MEDLEM database, a data collection on large Elasmobranchs in the Mediterranean and Black seas

The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains more than 3,000 records (with more than 4,000 individuals) of large elasmobranch species from 21 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The principal species included in the archive are the devil ray (1,868 individuals), the basking shark (935 individuals), the blue shark (622 individuals), and the great white shark (342 individuals). In the last decades, other species such as the thresher shark (187 individuals), the shortfin mako (180 individuals), and the spiny butterfly ray (138) were reported with increasing frequency. This was possibly due to increased public awareness on the conservation status of sharks, and the consequent development of new monitoring programs. MEDLEM does not have homogeneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the northern sectors and the absence of some species in our database does not imply their actual absence in these regions. However,the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected species, the overall area coverage, and which species are involved as bycatch by different fishing gears.S

Patrones temporales en la distribución y abundancia de larvas de peces en un área costera del norte de Grecia

Species composition, abundance and diversity of fish larvae were assessed in the Strymonikos and Ierissos Gulfs (northern Aegean Sea, Greece). Both gulfs are affected by the freshwater input of the Rivers Strymon and Rihios; water depth does not exceed 80 m. Samples were collected using a bongo net sampler (250 µm mesh size) over a grid of 35 stations in six cruises between June 1997 and May 1998. A total of 48 taxa of fish larvae (36 species, 5 genera and 7 families) were identified. The majority of identified fish larvae taxa consisted of demersal species that included larvae of Bothidae, Gobiidae, Callionymidae, Sparidae and Serranidae. The highest number of species occurred in the warm season (May, June, July, September) and this was attributed to the summer spawners that start their reproduction period during spring/early summer. The European anchovy (Engraulis encrasicolus) was the dominant species between July and September, and the European sardine (Sardina pilchardus) between November and March. Two distinct seasons (warm and cold) were identified by multivariate analysis, highlighting the importance of seasonality in shaping the community structure. The absence of well-defined larval fish associations revealed the importance of depth in the identification of different spatial patterns in an area.Se evaluaron la composición, abundancia y diversidad de las larvas de peces en los golfos de Strymonikos y Ierissos (norte del mar Egeo, Grecia). Ambos golfos están afectados por la llegada de agua dulce de los ríos Strymon y Rihios y, en ellos, la profundidad no supera los 80 m. Las muestras se recolectaron en seis campañas realizadas entre los meses de junio de 1997 y mayo de 1998, sobre una parrilla de 35 estaciones, utilizando una red Bongo (con malla de 250 µm). Entre las larvas de peces se identificó un total de 48 taxa (36 especies, 5 géneros y 7 familias). La mayoría de las larvas identificadas correspondieron a especies demersales de las familias Bothidae, Gobiidae, Callionymidae, Sparidae y Serranidae. El número más alto de especies apareció durante la estación cálida (mayo, junio, julio y septiembre) y esto se atribuyó a los ponedores de verano que inician su periodo de reproducción en primavera/principio de verano. La anchoa europea (Engraulis encrasicolus) fue la especie dominante de julio a septiembre, y la sardina europea (Sardina pilchardus) de noviembre a marzo. Mediante análisis multivariante se identificaron dos estaciones distintas (cálida y fría), destacando la importancia de la estacionalidad en la estructuración de la comunidad. La ausencia de asociaciones de larvas bien definidas reveló la importancia de la profundidad en la identificación de diferentes patrones espaciales en el área

Correction: Large-Scale Diversity of Slope Fishes: Pattern Inconsistency between Multiple Diversity Indices.

[This corrects the article DOI: 10.1371/journal.pone.0066753.]

Reproducibility of the multi-component aspect of species diversity across different areas and scales: towards the constitution of a shortlist of complementary indices for monitoring fish diversity?

Recent theoretical and field studies conducted in both terrestrial and marine ecosystems have suggested that diversity could be a more complex and multi-component concept than previously thought. However, it is still poorly understood to what extent the information provided by the various indices is complementary with regard to diversity, and to what extent this complementarity is reproducible in different situations or at different scales of observation. In the present work, we have analysed the reproducibility of the empirical relationships between 11 diversity indices related to four major aspects (components) of species diversity (species richness, rarity, evenness and species taxonomy) in order to determine whether there is a general pattern of redundancy or complementarity in diversity measures that holds across years, areas and spatial scales. We have applied this approach to groundfish diversity through the analysis of 2404 trawl hauls collected during the first large-scale annual surveys carried out using a single sampling design throughout the northern Mediterranean Sea (ranging from 36.3 to 45.7°N, and 5.3°W to 28°E). Whatever the years, areas and scales studied, we found a strong reproducibility in the number and the nature of the main complementary components of diversity. The whole set of diversity indices considered may be roughly split into 6 complementary groups of descriptors. This result highlights that, in contrast to what is still the usual practice, monitoring diversity should not be based on only one or two of the most widely used components, even at large scale. Finally, in a context where developing tools for monitoring diversity is considered as a high priority worldwide, the strong reproducibility of the relationships between diversity indices we observed offers a basis for discussion of the feasibility and relevance of proposing a general shortlist of indices for monitoring diversity at different management scales

Summer distribution of fish larvae in northern Aegean Sea

Larval fish and hydrographic data were collected in Kavala Gulf (northern Aegean Sea) across a fine scale grid of 17 stations in two surveys, carried out in the beginning of July 2002 and 2003. Despite the different taxonomic resolution and excluding the unidentified larvae, 22 taxa were caught in 2002 and 27 in 2003. Seventeen taxa were present in both years' collections. A total of 833 larvae were collected during the two samplings. The adults of several larvae caught, although sometimes at very low concentrations, are species with high commercial value or represent a major proportion of the captured production of the northern Aegean Sea. The larvae of European anchovy (Engraulis encrasicolus) were most abundant in both years followed by the brown comber (Serranus hepatus), the gobies (Gobius sp.) and, only for 2003, round sardinella (Sardinella aurita). Maximum anchovy larval densities reached 4145/10 m(2) and 13852/10 m(2) in the 2002 and 2003 surveys, respectively. The spatial extent Of anchovy larvae was also high as they were collected at 12 stations in 2002 and at 15 in 2003. Besides water circulation, the spatial distribution of fish larvae was largely influenced by temperature, salinity and dissolved oxygen

MEDLEM database, a data collection on large Elasmobranchs in the Mediterranean and Black seas

The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains more than 3,000 records (with more than 4,000 individuals) of large elasmobranch species from 21 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The principal species included in the archive are the devil ray (1,868 individuals), the basking shark (935 individuals), the blue shark (622 individuals), and the great white shark (342 individuals). In the last decades, other species such as the thresher shark (187 individuals), the shortfin mako (180 individuals), and the spiny butterfly ray (138) were reported with increasing frequency. This was possibly due to increased public awareness on the conservation status of sharks, and the consequent development of new monitoring programs. MEDLEM does not have homogeneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the northern sectors and the absence of some species in our database does not imply their actual absence in these regions. However,the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected species, the overall area coverage, and which species are involved as bycatch by different fishing gears

General results for GAM models of diversity indices.

<p>Deviance for Null model. ΔDeviance for the General model (including all the three variables/factors) and for each of the separated factors/variables. df: degree of freedom. ns: non significant effect when <i>p</i> (> ΔDeviance) >0.01. Percentage of the deviance of diversity indices explained by the factors/variables studied are given in brackets.</p

Spearman rank correlation coefficients calculated between all the diversity indices.

<p>All correlations are significantly different from zero (with <i>p</i><0.01), except for underlined values. The Spearman coefficient distribution under null hypothesis was approximated by a normal distribution with mean equal to 0 and standard deviation equal to 1/√ (n–1). Codes of diversity indices are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066753#pone-0066753-t001" target="_blank">Table 1</a>.</p

Geographical pattern in species diversity.

<p>Box-plot for (A) 1/<i>d</i>, (B) Δ^*, (C) Δ⁺, (D) Λ⁺ at the scale of the basin (left column), and the biogeographical zones (right column). Basin and biogeographical zone codes as in Fig. 5 Codes of diversity indices are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066753#pone-0066753-t001" target="_blank">Table 1</a>.</p