Alessandro Criscoli

Seagrass meadows (Posidonia oceanica) distribution and trajectories of change

Posidonia oceanica meadows are declining at alarming rates due to climate change and human activities. Although P. oceanica is considered the most important and well-studied seagrass species of the Mediterranean Sea, to date there has been a limited effort to combine all the spatial information available and provide a complete distribution of meadows across the basin. The aim of this work is to provide a fine-scale assessment of (i) the current and historical known distribution of P. oceanica, (ii) the total area of meadows and (iii) the magnitude of regressive phenomena in the last decades. The outcomes showed the current spatial distribution of P. oceanica, covering a known area of 1,224,707 ha, and highlighted the lack of relevant data in part of the basin (21,471 linear km of coastline). The estimated regression of meadows amounted to 34% in the last 50 years, showing that this generalised phenomenon had to be mainly ascribed to cumulative effects of multiple local stressors. Our results highlighted the importance of enforcing surveys to assess the status and prioritize areas where cost-effective schemes for threats reduction, capable of reversing present patterns of change and ensuring P. oceanica persistence at Mediterranean scale, could be implemented.

Diel feeding periodicity and daily ration of shelf break fish species

The evaluation of the daily ration and feeding periodicity in a Mediterranean demersal fish assemblage under natural conditions is presented. Data were obtained during four trawl surveys conducted on the shelf-edge of the central Mediterranean Sea. Recently, researchers have begun to consider this area an essential fish habitat due to its extremely high productivity and diversity. The species which typified the assemblage were the fish Macroramphosus scolopax, Lepidotrigla cavillone, Mullus barbatus, Serranus hepatus, Argentina sphyraena and Glossanodon leioglossus. Fish were collected at three hour intervals throughout four 24 h sampling periods representing annual seasons. The study was based on the analysis of catch data and stomach fullness per setting time. Results show significant variation of feeding periodicity among species within daytime. The amount of food consumed daily, calculated according to the Elliott & Persson model, is compared to the patterns reported in literature for Atlantic fish species with similar trophic habits. Higher values of daily consumption could be related to the reproductive period for most of the above mentioned species.

Effects of environmental and anthropogenic drivers on the spatial distribution of deep-sea shrimps in the Ligurian and Tyrrhenian Seas (NW Mediterranean)

In the Mediterranean Sea, Aristaeomorpha foliacea and Aristeus antennatus are the most important target species of deep-sea trawl fisheries. Previous studies performed in several areas of the Mediterranean highlighted the key role played by both environmental factors, such as temperature, and anthropogenic activities, such as fishing, in affecting the abundance and distribution of the two species. The present study is aimed at investigating the effects of environmental and anthropogenic drivers on the abundance and spatial distribution of A. foliacea and A. antennatus in the Ligurian and northern and central Tyrrhenian Seas (NW Mediterranean). To this end, the time series of MEDITS trawl survey data (1994–2015) were analyzed together with environmental variables, namely sea surface temperature, current speed, and fishing effort by means of GAM. The results show that fishing plays an important role in shaping the spatial distribution of the two species. A. antennatus is prevalent where fishing effort is higher; this can be related to the higher resilience of blue and red shrimp to fishery impact. In contrast, high temperatures are associated to the prevalence of A. foliacea. Therefore, the abundance and spatial distribution of this species is mainly driven by temperature.

Identification and Characterization of Nursery Areas of Red Mullet Mullus barbatus in the Central Tyrrhenian Sea

AbstractRed Mullet Mullus barbatus is an important target of fishing activities in the central Tyrrhenian Sea, so it is essential to identify its critical habitats in order to manage this resource efficiently. Our research specifically focused on the identification and characterization of nursery areas. The use of spatial interpolation techniques enabled us to identify five nurseries that were highly persistent through time. Moreover, the estimate of juvenile density confirmed the strong aggregation effect of these nursery grounds, as a great portion of young individuals were concentrated in a relatively small surface of the study area. The environmental characterization of these areas showed that juveniles were mainly distributed on bottoms with a relatively high percentage of sand (>70%; P < 0.05). Shannon biodiversity index analysis indicated that the southern nurseries reached the highest values of habitat quality (P < 0.0001). Multivariate analysis showed that nursery grounds were divided into three ...