The recruitment of the endangered limpet Patella ferruginea in the Chafarinas Islands (SW Mediterranean) was studied over a 17-year period (1999‒2015). A total of 8115 recruits <20 mm in maximum diameter were counted in 95 transect censuses sampled during the study period. The presence of recruits began at the end of winter or beginning of spring (March‒April), when they reached a maximum shell diameter (MD) of at least 4 mm, with a peak in abundance occurring in spring. Smaller recruits were found on the lower midlittoral on the fringe of the vermetid gastropod Dendropoma lebeche and the crustose coralline algae Neogoniolithon brassica-florida, which suggests that settlement occurs at this shore level. Recruits reach 12‒27 mm at the end of their first year of life. A regular recruitment was detected for all studied years, with an average of 11.71 recruits m−1 across the study period. However, recruitment exhibited high interannual variability and did not occur evenly along the coastline of the islands. Higher recruitment was observed in 2001, 2011 and 2012, with a maximum density of 69.07 recruits m−1 in one transect in 2012. The density of recruits decreased in summer. No significant correlation was found between the density of recruits and adults. Between 1999‒2010, 29.29% of recruits were ‘phoretic’ on the shell of adults (1.81 recruits per host on average). Recruits climbed on to adults sometime after settlement, thus we suggest that ‘phoresy’ could favour the survival of young limpets instead of being due to selective settlement on adults. To improve and standardize recruitment monitoring in future studies, we propose that recruits are considered as those specimens <20 mm in MD and that recruitment censuses are carried out in spring, with additional censuses after summer to detect juvenile mortality. Additionally, we propose that 1 mm interval size classes are used for growth studies based on size‒frequency analyses.

The Bay of Málaga is located in a high biodiversity and productivity area that harbours a wide variety of commercial species exploited by different fishing fleets. Benthic and demersal fauna from circalittoral soft bottoms have been studied using a benthic dredge (BD) (8 sampling stations) and an otter trawl (OT) (8 sampling stations on a seasonal basis). Some sediment and water column variables, as well as the trawling activity, have also been studied and used for analysing their linkage with the fauna. A total of 287 species have been found in these bottoms and fish, molluscs and crustaceans represented the most diverse and abundant faunistic groups. A new record of the decapod Hippolyte leptometrae for Spanish waters is also included in this study. Some multivariate analyses using BD samples indicated the presence of three assemblages, but these seem to represent different facies of a single benthic community due to the absence of acute sediment changes and significant differences in the fauna. OT samples only displayed differences related to seasons but not to sediment types or depth. These seasonal differences seem to be linked to biological and ecological features of both dominant and/or commercial species. Mud and organic matter contents (%OM) in sediment, as well as the temperature, were the main variables linked to the spatial distribution of the benthic community identified with BD, whereas medium and coarse sand as well as gravel contents were the main variables linked to the changes of the epibenthic and demersal assemblage resulting from OT samples. The information of this study is of importance for improving the knowledge on the biodiversity of circalittoral soft bottoms of the Mediterranean and Alboran Sea as well as for the potential creation of a Marine Fisheries Reserve in the Bay of Málaga.

Mechanized dredging impact on discards was assessed along the northern Alboran Sea (W Mediterranean Sea). Data from 101 dredging operations were analysed for contrasting spatial and seasonal variability of damage, with the use of a three-level damage scale. 4.5% of discarded individuals displayed intermediate damage, whereas 11.3% displayed severe damage. Echinoderms displayed the highest level of damage (~75% of total collected individuals) and Echinocardium cf. mediterraneum was the most susceptible discarded species (85% with severe damage), followed by bivalves (7.3%) and crustaceans (3.3%). The target Chamelea gallina showed a low proportion of damaged individuals, probably due to their thick protective shell, which promotes the survival of discarded undersized target individuals. Spatial differences in damage level on discards were linked to some gear characteristics, to the higher amount of gravels and to longer tow durations, whereas damage was generally higher in cold months and partly related to higher quantities of hard shelled molluscs, in both cases increasing the abrasion and damage to retained organisms. Data suggest that dredges with a lower number of narrower iron teeth and towed for a shorter time could decrease the damage rate in discards of this fishery. A spatial management plan based on the type of grounds would be useful in order to improve efficiency of these fisheries and minimize their impact to soft bottoms with different commercial catches and biological communities.

The composition and structure of sublittoral faunal assemblages inhabiting soft bottoms (15–72 m depth) within the Marine Protected Area ‘Acantilados y Fondos Marinos de Calahonda-Castell de Ferro’ in southern Spain (North Alboran Sea, Mediterranean) have been studied in relation to sediment and water column variables. Three assemblages were identified and corresponded to mixed bottom, unstable bottom and coastal detritic bottom assemblages, based on Pérès & Picard's (1964) benthic classification. A total of 14,318 individuals were collected and 218 species identified, molluscs being the best represented group (141 species). Species richness displayed significant differences with depth and transect, with the highest values observed in the medium to very fine sand and muddy bottoms with bioclasts located at the shallowest sampling stations. The presence of some rare and poorly known invertebrates that are scarce in other areas of the Mediterranean Sea is remarkable, such as the crustacean decapods Bythocaris cosmetops and Pagurus mbizi, Atlantic species with no records in the Mediterranean Sea, and the bathyal molluscs Poromya granulata and Alvania testae, collected at shallow depths. The spatial distribution of faunal assemblages was mainly related to depth and percentage of gravel and clay according to the canonical correspondence analysis. The geographic location of the area, the heterogeneity of soft bottoms and the presence of upwellings in the area may favour the high biodiversity found in the studied soft bottoms. This study increases the scarce knowledge of the circalittoral fauna of sedimentary habitats of the Alboran Sea, providing a baseline for the management of this interesting SCI and for the EU Marine Strategy Framework Directive.

An ovigerous Maja spider crab was captured during a fishery research cruise in the North Alboran Sea, western Mediterranean, near the city of Malaga. From morphological characters this individual was identified as Maja brachydactyla. Prior to the specimen being returned alive back to sea, it was measured, photographed, and a portion of a pleopod excised for genetic analysis. The latter confirmed the identification as correct. An additional seven specimens collected from Caleta de Velez in the vicinity of Malaga were morphologically examined, confirming the presence of M. brachydactyla in the Alboran Sea. This finding would represent the first evidence of the species occurring in the western Mediterranean Sea, with apparently well-established populations.

The population of the endangered limpet Patella ferruginea in the Peñón de Vélez de la Gomera, a small Spanish peninsula located on the North African coast (south-west Mediterranean) was evaluated by surveys carried out in June and October 2012. Overall, 567 specimens were recorded along the entire coastline (about 1320 m) of this enclave (169 individuals measured >30 mm in maximum diameter of the shell, likely adults, and 398 specimens were <30 mm, likely immature individuals). In this site an average 0.13 adults/m was registered, and the maximum density observed was 0.90 adults/m in some zones. This points out the importance of this enclave among the present known populations existing in Spanish territories of this highly endangered limpet, but particularly highlights the role of the adjacent North African coastal protected areas in the conservation of this species.

The composition and structure of a molluscan assemblage inhabiting an outcrop with a coralligenous community was studied in southern Spain. A total of 117 molluscan species were identified, with gastropods as the dominant group. Calyptraea chinensis was the dominant species and the family Conidae presented the highest number of species. The Shannon–Wiener diversity index and the Evenness showed non-significant changes between cold and warm months, displaying high values (~4 bits and ~0.8 bits respectively). Some of the dominant and/or frequent species are strictly associated with coralligenous-building organisms, such as Neosimnia spelta with gorgonians. Regarding trophic guilds, carnivores are the dominant group, followed by filter feeders due to the high abundance of C. chinensis. Regarding biogeographical distributions, most of these species (<95%) are widely distributed in European waters, the number of strictly Mediterranean species being very low. The Alboran Sea represents the distributional limit towards the Mediterranean for some species found in this bottom, such as the Atlantic Bela powisiana. Rocky–coralligenous bottoms are scarce in the western Alboran Sea but support a high species richness molluscan assemblage, displaying higher diversity values than the surrounding soft bottoms and increasing the biodiversity at local scale. This high biodiversity is partly explained by the coexistence of different taxa with contrasting biogeographical affinities promoted by the geographical location of the area. Due to this, conservation efforts should be required to protect this stretch of coastline where one of the most biodiverse invertebrate assemblages along the European coasts can be found.

The biology, growth and reproduction of the axillary seabream, Pagellus acarne, was studied based on data obtained from the catches of the Andalusia commercial fleet operating off the coasts of southern Spain from October 2003 to September 2004. The axillary seabream had a very wide depth distribution, appearing from the surface down to 500 m depth. The length–weight relationship was given by TW = 0.0048 TL3.3207 (R2 = 0.98) (TW = total weight; TL = total length) for all fish from the Gulf of Cadiz and TW = 0.0093 TL3.1132 (R2 = 0.94) for all fish from the Alboran Sea. The proportion of females to males increases as length increases in both populations and the species is characterized by protandric hermaphroditism. Spawning males were present almost throughout the year although higher percentages were observed in spring and early summer. In females, the spawning period occurred mainly in spring. In both areas, the mean size at first maturity for males was smaller than for females. The mean lengths at first maturity were 18.04 cm for males and 21.7 cm for females from the Gulf of Cadiz, and 17.7 cm and 20.1 cm for males and females from the Alboran Sea, respectively. The average total fecundity was estimated at 290,070 and 173,509 oocytes for Atlantic and Mediterranean individuals, respectively. The parameters of the von Bertalanffy growth model were estimated by age readings of the 247 sagitta collected. Two rings, one opaque and one hyaline, were laid down each year on the otoliths. The opaque zone was formed during spring and summer and the hyaline one during the remaining months of the year. The relationship between otolith radius and total length of the fish was described by the equation: TL = 27.7 OR – 1.8 (r = 0.96) (where OR = otolith radius). The parameters of the fitted Von Bertalanffy growth equation were L∞ = 31.65 cm, k = 0.21 yr−1 in the Gulf of Cadiz and L∞ = 32.14 cm, k = 0.17 yr−1 in the Alboran Sea.

We analysed variations in swordfish capture and total by-catches, under different oceanographic and technical conditions, in the artisanal longline fishery operating in the Alboran Sea during the summer period. The oceanographic variable Sea Surface Velocity absolute component (SSV; m s−1) was the variable with the greatest explanatory power, as it was present in all models.

The composition and structure of a molluscan assemblage was studied in a deep subtidal eelgrass bed located in southern Spain before and after the eelgrass decline experienced during 2005 and 2006 due to illegal trawling by fishermen. Sampling was undertaken in summer 2004 (with eelgrass) and summer 2007 (without eelgrass) in an extensive eelgrass bed located in Cañuelo Bay (12–14 m depth) and in the same area once the eelgrass bed disappeared. Eelgrass was completely absent in those samples of summer 2007 and an increase of the organic content and mud was registered in the sediment between 2004 and 2007. The density and the richness of molluscan species decreased significantly in summer 2007, especially for epifaunal gastropods associated with the leaf and sediment stratum. Some species disappeared completely in summer 2007 such as the dominant periphyton grazers Jujubinus striatus and Rissoa spp., the egg feeder Mitrella minor and the seagrass feeder Smaragdia viridis as well as the infaunal bivalve Solemya togata. Other species increased their densities such as the carnivores Cylichna crossei or C. cylindracea as well as the bivalve Nucula nitidosa. Some dominant infaunal species, such as Chamelea gallina, Spisula subtruncata or Tellina fabula did not significantly change their densities. The composition and structure of the assemblages in summer 2004 and summer 2007 was significantly different according to the Bray–Curtis similarity index using qualitative and quantitative data and considering the entire assemblage (epifaunal and infaunal species) or only the infaunal species. The registered changes in the molluscan assemblage may have produced cascade effects in higher trophic levels because molluscs generally represent an important food source for some decapods and fish. Urgent conservation measures are needed for protecting the remaining fragmented eelgrass beds of southern Spain from further illegal fisheries activities and other types of human impacts (e.g. sand extraction and coastal infrastructures), because they support the most diverse faunistic communities for eelgrass beds in Europe due to their bathymetry and geographical location.

In March 2000 a 384 mm SL adult male specimen of the unicorn leatherjacket Aluterus monoceros was captured off the Chafarinas Islands (south-western Mediterranean). This report increases the list of fish species recently found for the first time in the Mediterranean Sea.