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Future Oceans2 Integrated Marine Biosphere Research (IMBeR) Open Science Conference, 17-21 June 2019, Brest, France, Small pelagic fishes (SPF) in the western Mediterranean Sea are key elements of the marine food web and are important in terms of biomass and catches. Significant declines in biomass, landings and changes in the age/size structure of European anchovy Engraulis encrasicolus and European sardine Sardina pilchardus have been observed in recent decades in the northwestern Mediterranean Sea (in GSA06 Northern Spain and GSA07 Gulf of Lions, France). Instead, SPF in the southwestern Mediterranean Sea (GSA01 Alboran Sea, Spain) showed different patterns without a clear trend. Fluctuations of SPF have been related to local and regional scale environmental changes, driving annual recruitment and growth, mainly by river runoff, temperature and primary production. To understand the different patterns observed in SPF populations in the western Mediterranean Sea, we analysed seasonal and inter-annual variability of key life-history traits (size at first maturity, gonadosomatic index and body condition) collected in different fishing harbours of Spain distributed along a latitudinal gradient from Tarragona and Torrevieja, in GSA06, norther Spain, to Malaga, in GSA01, southern Spain. Results showed a clear decline in size at first maturity and body condition of sardine and anchovy since 2008 until 2017, with minimum values in 2012 and 2014 in the north of the area. On the contrary, in the south inter-annual fluctuations in body condition did not present a clear temporal trend while size at first maturity increased. However, in absolute terms, levels of energy stored and energy invested in reproduction were lower in the southern area compared with the northern populations. Maximum values of body condition of European sardine also differed between areas at seasonal scale. The decline in size at first maturity may have been translated into lower reproductive capacity in the north, since younger females have proportionally lower fecundity and shorter spawning season. Overall, the most plausible combined causes to explain observed changes in life-history traits of small pelagic fish in the western Mediterranean Sea were (1) a combination of environmental factors affecting the body condition, (2) a phenotypic selection by fisheries for the individuals that mature earlier and (3) the disappearance of larger and older individuals due to historical overfishing. The decline in body condition and size at first maturity of both species should be taken into account when evaluating the commercial stocks since natural mortality may have increased and earlier maturation, in combination with the removal of older individuals, could highly reduce the reproductive potential of the stocks. This study highlights the importance of understanding the trade-off between the energy invested in reproduction, maintenance and growth to better predict how environmental and human pressures influence population dynamics of small pelagic fish

SC NR. 02 - TENDER EASME/EMFF/2016/32 - SPELMED.-- 119 pages, figures, tables, The status of the sardine and anchovy stocks in GSA 06 and GSA 07 were investigated using statistical catch-at-age (a4a) and two-stage biomass models. Life-history parameters of both species were reviewed and new estimates of the von Bertalanffy growth parameters (improving the value of t0) were used. The input data to the stock assessment model were updated, as required (including the natural mortality parameter, M). The new estimates for the growth parameters were for European sardine: Linf = 20.1 cm TL, k = 0.817 yr-1, t0 = -0.246 yr, and for European anchovy: Linf = 18.0 cm TL, k = 0.984 yr-1, t0 = -0.255 yr. [...]

SC NR. 02 - TENDER EASME/EMFF/2016/32 - SPELMED.-- 29 pages, 14 figures, 1 table, 2 annexes, Body condition is a proxy of the quantity of energy stored and is dependent on food supply and energy allocation strategies. Population reproductive potential, growth and survival (i.e. natural mortality) can be affected by body condition. European sardine is a winter spawner with a capital breeding strategy, it spawns and feed in separate areas, during different seasons by storing energy and utilizing it later for reproduction. It acquires and stores energy in spring and summer to be used in the reproductive period. Instead, anchovy spawns in spring and summer using the current energy income for reproduction, and is considered to have an income breeding strategy, this is using energy acquired locally and allocating energy directly to reproduction. [...]

SC NR. 02 - TENDER EASME/EMFF/2016/32 - SPELMED.-- 27 pages, 13 figures, 3 tables, Long term trends in the variation of reproduction parameters can be indicative of a change in the life-history traits of the species and could have consequences for survival (i.e. natural mortality) and condition, and ultimately affect recruitment success and population growth and persistence. In this deliverable we analysed potential historical changes in reproduction parameters calculated for the reproduction period, gonadosomatic index (GSI) and size at first maturity (L50) of European sardine and anchovy from GSA06 (Northern Spain) and GSA01 (Alboran Sea). In the case of European sardine, GSA06 data was divided in two subareas, GSA6 north (data from Tarragona harbour) and GSA06 south (data from Torrevieja harbour). Results are compared with previous historical analysis on GSA07 (Gulf of Lions, Brosset et al., 2016) and with the information gathered from the review performed under SPELMED and presented in deliverable D1.3.2.2. [...]

SC NR. 02 - TENDER EASME/EMFF/2016/32 - SPELMED.-- 77 pages, 10 figures, 7 tables, 56 annexes, In order to manage small pelagic fish species, such as European anchovy (Engraulis encrasicolus) and European sardine (Sardina pilchardus), and enable to implement properly stock assessment analysis, it is essential to study the growth and age determination of these species (Arneri et al. 2011). We (1) reviewed current information on growth of both species, (2) calculated new von Bertalanffy growth parameters, and (3) estimated age-length structure for both species in the GSA 06. Our review shows that the validation of the age interpretation is still rather incomplete to date, only indirect methods have been used and even some studies lack formal precision and accuracy. In some cases, length frequency analyses supported the data for the adults and birthdate distributions for the larvae. [...]

Daily growth rates were estimated from larval anchovy (Engraulis encrasicolus) sampled in their main nursery grounds off the Bay of Málaga (SW Mediterranean) during the 2000 and 2001 spawning seasons. Significantly higher growth rates were observed in the 2001 larval population, representing a 20% increase through the larval size classes analysed. The decimated SW Mediterranean anchovy population experienced a successful anchovy recruitment during this year estimated at 13,000 tons for the Bay of Málaga by the acoustic evaluation of small pelagic resources. The size distribution of the recruited anchovy juveniles during 2000 and 2001 showed an increase of approximately 2 cm. Their corresponding anchovy spawning seasonality agrees with the estimates from the growth model fits of each year. Data on the environmental background for the two years sampled are provided by a historical quarterly monitoring project. Zooplankton showed a two-fold significant increase during July 2001, coastwise as well as offshore. No significant changes in surface temperature were observed between years. Instead of the usual summer spawning peak, anchovy peak spawning shifted towards early spring during the 2001 spawning season. The study provides evidence from field data on the relationships of larval growth variability and recruitment., Las tasas de crecimiento diario de larvas de anchoa (Engraulis encrasicolus) fueron estimadas de una población larvaria procedente de la principal zona de alevinaje de la Bahía de Málaga (Mediterráneo Sur-occidental) durante la época de puesta de los años 2000 y 2001. Las tasas de crecimiento diario de la población del 2001 fueron significativamente mas altas, representando un aumento del 20% en todas las clases de tallas larvarias analizadas. Durante el año 2001, se produjo un importante aumento del reclutamiento de anchoa estimado por el método acústico en 13,000 TM en la Bahía de Málaga. La distribución de tallas de los reclutas de anchoa presentó un aumento de 2 cm aproximadamente entre los años 2000 y 2001. La estacionalidad de la puesta se corresponde con las estimaciones del modelo de crecimiento para cada año. Los datos del medio-ambiente para los 2 años muestreados son aportados por un proyecto de seguimiento trimestral de las condiciones oceanográficas. La biomasa zooplanctónica aumentó de forma significativa, en costa como en mar abierto, durante Julio del 2001. Sin embargo, no se observaron cambios significativos en la temperatura superficial entre años. En el 2001, se observa un adelanto a primavera de la puesta de la anchoa. Este estudio evidencia a partir de datos de campo la relación entre variabilidad del crecimiento larvario y reclutamiento.