Occurrence of adult anchovy in Catalonia (NW Mediterranean) in relation to sea surface conditions

Abstract

Summary:Generalized additive and generalized additive threshold models were used to study the relationship between landings per unit effort (LPUE) of anchovy, Engraulis encrasicolus, during the spawning season (May-October) from 2000-2010, and environmental variables, using sea surface data derived from satellite imagery (temperature, salinity, chlorophyll a, and meridional and zonal velocity current) in three fishing zones defined along the Catalan coast. The configuration of the environment where spawning aggregations occur affects early life stages and therefore the future demographic structure of the population. It is therefore fundamental to define the environmental conditions and their variations during the spawning season. Our results show that the low salinity in the Northern and Central sector and the velocity of the zonal and meridional currents in the Central and Southern sector, respectively, implicated in retention processes, increase LPUE during the spawning period. Temperature was related to LPUE in the Southern and in the Northern sectors, in both of which a non-linear positive effect with a local maximum peak at lower temperature values was present. However, in the Northern sector, this relationship held only for the period before 2007. After 2007 the decrease in preferred temperature suggests a reduction of the thermal window in which adult spawner aggregations occur. In agreement with previous studies on this species, the relationships were non-linear, stressing the importance of the match in timing and location between favourable conditions and spawning period as a crucial event for understanding the dynamics of small pelagics populations.Keywords: Engraulis encrasicolus; NW Mediterranean; environmental conditions; anchovy landings; generalized additive models. Ocurrencia de anchoa adulta en Cataluña (Mediterráneo noroccidental) en relación a las condiciones superficiales del marResumen: Con el objeto de estudiar la relación entre descargas por unidad de esfuerzo (LPUE) de la anchoa, Engraulis encrasicolus, durante la época de puesta (Mayo-Octubre) y variables ambientales marinas obtenidas por observación de satélite (temperatura, salinidad, clorofila-a, velocidad de corriente zonal y meridional) se analizaron series de datos para el periodo 2000-2010 mediante modelos aditivos generalizados, con y sin umbral, en tres zonas de pesca de la costa catalana. La configuración del ambiente en que ocurren las agregaciones de puesta afecta a los estadios tempranos y, por consiguiente, a la estructura demográfica futura de las poblaciones. Por lo tanto es de gran importancia definir las condiciones ambientales y sus variaciones durante la época de puesta. Los resultados del análisis muestran que bajas salinidades en los sectores norte y central, y las velocidades zonal y meridional de la corriente, en los sectores central y sur respectivamente, implicadas en los procesos de retención hacen aumentar la LPUE durante el periodo de puesta. La temperatura se relacionó con la LPUE en los sectores sur y norte...

Current and Future Influence of Environmental Factors on Small Pelagic Fish Distributions in the Northwestern Mediterranean Sea

“…In GSA06, mixed effects were found among temporal patterns of sardine indexes and temperature, while in GSA07 the relationship was mainly negative. These results are in accordance with literature in which the effect of temperature on sardine indexes was found mainly negative throughout the Mediterranean basin (Bellido et al, 2008;Martín et al, 2008;Katara et al, 2011;Tugores et al, 2011;Martín et al, 2012;Giannoulaki et al, 2013;Brosset et al, 2015;Bonanno et al, 2016;Quattrocchi et al, 2016). Cooler temperature can be indicative of nutrient enrichment processes such as wind mixing, upwelling FIGURE 14 | Predicted probability of occurrence of the European anchovy (Engraulis encrasicolus) in Geographical Sub-Area 07 for the present situation and using IPCC pathway scenarios obtained with RAC-BRT models.…”

“…Regarding changes in sardine abundance and biomass, our results demonstrate a general decreasing temporal trend of biomass of sardine in both GSA06 and GSA07, which coincides with a significant decline in landings in both areas, likely reinforced by the depletion of the commercial stock (Quattrocchi et al, 2016;Coll and Bellido, 2018;Coll et al, 2019).The abundance and biomass of anchovy showed a general increase over time in both GSA06 and GSA07, which coincides with a significant increase of catches in GSA06. On the contrary, we observe a decline in landings in GSA07, which can be motivated by changes in the fishing strategy that shifted from pelagic to demersal target species (Van Beveren et al, 2016), and also due to the fact that most of the pelagic vessels targeting sardine stopped their activity at the end of 2009 due to the stock decline (Fisheries in the Gulf of Lions, UNEP-MAP-RAC/SPA, 2013).…”

“…In the same area, Bellido et al (2008) found a relatively weak but positive relationship between primary productivity indicators (i.e., Chl-a) and small pelagic species occurrence, suggesting that fish were not directly related to this environmental factor, but that areas with higher primary productivity were more favorable for both sardine and anchovy. However, other studies pointed out that sardine juveniles prefer areas with moderate primary productivity values (Giannoulaki et al, 2011;Tugores et al, 2011) and negative relationships were also found between anchovy adults and primary productivity in other Mediterranean areas (Giannoulaki et al, 2008(Giannoulaki et al, , 2013Martín et al, 2008;Quattrocchi et al, 2016). Recent studies point out that primary productivity concentration is negatively correlated with anchovy individuals of age −1 (Bacha et al, 2010;Basilone et al, 2017).…”

Changes in Life History Traits of Small Pelagic Fish in the Western Mediterranean Sea

“…Four different variables were used: Sea Temperature (ST150 in • C) averaged over the first 150 m, mean Meridional (MC in m/s, current from south to north, positive northward) and Zonal Component of the water current field (ZC in m/s, current from west to east, positive eastward) and Net Primary Productivity (NPP in mol/m 3 /s) (Supplementary Figure 1). These variables were selected as they have been previously seen to influence sardine and anchovy biological processes (Giannoulaki et al, 2013;Quattrocchi et al, 2016;Pennino et al, 2020;Fernandez-Corredor et al, 2021). These variables are related to food availability and changes in temperature; the two main hypothesized drivers in previous studies to explain changes in Kn and GSI (Brosset et al, 2017;Véron et al, 2020a).…”

Effects of Nutrient Management Scenarios on Marine Food Webs: A Pan-European Assessment in Support of the Marine Strategy Framework Directive

“…Yet, spatial differences were detected between the two models which could be related to the model structure and/or to the drivers used to spatially distribute the marine species and condition growth and consumption (such as changes in sea temperature). Ecosystem productivity, together with other environmental drivers such as temperature and salinity, are important factors affecting the distribution of small pelagic fishes (Bonanno et al, 2014;Quattrocchi et al, 2016;Quattrocchi and Maynou, 2017) so, including or excluding these factors may produce different outputs. The Osmose model, on the other hand, showed a different picture from the two EwE models, highlighting no clear spatial patterns among the criterion and TL indicators assessed.…”