after 2002, along with changes in the species demography and spatial distribution. These changes represent a spatial re-distribution of the stock (latitude, longitude, and depth) which was associated with concomitant changes in environmental conditions (temperature, salinity, and dissolved oxygen). The main aim of this paper is to determine habitat preferences in Chilean hake and associated changes in its abundance with environmental conditions. Estimates of Chilean hake abundance were based on acoustic survey conducted between 1993 and 2006 from Coquimbo (29°30′S) to Chiloé Island (41°28.6′S). Chilean hake abundance was modelled using generalised additive models with environmental variables and location as covariates. In the interannually analysis, location and temperature were the most important explanatory covariates of Chilean hake abundance. Analyses of the data across years revealed that time, Chilean hake aggregation depth, and temperature were the most important covariates. The changes observed in spatial distribution can be divided into two periods. During the first period (1993–2001) high values of Chilean hake abundance were found in salinities between 34 and 34.4psu, temperatures of 8 and 11°C, and depths between 125 and 400m. During the second period (2002–2006) the stock increased in the southernmost area closer to the coast and were associated with low salinities (<34psu). In this paper we discuss the spatial and temporal changes in Chilean hake abundance, their habitat preferences, and how the association between abundance and environmental variables changes during these periods of high and low abundance. [Copyright &y& Elsevier]