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The present review is an outcome of discussions at the ICES-PICES Symposium on Drivers of Dynamics of Small Pelagic Fish convened in Victoria, B.C., Canada in spring 2017.-- This review is a first contribution of a new international Working Group on Small Pelagic Fish started jointly by ICES (WGSPF) and PICES (WG43) to continue world-wide collaboration to advance knowledge on the drivers of populations of SPF., Small pelagic fish (SPF) play extremely important ecological roles in marine ecosystems, form some of the most economically valuable fisheries resources, and play a vital role in global food security. Due to their short generation times and tight coupling to lower trophic levels, populations of SPF display large boom-and-bust dynamics that are closely linked to climate variability. To reveal emerging global research trends on SPF as opposed to more recently published, ecosystem-specific reviews of SPF, we reviewed the literature published in two, 6-year periods in the new millennium (2001–2006, and 2011–2016) straddling the publication of a large, global review of the dynamics of SPF in 2009. We explored intrinsic and extrinsic (bottom-up) factors influencing the dynamics of SPF such as anchovies, sardines, herrings and sprats within the sub-order Clupeidae. Published research efforts within 16 different biogeographic ocean regions were compiled (more than 900 studies) and compared to identify i) new milestones and advances in our understanding, ii) emerging research trends and iii) remaining gaps in knowledge. Studies were separated into 5 categories (field, laboratory, mesocosms, long-term statistical analyses and spatially-explicit modelling) and discussed in relation to 10 bottom-up categories including 5 abiotic factors (temperature, salinity, pH, dissolved oxygen, density), 3 physical processes (advection, turbulence, turbidity) and 2 biotic factors (prey quantity and quality). The peer-reviewed literature reflects changes in the number of studies between the two time periods including increases (Mediterranean Sea, Humboldt Current) and decreases (Australia, Benguela Current). Our review highlights i) gaps in ecological knowledge on young juveniles and, in general, on the impacts of hypoxia and heatwaves on SPF, ii) the utility of paleo studies in exploring population drivers, iii) the continued need to develop spatially-explicit, full life-cycle models, iv) the importance of exploring how density-dependent processes impact vital rates (growth, survival, reproduction), and v) the benefits of international collaboration for knowledge transfer and building unifying hypotheses on the role of bottom-up factors and processes that regulate SPF populations., MAP received partial funding from ‘PANDORA’ (Paradigm for New Dynamic Ocean Resource Assessments and Exploitation, (EU H2020, No. 773713).

WOS:000744169400002; International audience; Acoustic surveys represent the standard fishery-independent method worldwide for evaluating the biomass and spatial distribution of small pelagic fish populations. Considering the peculiarities of the spatial behaviour of pelagic fishes, the efficiency of the survey design in determining their biomass and spatial distribution is related to the ability to capture the portion of the patches accounting for a larger part of the total biomass. However, the spatial structure of the patches could be strongly influenced by ecosystem characteristics as well as by changes in total biomass related to a density-dependent mechanism. This is of particular interest for anchovies and sardines, which are known for their wide fluctuations and high sensitivity to the environment. In this study, we analysed the efficiency of acoustic surveys targeting European anchovies (Engraulis encrasicolus) and European sardines (Sardina pilchardus) in 10 different areas of the Mediterranean Sea spanning three years of different biomass levels. Using the geostatistical coefficient of variation (CVgeo) of the average occurrence probability of high/medium density values, we showed different patterns in terms of survey design efficiency among areas and species. Anchovies usually showed a lower CVgeo than sardines in the Alboran Sea. In 4 out of 20 cases, CVgeo values showed a consistent decrease with increasing biomass, while in the remaining cases, the CVgeo did not follow any clear pattern, suggesting the presence of important environmental effects. Higher survey design efficiency was found in highly productive sectors influenced by river run-off, allowing us to hypothesize that higher productivity along with the presence of well-localized enrichment mechanisms could favour a spatially consistent distribution and coherent organization of fish populations, leading to higher precision estimates with a given transect design. While most surveys displayed CVgeo close to 10% or less even at low biomass, indicating generally good performances of the survey design, a few areas exhibited higher CVgeo, yielding a potential need to decrease the intertransect distance, always keeping in mind that any survey should be as synoptic as possible.

International audience; Recently, the abundance of young Atlantic bluefin tuna (Thunnus thynnus) tripled in the northwestern Mediterranean following effective management measures. We investigated whether its predation on sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) could explain their concurrent size and biomass decline, which caused a fishery crisis. Combining the observed diet composition of bluefin tuna, their modelled daily energy requirements, their population size, and the abundance of prey species in the area, we calculated the proportion of the prey populations that were consumed by bluefin tuna annually over 2011-2013. To assess whether tuna could alter the size structure of the three small pelagic fish populations (anchovy, sardine, and sprat (Sprattus sprattus)), the size distributions of the consumed prey species were compared with those of the wild populations. We estimated that the annual consumption of small pelagic fish by bluefin tuna is less than 2% of the abundance of these populations. Furthermore, size selectivity patterns were not observed. We thus concluded that tuna predation is unlikely to be the main cause of major changes in the small pelagic fish populations from this area.

Small pelagic fishes have the ability to disperse over long distances and may present complex evolutionary histories. Here, Old World Anchovies (OWA) were used as a model system to understand genetic patterns and connectivity of fish between the Atlantic and Pacific basins. We surveyed 16 locations worldwide using mtDNA and 8 microsatellite loci for genetic parameters, and mtDNA (cyt b; 16S) and nuclear (RAG1; RAG2) regions for dating major lineage-splitting events within Engraulidae family. The OWA genetic divergences (0-0.4%) are compatible with intra-specific divergence, showing evidence of both ancient and contemporary admixture between the Pacific and Atlantic populations, enhanced by high asymmetrical migration from the Pacific to the Atlantic. The estimated divergence between Atlantic and Pacific anchovies (0.67 [0.53-0.80] Ma) matches a severe drop of sea temperature during the Gunz glacial stage of the Pleistocene. Our results support an alternative evolutionary scenario for the OWA, suggesting a coastal migration along south Asia, Middle East and eastern Africa continental platforms, followed by the colonization of the Atlantic via the Cape of the Good Hope. Portuguese Foundation for Science & Technology (FCT) [SFRH/BD/36600/2007]; FCT [UID/MAR/04292/2013, SFRH/BPD/65830/2009]; FCT strategic plan [UID/Multi/04326/2013] info:eu-repo/semantics/publishedVersion

Special issue Future of oceanic animals in a changing ocean.-- This study is a contribution to the project ECOTRANS (CTM2011-26333, MINECO, Spain).-- 9 pages, 3 figures, 4 tables, Small and medium pelagic fishes play a central role in marine food webs by transferring energy from plankton to top predators. In this study, direct calorimetry was used to analyze the energy density of seven pelagic species collected over four seasons from the western Mediterranean Sea: anchovy Engraulis encrasicolus, sardine Sardina pilchardus, round sardinella Sardinella aurita, horse mackerels Trachurus trachurus and T. mediterraneus, and mackerels Scomber scombrus and S. colias. Inter-specific differences in energy density were linked to spawning period, energy allocation strategies for reproduction and growth, and feeding ecologies. Energy density of each species varied over time, with the exception of S. colias, likely due to its high energetic requirements related to migration throughout the year. In general, higher energy density was observed in spring for all species, regardless of their breeding strategy, probably as a consequence of the late-winter phytoplankton bloom. These results provide new insights into the temporal availability of energy in the pelagic ecosystem of the Mediterranean Sea, which are pivotal for understanding how the population dynamics of small and medium pelagic fishes and their predators may respond to environmental changes and fishing impacts. In addition, the differences found in energy density between species highlighted the importance of using species specific energy-values in ecosystem assessment tools such as bioenergetic and food web models, M.A.-P. was supported by a predoctoral contract of the FPI program (BES-2012–054267, Spanish Ministry of Economy and Competitiveness). J.N. was supported by the Andalucía Talent Hub Program (Andalusian Knowledge Agency, European Marie Skłodowska-Curie actions – 267226). M.C. was partially funded by the European Commission through the Marie Curie Career Integration Grant Fellowships – PCIG10-GA-2011-303534 - to the BIOWEB project

Estimates of copepod secondary production are of great importance to infer the global organic matter fluxes in aquatic ecosystems and species-specific responses of zooplankton to hydrologic variability. However, there is still no routine method to determine copepods secondary production in order to eliminate time consuming experimental analyses. Therefore, we determined whether there is a correlation between Egg Production Rates (EPR) and RNA:DNA ratios of Acartia species, by measuring their seasonal and spatial variability and the influence of environmental factors for Acartia sp. collected in the Guadiana river estuary. EPR of Acartia tonsa was positively related with chlorophyll a concentration, freshwater inflow and biomass of dinoflagellates, while Acartia clausi was only related to dinoflagellates. Dinoflagellates seem to be the optimal food item influencing the reproduction of both Acartia species in the studied area. The biochemical index RNA:DNA was positively related to EPR, indicating that it is a good proxy of copepod production and a promising method to use in the future to estimate secondary production. The authors wish to thank to Antero Fernandes, David Pil? and Renata Gon?alves for their support during field work. J.C. was supported by Portuguese Foundation for Science and Technology (FCT) through a Doctoral Fellowship (SFRH/BD/28198/2006). MAT would like to thanks also FCT through a sabbatical fellowship (SFRH/BSAB/113684/2015). The authors also acknowledge European Regional Development Fund (COMPETE program- Operational Competitiveness Programme), and by national funds from FTC through project UID/Multi/04326/2013. S.G. is supported by FCT through a Post-Doctoral Fellowship (SFRH/BPD/105419/2014) and by the Investigador FCT Program (IF/01546/2015). Scopus

WOS:000412425500005; International audience; European sardine (Sardina pilchardus) and round sardinella (Sardinella aurita) comprise two-thirds of total landings of small pelagic fishes in the Canary Current Eastern Boundary Ecosystem (CCEBE). Their spawning habitat is the continental shelf where upwelling is responsible for high productivity. While upwelling intensity is predicted to change through ocean warming, the effects of upwelling intensity on larval fish habitat expansion is not well understood. Larval habitat characteristics of both species were investigated during different upwelling intensity regimes. Three surveys were carried out to sample fish larvae during cold (permanent upwelling) and warm (low upwelling) seasons along the southern coastal upwelling area of the CCEBE (13 degrees-22.5 degrees N). Sardina pilchardus larvae were observed in areas of strong upwelling during both seasons. Larval habitat expansion was restricted from 22.5 degrees N to 17.5 degrees N during cold seasons and to 22.5 degrees N during the warm season. Sardinella aurita larvae were observed from 13 degrees N to 15 degrees N during cold seasons and 16-21 degrees N in the warm season under low upwelling conditions. Generalized additive models predicted upwelling intensity driven larval fish abundance patterns. Observations and modeling revealed species-specific spawning times and locations, that resulted in a niche partitioning allowing species' co-existence. Alterations in upwelling intensity may have drastic effects on the spawning behavior, larval survival, and probably recruitment success of a species. The results enable insights into the spawning behavior of major small pelagic fish species in the CCEBE. Understanding biological responses to physical variability are essential in managing marine resources under changing climate conditions.

Special issue Ecopath 30 years – Modelling ecosystem dynamics: beyond boundaries with EwE.-- 15 pages, 8 figures, 3 tables, 2 appendixes, supplementary data https://dx.doi.org/10.1016/j.ecolmodel.2016.03.020, To realistically predict spatial-temporal dynamics of species in marine ecosystems it is essential to consider environmental conditions in conjunction with human activities and food web dynamics. In this study, we used Ecospace, the spatial-temporal dynamic module of Ecopath with Ecosim (EwE) food web model, to drive a spatially explicit marine food web model representing the Southern Catalan Sea (NW Mediterranean) with various environmental drivers and with fishing. We then evaluated the individual and joint effects of environmental conditions and fishing in various compartments of the food web. First we used a previously developed EwE model fitted to time series of data from 1978 to 2010 as a baseline configuration. The model included 40 functional groups and four fishing fleets. We first ran the original Ecospace spatial-temporal dynamic model using the original habitat configuration, in addition to fishing, and we predicted species distributions and abundances. Afterwards, we ran the new habitat foraging capacity model using the most important environmental drivers linked with the Ebro River delta dynamics (salinity, temperature, and primary production), in addition to depth, substrate and fishing, and we compared results with those from the original implementation of Ecospace. Three commercial species, European hake (Merluccius merluccius), anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus), were used to analyse results. Species distributions more closely matched the empirical information available from the study area when using the new habitat capacity model. Results suggested that the historical impacts of fishing and environmental conditions on the biomass and distributions of hake, anchovy and sardine were not additive, but mainly cumulative with a synergistic or antagonistic effect. Fishing had the highest impact on spatial modelling results while the spatial distribution of primary producers and depth followed in importance. This study contributes to the development of more reliable predictions of regional change in marine ecosystems of the Mediterranean Sea, MC was partially funded by the European Commission through the Marie Curie Career Integration Grant Fellowships – PCIG10-GA-2011-303534 – to the BIOWEB project and by the Spanish National Program Ramon y Cajal. This study is a contribution to the project ECOTRANS (CTM2011-26333, Ministerio de Economía y Competitividad, Spain)

To anticipate the response of fish populations to climate change, we developed a framework that integrates requirements in all life stages to assess impacts across the entire life cycle. The framework was applied on plaice (Pleuronectes platessa) and Atlantic herring (Clupea harengus) in the North Sea, Atlantic cod (Gadus morhua) in the Norwegian/Barents Seas and European anchovy (Engraulis encrasicolus) in the Bay of Biscay. In each case study, we reviewed habitats required by each life stage, habitat availability, and connectivity between habitats. We then explored how these could be altered by climate change. We documented environmental processes impacting habitat availability and connectivity, providing an integrated view at the population level and in a spatial context of potential climate impacts. A key result was that climate-driven changes in larval dispersion seem to be the major unknown. Our summary suggested that species with specific habitat requirements for spawning (herring) or nursery grounds (plaice) display bottlenecks in their life cycle. Among the species examined, anchovy could cope best with environmental variability. Plaice was considered to be least resilient to climate-driven changes due to its strict connectivity between spawning and nursery grounds. For plaice in the North Sea, habitat availability was expected to reduce with climate change. For North Sea herring, Norwegian cod and Biscay anchovy, climate-driven changes were expected to have contrasting impacts depending on the life stage. Our review highlights the need to integrate physiological and behavioural processes across the life cycle to project the response of specific populations to climate change.

Special issue Egg Production Methods in Marine Fisheries.-- 5 pages, This paper is an introduction of the Fisheries Research special issue on egg production methods (EPM) that emerged from a dedicated workshop held in Athens, Greece, in 2010. The workshop considered if EPMs are still valid today, it reviewed recent developments in the methods and discussed the utility of EPMs in the future. Importantly, experts from both the daily and the annual egg production methods took part in the workshop. This introduction provides the main concepts underlying EPMs. It also gives a brief history of EPM development over the last two decades with examples of their use worldwide. It provides a review on whether EPMs have fulfilled their objectives. Given their increased utilisation on new fish stocks, and their contribution to scientific advances, EPMs continue to be useful. However, concerns about the bias and precision of the methods remain, and a continuous effort to improve those issues together with the cost-efficiency of the methods is still required. © 2012., The workshop was sponsored and funded by FRESH (Fish Reproduction and Fisheries; COST Action FA0601; www.fresh-cost.org) and supported by the International Council for the Exploration of the Sea (ICES). We would like to thank FRESH for providing funds for the workshop and ICES for supporting the creation of the workshop

Special issue Egg Production Methods in Marine Fisheries.-- 6 pages, The special theme volume of Fisheries Research is intended to synthesise the current understanding of the methods and applicability of egg production methods (EPM). It originates from a workshop in Athens which also focused on the future challenges to both the science and logistics of carrying out and using egg production methods. This synthesis addresses three interlinked challenges for those using EPM; how methods have, and need to be, improved, what added value can EPM provide directly to aid advice for management of the marine environment and lastly what extra understanding can EPM bring to marine science? EPM surveys offer some of the most intensive sampling of plankton and adult fish populations in fisheries science. They provide, and will probably provide further insights into fish reproductive processes, embryonic development and spatial and temporal variability in fish populations. Researchers should be encouraged to examine new methods for representative real-time sampling, swift processing of samples and integration of sampling of adults and plankton. EPM provides managers with many >added value> products on habitats and spawning and already provides platforms for monitoring hydrography, zooplankton distributions and acoustic back scatter. Some EPM surveys also incorporate monitoring of birds and sea mammals. EPM, together with aquaculture, has progressed understanding of fish reproductive biology and embryo development. EPM provides long time series of both the ichthyoplankton and fish reproductive traits thus enabling informed study of regime change, variability and ecosystem status. As the EPM become more developed, we expect that these contributions to marine science will increase. © 2012

Industrial-scale fisheries are often thought to reduce food availability for top predators. It is essential to estimate the spatial and temporal overlap over a fine scale between fisheries and pre- dators during their breeding season, when their energy demand is greatest and when they are most spatially constrained, in order to understand and manage this potential impact on their populations. In the Benguela upwelling region, 2 endemic vulnerable seabirds, Cape gannets Morus capensis and African penguins Spheniscus demersus, mainly eat anchovy Engraulis encrasicolus and sardine Sardinops sagax, both of which are exploited by the purse-seine fishery. A recent eastward displace- ment of small pelagic fish off the South African coast has reduced fish availability for both birds and fisheries along the west coast. Using GPS-recorders, we studied the foraging dispersal of birds from 8 colonies containing 95% of the global Cape gannet and 60% of the global African penguin popu- lations to assess their overlap with fish catches. Despite the fact that bird data were gathered at very fine spatial and temporal scales (meters and hours), and fisheries data were recorded at much coarser spatial and temporal scales (20 km and months), there was clear overlap in areas used. The main for- aging areas of both species were located where purse-seine fisheries caught most fish, with most catches occurring during the birds' breeding season. As birds and fisheries also overlap in the size of the targeted prey and the depth of exploitation, our study suggests the potential for intense competi- tion between purse-seine fisheries and decreasing seabird populations in the southern Benguela. Long-term protection of these seabird species requires the inclusion of a suitable ecological buffer when setting fishery quotas, and implementing marine protected areas closed to fishing around key breeding sites and foraging hotspots may improve their breeding success.

The pattern of genetic variability of two species of Mediterranean gobiids was compared, with reference to their different life history traits (Aphia minuta paedomorphic and pelagic; Gobius niger metamorphosed and benthic). The aim was to evaluate how different life histories can affect the genetic structure in these marine teleosts. The study was carried out on populations of both species sampled in the western Mediterranean and in the Adriatic Sea. Seven restriction endonucleases were used for the RFLP analysis of a mitochondrial DNA segment comprising the NADH dehydrogenase subunits 3, 4L and 4. The results highlighted two different patterns of genetic variation, a weak genetic structure in A. minuta and population subdivision in G. niger. These observations may be explained not only in terms of the different dispersal capabilities of these species, but also considering that A. minuta is an abbreviate iteroparous spawner while G. niger is a protracted iteroparous spawner. Because abbreviate iteroparity is a reproductive strategy selected in stable environments with high resource availability, Pliocene and Pleistocene climate oscillations may have represented factors that negatively influenced the reproductive success of A. minuta, producing demographic fluctuations and bottlenecks, as suggested by the mismatch distribution analysis. The weak genetic structure of A. minuta populations seems to be therefore due to a more recent re-colonization of the Mediterranean basin after a severe population decline, rather than to the high vagility of this pelagic goby.