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[EN] We present the Terms of Reference for a case study on a Mediterranean eco-region focusing on the environmental component of the Ecosystem Report Card. The objective of this case study is to describe and monitor the variability of environmental processes in the Mediterranean Sea that affect the ecology of large pelagic fishes, with a particular attention on tunas, and the possible role of climate change on this variability. Here we define the objectives and activities of the initiative, the participant roles, primary indicators and the methodological approach, [FR] Ce document présente les termes de référence d’une étude de cas sur une écorégion méditerranéenne consacrée à la composante environnementale de la fiche informative sur les écosystèmes. L'objectif de cette étude de cas est de décrire et de suivre la variabilité des processus environnementaux en mer Méditerranée qui affectent l'écologie des grands poissons pélagiques, en accordant une attention particulière aux thonidés, et de déterminer le rôle possible du changement climatique sur cette variabilité. Nous définissons ici les objectifs et les activités de l'initiative, les rôles des participants, les indicateurs primaires et l'approche méthodologique., [ES] En el documento se presentan los términos de referencia para un estudio de caso sobre una ecorregión mediterránea centrado en el componente medioambiental de la ficha informativa sobre ecosistemas. El objetivo de este estudio de caso es describir y hacer un seguimiento de la variabilidad de los procesos medioambientales en el mar Mediterráneo que afectan a la ecología de los grandes peces pelágicos, con especial atención a los túnidos, y el posible papel del cambio climático en esta variabilidad. A continuación, se definen los objetivos y actividades de la iniciativa, las funciones de los participantes, los indicadores principales y el enfoque metodológico.

The Balearic Sea, in the western Mediterranean, is a remarkable reproductive area for many marine species, among which large oceanic migrants stand out. This region presents unique oceanic features with fronts and eddies, favouring the early-life stages of these species. We take advantage of already existing biological and oceanographic data and know how to advance in the understanding of the open-ocean pelagic ecosystem. We purpose indicators to monitor the environmental variability of the pelagic habitat, such as temperature anomalies that affect the survival of tuna larvae. The indicators are designed to inform climate aspects of the ecosystem approach to fisheries management for tunas and other related species in the framework of the International Commission for the Conservation of Atlantic Tuna, the organisation in charge of the fisheries management of these species. We take swordfish (Xiphias gladius) as a case study. Swordfish is a highly migratory species that, in the Mediterranean, reproduces at several locations and has the Balearic Islands as one of the main breeding areas. We investigate if climate change has already affected the suitability of this potential spawning ground. For that, we analyse how the variability of ocean characteristics and features affects the presence of swordfish larvae collected in ichthyoplanktonic surveys and identify their preferential habitat. Results of this work show that, during reproductive season and early developmental time of this species, significant heatwaves impact the pelagic realm in the Balearic Sea, a prominent hydrodynamic retention area of the western Mediterranean, with direct effects on the distribution of the swordfish larval habitat.

This document presents the update of the bluefin tuna retrocalculated larval abundance indices from the Balearic archipelago (western Mediterranean). The index has been calculated following methods presented in 2020 (SCRS/2020/067) and 2021 (SCRS/2021/033). The abundance index shows an increasing trend with a maximum value in 2020. A previous version of the index (SCRS/P/2019/055) is also provided for comparison.

Larval abundance indices express retrocalculated abundances of larval densities at hatching time. They provide a proxy for assessing spawning stock biomass and are applied to assess population status of various species in the Gulf of Mexico and in the Balearic Sea. Recently, the methodological approach to calculate the indices was improved to accommodate for non-linear responses of environmental effects on catchability. This improved methodology is routinely applied in the Balearic Sea to assess the bluefin tuna (Thunnus thynnus) spawning stock biomass. Here we apply the same methodology to update the larval index of albacore (Thunnus alalunga) from surveys conducted from 2001 to 2019 in the Balearic Sea, the most relevant spawning ground of this species in the Western Mediterranean. Albacore larval abundances show a decreasing trend and significant lower abundances from 2013 onwards, despite a slight recovery between 2016 and 2017. This larval index, standardized for gears, sampling coverage, salinity, date and sea surface temperature, provides information on the dynamics of the western Mediterranean stock of albacore, which is considered a data poor stock.

In this study we explore the potential for improving the stock assessment of Mediterranean Albacore by integrating environmental indicators. For this purpose we developed a catch at age model within the A4A stock assessment approach. The input data was similar to that used in the official SCRS stock assessment in 2017 but with an updated larval index. The environmental indicator provides information on the interannual variability of the sea surface temperature in the Balearic Sea during the spawning season, and it is included in the “Environmental pressure” component of the Ecosystem Report Card. The indicator is included in the assessment model in different ways, as index of the class age 0, as vector for the Stock/recruitment model, and as productivity value in other stock recruitment models (Ricker, Beverton-Holt). The results showed that incorporating the environmental variability indicators provide a better stock assessment fits (AIC, BIC), and also show the need for more advanced techniques to test stock assessment performance when testing the inclusion of environmental variability

The main objective of this study is to provide the knowledge to design adequate sensitivity analyses on the assessment models used for the Eastern stock of Bluefin tuna. We analyze how different configuration for the same environmental variable (temperature in the mixed layer depth) and different modeling approaches (nonlinear Delta-log,delta-gamma, tweedy and bayesian) affects to the variability of the larval indices of the Eastern bluefin tuna from data collected in the Balearic Sea (Western Mediterranean). We also investigate the effects on the index caused from having differences in the total sampled area among years. We used these results to interpolate larval index values in years with not standard larval surveys but with some ichthyoplankton surveys available, and to propose a “revised version” of the index providing parameters of uncertainty.

1. Since the 1990s, most currently assessed Mediterranean nekto‐benthic stocks have been exploited above maximum sustainable yield and have declined. This study explores the co‐occurrence of essential fish habitats for the most important nekto‐benthic resources exploited by bottom‐trawl fisheries in the western Mediterranean and areas of importance for nekto‐benthic communities. 2. Fishery‐independent data obtained from Mediterranean scientific bottom‐trawl surveys were used to identify persistent hotspots of recruitment for the most important nekto‐benthic species around the Iberian Peninsula and the Balearic Islands between 2002 and 2016, as an indicator of their essential fish habitats. Likewise, hotspots of nekto‐benthic community diversity and density were also determined, as an estimate of key areas for nekto‐benthic communities. 3. Areas of overlap of persistent hotspots of recruitment and of community species richness and density were mainly found on the deep shelf and the upper slope (100–200 m and 200–500 m deep respectively). 4. These overlapping areas could be of particular interest in the development of fishery management plans aiming to implement an ecosystem approach to fisheries. Protection, through temporary or permanent closures, of the overlapping areas identified would contribute to improving both the sustainable exploitation of the main target species of bottom‐trawl fisheries and the conservation of nekto‐benthic communities.

A new approach to recruitment overfishing diagnosis is presented. We hypothesize that condition of recruits should increase when recruitment failures are caused by fishing activity. This would be a consequence of the increase in trophic resource availability, because the population is smaller than that which the ecosystem could support. Temporal series of hake recruit condition were calculated from MEDITS survey data collected in Mediterranean geographical sub-areas (GSAs) 1, 6, 17 and 19 from 1994 to 2015. Multiple linear regressions were used to analyse the relationship between mean annual condition and abundance of recruits and climatic indices in each GSA. Significant correlations were only detected in GSA 6, where 69% of condition variability was explained by the negative correlation with recruit abundance, and with two climatic indices, the Western Mediterranean Oscillation and the standardized air temperature anomaly at surface from the Gulf of Lions. Despite the differences in recruit abundance among GSAs, their mean annual condition oscillated around the same basal value during most of the time series, pointing to density-dependent mortality rates as an important mechanism stabilizing hake recruitment to levels close to the carrying capacity when populations do not suffer recruitment overfishing. This pattern changed when the decreasing recruit abundance trend drove GSA 6 condition values persistently above those of the rest of the GSAs. According to our hypothesis, hake in GSA 6 is in recruitment overfishing.

In the Mediterranean Sea, the European anchovy (Engraulis encrasicolus) displays a key role in ecological and economical terms. Ensuring stock sustainability requires the provision of crucial information, such as species spatial distribution or unbiased abundance and precision estimates, so that management strategies can be defined (e.g. fishing quotas, temporal closure areas or marine protected areas MPA). Furthermore, the estimation of the precision of global abundance at different sampling intensities can be used for survey design optimisation. Geostatistics provide a priori unbiased estimations of the spatial structure, global abundance and precision for autocorrelated data. However, their application to non-Gaussian data introduces difficulties in the analysis in conjunction with low robustness or unbiasedness. The present study applied intrinsic geostatistics in two dimensions in order to (i) analyse the spatial distribution of anchovy in Spanish Western Mediterranean waters during the species’ recruitment season, (ii) produce distribution maps, (iii) estimate global abundance and its precision, (iv) analyse the effect of changing the sampling intensity on the precision of global abundance estimates and, (v) evaluate the effects of several methodological options on the robustness of all the analysed parameters. The results suggested that while the spatial structure was usually non-robust to the tested methodological options when working with the original dataset, it became more robust for the transformed datasets (especially for the log-backtransformed dataset). The global abundance was always highly robust and the global precisión was highly or moderately robust to most of the methodological options, except for data transformation.

The ecology of highly migratory marine species is tightly linked to dynamic oceanographic processes occurring in the pelagic environment. Developing and applying techniques to characterize the spatio-temporal variability of these processes using operational oceanographic data is a challenge for management and conservation. Here we evaluate the possibility of modelling and predicting spawning habitats of Atlantic bluefin tuna in the Western Mediterranean, using pelagic seascape metrics specifically designed to capture the dynamic processes affecting the spawning ecology this species. The different seascape metrics applied were processed from operational oceanographic data products providing information about the temporal and spatial variability of sea surface temperature, kinetic energy and chlorophyll a. Spawning locations were identified using larval abundances sampled in the Balearic Sea, one of the main reproductive areas for this species in the Mediterranean Sea. Results confirm the high dependence of bluefin tuna spawning ecology on mesoscale oceanographic processes while providing spawning habitat maps as a tool for bluefin tuna assessment and management, based on operational oceanographic data. Finally, we discuss the coming challenges that operational fisheries oceanography and pelagic seascape ecology face to become fully implemented as predictive tools

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem a

Summary: Small pelagic fish are species that live in the water column and have little relationship with the sea bottom. During the day they may form schools with feeding, defence or energetic efficiency purposes and disperse during the night. The importance of small pelagic fishes within the marine ecosystem rely in the proportion of biomass they represent and the clue function they develop as intermediate links in the energy transfer between lower and upper levels of the trophic chain. Their populations are particularly sensitive to environmental fluctuations and frequently highly exploited by commercial fisheries. These may occasionally collapse the stocks affecting both the marine ecosystem and the fisheries they sustain. In the Mediterranean, almost 50% of the total annual landings are attributable to small pelagic fishes. In the Western Mediterranean Sea, sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) are the two most important species in terms of landed biomass and commercial interest. Despite their importance little is known about the spatial distribution of these stocks or about the relationship between the spatial distribution and environmental variables. Since the ‘90s acoustic surveys are annually performed in the Spanish Mediterranean continental shelf in late autumn coinciding with anchovy’s recruitment and the beginning of the spawning season for sardine. Although the main goal of these surveys is to estimate abundance and biomass of sardine and anchovy, data about the whole pelagic community has also been gathered. Furthermore, in the last decade it was detected an increasing appearance of other small and medium-sized pelagic species and the application of a multi-species approach to Mediterranean fisheries assessment was advised. The present work is structured in two sections. The first section of the work will analyse the spatial distribution (1D and 2D) of sardine and anchovy by means of geostatistical techniques, both transitive, Resumen: Los pequeños peces pelágicos son especies que viven en la columna de agua y que tienen poca relación con el fondo marino. Durante el día forman bancos de peces con el objetivo de alimentarse, defenderse de potenciales depredadores o por motivos de eficiencia energética, dispersándose durante la noche. La importancia de los pequeños pelágicos en el ecosistema marino radica en la proporción de biomasa que representan y en la función clave que desempeñan como eslabones intermedios, transfiriendo energía entre los niveles tróficos inferiores y superiores de la cadena trófica. Sus poblaciones son particularmente sensibles a las fluctuaciones ambientales y frecuentemente se encuentran en un régimen de explotación elevado por parte de las pesquerías comerciales. Esto puede comportar de manera ocasional el colapso de sus poblaciones explotables, afectando al ecosistema marino y a las pesquerías que las mantienen. Casi el 50% del total de la biomasa anual desembarcada en los puertos del Mediterráneo provienen de los pequeños peces pelágicos. En el Mediterráneo Occidental, la sardina (Sardina pilchardus) y el boquerón (Engraulis encrasicolus) son las dos especies más importantes, tanto en términos de biomasa como capturada como por su interés comercial. A pesar de su importancia, la distribución espacial de las poblaciones explotables es poco conocida así como también lo es la relación de la distribución espacial con los parámetros ambientales. Desde principios de los años 90, se llevan a cabo campañas acústica en la plataforma continental española del Mediterráneo a finales de otoño, coincidiendo con el reclutamiento de la anchoa y la época de puesta de la sardina. A pesar de que el principal objetivo de estas campañas es la estimación de la abundancia y de la biomasa de la sardina y el boquerón, datos de la comunidad pelágica en conjunto también se recogen periódicamente. Además, a lo largo de la última década se ha detectado una aparición incremental de otras espe, Resum: Els petits peixos pelàgics són espècies de peixos que viuen a la columna d’aigua i que tenen poca relació amb el fons marí. Durant el dia formen bancs de peixos amb l’objectiu alimentar-se, defensar-se en front potencial depredadors o per eficiència energètica, dispersant-se durant la nit. La importància dels petits pelàgics a l’ecosistema marí radica en la proporció de biomassa que representen i en la funció clau que exerceixen com esglaons intermedis, transferint energia entre les nivells inferiors i superiors de la cadena tròfica. Les seves poblacions són particularment sensibles a les fluctuacions ambientals i freqüentment es troben baix un règim d’explotació elevat per part de les pesqueres comercials. Això pot comportar de manera ocasional el col•lapse de les seves poblacions explotables, afectant a l’ecosistema marí i a les pesqueries que sostenen. Gairebé el 50% del total de la biomassa anual desembarcada als ports del Mediterrani prové dels petits peixos pelàgics. Al Mediterrani Occidental, la sardina (Sardina pilchardus) i l’aladroc (Engraulis encrasicolus) són les dues espècies més importants, tant en termes de biomassa capturada com pel seu interès comercial. Malgrat la seva importància, la distribució espaial de les poblacions explotables és poca coneguda així com també ho és la relació d’aquesta distribució espaial amb variables ambientals. D’ençà de principis dels anys 90, es duen a terme campanyes acústiques a la plataforma continental del Mediterrani espanyol a finals de la tardor, coincidint amb el reclutament de l’aladroc i amb l’època de posta de la sardina. Tot i que el principal objectiu d’aquestes campanyes és l’estimació de l’abundància i de la biomassa de la sardina i l’aladroc, dades del conjunt de la comunitat pelàgica també es recolleixen. A més a més, al llarg de la darrera dècada s’ha detectat una aparició incremental d’altres espècies de petits i mitjans pelàgics i per tant, es va aconsellar l’aplicació d’un enfoc multiespecífic

Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed

Acoustic surveys are used worldwide for the assessment of pelagic fish stocks. In the Spanish Mediterranean area acoustic surveys are performed annually in late autumn and cover the entire continental shelf between 30 and 200 m depth. This survey was initiated to obtain estimates of anchovy recruitment (Engraulis encrasicolus), but additionally provide a general overview of the whole pelagic fish community in the study area during the time of the year it is performed. Our study area has a diverse assemblage of small and medium-sized pelagic fish (up to nine species) and thus we rely on the proportion of species obtained in middle-water pelagic fishing trawls to attribute the amount of echo corresponding to every single species and estimate their abundance. Although uncertainties may arise from many different sources (e.g. transducer motion, target strength, migration) we focus our study on the estimation of overall sampling uncertainty, one of the main contributors to random error. We apply geostatistical techniques to deal with spatial correlation and discuss benefits and pitfalls in their application. Although transitive geostatistics have seldom been used, most probably due to their inability to produce spatial maps of abundance and variance estimations, they constitute a powerful tool to routinely estimate sampling variance and its variation in time in a multi-specific context. They may also help to assess the effects of varying sampling intensity and could potentially be useful to detect possible processing errors, for example, in echogram scrutinizing. These techniques may therefore potentially help improve both the precision and the accuracy of acoustic data

The sociology and habits of recreational anglers on the Island of Majorca (western Mediterranean) were evaluated using telephone and on-site surveys, as well as fishing logbooks and recreational fishing competitions. The recreational fishery is one of the island's main leisure activities, 5.14% of the population (37 265 people) participating. Enthusiasts tend to be mainly middle class (most anglers own boats moored at marinas), middle-aged males (90% male, mean age 46 ± 2 years). The most popular fishing method is from a boat (62.9%), followed by fishing from shore (32.4%), and spearfishing (3.6%). The mean time spent fishing is 3.86 ± 0.03 h d-1, and more than one type of gear (mean 1.27 ± 0.21) is used simultaneously by a single angler. The frequency of fishing is 4-6 times per month, mainly on holidays and weekends, increasing in summer. The activity has a sizeable impact on the coastal fauna, with diverse catches of at least 1209.25 t year-1 (about 615 000 fishing outings year-1). Thus, the amount of carbon extracted annually is at least 137.34 kg C km-2 year-1, and the recreational fishery removes about 31% of production at trophic level 4. Although these are gross estimates and more detailed study of the effect on trophic level and local production is needed, the values do highlight the pressure the recreational fishery exerts on coastal fish communities. Assuming that this level of exploitation is common to north-shore Mediterranean countries, there may be cause for concern about sustainable exploitation in the recreational fishery, and the effectiveness of current protection measures is discussed. Despite the limitations of the study, recreational fisheries clearly should be taken into account when considering measures for fisheries management. Moreover, fishing has considerable social import, and the benefits must be taken into account when investments to protect exploited resources are being contemplated. © 2005 International Council for the Exploration of