Decapod crustacean assemblages on trawlable grounds in the northern Alboran Sea and Gulf of Vera

Scientia Marina 86(3) September 2022, e039, Barcelona (Spain) ISSN-L: 0214-8358 https://doi.org/10.3989/scimar.05265.039 Decapod crustacean assemblages on trawlable grounds in the northern Alboran Sea and Gulf of Vera Cristina Ciércoles 1, 2, Cristina García-Ruíz 2, Pere Abelló 3, Manuel Hidalgo 4, Pedro Torres 2, María González 2, Ángel Mateo-Ramírez 2, José Luis Rueda 2 1 Universidad de Málaga (UMA), Campus de Teatinos s/n, 29071 Málaga, Spain. (CC) (Corresponding author) E-mail: [email protected]. ORCID iD: https://orcid.org/0000-0002-6196-8133 2 Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, (CN IEO-CSIC). (CG-R) E-mail: [email protected]. ORCID iD: https://orcid.org/0000-0003-2767-4200 (PT) E-mail: [email protected]. ORCID iD: https://orcid.org/0000-0002-7076-6023 (MG) E-mail: [email protected]. ORCID iD: https://orcid.org/0000-0003-4248-1765 (AM-R) E-mail: [email protected]. ORCID iD: https://orcid.org/0000-0002-3825-3279 (JLR) E-mail: [email protected]. ORCID iD: https://orcid.org/0000-0003-4632-1523 3Institut de Ciències del Mar-CSIC, Barcelona, Spain. (PA) E.mail: [email protected]. ORCID iD: https://orcid.org/0000-0001-6034-2465 4Centro Oceanográfico de Baleares, Instituto Español de Oceanografía (CN IEO-CSIC), Palma, Spain. (MH) E-mail: [email protected]. ORCID iD: https://orcid.org/0000-0002-3494-9658 Summary: This study analyses the samples collected annually (2012 to 2018) on circalittoral and bathyal soft bottoms (30 to 800 m) by the MEDITS surveys in the northern Alboran Sea (including Alboran Island) and the Gulf of Vera to determine the composition, structure and distribution of decapod crustacean assemblages. A total of 94 decapod crustacean species were identified. Non-metric multidimensional scaling showed depth to be the main factor for distinguishing four main decapod assemblages: the inner shelf (30-100 m depth), outer shelf (101-200 m), upper slope (201-500 m) and middle slope (501-800 m). PERMANOVA analyses revealed further significant depth-related differences between three established geographical sectors of the study area (northern Alboran Sea, Gulf of Vera and Alboran Island). Generalized additive model analyses were used to assess the bathymetrical, geographical and environmental effects on the ecological indices of each assemblage. Results showed that depth and the geographical effect were the main drivers in all cases. Decreases in abundance and increases in species richness, Shannon-Wiener diversity and Pielou’s evenness indices with depth were detected. This study shows the primacy of depth and geographical effect on the distribution of decapod species in the study area, in alignment with findings from other parts of the Mediterranean Sea. Keywords: Alboran Sea; crustaceans; decapods; assemblages; GAM; circalittoral; bathyal; biodiversity. Asociaciones de crustáceos decápodos en fondos arrastrables del norte del mar de Alborán y golfo de Vera Resumen: En este estudio se analizan muestras obtenidas anualmente (2012 al 2018) en fondos blandos circalitorales y batiales (30 a 800 m) del norte del mar de Alborán (incluida la Isla de Alborán) y golfo de Vera durante siete campañas de arrastre de fondo, MEDITS, con el fin de determinar la composición, estructura y distribución de las asociaciones de crustáceos decápodos. En total se identificaron 94 especies de decápodos. El escalamiento multidimensional no métrico indicó la profundidad como factor principal en la diferenciación de cuatro asociaciones de decápodos: plataforma interna (30-100 m de profundidad), plataforma externa (101-200 m), talud superior (201-500 m) y talud medio (501-800 m). Los análisis PERMANOVA revelaron diferencias significativas relacionadas con la profundidad entre los tres sectores geográficos establecidos en el área de estudio (norte del mar de Alborán, golfo de Vera e Isla de Alborán). Los modelos aditivos generalizados se utilizaron para evaluar los efectos batimétricos, geográficos y ambientales sobre los índices ecológicos de cada una de las asociaciones encontradas. Los resultados mostraron la profundidad y el efecto geográfico como los principales factores en todos los casos. Se detectó una disminución de la abundancia con la profundidad mientras que la riqueza de especies, el índice de diversidad de Shannon-Wiener y el índice de equidad de Pielou aumentaron. Este estudio muestra la importancia de la profundidad y el efecto geográfico en la distribución de las especies en el área de estudio en consonancia con lo descrito en otras áreas del mar Mediterráneo. Palabras clave: mar de Alborán; crustáceos; decápodos; asociaciones; GAM; circalitoral, batial, biodiversidad. Citation/Como citar este artículo: Ciércoles C., García-Ruíz C., Abelló P., Hidalgo M., Torres P., González M., Mateo-Ramírez A., Rueda J.L. 2022. Decapod crustacean assemblages on trawlable grounds in the northern Alboran Sea and Gulf of Vera. Sci. Mar. 86(3): e039. https://doi.org/10.3989/scimar.05265.039 Editor: J. Templado. Received: January 12, 2022. Accepted: June 9, 2022. Published: August 23, 2022. Copyright: © 2022 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License. 2 • C. Ciércoles et al. SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 INTRODUCTION The Alboran Sea, located in the westernmost part of the Mediterranean Sea, is a transitional area between the Atlantic Ocean and the Mediterranean Sea that has been reported as a self-standing ecoregion harbouring a large marine biodiversity and a wide variety of habitats (Spalding et al. 2007, Rueda et al. 2021, Templado et al. 2021). Because of its distinctive geomorphological and oceanographical features, the Alboran Sea has been identified as a specific biogeographical sector for several marine groups (Real et al. 2021), including demersal fish (Gaertner et al. 2005, González et al. 2021), molluscs (Gofas et al. 2011, Ciércoles et al. 2018) and crustaceans (Abelló et al. 2002). Crustaceans are one of the most morphologically diverse taxonomic groups of the aquatic ecosystems, where they are one of the top dominant groups (Martin and Davis 2001). Within the crustaceans, the order Decapoda constitutes a dominant component of Mediterranean benthic and demersal communities of both the continental shelf and slope (Maynou and Cartes 2000, Guijarro 2012). Their relative importance in the Mediterranean Sea has been hypothesized because of their very high competitive trophic strategy (Cartes and Sardà 1992, Maynou and Cartes 2000). Moreover, decapods are a key taxon linking lower and higher trophic levels (Cartes 1998, Fanelli 2007). Several decapod species are of commercial interest and form an important component of the catches of the bottom trawl fishery in the Alboran Sea and the Gulf of Vera. In fact, some decapod species, such as the deep-water rose shrimp, Parapenaeus longirostris, the Norway lobster, Nephrops norvegicus, and the red shrimp Aristeus antennatus are economically valuable target species in demersal fisheries, so their populations are regularly assessed in the Alboran Sea (González et al. 2021), as well as in other parts of the Mediterranean Sea (Guijarro 2012; Regulation (EU) 2019/1022). Knowledge of the distribution and abundance of species along environmental gradients has traditionally been important to characterize and understand the role of biological communities in aquatic systems (Wenner and Boesch 1979). Studies of biological communities are also essential tools for understanding the dynamics of exploited species from an ecosystem point of view, which is a key element in considering separate management units (Abelló et al. 2002). Additionally, species-specific studies on decapod species have revealed geographical variability patterns throughout the Mediterranean Sea, reflecting the importance of studies at a small-scale geographical level. This approach has been shown to be more efficient for the management of certain species in contrast to large regional approaches (Gaertner et al. 2005, Guijarro et al. 2019) and it is particularly important for scientifically sustaining spatial management. The Alboran Sea, together with the Gulf of Vera, can be considered a transition zone between the Mediterranean and Atlantic biota of crustaceans, since it also constitutes a semipermeable barrier for genetic population exchanges between the Mediterranean Sea and the Atlantic Ocean (Abelló et al. 2002, Mateo-Ramírez et al. 2015, Pascual et al. 2016). Several studies on decapod assemblages have been carried out in different habitats of the Alboran Sea, particularly those of the infralittoral zone (soft bottoms, García Muñoz et al. 2008; seagrass meadows, García-Raso 1990, García Raso et al. 2006, Mateo-Ramírez et al. 2016; macroalgal communities, Mateo-Ramírez et al. 2018). However, despite their ecological and economical interest, few studies of decapod assemblages in circalittoral and bathyal soft bottoms have been carried out in the Alboran Sea using beam-trawl samples (Mateo-Ramírez et al. 2015) or including the Alboran Sea as part of studies with a wider scope covering the Spanish Mediterranean waters (Abelló et al. 2002). The aims of this study were to (1) update faunistic inventories of decapod crustacean species in the Alboran Sea and the adjacent Gulf of Vera; (2) identify and characterize the main decapod assemblages; (3) analyse significant differences between assemblages in the ecological indices considered as community descriptors (decapod abundance, species richness, Pielou’s evenness and the Shannon-Wiener diversity index) in order to study the spatial and temporal changes of the composition and structure of the decapod assemblages; and (4) model spatio-temporal trends of ecological indices in terms of potential environmental driving. MATERIALS AND METHODS Study area The study area covers approximate 12753 km2 and encompasses the northern Alboran Sea and Gulf of Vera, from Punta Europa (Strait of Gibraltar) to Cabo de Palos (Cartagena), including also the Alboran Island (Fig. 1). The main hydrological characteristics of this area are the mixture of Atlantic and Mediterranean water masses with (1) Atlantic surficial water masses entering the Mediterranean Sea and extending from the surface to 200 m depth; (2) Intermediate Levantine water masses from the Mediterranean Sea, flowing towards the Atlantic Ocean and usually extending from 200 to 600 m depth; and (3) deep water masses extending below the Levantine water masses to the sea bottom (Parrilla et al. 1986, Vargas-Yáñez et al. 2017). The different physico-chemical characteristics of these water masses, together with the density contrast and the geomorphology of the Alboran basin, are responsible for the complex hydrodynamic processes that take place in the area, along with the presence of the Alboran Gyre and nutrient-rich coastal upwellings (Tintoré et al. 1991, Vargas-Yáñez et al. 2010, 2021). The seafloor of the study area has a high geomorphological complexity with a wide variety of reliefs, such as depressions, banks, ridges and canyons (Parrilla and Kinder 1987, Ercilla et al. 1992, 2021). The northern Alboran Sea and the Gulf of Vera are both characterized by a very narrow continental shelf with alternating predominance of sands and muds, while the continental slope is mainly composed of very fine sediments (Rey and SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Decapods in northern Alborán Sea and Gulf of Vera • 3 Medialdea 1989, Ercilla et al. 2021). In addition, the Alboran Sea, together with the Gulf of Lion and the mouth of different rivers (e.g. the Ebro River on the northeastern Spanish Mediterranean coast), is one of the areas with the highest primary production in the western Mediterranean (Vargas-Yáñez et al. 2010). This is due to several processes (e.g. nutrient flows from rivers and nutrient-rich coastal upwelling) that favour the injection of nutrients into the photophilous zone of the water column (Báez et al. 2021). The Gulf of Vera is also a strategic location in the western Mediterranean since it is adjacent to the Almería-Oran front, which forms a semi-permanent hydrographic barrier and a transition zone between the Alboran Sea (an area with greater Atlantic water influence) and the rest of the western Mediterranean basin (Tintoré et al. 1988, Millot 1999). The meridional sector of the Alboran Sea is characterized by the presence of an old volcanic ridge oriented SW-NE, on which Alboran Island is located (Vázquez 2005). This island is affected by the circulation of the water masses present in the Alboran basin and has been described as an anticyclonic area located between two geostrophic gyres of the incoming Atlantic surface water. These peculiar hydrological characteristics result in the singularity and extraordinary biodiversity of the benthic communities of the Alboran Island (Gofas et al. 2014), as well as of the Alboran Sea (Rueda et al. 2021). This high diversity promoted the protection of the Alboran Island and its surrounding bottoms through protection measures such as a Marine and Fishing Reserve, a Site of Community Importance and a Specially Protected Area of Mediterranean Importance (Mateo-Ramírez et al. 2021). Sampling The data for this study were obtained from 413 hauls performed on circalittoral and bathyal soft bottoms (30-800 m depth) of the northern Alboran Sea and the Gulf of Vera during seven MEDITS surveys (International Trawl Surveys in the Mediterranean Sea) between 2012 and 2018 (Bertrand et al. 2002, Spedicato et al. 2019), which are carried out annually in spring (Fig. 1). A stratified random sampling design was applied in the surveys, with the following bathymetric strata: 30-50, 51-100, 101-200, 201-500 and 501-800 m depth. No samples could be obtained at depths shallower than 100 m at Alboran Island as the depths shallower than 100 m around the island are a Marine and Fishing Reserve where trawling is not allowed (see study area section). Haul duration was a function of depth, with 30-minute duration for stations located at less than 200 m (continental shelf) and a 60-minute duration for those located at more than 200 m depth (continental slope) (Bertrand et al. 2002, Spedicato et al. 2019). According to the MEDITS protocol, the number of sampling stations (hauls) in each stratum is proportional to the area of these strata (MEDITS-Handbook 2017). Except for unusual problems (damage noted in previous years, etc.), the hauls are made at the same sampling stations from year to year. In the present study the number of hauls in each of the three established geoFig. 1. – Map of the study area showing the sampling stations (black points) used during MEDITS surveys (2012 to 2018) and the sectors considered. 4 • C. Ciércoles et al. SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 graphical sectors were 309 for the northern Alboran Sea sector, 51 for the Alboran Island sector and 53 for the Gulf of Vera sector. The geographical position of each haul was recorded using the global positioning system of the research vessel. Haul performance and gear geometry were monitored using SCANMAR and, more recently, MARPORT sensors. The sampling device was a bottom trawl gear (GOC-73) with a cod-end mesh size of 20 mm, an average horizontal opening of 21.5 m and an average vertical opening of 2.5 m (Fiorentini et al. 1999). Temperature and salinity were recorded close to the bottom using a CTD SBE-37 coupled to the net. Every specimen caught was identified to the lowest possible taxonomic level. Finally, specimens of each species were counted and weighed on board. Scientific names for species followed the nomenclature of the World Register of Marine Species (WoRMS 17/02/2021). Data analysis The swept area from each haul was estimated by monitoring the horizontal opening of the gear and the distance covered during the haul. These values were used to standardize catches in the trawled area, in order to obtain an estimation of abundance as the number of individuals per square km (ind. km–2). The frequency index (%F, percentage of hauls in which the species was present in relation to the total hauls carried out) and the dominance index based on abundance (%DN, percentage of individuals caught of a species over the total number of caught species in the total hauls of the study) were estimated for each species. In order to analyse the potential differences in assemblages over the study area, three geographical sectors were assessed according to their different oceanographic characteristics (Sarhan et al. 2000, Vargas-Yáñez et al. 2010): (1) northern Alboran Sea (from Gibraltar to Cabo de Gata), characterized by a high Atlantic influence and the presence of permanent nutrient-rich coastal upwellings; (2) Gulf of Vera (from Cabo de Gata to Cabo de Palos), with a higher influence of the typical western Mediterranean conditions; and (3) Alboran Island, an insular area located at the top of the Alboran Ridge, which is far away from the continental margin and influenced to a certain extent by the eastern anticyclonic gyre of the Alboran Sea. The decapod crustacean assemblages were identified using non-parametric multivariate classification (cluster) and ordination (non-metric multidimensional scaling, nMDS) techniques (Clarke 1993, Clarke and Warwick 2001). The resemblance matrix was calculated using the Bray-Curtis similarity index, with a previous square root data transformation in order to reduce the differences in the abundance of highly dominant species (Clarke and Warwick 2001). One-way SIMPER analysis was applied to determine the contribution of each species to the dissimilarity between the groupings of samples obtained in the cluster and nMDS analyses, which are defined as different assemblages (Clarke and Warwick 2001). A distance-based permutational multivariate analysis of variance (PERMANOVA) (McArdle and Anderson 2001) based on the Bray-Curtis similarity matrix was used to test significant differences between the obtained assemblages (except for shallowest depths), with sector (fixed factor, three levels) and depth (fixed factor, three levels) as a source of variation. The PERMANOVA routine performs a partitioning of the total sum of squares according to the full experimental design, calculating an appropriated distance-based pseudo-F statistic for each term in the model, based on the expectations of mean squares. P-values are obtained using a permutation procedure (a permutation of residuals under a reduced model in our analysis) (Anderson et al. 2008). All these multivariate analyses were performed using PRIMER v6.0 & PERMANOVA+ software. The abundance (N, ind. km–2), species richness (S), Shannon-Wiener diversity index (H’) and Pielou’s evenness index (J’) were calculated for the crustacean decapods of each haul using PRIMER 6.0 software, and mean values were calculated for the main assemblages obtained after the multivariate analyses. The differences between assemblages were tested using the non-parametric Kruskal-Wallis test (Kruskal and Wallis 1952) because the data did not fit the conditions for parametric analyses (e.g. ANOVA). These analyses were carried out using SPSS v15.0 software. Generalized additive modelling (GAM, Hastie and Tibshirani 1990) was used to test the relationships of abundance, species richness, Shannon-Wiener diversity index and Pielou’s evenness index with depth, geographic location and environmental variables: chlorophyll a (Chl a) concentration (Chl-a; mg m–3), nitrate (NO3), phosphate (PO4), sea bottom temperature (SBT; ºC), sea bottom salinity (SBS; psu) and the annual NAO index. Year was considered as a factor in these analyses. Data of Chl a, NO3 and PO4 were obtained from satellite-data with a monthly time resolution developed within the Copernicus Programme (http:// marine.copernicus.eu). Temperature and salinity were obtained from the CTD SBE 37 placed on the net. The North Atlantic Oscillation climate annual index (NAO) was obtained from https://climatedataguide.ucar.edu/ climate-data/hurrell-north-atlantic-oscillation-nao-index-station-based. A Pearson correlation test was previously performed and environmental variables that had a high correlation (more than 0.9) were eliminated. A two-dimensional smoother was used by combining latitude and longitude to account for the geographical effect, representing the remaining spatially structured variance once the effect of the rest of covariates was removed. A one-dimensional smoother was used to investigate the geographical and environmental effects. The logarithmically transformed values (log[x+1]) of abundance were used to ensure a Gaussian distribution of the residuals. We adopted a backwards stepwise produced from an initial GAM model including all the variables, removing one non-significant covariate at time. The selection of the best model for each variable was based on the minimization of the Akaike information criterion in models with all covariates statistically significant (i.e. p<0.05). For all GAM analyses, residual SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Decapods in northern Alborán Sea and Gulf of Vera • 5 plots were checked and the assumptions of variance homogeneity and normal distribution were confirmed. The mgcv package in R (http://www.r-project. org) was used in the GAM analyses (Wood 2017). RESULTS Composition and structure of decapod crustaceans A total of 94 decapod species were collected. The families showing the largest number of species were the Pandalida (epibenthic caridean shrimps), with nine spp., followed by the Inachidae (Brachyuran crabs) and the Paguridae (Anomuran hermit crabs) (with eight spp. each of them), and the Crangonidae (benthic caridean shrimps) (5 spp.) (Table 1). The most abundant species were Plesionika heterocarpus (13094.81±10812 ind. km–2, mean per haul±- standard error) (%DN: 70) followed by Pasiphea sivado (635.92±403.65 ind. km–2) (%DN: 6) and Dardanus arrosor (547.59±153.90 ind. km–2) (%DN: 2.49). Other dominant decapods were P. martia (%DN: 4.02), Pagurus prideaux (%DN: 1.91), Liocarcinus depurator (%DN: 1.58) and P. longirostris (%DN: 1.97). The most frequently captured species were D. arrosor (%F: 79), which also displayed the widest depth range (40-839 m), followed by Macropodia longipes (%F: 57), L. depurator (%F: 43), P. martia (%F: 42), and Solenocera membranacea (%F: 42). A total of 27 species (29% of the total decapods) were only recorded in one or two hauls, such as Polybius henslowii, Alpheus platydactylus, Ebalia nux and Calocarides coronatus (Table 1). Table 1. – Decapod crustacean species caught with bottom trawl during MEDITS surveys (2012-2018) in circalittoral and bathyal soft bottoms of the northern Alboran Sea, Alboran Island and the Gulf of Vera. Depth range for collected specimens (metres); Nt , total abundance (individuals); %DN, dominance index of abundance expressed as a percentage; %F, frequency of occurrence expressed as a %. Systematic and taxonomical classification according to WoRMS. Depth range Nt%DN %F Family Acanthephyridae Acanthephyra pelagica (Risso, 1816) 449-794 27 <0.01 3.39 Family Alpheidae Alpheus dentipes Guérin, 1832 93 30 <0.01 0.24 Alpheus glaber (Olivi, 1792) 40-668 795 0.18 30.51 Alpheus platydactylus Coutière, 1897 641 1 <0.01 0.24 Synalpheus gambarelloides (Nardo, 1847) 154 4 <0.01 0.24 Family Aristeidae Aristaeomorpha foliacea (Risso, 1827) 554 1 <0.01 0.24 Aristeus antennatus (Risso, 1816) 393-879 2993 0.67 13.32 Family Atelecyclidae Atelecyclus rotundatus (Olivi, 1792) 43-362 20 <0.01 3.63 Family Axiidae Calocarides coronatus (Trybom, 1904) 667 1 <0.01 0.24 Calocaris macandreae Bell, 1846 363-869 198 0.04 12.11 Family Benthesicymidae Gennadas elegans (Smith, 1882) 431-794 11 <0.01 1.94 Family Calappidae Calappa granulata (Linnaeus, 1758) 43-529 25 <0.01 1.94 Family Crangonidae Aegaeon cataphractus (Olivi, 1792) 43-86 44 0.01 5.33 Aegaeon lacazei (Gourret, 1887) 119-762 98 0.02 13.32 Philocheras echinulatus (M. Sars, 1862) 135-554 123 0.02 9.69 Philocheras sculptus (Bell, 1847) 135 2 <0.01 0.24 Pontophilus spinosus (Leach, 1816) 78-538 494 0.11 17.43 Family Diogenidae Dardanus arrosor (Herbst, 1796) 40-839 10975 2.49 79.42 Paguristes eremita (Linnaeus, 1767) 74 1 <0.01 0.24 Family Dorippidae Medorippe lanata (Linnaeus, 1767) 49-573 31 <0.01 5.08 Family Dromiidae Dromia personata (Linnaeus, 1758) 54 1 <0.01 0.24 Family Epialtidae 6 • C. Ciércoles et al. SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Depth range Nt%DN %F Lissa chiragra (Fabricius, 1775) 56 1 <0.01 0.24 Pisa armata (Latreille, 1803) 46-86 104 0.02 2.42 Scyramathia carpenteri (C. W. Thomson, 1873) 329-879 232 0.05 16.71 Family Ethusidae Ethusa mascarone (Herbst, 1785) 46 1 <0.01 0.24 Family Galatheidae Galathea dispersa Bate, 1859 59-249 34 <0.01 3.63 Galathea intermedia Lilljeborg, 1851 40-327 17 <0.01 3.39 Galathea strigosa (Linnaeus, 1761) 61 3 <0.01 0.24 Family Geryonidae Geryon longipes A. Milne-Edwards, 1882 440-869 259 0.05 14.77 Family Goneplacidae Goneplax rhomboides (Linnaeus, 1758) 40-766 600 0.13 30.51 Family Homolidae Homola barbata (Fabricius, 1793) 74-288 7 <0.01 1.21 Paromola cuvieri (Risso, 1816) 654 1 <0.01 0.24 Family Inachidae Dorhynchus thomsoni C. W. Thomson, 1873 329-808 32 <0.01 4.60 Inachus aguiarii Brito Capello, 1876 116 1 <0.01 0.24 Inachus communissimus Rizza, 1839 43-132 25 <0.01 3.87 Inachus dorsettensis (Pennant, 1777) 42-540 238 0.05 12.59 Inachus thoracicus P. Roux, 1830 [in P. Roux, 1828-1830] 46-118 27 <0.01 1.21 Macropodia linaresi Forest & Zariquiey lvarez, 1964 42-95 73 0.01 2.91 Macropodia tenuirostris (A. Milne-Edwards & Bouvier, 1899) 40-774 2335 0.53 57.38 Macropodia rostrata (Linnaeus, 1761) 43-123 102 0.02 3.63 Family Leucosiidae Ebalia nux A. Milne-Edwards, 1883 554 1 <0.01 0.24 Family Lysmatidae Ligur ensiferus (Risso, 1816) 357-668 3 <0.01 0.73 Family Majidae Eurynome aspera (Pennant, 1777) 45-117 5 <0.01 1.21 Family Munididae Munida intermedia A. Milne-Edwards & Bouvier, 1899 121-664 52 0.01 5.08 Munida rugosa (Fabricius, 1775) 122 1 <0.01 0.24 Munida speciosa von Martens, 1878 85-554 457 0.10 11.14 Munida perarmata Sars, 1872 374-779 5 <0.01 0.97 Family Nephropidae Nephrops norvegicus (Linnaeus, 1758) 143-852 1301 0.29 30.51 Family Oregoniidae Ergasticus clouei A. Milne-Edwards, 1882 362-774 42 0.01 4.36 Family Paguridae Anapagurus bicorniger A. Milne-Edwards & Bouvier, 1892 249 1 <0.01 0.24 Anapagurus laevis (Bell, 1845) 49-424 9 <0.01 1.69 Pagurus alatus Fabricius, 1775 329-879 2252 0.51 32.20 Pagurus anachoretus Risso, 1827 54 1 <0.01 0.24 Pagurus cuanensis Bell, 1845 44-118 8 <0.01 1.45 Pagurus excavatus (Herbst, 1791) 40-529 119 0.02 16.71 Pagurus mbizi (Forest, 1955) 50-361 42 0.01 5.81 Pagurus prideaux Leach, 1815 40-831 8459 1.91 32.69 Family Palaemonidae Ascidonia flavomaculata (Heller, 1864) 62 1 <0.01 0.24 Periclimenes granulatus Holthuis, 1950 301 1 <0.01 0.24 SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Decapods in northern Alborán Sea and Gulf of Vera • 7 Depth range Nt%DN %F Family Palinuridae Palinurus elephas (Fabricius, 1787) 114-118 3 <0.01 0.73 Palinurus mauritanicus Gruvel, 1911 251-664 21 <0.01 3.63 Family Pandalidae Chlorotocus crassicornis (A. Costa, 1871) 74-441 356 0.08 8.96 Pandalina profunda Holthuis, 1946 256-296 3 <0.01 0.48 Plesionika acanthonotus (Smith, 1882) 424-879 3903 0.88 29.30 Plesionika antigai Zariquiey lvarez, 1955 79-534 1590 0.36 8.72 Plesionika edwardsii (J.F. Brandt in von Middendorf, 1851) 256-585 9756 2.21 12.83 Plesionika gigliolii (Senna, 1902) 117-650 3269 0.74 23.00 Plesionika heterocarpus (A. Costa, 1871) 56-764 309314 70.1 40.44 Plesionika martia (A. Milne-Edwards, 1883) 161-879 17740 4.02 42.37 Plesionika narval (Fabricius, 1787) 247-362 3955 0.89 0.73 Family Parthenopidae Spinolambrus macrochelos (Herbst, 1790) 251-424 3 <0.01 0.73 Parthenopoides massena (P. Roux, 1830 ) 65-331 2 <0.01 0.48 Family Pasiphaeidae Pasiphaea multidentata Esmark, 1866 336-879 1044 0.23 28.33 Pasiphaea sivado (Risso, 1816) 58-779 26473 6.00 24.46 Family Penaeidae Parapenaeus longirostris (Lucas, 1846) 61-688 8716 1.97 34.38 Penaeopsis serrata Spence Bate, 1881 586 1 <0.01 0.24 Family Pilumnidae Pilumnus hirtellus (Linnaeus, 1761) 43 1 <0.01 0.24 Pilumnus spinifer H. Milne-Edwards, 1834 43-394 104 0.02 8.72 Family Pinnotheridae Pinnotheres pisum (Linnaeus, 1767) 46-47 9 <0.01 0.48 Pinnotheres bicristatus Garcia Raso & Cuesta, 2019 63 1 <0.01 0.24 Family Polybiidae Bathynectes maravigna (Prestandrea, 1839) 329-840 200 0.04 14.29 Liocarcinus depurator (Linnaeus, 1758) 40-773 6974 1.58 42.86 Macropipus tuberculatus (P. Roux, 1830) 65-766 782 0.17 20.34 Polybius henslowii Leach, 1820 116 1 <0.01 0.24 Family Polychelidae Polycheles typhlops Heller, 1862 288-879 1198 0.27 30.27 Family Porcellanidae Pisidia longicornis (Linnaeus, 1767) 44-120 31 <0.01 3.39 Family Processidae Processa canaliculata Leach, 1815 74-688 400 0.09 19.61 Processa nouveli Al-Adhub & Williamson, 1975 43-527 171 0.03 8.72 Family Sergestidae Deosergestes arachnipodus (Cocco, 1832) 541-831 1044 0.23 8.72 Eusergestes arcticus (Krøyer, 1855) 291-644 3791 0.86 5.08 Robustosergia robusta (Smith, 1882) 95-879 2276 0.51 32.20 Family Solenoceridae Solenocera membranacea (Risso, 1816) 61-679 4605 1.04 42.37 Family Stenopodidae Richardina fredericii Lo Bianco, 1903 311-431 2 <0.01 0.48 Family Xanthidae Monodaeus couchii (Couch, 1851) 66-879 346 0.07 29.30 8 • C. Ciércoles et al. SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Table 2. – Abundance (ind. km–2) of each decapod species caught during MEDITS surveys (2012-2018) in each geographical sector (See Fig 1. for location of the geographical sectors). Species Northern Alboran Alboran Island Gulf of Vera Acanthephyra pelagica 68.77 85.45 99.93 Aegaeon cataphractus 898.01 0.00 66.92 Aegaeon lacazei 689.11 38.36 206.73 Alpheus dentipes 0.00 0.00 583.23 Alpheus glaber 12434.05 19.75 299.92 Alpheus platydactylus 10.44 0.00 0.00 Anapagurus bicorniger 8.53 0.00 0.00 Anapagurus laevis 172.21 0.00 0.00 Aristaeomorpha foliacea 8.51 0.00 0.00 Aristeus antennatus 5352.82 10198.05 13400.08 Ascidonia flavomaculata 25.51 0.00 0.00 Atelecyclus rotundatus 353.73 74.90 0.00 Bathynectes maravigna 557.31 1297.15 27.20 Calappa granulata 96.15 192.73 29.67 Calocarides coronatus 8.89 0.00 0.00 Calocaris macandreae 1910.65 79.56 0.00 Chlorotocus crassicornis 2786.01 98.91 834.97 Dardanus arrosor 194955.77 21378.80 9820.69 Deosergestes arachnipodus 9729.64 269.66 165.71 Dorhynchus thomsoni 233.26 82.45 0.00 Dromia personata 22.09 0.00 0.00 Ebalia nux 0.00 8.83 0.00 Ergasticus clouei 107.79 314.10 0.00 Ethusa mascarone 20.32 0.00 0.00 Eurynome aspera 96.83 22.67 0.00 Eusergestes arcticus 35430.99 0.00 1135.72 Galathea dispersa 696.09 0.00 0.00 Galathea intermedia 350.71 0.00 0.00 Galathea strigosa 75.04 0.00 0.00 Gennadas elegans 76.34 23.04 8.13 Geryon longipes 1257.82 983.33 263.06 Goneplax rhomboides 10731.09 0.00 859.18 Homola barbata 23.57 0.00 114.61 Inachus aguiarii 0.00 24.19 0.00 Inachus communissimus 575.34 0.00 0.00 Inachus dorsettensis 4983.92 74.91 182.96 Inachus thoracicus 573.32 38.46 0.00 Ligur ensiferus 29.57 0.00 0.00 Liocarcinus depurator 158769.15 566.18 594.13 Lissa chiragra 23.85 0.00 0.00 Macropipus tuberculatus 5736.43 3446.73 1948.39 Macropodia linaresi 1709.79 0.00 23.93 Macropodia tenuirostris 42188.56 298.78 766.04 Macropodia rostrata 2246.16 0.00 0.00 Medorippe lanata 223.37 52.87 108.70 Monodaeus couchii 3015.45 256.68 251.24 Munida intermedia 260.07 274.12 20.68 Munida rugosa 19.39 0.00 0.00 SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Decapods in northern Alborán Sea and Gulf of Vera • 9 Species Northern Alboran Alboran Island Gulf of Vera Munida speciosa 5289.25 8.87 1066.52 Munida perarmata 10.14 0.00 39.21 Nephrops norvegicus 7186.43 920.90 4001.20 Paguristes eremita 23.57 0.00 0.00 Pagurus alatus 14597.01 6349.94 607.52 Pagurus anachoretus 28.71 0.00 0.00 Pagurus cuanensis 142.57 0.00 47.42 Pagurus excavatus 1806.95 10.71 108.70 Pagurus mbizi 856.28 0.00 0.00 Pagurus prideaux 117912.81 35838.64 11569.99 Palinurus elephas 0.00 62.89 0.00 Palinurus mauritanicus 30.98 147.74 30.45 Pandalina profunda 9.34 0.00 18.97 Parapenaeus longirostris 72582.60 6830.78 13401.46 Paromola cuvieri 10.62 0.00 0.00 Spinolambrus macrochelos 10.41 11.34 9.86 Parthenopoides massena 20.95 10.28 0.00 Pasiphaea multidentata 3676.74 2128.73 4074.06 Pasiphaea sivado 235411.79 11.34 27214.36 Penaeopsis serrata 0.00 10.82 0.00 Periclimenes granulatus 10.38 0.00 0.00 Philocheras echinulatus 1247.97 32.14 25.77 Philocheras sculptus 47.49 0.00 0.00 Pilumnus hirtellus 21.80 0.00 0.00 Pilumnus spinifer 2012.36 0.00 350.42 Pinnotheres pisum 196.44 0.00 0.00 Pinnotheres bicristatus. 22.36 0.00 0.00 Pisa armata 2196.13 0.00 0.00 Pisidia longicornis 712.28 0.00 0.00 Plesionika acanthonotus 23724.90 9813.55 3268.71 Plesionika antigai 2420.22 9241.23 3740.36 Plesionika edwardsii 23044.95 5302.86 61761.50 Plesionika gigliolii 4569.02 46.49 26194.99 Plesionika heterocarpus 5221700.78 43885.18 142573.02 Plesionika martia 122055.52 27724.52 17985.68 Plesionika narval 0.00 10.71 45811.89 Polybius henslowii 0.00 24.19 0.00 Polycheles typhlops 10118.58 867.70 367.17 Pontophilus spinosus 5357.67 10.71 95.65 Processa canaliculata 5310.32 112.49 203.37 Processa nouveli 712.73 21.42 957.59 Richardina fredericii 19.12 0.00 0.00 Scyramathia carpenteri 1841.02 236.72 52.22 Robustosergia robusta 6561.02 13732.13 1930.25 Solenocera membranacea 44110.91 365.55 2139.31 Synalpheus gambarelloides 0.00 0.00 100.42 Number of species present 86 55 54 16 • C. 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Signif. codes: ***, p< 0; **, p<0.001; *, p< 0.01. Abundance (LOGPONN) (LOGPONN) ~ factor(Year) + s(Depth) + s(Longitude, Latitude) Parametric coefficients Estimate Std. Error (Intercept) 8.723 0.186 factor(Year)2013 -1.048 0.25 factor(Year)2014 -0.434 0.238 factor(Year)2015 -0.86 0.234 factor(Year)2016 -0.905 0.232 factor(Year)2017 -1.097 0.231 factor(Year)2018 -0.007 0.235 Smooth terms edf Ref.df F p-value s(Depth) 5.402 6.448 17.92 <2e-16*** s(Longitude,Latitude) 23.382 26.919 3.84 1.32e-09*** R-sq.(adj)=0.412 Deviance explained= 46.2% Species richness (S) (S) ~ factor(Year) + s(Depth) + s(Longitude, Latitude) Parametric coefficients Estimate Std. Error (Intercept) 13.716 0.489 factor(Year)2013 -4.076 0.657 factor(Year)2014 -2.369 0.626 factor(Year)2015 -4.759 0.614 factor(Year)2016 -4.369 0.609 factor(Year)2017 -4.333 0.608 factor(Year)2018 -1.549 0.617 Smooth terms edf Ref.df F p-value Vargas-Yáñez M., García-Martínez M.C., Moya F., et al. 2021. 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ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Decapods in northern Alborán Sea and Gulf of Vera • 19 s(Depth) 5.76 6.821 44.246 <2e-16*** s(Longitude,Latitude) 18.5 22.935 2.345 0.000637*** R-sq.(adj)=0.618 Deviance explained= 64.6% Shannon-Wiener diversity index (H) (H) ~ factor(Year) + s(Depth) + s(Longitude, Latitude) Parametric coefficients Estimate Std. Error (Intercept) 1.293 0.065 factor(Year)2013 -0.058 0.087 factor(Year)2014 -0.087 0.083 factor(Year)2015 -0.272 0.082 factor(Year)2016 -0.154 0.081 factor(Year)2017 -0.187 0.081 factor(Year)2018 0.097 0.082 Smooth terms edf Ref.df F p-value s(Depth) 8.012 8.697 18.261 <2e-16*** s(Longitude,Latitude) 19.929 24.272 1.875 0.00752** R-sq.(adj)=0.45 Deviance explained= 49.6% Pielou’s evenness index (J) (J) ~ factor(Year) + s(Depth) + s(Longitude, Latitude) Parametric coefficients Estimate Std. Error (Intercept) 0.498 0.03 factor(Year)2013 0.083 0.04 factor(Year)2014 0.015 0.038 factor(Year)2015 0.008 0.038 factor(Year)2016 0.035 0.037 factor(Year)2017 0.041 0.037 factor(Year)2018 0.002 0.038 Smooth terms edf Ref.df F p-value s (Depth) 6.478 7.536 11.284 1.08e-13*** s (longitude,latitude) 20.811 25.008 2.121 0.00155** R-sq.(adj)=0.285 Deviance explained= 34.4% 20 • C. Ciércoles et al. SCI. MAR. 86(3), September 2022, e039. ISSN-L 0214-8358 https://doi.org/10.3989/scimar.05265.039 Appendix 2 – Basic residual plots for checking each generalized additive model fitting process. The upper left normal (Q-Q) plots close to a straight line, suggesting reasonable distributional assumption. The upper right, Residuals vs linear predictor plots suggest that variance is approximately constant as the mean increases. The histogram of residuals at the lower left appears consistent with normality. The lower right plot of response against fitted values shows a positive linear relation with a good deal of scatter: nothing problematic. Resids., residuals; pred., predictor; Q-Q, QuantilesQuantiles. N, abundance (LOGPONN); S, species richness, H’, Shannon-Wiener diversity index; J’, Pielou’s evenness index.