Sardine Landings Research Articles

Bayes factors for longitudinal model assessment via power posteriors

Bayes factor, defined as the ratio of the marginal likelihood functions of two competing models, is the natural Bayesian procedure for model selection. Marginal likelihoods are usually computationally demanding and complex. This scenario is particularly cumbersome in linear mixed models (LMMs) because the marginal likelihood functions involve integrals of large dimensions determined by the number of parameters and the number of random effects, which in turn increase with the number of individuals in the sample. Power posterior is an attractive proposal in the context of the Markov chain Monte Carlo algorithms that allows expressing marginal likelihoods as one-dimensional integrals over the unit range. This paper explores the use of power posteriors in LMMs and discusses its behavior through three simulation studies and a real data set on European sardine landings in the Mediterranean Sea.

Explaining technical change and its impacts over the very long term: The case of the Atlantic sardine fishery in France from 1900 to 2017

As an industry based upon the harvesting of wild resources, the fishery is often used in economics to showcase the effects of its specific nature on human behavior and the impacts of that behavior on the fish stock itself. The common-pool status usually encountered in the use of these resources makes them especially vulnerable to major shifts in the supporting ecosystems, but also to rapid technical change. In most other parts of the economy, technical change and the creative destruction that it brings along are viewed positively, and even given central role in recent theories of growth. Happily for the creatures of the ocean that are hunted, fishers do not fit the mould of Schumpetarian entrepreneurs bent on creative destruction. However, the technology that does drift onto boats has had concerning effects on the status of fish stocks with important economic and cultural consequences. We present a narrative of the French sardine fishery using the evolutionary theory of technical change. The wild binary segmentation approach was applied on a time-series of French sardine landings from 1900 to 2017. This analysis revealed three significant production change points associated with important technical changes in the fishery. The first change point, in 1927, is related to the introduction of the purse-seine in France. The introduction of the mid-water trawl is the second change point in the early 1970s. A third change point occurred in 1998, where we see a reswitch from mid-water trawl to purse-seine. Collectively, these results highlight the technological changes in sardine production that occurred, but more importantly, the impacts of these changes both on the structure of the population of sardines, and on the industry. The lesson we derive from this case study is that technical change should be considered as a succession of shifts rather than a unidirectional history.

Economic and livelihood impacts of the decline in Indian oil sardine landings in Kerala state, India

Kerala state in the south west coast of India is a significant contributor of Indian oil sardine, and also a major consumer of the fish. Indian oil sardine landings in the state declined from 3,22,103 t in 2011 to a meagre 13,154 t in 2020. In the past decade, ring seiners contributed more than 90 per cent of the Indian oil sardine landings in the state, and the livelihoods of small-scale fishers operating ring seiners were largely affected by the decline. In this context, an analysis was carried out to study the economic impact of oil sardine decline on the marine fisheries sector and its impacts on livelihood of small-scale fishers. The economic impacts were assessed in terms of changes in gross value and inflation at landing centre and retail levels during 2011–2020. A survey was conducted at 500 fisher households to assess the livelihood impacts based on loss of employment, income and alternate livelihood options. The gross value of oil sardine declined from ₹12,562 million to ₹1,710 million at the landing centre level and from ₹22,869 million to ₹2,687 million at the retail level during 2011–2020. The annual income earned by the fish workers declined from ₹335,593 to ₹90,260 due to the decline in oil sardine landings. Likert scale analysis of the fisher’s perceptions indicated climate change, over exploitation and marine pollution as the major causes of catch decline. Sixty five per cent of the respondents strongly supported the actions for the protection of fisher’s livelihood and suggested incentive (80% strongly supported) and regulatory (45% strongly supported) based fisheries management measures for sustaining the small-scale fisher’s livelihood.

Predator-prey collapses at the edge of predator distribution: the case of clupeids and common guillemots (Uria aalge) in NW Iberia

The spatial structuring of seabird populations makes individual colonies very dependent on regional factors. That is especially the case in small edge populations located far from large colonies. We analysed retrospectively the poorly known collapse, some 50 years ago (around 1962-1973), of a relatively small population of breeding common guillemots (Uria aalge) located at their southernmost limit of distribution in Europe (NW Iberia). We assumed that guillemots behaved locally as facultative specialists in small pelagic fish due to the occurrence of a strong clupeid fishery, and we studied the association between the guillemot collapse and annual regional landings of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus), used as a proxy of total stock size. The overall relationship between ln-transformed guillemot counts (May-June) and ln-transformed sardine landings (May-October) was stronger than the fit on untransformed variables (r2 =0.52 vs. 0.27), indicating an exponential relationship between the non-transformed variables. This relationship was somewhat stronger and linear after the collapse, when only a few tens of guillemots remaining (r2 =0.60). A strong regime shift in sardine landings was detected in 1968 and also in anchovy landings in 1969. The overall relationship between guillemot numbers and anchovy landings was linear and strong (r2 =0.72) but completely dependent on the large 1960s estimate of guillemots. However, no relationship was found between guillemot numbers and anchovy landings (April-June) after the guillemot collapse. The most likely period for the guillemot collapse was therefore 1968-1970, as seabird colonies are known to collapse immediately after their staple prey crashes. Local guillemot colonies were not subsequently rescued by immigration and have remained empty or almost empty until present, showing the high sensitivity of edge populations to environmental variability at the regional scale.

Effect of marine climate and baitfish availability on the tuna baitboat fishery CPUE OFF northwestern Mexico

Tunas caught by the baitboat fleet are one of the most sustainable products of the high seas. We analyzed catches of the baitboat fleet operating off northwestern Mexico from 1978 to 2013. We assessed the relationship between the standardized tuna catch and the Multivariate El Niño Index (MEI), the Pacific Decadal Oscillation (PDO), and landings of the two main species (Pacific sardine, Sardinops sagax, and northern anchovy, Engraulix mordax) used as baitfish in the Northeastern Pacific Ocean tuna fishery. Results showed a strong correlation between yellowfin tuna (Thunnus albacares) catches and sardine landings, and an inverse correlation between yellowfin tuna catches and both MEI and PDO. Yellowfin tunas are more abundant during colder-than-normal conditions. We hypothesized that, when the sardine population is more vulnerable to the small-pelagic fishery in the Gulf of California, environmentally ideal conditions, as well as baitfish (sardine) availability, resulted in high yellowfin tuna landings. The opposite behavior was observed for the standardized catch of skipjack tuna (Katsuwonus pelamis): a strong correlation with anchovy landings and a positive correlation with both MEI and PDO suggested that there is an alternation between tuna and small pelagic species.

Long term oscillations of Mediterranean sardine and anchovy explained by the combined effect of multiple regional and global climatic indices

It is widely known that the abundance and distribution dynamics of populations of small pelagic clupeid fish, such as sardines and anchovies, are affected by large-scale climate variability, which may lead to changeovers to new regimes of small pelagics. However, long-distance climatic oscillations, such as El Niño/La Niña and the Pacific Decadal Oscillation, have been little explored in the Western Mediterranean Sea. We investigated the possible effects of the South Oscillation Index (i.e. the atmospheric oscillation coupled with the El Niño/La Niña) and Pacific Decadal Oscillation on fluctuations in catches of European anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Western Mediterranean Sea, and their association with regional climate oscillations (i.e. the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, the Western Mediterranean Oscillation index, and the Arctic Oscillation). The study covered two periods: (a) landings between 1950 and 2016; and (b) abundance, biomass, and physical condition (i.e., relative condition index) between 2004 and 2016. The main large-scale climatic oscillations in the region were studied using General Additive Models to investigate the relationship between a time series of species measures of European sardine and anchovy from Geographical Subarea 06. Results show that the long-term Pacific Decadal Oscillation favours sardine landings, whereas the combined effect of the Western Mediterranean Oscillation Index and the Atlantic Multidecadal Oscillation favours anchovy. We discuss potential links between the present findings and changes in the plankton community caused by prevailing winds in the region driven by long-distance climate oscillations and their impact on the reduction in small pelagic fish populations in the study area.

The puzzle of the anchovy–sardine inverse fishery at the south‐eastern coast of the Arabian Sea and climate variability

AbstractAn out‐of‐phase pattern of fishery between anchovy and sardine exists in upwelling systems of different geographical locations. We examined the inverse relationship of anchovy (Stolephorus sp., Engraulidae) and sardine (Sardinella longiceps, Clupeidae) fishery along the coast of the south‐eastern Arabian Sea (SEAS) by analysing the annual landing data of Kerala, Karnataka, and Goa states. Landings of anchovy and sardine showed wide fluctuations with distinct episodes of abundance and decline. We selected anchovy period (1984–1996) and sardine period (2000–2013) for close examination according to the environmental data availability. The study reveals that the observed inverse fishery along the coast of SEAS is well connected to regional environmental parameters and global climate variability. During the abundant anchovy period, the anomalies of surface currents were observed towards the north and also towards the coast during the spawning periods of anchovy (March–May, October–December). The pattern of surface current anomalies is reversed during the abundant sardine period. Anomalies of surface current is directed towards offshore during the early life stage of sardine (June–September), but it reversed towards the coast during the abundant sardine period. Similarly, an opposite upwelling pattern is noted in both species’ spawning seasons during the anchovy and sardine abundant periods. During these periods, the spatial distribution of global surface air temperature and wind anomalies showed contrasting spatial patterns and hence they are related to various climate indices in sardine and anchovy abundant periods in the SEAS.

Effect of climatic oscillations on small pelagic fisheries and its economic profit in the Gulf of Cadiz

Several studies have shown the effect of climatic oscillations on fisheries. Small pelagic fish are of special global economic importance and very sensitive to fluctuations in the physical environment in which they live. The main goal of this study was to explore the relationship between the North Atlantic Oscillation (NAO), the East Atlantic pattern (EA), and the Arctic Oscillation (AO) on the landings and first sale prices of the most representative small pelagic commercial species of the purse-seine fisheries in the Gulf of Cadiz (North East Atlantic), the European anchovy Engraulis encrasicolus and the European sardine Sardine pilchardus. Generalised linear models (GLMs) with different data transformations and distribution errors were generated to analyse these relationships. The best results of the models were obtained by applying a moving average of order 3 to the dataset with a double weighted median. Our results demonstrate relationships between NAO, AO, and EA and European anchovy and sardine landings. These cause an indirect effect on the first sale price in markets through catch variations, which affect the price according to the law of supply and demand. The limitations of this study and management implications are discussed.

Trophic niche overlap between round sardinella (Sardinella aurita) and sympatric pelagic fish species in the Western Mediterranean.

The northward expansion of round sardinella (Sardinella aurita) in the Mediterranean Sea, together with declines and fluctuations in biomass and landings of European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) observed in recent decades, may suggest potential inter‐specific competition in the pelagic domain. The coexistence of sympatric zooplanktivorous fish species might therefore be exposed in part to trophic niche overlap and competition for food. Combining visual diet characterization under the microscope with DNA metabarcoding from stomach contents of fish collected in spring results show that predation on relatively large krill is equally important for sardinella than for the other two niche overlapping species. Furthermore, an important overlap is found in their isotopic niche, especially with anchovy, using nitrogen (δ15N) and carbon (δ13C) stable isotopes in muscle tissue. In fact, the three fish species are able to feed effectively in the whole prey size spectrum available during the sampled season, from the smallest diatoms and copepods to the larger prey (i.e., decapods and euphausiids), including fish larvae. Moreover, effective predation upon other large prey like siphonophores, which is observed only when multi‐proxy analyses in stomach contents are applied, might also be relevant in the diet of sardinella. The overlapping diet composition in spring, together with the effective use of food resource by sardinella, can be of special interest in potential future scenarios with warmer water temperature leading to lower zooplankton and/or higher jellyfish availability, where sardinella may take advantage over other species due to its feeding plasticity.

Improving landings forecasts using environmental covariates: A case study on the Indian oil sardine (Sardinella longiceps)

AbstractCommercial landings of sardines are known to show strong year‐to‐year fluctuations. A key driver is thought to be environmental variability, to which small forage fish are especially sensitive. We examined the utility of including environmental covariates in forecasts for landings of the Indian oil sardine using a long‐term time series of quarterly catches. Potentially influential variables examined included precipitation, upwelling intensity, sea surface temperature (SST), and chlorophyll‐a concentration. All of these have been shown to be important for oil sardine growth and survival, spawning and/or movement into the nearshore fishing regions. However, improving out‐of‐sample landings forecasts using environmental covariates has often proven elusive. We tested the inclusion of environmental covariates in forecast models using generalized additive models, which allow for non‐linear responses, and dynamic linear models, which allow for time‐varying responses. Only two environmental covariates improved out‐of‐sample prediction: the 2.5‐year average regional SST and precipitation over land during June–July. The most significant improvement was with the SST covariate and post‐monsoon landings with a 19%–22% reduction in mean‐squared prediction error. Models with the second best covariate, monsoon precipitation over land, provided a 4%–8% reduction in prediction error. We also tested large‐scale ocean climate teleconnection indices. One, an index of the Atlantic Multidecadal Oscillation, also improved out‐of‐sample predictions similarly to the multiyear average regional SST. The earth's changing climate is associated with both rapid warming in the Western Indian Ocean and changes to monsoon rainfall patterns. Our work highlights these as key variables that can improve forecasting of oil sardine landings.

The potential impact of a shifting Pacific sardine distribution on U.S. West Coast landings

AbstractMany fish species are shifting spatial distributions in response to climate change, but projecting these shifts and measuring their impact at fine scales are challenging. We present a simulation that projects change in fishery landings due to spatial distribution shifts, by combining regional ocean and biogeochemical models (forced by three earth system models, ESMs: GFDL‐ESM2M, HadGEM2‐ES, IPSL‐CM5A‐MR), correlative models for species distribution and port‐level landings, and a simulation framework which provides realistic values for species abundance and fishery conditions using an historical “reference period”. We demonstrate this approach for the northern subpopulation of Pacific sardine, an iconic commercial species for the U.S. West Coast. We found a northward shift in sardine landings (based on the northern subpopulation's habitat suitability), with projected declines at southern ports (20%–50% decline by 2080) and an increase (up to 50%) or no change at northern ports, and this was consistent across the three ESMs. Total sardine landings were more uncertain, with HadGEM2 indicating a 20% decline from 2000 to 15 levels by 2070 (a rate of 170 mt/y), IPSL a 10% increase (115 mt/y), and GFDL an 15% increase by the year ~2050 followed by a sharp decrease. The ESMs also differed in their projected change to the timing of the fishing season and frequency of fishery closures. Our simulation also identified key constraints on future landings that can be targeted by more tactical assessment; these included the seasonality of quota allocation and the abundance of other species in the catch portfolio.

Climate impacts on the landings of Indian oil sardine over the south‐eastern Arabian Sea

AbstractThe landings of Indian oil sardine (Sardinella longiceps, Clupeidae) along the south‐eastern Arabian Sea are about 43.8% of total Indian oil sardine production. The annual landings of this species exhibit large‐scale variability with prolonged years of surplus or deficit landings without identified reason. Evaluating Indian oil sardine landings along the Kerala coast during 1961–2017 in relation to environmental variations, we have elucidated a putative link between variability in landings versus environmental parameters and climate indices. The variables examined in this study, such as salinity and temperature along with physical indices such as upwelling and mixed layer depth (MLD) of the ocean help to propose a mechanism to temporal variability in the landings of Indian oil sardine. Colder temperature and timely intense upwelling lead to nutrient enrichment in the surface water, which promotes the growth of phytoplankton (chl‐a) and thereby food availability to Indian oil sardine are found during years with surplus catch. Less saline surface waters and shoaling of MLD at these times could lead to the aggregation of fish at particular depths and thereby a good catches. The reverse mechanism, such as more surface saline water, warm temperature, downwelling or weak upwelling, and less nutrient enrichment, leads to deficit landings. Further, it was noticed that the Pacific decadal oscillation and Atlantic multidecadal oscillation have a more pronounced impact on Indian oil sardine landings over the coast of south‐eastern Arabian Sea than previously reported ENSO associated impacts. All these point towards climate change implications for the Indian oil sardine fishery.

Variability of oceanographic and meteorological conditions in the northern Alboran Sea at seasonal, inter‐annual and long‐term time scales and their influence on sardine (Sardina pilchardus Walbaum 1792) landings

AbstractTime series of European sardine (Sardina pilchardus) landings from 1962 and environmental variables from 1978 in the northern Alboran Sea are analysed. European sardine spawns in the northern Alboran Sea from mid‐autumn to late winter at a temperature range slightly higher than the one observed in the nearby Eastern North Atlantic and the North Western Mediterranean. Individuals hatched during autumn and winter are incorporated to the fishery during the following summer and autumn producing the maximum annual landings. These landings show both a decreasing long‐term trend and a strong inter‐annual variability. Although further research is needed, the warming trend of sea surface temperature and the decrease in upwelling intensity inferred from empirical orthogonal function (EOF) analyses could have some influence on the negative trends of sardine landings. The inter‐annual variability of sardine abundance seems to be related to the wind intensity at a local scale, the second principal component of the chlorophyll concentration and the sardine abundance during the preceding year. If the inter‐annual variability is considered, a linear model including these three variables with a one‐year time lag allows to explain 79% of the sardine landings variance. If the negative linear trend is also considered, the model explains 86% of the variance. These results indicate that the body condition of spawners, linked to the food availability during the preceding year, is the main factor controlling the recruitment success. The possibility of predicting sardine landings 1 year in advance could have important implications for fishery management.

Anthropogenic food resources, sardine decline and environmental conditions have triggered a dietary shift of an opportunistic seabird over the last 30 years on the northwest coast of Spain

Human activities and environmental conditions are the main drivers of ecosystem change. One major alteration near the western Iberian coast has been the collapse of the Atlanto-Iberian sardine Sardina pilchardus stock, with important cascading effects on marine top predators. We investigated the effect of long-term changes in fishery landings, sardine availability and environmental conditions on the diet of the yellow-legged gull Larus michahellis in the northwest coast of Spain, over the last 30 years (1987–2017). Dietary trends of gulls were investigated through the analysis of 5010 pellets that revealed a sharp decline of fish and refuse and a shift to a crustacean-based diet. General additive mixed models showed that both total fish and sardine occurrences in gull pellets were negatively associated with total fishery landings and positively associated with sardine landings, suggesting fish depletion and higher fishing efficiency (i.e. reduced discards) during the study period. The winter North Atlantic Oscillation (NAO) index was also positively related with sardine occurrence in gull pellets, possibly due to low sardine abundance and rough conditions in years with very low NAO values. The refuse decline was most probably caused by the closure of open-air landfills, implemented under the European Union Landfill Directive. Our results suggest that changes in fishing practices and waste disposal were the main factors responsible for the sharp decline of fish and refuse in yellow-legged gull diet.

Delayed predator-prey collapses: the case of black-legged kittiwakes and Iberian sardines

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 631:201-207 (2019) - DOI: https://doi.org/10.3354/meps13164 Delayed predator-prey collapses: the case of black-legged kittiwakes and Iberian sardines A. Martínez-Abraín1,*, P. Santidrián Tomillo2, J. Mouriño3, S. Tenan4, D. Oro5,6 1Universidade da Coruña, Facultad de Ciencias, Evolutionary Biology Group, Campus da Zapateira s/n, 15071 A Coruña, Spain 2The Leatherback Trust, Goldring-Gund Marine Biology Station, Playa Grande, Costa Rica 3Arcea, Xestión de Recursos Naturais S.L., Velázquez Moreno 9, oficina 305, 36201 Vigo, Spain 4MUSE - Museo delle Scienze, Sezione di Zoologia dei Vertebrati, Corso del Lavoro e della Scienza, 3, 38122 Trento, Italy 5Instituto Mediterráneo de Estudios Avanzados IMEDEA (CSIC-UIB), Miquel Marquès 21, 07190 Esporles, Spain 6Centre d’Estudis Avançats de Blanes CEAB (CSIC), Acces Cala Sant Francesc 14, 17300 Blanes, Spain *Corresponding author: a.abrain@udc.es ABSTRACT: We analysed the long-term (1975-2017) population response of a colony of a marine top predator, the black-legged kittiwake Rissa tridactyla, to the population dynamics of sardine Sardina pilchardus, its main local prey. The study site (Sisargas Islands, Spain) is located at the southernmost edge of the geographical distribution of the predator. Kittiwake counts of breeding pairs started with the discovery of the colony (1975), likely close to the actual year of first colonization. Sardine landings by age class (1978-2016) were taken from the International Council for the Exploration of the Sea (ICES) database. Sequential t-test analysis revealed that a regime shift of the oldest sardine age class (age 6+) took place in 1991 and that kittiwakes experienced a regime shift in the number of breeding pairs in 1993, 2 yr after the prey shift. Multiple autocorrelation functions for the detrended time series of sardines and kittiwakes indicated an autocorrelation with a time lag of 2 yr. Despite much reduced fishing effort, sardine densities have not recovered since the collapse, likely due to changes in large-scale atmospheric circulation in the Northern Hemisphere in the late 1990s. Kittiwakes at Sisargas have not recovered demographically, remaining nearly extinct during the last ca. 20 yr. Although we lack detailed demographic data for the studied kittiwake population, we suggest that massive breeding failure and subsequent dispersal to higher-quality patches might explain the rapid non-linear collapse in breeding population density. We discuss some behavioural social responses that may have occurred during and after the collapse to explain the dynamics of the study colony. KEY WORDS: Population crash · Black-legged kittiwakes · Time delay · Non-linearities · Predator-prey dynamics · Food availability · Iberian sardine · Fisheries collapse Full text in pdf format Supplementary material PreviousNextCite this article as: Martínez-Abraín A, Santidrián Tomillo P, Mouriño J, Tenan S, Oro D (2019) Delayed predator-prey collapses: the case of black-legged kittiwakes and Iberian sardines. Mar Ecol Prog Ser 631:201-207. https://doi.org/10.3354/meps13164 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 631. Online publication date: November 21, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

The influence of environmental factors and hydrodynamics on sardine (Sardina pilchardus, Walbaum 1792) abundance in the southern Alboran Sea

Abstract The study of environmental variables and their influence on the small pelagic fish stocks of the Alboran Sea (Western Mediterranean) is asymmetrical, with studies focused on the southern coast being scarce compared with those looking at the northern margin. In this work, time series of sardine landings from the Moroccan coast of the Alboran Sea from 1981 to 2016 were analyzed together with environmental variables such as Sea Surface Temperature (SST), Sea Surface Salinity (SSS), Surface Chlorophyll-a concentrations (Chl-a), and the velocity of the Atlantic Jet (AJ) flowing into the Mediterranean Sea through the Strait of Gibraltar. Annual sardine catches decreased from 1981 to 2016 at a rate of −258 t/year. At the same time, the SST and SSS increased at rates of 0.03 °C/year and 0.004 ups/year, respectively, very likely as a result of climate change. Linear models reflect a negative relationship between sardine landings and SST and SSS, indicating that the long-term temperature and salinity changes in the Mediterranean could have a negative impact on sardine abundance. At an inter-annual time scale, chlorophyll concentrations seem to be positively related to sardine abundances. A decrease in the kinetic energy of the AJ is also inferred from the cross-strait sea level difference (SLD). This variable has an important influence (positive correlation) on sardine landings, both in the long term and at the inter-annual time scale, with higher sardine abundances associated to higher SLD. This work shows that environmental variables such as SLD, SST, SSS, and Chl-a are the main driving factors for the variability of sardine landings in the southern Alboran Sea.

Identifying ecosystem patterns from time series of anchovy (Engraulis ringens) and sardine (Sardinops sagax) landings in northern Chile

ABSTRACTUseful knowledge acquisition from known and systematized information (data) is a big challenge for researchers, users and finally, decision makers. In this sense, knowledge discovery from data (KDD) process represents a valuable tool for information analysis. Moreover, this work presents an approach through KDD in time series pattern identification for anchovy and sardine fisheries and environmental data, in northern Chile. Time series, multivariate analysis and data mining techniques, along with technical literature review for results validation. The KDD approach and the data mining techniques implemented achieved an integration between these variables, identifying relevant patterns associated with fisheries abundance fluctuations and strong association with environmental changes such as El Niño and long-term cold–warm regimes between them, establishing anchovy and sardine pre-dominant time-periods, associated with environmental conditions are identified. The latter establishes groundwork for studying underlying functional relationships that could reduce gaps in the national fisheries management policies for those fisheries.

Modelling climate change impacts on anchovy and sardine landings in northern Chile using ANNs

Artificial Neural Networks (ANN) are adjusted to predict monthly landings of anchovy ( Engraulis ringens ) and sardine ( Sardinops sagax ) in northern Chile (18°21’-24°00’S). Fishing effort (FE), landings and twelve environmental variables are considered from 1980 to 2012. External validation for the best models using all variables showed an R 2 of 95% for anchovy and 99% for sardine, with an efficiency of 0.94 and 0.96, respectively. The models were simplified by considering only FE and sea surface temperature (SST) from NOAA satellites (SST-NOAA). Using these variables, very similar fits were achieved, comparing with the previous models, maintaining their predictive capacity. Downscaled SST for A2 climate change scenario (20152065) obtained by statistical regionalization from the Community Climate System Model (CCSM3) from National Center for Atmospheric Research (NCAR) and three FE scenarios (2010-2012 average, + 50% and 50%), were used as inputs for ANN simplified models. For A2 future climate change scenario (2015-2065) using 2010-2012 average FE as inputs, anchovy and sardine landings would increase 2.8% and 19.2% by 2065 respectively. With FE variations (-50%), sardine landings show the highest increase (22.6%) by 2065 when FE is decreased.

Do the Brazilian sardine commercial landings respond to local ocean circulation?

It has been reported that sea surface temperature (SST) anomalies, flow intensity and mesoscale ocean processes, all affect sardine production, both in eastern and western boundary current systems. Here we tested the hypothesis whether extreme high and low commercial landings of the Brazilian sardine fisheries in the South Brazil Bight (SBB) are sensitive to different oceanic conditions. An ocean model (ROMS) and an individual based model (Ichthyop) were used to assess the relationship between oceanic conditions during the spawning season and commercial landings of the Brazilian sardine one year later. Model output was compared with remote sensing and analysis data showing good consistency. Simulations indicate that mortality of eggs and larvae by low temperature prior to maximum and minimum landings are significantly higher than mortality caused by offshore advection. However, when periods of maximum and minimum sardine landings are compared with respect to these causes of mortality no significant differences were detected. Results indicate that mortality caused by prevailing oceanic conditions at early life stages alone can not be invoked to explain the observed extreme commercial landings of the Brazilian sardine. Likely influencing factors include starvation and predation interacting with the strategy of spawning “at the right place and at the right time”.

Pelagic resources landings in central-southern Chile under the A2 climate change scenarios

Artificial neural networks (ANNs) were used to predict landings of anchovy (Engraulis ringens), common sardine (Strangomera bentincki), and jack mackerel (Trachurus murphyi) in central-southern Chile. Twelve environmental variables were considered along with fishing effort (fe) and landing statistics from 1973 to 2012. During external validation, the best models with all of the selected variables gave r2 values of 90 % for anchovy, 96 % for common sardine, and 88 % for jack mackerel. The models were simplified by considering only fe and sea surface temperature from NCEP/NCAR reanalysis data (SST-NOAA), and very similar fits were achieved (87, 92, and 88 %, respectively). Future SSTs were obtained from the A2 climate change scenario and regionalized using statistical downscaling techniques. The downscaled SSTs were used as input for landings predictions using ANN simplified models. In addition, three scenarios of future fishing efforts (2010–2012 average, average + 50 %, and average − 50 %) were used as the input data for landing simulations. The results of the predictions show a decrease of 9 % in future landings of sardine and an increase of 17 % for jack mackerel when comparing 2015 and 2065 monthly projections. However, no significant differences are shown when comparing the estimated landings for the three fishing effort scenarios. Finally, more integrative and complex conceptual models that consider oceanographic-biophysical, physiological, environmental-resource, and interspecies processes need to be implemented.