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Small pelagic fishes occupy an important trophic role in every global aquatic ecosystem, and many species are heavily exploited by fisheries, including some of the largest and most valuable capture fisheries in the world. In November 2022, a symposium on small pelagic fish titled "Small Pelagic Fish: New Frontiers in Science and Sustainable Management" was cohosted by PICES, ICES, and FAO in Lisbon, Portugal. This special issue contains a collection of research manuscripts that explore approaches currently being used and developed to assess and manage small pelagic fishes. In particular, this issue covers topics on novel approaches to surveying small pelagic fishes, incorporating environmental covariates into management, management strategy evaluation, and aspects of the economics of small pelagic fisheries. The conclusions highlight the importance of new approaches that seek to enhance small pelagic fish surveys and ecosystem monitoring, incorporate that ecosystem information into management strategy evaluation, and predict the potential impacts of ecosystem changes on outcomes for economies and communities that rely on sustainable populations of small pelagic fishes. [ABSTRACT FROM AUTHOR]

Abstract: In the absence of pre-recruit surveys, environmental indices could potentially be used as predictors of recruitment to provide management advice for short-lived species such as anchovy. Environment–recruitment relationships have been established for the Bay of Biscay anchovy population, but their performance is still being tested. The purpose of this paper is to investigate under what circumstances incorporating environmental indices would lead to improvements in managing this anchovy stock in terms of increasing yields and reducing the risk of spawner biomass falling below a pre-defined reference level (e.g. B lim). The assessment is made by stochastic simulation of the anchovy population and its management. Management actions resulting from advice based on geometric mean recruitment or on precautionarily low levels of recruitment are compared with those resulting from recruitment predictions. Recruitment predictions could be used directly (expected recruitment used in TAC formulation) or indirectly (expected recruitment used as a trigger to increase or decrease the TAC). Linear models for environment–recruitment relationships with a coefficient of determination (r 2) of 0, 0.25, 0.5 and 1 are considered in the simulations for cases when such relationships are known perfectly or when the parameters are estimated and selected with measurement error. Results highlight factors that appear to be important in determining how much improvement is possible when incorporating environmental indices to provide TAC advice. In particular, they show that precautionary approaches may better ensure successful management, in terms of increasing yields and reducing risk, than consideration of uncertain or moderate to weak (in terms of the relationship to recruitment) environmental effects. [Copyright &y& Elsevier]

Biomass estimates of fish resources by the daily egg production method (DEPM) are sensitive to the high variability of the daily egg production (P0) and egg mortality (Z) in space. This work presents a Bayesian approach to estimate these parameters. A prior distribution of Z based on literature serves to overcome the biologically implausible Z estimates that can result from frequentist approaches. In addition to the classical estimation of a single P0 over the spawning area, the Bayesian framework allows also the modelling of egg densities in space, by including either spatial random effects, smoothing functions, or kriging like models, providing insights into the spatial variability of P0. The Bayesian approach was applied to the Bay of Biscay anchovy DEPM surveys. Results showed that this Bayesian approximation solved the implausible Z problem resulting in tighter credible intervals of both P0 and Z. Overall, spatial models outperformed the non-spatial model in terms of goodness of fit and resulted in slightly different total production estimates across models for each year, with a moderate decrease on uncertainty estimates. [ABSTRACT FROM AUTHOR]

Bianchetto ["white" late-larval and juvenile stages ('fry') mainly of sardine (Sardina pilchardus)] was fished traditionally along most of the Italian coast. The Gulf of Manfredonia (southwest Adriatic Sea) hosts a sardine nursery which was historically exploited by the bianchetto fishery using trawlnets; the fishery was banned in 2010. Here, we model this larval fishery under different assumptions of catch and natural mortality to assess its impact on the adult sardine stocks in the Adriatic Sea. The results show that the impact of the fishery is heavily dependent on the choice of early-stage natural mortality. The model proposed by Pepin (1991). Effect of temperature and size on development, mortality, and survival rates of the pelagic early life history stages of marine fish. Canadian Journal of Fisheries and Aquatic Sciences, 48: 503-518. was selected as the most plausible. Under this assumption, the direct effect of the bianchetto fishery in the Gulf of Manfredonia on the Adriatic adult sardine stock appears to be low, but not negligible, with impacts estimated as a 0.1-2% increase in the numbers of sardine at age 1 in the absence of a bianchetto fishery. Projections show that a 5% impact on age 1 sardine may be sufficient to bring the adult stock below safe levels. Therefore, given the uncertainties surrounding the impact assessment and the current status of the stock, if this fishery were to be resumed, catches should be kept at the lowest possible level until the underlying processes are better understood. [ABSTRACT FROM AUTHOR]

Abstract This work investigated adult-mediated connectivity and spatial population structure of sardine in the European Atlantic waters. The spatial and temporal progress of cohorts was modelled using abundance-at-age survey data by area in the period 2000–2016, covering the region from the northern Bay of Biscay to the eastern Gulf of Cadiz. A novel methodology was used to calculate indices of cohort movement between areas. Movement was relatively low between three large regions, the Bay of Biscay, the northern Spanish and Portuguese waters and the Gulf of Cadiz, each hosting a recruitment hotspot. On the other hand, one half of the sardines recruited in North Portugal and a quarter of those recruited in Southwest Portugal moved to northern Spanish waters and South Portugal, sustaining local populations and fisheries. Movement was mainly driven by recruitment strength and, in a less extent, by food availability during fall. The connectivity and dynamic patterns suggest a metapopulation with three weakly connected populations and density-dependent source-sink movement within the northern Spanish and Portuguese waters population. While the weak connectivity does not invalidate the management boundary between the Bay of Biscay and the Iberian Peninsula, the Gulf of Cadiz may be treated as a separate stock. Multi-area/metapopulation assessment approaches should be applied to account for complex population structure, the higher risks of depleting source areas and/or less productive populations. [ABSTRACT FROM AUTHOR]

This paper describes a methodology that combines meta-population theory and stock assessment models to gain insights about spatial heterogeneity of the meta-population in an operational time frame. The methodology was tested with stochastic simulations for different degrees of connectivity between sub-populations and applied to two case studies, North Sea cod (Gadus morua) and Northeast Atlantic sardine (Sardina pilchardus). Considering that the biological components of a population can be partitioned into discrete spatial units, we extended this idea into a property of additivity of sub-population abundances. If the additivity results hold true for putative sub-populations, then assessment results based on sub-populations will provide information to develop and monitor the implementation of finer scale/local management. The simulation study confirmed that when sub-populations are independent and not too heterogeneous with regards to productivity, the sum of stock assessment model estimates of sub-populations’ SSB is similar to the SSB estimates of the meta-population. It also showed that a strong diffusion process can be detected and that the stronger the connection between SSB and recruitment, the better the diffusion process will be detected. On the other hand it showed that weak to moderate diffusion processes are not easy to identify and large differences between sub-populations productivities may be confounded with weak diffusion processes. The application to North Sea cod and Atlantic sardine exemplified how much insight can be gained. In both cases the results obtained were sufficiently robust to support the regional analysis. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Bernal, M., Stratoudakis, Y., Wood, S., Ibaibarriaga, L., Uriarte, A., Valdés, L., and Borchers, D. 2011. A revision of daily egg production estimation methods, with application to Atlanto-Iberian sardine. 1. Daily spawning synchronicity and estimates of egg mortality. – ICES Journal of Marine Science, 68: .Assumptions of daily spawning synchronicity and estimation of egg mortality for Atlanto-Iberian sardine are revised in the context of daily estimators of egg production. An extensive database of ichthyoplankton surveys from 1985 to 2008, aggregated at different levels, is used, a set of mortality models is derived, and a comparison among them is carried out using standard statistical techniques. Analysis of the database shows Atlanto-Iberian sardine to be a late-evening spawner, in agreement with previous knowledge, but suggests a lengthier daily period of spawning. Comparison among the set of mortality models used suggests that estimates of mortality from single surveys for Atlanto-Iberian sardine are often unreliable, and that the mean estimates obtained after aggregating data from various years are statistically significant, more robust, and in line with existing information gathered from the literature. [ABSTRACT FROM PUBLISHER]

In this study the spatial distribution of eggs, larvae and juveniles of European anchovy ( Engraulis encrasicolus) was followed in 2004 and 2005 during three consecutive cruises each year in spring–summer to test what the limits of retention are in a non-upwelling area. Eggs, small larvae and large juveniles were mainly distributed over the shelf, whereas large larvae and small juveniles were found mainly off the shelf. Although overall distributions were similar, the 2 yr differed in that there was more of a coastal distribution of individuals in 2004, whereas in 2005 more individuals were found off the shelf. There were no significant differences in the length–weight relationships for individuals found on and off the shelf or between years. The correspondence in circulation patterns and the lack of difference in the length–weight relationships suggest that a single population is present, larvae drifting off the shelf due to currents and returning as mobile juveniles. Quantile regression analysis of the long-term recruitment index suggests that transport off the shelf may favour good recruitments. This would suggest that in non-upwelling regions the retention area resulting in good recruitment may not be restricted to the shelf. [ABSTRACT FROM AUTHOR]

• Purse seine is one of the most selective fisheries among those in the Bay of Biscay. • The discard rate was negligible thanks to the purse seine slipping practices. • Reasons for slipping were mostly related to the low market price of the catch. • Bycatch of Endangered Threatened and Protected species is practically non-existent. • It is important to define specific metiers to be used for management purposes. Ecosystem-based fishery management (EBFM) is based on a holistic approach, recognising all the interactions within an ecosystem rather than considering single species or issues in isolation. Studies of catch profiles of target and bycatch species for different fleets and metiers are necessary for successful management of target species. Such studies are also needed for the assessment of the interactions and evaluation of the impact on the ecosystems. This paper presents a study of the Spanish purse-seine fleet operating in the Bay of Biscay during the years 2016–2019. It considers the species selectivity and the effect of fishing activities on the pelagic community by assessing the interactions with the endangered, threatened and protected (ETP) species and estimating the discard sizes. For the purpose of this study, the metiers were defined by grouping similar catch profiles, using hierarchical agglomerative cluster analysis. This definition of metier goes beyond the Data Collection Framework (DCF) concepts; it includes specific target species, thus increasing the accuracy. Sampling conducted at sea during the four years of the study demonstrated that; 1) the discards were scarce both in terms of overall values and the proportion of the catch (below 1% for almost all metiers and years); 2) The studied purse-seine fishery is one of the most selective among those harvesting the pelagic domain in the Bay of Biscay; 3) The results also showed that the fleet avoided the unwanted catches, mostly by practising slipping;4) The interaction with the ETPs was almost non-existent. Only a single case of a yellow-legged gull entanglement was recorded, and the bird was released alive. Notably, more than 7500 individuals of 16 species of seabirds and marine mammals were recorded in the vicinity of the fishing grounds. Thus, we conclude that this purse-seine fishery has only a slight impact on the main species of the pelagic ecosystem, due to the purse-seine slipping practices. [ABSTRACT FROM AUTHOR]