Time-series analysis of abundance indices of deep sea resources in the Strait of Sicily

Time-series of abundance indices of deep sea demersal resources (501-800m) derived by the MEDITS trawl survey in the Strait of Sicily (GSA 16) were analysed by aggregated taxa (bony fish, cartilaginous fish, cephalopods and crustaceans) and species using a polynomial approach. The results showed a significant increasing trend of the cartilaginous fish and cephalopods, in terms of biomass (kg/km) and density (n/Km) indices, whereas temporal pattern in bony fish and crustaceans resulted not significant. Helicolenus dactylopterus, Hoplostetus mediterraneus, Galeus melastomus, Nephrops norvegicus and Aristaeomorpha foliacea showed significant trends in both number and weight, whereas Aristeus antennatus, Etmopterus spinax and Chimera monstrosa only in biomass.This work was carried out within the Data Collection Regulation and Framework - module trawl surveys MEDITS funded by European Union and the Italian Ministry of Agricultural, Food and Forestry Policies.peer-reviewe

MESMA : a European project for the evaluation of spatially managed areas. The Strait of Sicily case study

The EU-funded MESMA project aims at developing tools for the monitoring and evaluation of spatially managed areas (SMAs). The Strait of Sicily (central Mediterranean), which is one of the selected case studies, is an area characterized by several human activities impacting on the ecosystem and generating conflicts. The main output of MESMA will be a generic framework for the evaluation of SMAs coupled to a governance analysis carried out in each case study.Il progetto MESMA è finanziato dalla Commissione Europea, 7° Programma Quadro, bando FP7-ENV-2008-1, grant agreement n° 226661.peer-reviewe

Campionamento biologico delle catture commerciali Sezione III.C - Variabili biologiche relative al mestiere e dei parametri biologici Sezione III.E - Variabili biologiche relative agli stock del Programma Nazionale Sub-area Geografica (GSA16) – Stretto di Sicilia Anno 2015

Il campionamento biologico delle catture/sbarcati commerciali, sezione C – Relative al mestiere ed E – Relative agli stock, nell’ambito del Programma Nazionale per la Raccolta Dati Alieutici (PNRDA) (Reg. Ce. N°199/2008; N°665/2008 e decisione della commissione N°949/2008), ha l’obiettivo di valutare la composizione in taglia e/o età del pescato ed ottenere altre informazioni sulla biologia delle specie bersaglio, quali le chiavi età/lunghezza, la relazione lunghezza/peso, i parametri di crescita, la composizione in sesso e le condizioni di maturità sessuale. Il campionamento delle catture/sbarchi commerciali (campionamento biologico - CAMPBIOL) risulta di grande importanza per conoscere come agisce il prelievo dei diversi ”metiers” sulle diverse specie, in termini di variazioni dell’abbondanza e struttura demografica delle risorse da pesca. Il campionamento biologico risponde, quindi, principalmente alle seguenti esigenze: 1. Ricostruire il pattern di sfruttamento dei diversi ”métiers” per le diverse specie. 2. Ricostruire la struttura demografica delle catture commerciali/sbarchi di ogni specie (in taglia/età), considerando tutti i ”métiers” che incidono significativamente sull’ammontare globale delle catture. 3. Consentire lo studio dei fenomeni biologici rilevanti, quali la crescita ed il ciclo sessuale, che variano nel corso dell’anno. 4. Acquisire informazioni sulla struttura demografica con specifico riferimento allo stadio di maturazione gonadica (maturità/taglia-età) ed alla relazione fra lunghezza e peso corporeo (taglia-peso/età). Il Programma Nazionale prevede il rilievo dei parametri significativi ai fini della caratterizzazione biologica del prodotto della pesca, principalmente nell’ambito di due differenti moduli: Modulo di valutazione del settore della pesca Sezione C – “Variabili biologiche relative al mestiere” Sezione E – “Variabili biologiche relative agli stock

The Seascape of Demersal Fish Nursery Areas in the North Mediterranean Sea, a First Step Towards the Implementation of Spatial Planning for Trawl Fisheries

The identification of nursery grounds and other essential fish habitats of exploited stocks is a key requirement for the development of spatial conservation planning aimed at reducing the adverse impact of fishing on the exploited populations and ecosystems. The reduction in juvenile mortality is particularly relevant in the Mediterranean and is considered as one of the main prerequisites for the future sustainability of trawl fisheries. The distribution of nursery areas of 11 important commercial species of demersal fish and shellfish was analysed in the European Union Mediterranean waters using time series of bottom trawl survey data with the aim of identifying the most persistent recruitment areas. A high interspecific spatial overlap between nursery areas was mainly found along the shelf break of many different sectors of the Northern Mediterranean indicating a high potential for the implementation of conservation measures. Overlap of the nursery grounds with existing spatial fisheries management measures and trawl fisheries restricted areas was also investigated. Spatial analyses revealed considerable variation depending on species and associated habitat/depth preferences with increased protection seen in coastal nurseries and minimal protection seen for deeper nurseries (e.g. Parapenaeus longirostris 6%). This is partly attributed to existing environmental policy instruments (e.g. Habitats Directive and Mediterranean Regulation EC 1967/2006) aiming at minimising impacts on coastal priority habitats such as seagrass, coralligenous and maerl beds. The new knowledge on the distribution and persistence of demersal nurseries provided in this study can support the application of spatial conservation measures, such as the designation of no-take Marine Protected Areas in EU Mediterranean waters and their inclusion in a conservation network. The establishment of no-take zones will be consistent with the objectives of the Common Fisheries Policy applying the ecosystem approach to fisheries management and with the requirements of the Marine Strategy Framework Directive to maintain or achieve seafloor integrity and good environmental status.Versión del editor4,411

Large-Scale Spatio-Temporal Patterns of Mediterranean Cephalopod Diversity

Species diversity is widely recognized as an important trait of ecosystems’ functioning and resilience. Understanding the causes of diversity patterns and their interaction with the environmental conditions is essential in order to effectively assess and preserve existing diversity. While diversity patterns of most recurrent groups such as fish are commonly studied, other important taxa such as cephalopods have received less attention. In this work we present spatio-temporal trends of cephalopod diversity across the entire Mediterranean Sea during the last 19 years, analysing data from the annual bottom trawl survey MEDITS conducted by 5 different Mediterranean countries using standardized gears and sampling protocols. The influence of local and regional environmental variability in different Mediterranean regions is analysed applying generalized additive models, using species richness and the Shannon Wiener index as diversity descriptors. While the western basin showed a high diversity, our analyses do not support a steady eastward decrease of diversity as proposed in some previous studies. Instead, high Shannon diversity was also found in the Adriatic and Aegean Seas, and high species richness in the eastern Ionian Sea. Overall diversity did not show any consistent trend over the last two decades. Except in the Adriatic Sea, diversity showed a hump-shaped trend with depth in all regions, being highest between 200–400 m depth. Our results indicate that high Chlorophyll a concentrations and warmer temperatures seem to enhance species diversity, and the influence of these parameters is stronger for richness than for Shannon diversityVersión del editor4,411

Spatio-temporal composition of discard associated with the deep water rose shrimp fisheries (Parapenaeus longirostris, Lucas 1846) in the south-central Mediterranean Sea

Discarding in fisheries is the fraction of the total catch brought on board and returned to the sea dead or alive for legal or economic reasons. The reduction of discard is one of the main objectives of the European Common Fishery Policy. This study aimed to improve the current knowledge of the discard associated with the deep-water rose shrimp (DPS) fisheries in the south-central Mediterranean Sea. We analyzed data collected from January 2009 to December 2013. Multivariate data analysis and generalized additive models (GAMs) were used to assess the spatio-temporal composition of the discard (which represented 36% of the total catch) and factors influencing its distribution. Multiple analysis of variance highlighted the significant effect of depth factor on discard assemblage. Moreover, in general, bony fish were the most discarded organisms (23.5%), while cartilaginous fish, crustaceans and other invertebrates represented approximately 13% of the total catch. GAMs showed that the fraction of discard in the catch presented significant variation regarding the years, depth and fishing ground. Although the negative trend in discard suggested that the DPS fisheries are moving towards a more sustainable exploitation, the discard fraction in some areas/assemblages remains high. Our results showed that most of the discard was due to species that had a minimum legal size (Hake, DPS, Trachurus spp.), and consequently would be subjected to the European discard ban. In order to improve the fisheries management, specific measures aimed to minimize the unwanted catches of undersized species need to be implemented

Spatial distribution pattern of European hake Merluccius merluccius (Pisces: Merlucciidae) in the Mediterranean Sea

The present study provides updated information on the occurrence, abundance and biomass distribution patterns and length frequencies of Merluccius merluccius in the Mediterranean Sea, by analysing a time series of data from the Medi- terranean International Trawl Surveys (MEDITS) from 1994 to 2015. The highest values of abundance and biomass were observed in the Sardinian Seas. The use of a generalized additive model, in which standardized biomass indices (kg km–2) were analysed as a function of environmental variables, explained how ecological factors could affect the spatio-temporal distribution of European hake biomass in the basin. High biomass levels predicted by the model were observed especially at 200 m depth and between 14°C and 18°C, highlighting the preference of the species for colder waters. A strong reduction of biomass was observed since the year 2009, probably due to the strengthening of the seasonal thermocline that had greatly reduced the availability of food. The general decrease in biomass of several stocks of anchovy and sardine, preys of European hake, might be indirectly connected to the decreasing biomass detected in the present study. The length analysis shows me- dian values lower than 200 mm total length of most of the investigated areas

Environmentally driven synchronies of Mediterranean cephalopod populations

The Mediterranean Sea is characterized by large scale gradients of temperature, productivity and salinity, in addition to pronounced mesoscale differences. Such a heterogeneous system is expected to shape the population dynamics of marine species. On the other hand, prevailing environmental and climatic conditions at whole basin scale may force spatially distant populations to fluctuate in synchrony. Cephalopods are excellent case studies to test these hypotheses owing to their high sensitivity to environmental conditions. Data of two cephalopod species with contrasting life histories (benthic octopus vs nectobenthic squid), obtained from scientific surveys carried out throughout the Mediterranean during the last 20 years were analyzed. The objectives of this study and the methods used to achieve them (in parentheses) were: (i) to investigate synchronies in spatially separated populations (decorrelation analysis); (ii) detect underlying common abundance trends over distant regions (dynamic factor analysis, DFA); and (iii) analyse putative influences of key environmental drivers such as productivity and sea surface temperature on the population dynamics at regional scale (general linear models, GLM). In accordance with their contrasting spatial mobility, the distance from where synchrony could no longer be detected (decorrelation scale) was higher in squid than in octopus (349 vs 217 km); for comparison, the maximum distance between locations was 2620 km. The DFA revealed a general increasing trend in the abundance of both species in most areas, which agrees with the already reported worldwide proliferation of cephalopods. DFA results also showed that population dynamics are more similar in the eastern than in the western Mediterranean basin. According to the GLM models, cephalopod populations were negatively affected by productivity, which would be explained by an increase of competition and predation by fishes. While warmer years coincided with declining octopus numbers, areas of high sea surface temperature showed higher densities of squid. Our results are relevant for regional fisheries management and demonstrate that the regionalisation objectives envisaged under the new Common Fishery Policy may not be adequate for Mediterranean cephalopod stocks.Versión del edito

Size-dependent survival of European hake juveniles in the Mediterranean Sea.

Most studies on European hake focus on the recruitment process and nursery areas, whereas the information is comparatively limited on the ecology of the juvenile stage (ca. second year of life)—the one most exploited by the Mediterranean trawl fisheries. Using information of the MEDITS programme, we provide a spatial and temporal assessment of the influence of body size and growth on hake survival from recruits (age 0) to juveniles (age 1), along with the impact of surface temperature and chlorophyll variability. At a biogeographic scale, size-dependent survival is supported, with areas with higher mean length of recruits and juveniles yielding higher survival. A similar pattern was observed at interannual level in some western Mediterranean areas, also mediated by a density-dependent effect on growth. However, the most recurrent inter-annual pattern was a negative effect of size on survival, which could be attributed to potential ontogenetic changes in catchability and underrepresentation of intra-annual recruitment pulses that are seasonally inaccessible to the MEDITS sur- vey. Results also evidence that survival in the Alboran and Adriatic seas is dependent on the primary production variability, and that Corsica and Sardinia could be potential feeding grounds receiving juveniles from neighbouring areas. The present study reveals the importance of size- and growth-dependent survival in the juvenile stage of European hake in the Mediter- ranean Sea

Contrasting life history and reproductive traits in two populations of Scyliorhinus canicula

The role of natural and sexual selection in generating variability in biological traits between populations represents an intriguing issue in evolutionary biology. Considering their occurrence in different environments and the extensive incidence of post-copulatory sexual selection, elasmobranchs represent an interesting, yet still poorly investigated group. In this study, the life history and reproductive traits of two populations of Scyliorhinus canicula from the northern Adriatic Sea and the Strait of Sicily were compared. Differences in maximum size and size at sexual maturity were observed. The two populations also displayed differences in male and female genitalia. Males in the northern Adriatic Sea presented heavier testes, longer epididymis, seminal vesicles and claspers compared with those in the Strait of Sicily, suggesting the occurrence of stronger sperm competition at the former site. Similarly, females in the northern Adriatic Sea showed heavier oviducal glands and longer reproductive tracts compared with those in the Strait of Sicily. The coevolution between male and female genitalia suggests the occurrence of stronger sexual conflict and/or cryptic female choice in the population from the northern Adriatic Sea. Therefore, natural selection, represented by the different selective pressures occurring at different latitudes, and sexual selection, represented by potentially differing strengths of post-copulatory sexual selection and sexual conflict, may act individually in driving divergence in life history and reproductive traits in these two populations of S. canicula