Paolo Sartor

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.

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 diversity.

Once upon a Time in the Mediterranean Long Term Trends of Mediterranean Fisheries Resources based on Fishers' Traditional Ecological Knowledge

We investigate long-term changes in the Mediterranean marine resources driving the trawl fisheries by analysing fishers’ perceptions (Traditional Ecological Knowledge, TEK) throughout the Mediterranean Sea during the last 80 years. To this end, we conducted an extended set of interviews with experienced fishers that enabled us to classify species (or taxa) as ‘decreasing’ or ‘increasing’ both in terms of abundance, as well as average size in the catch. The aspect that most clearly emerged in all the investigated areas over time was the notable increase of fishing capacity indicators, such as engine power and fishing depth range. Atlantic mackerel, poor cod, scorpionfishes, striped seabream, and John Dory demonstrated a decreasing trend in the fishers’ perceived abundance, while Mediterranean parrotfish, common pandora, cuttlefish, blue and red shrimp, and mullets gave indications of an increasing temporal trend. Although, as a rule, trawler captains did not report any cataclysmic changes (e.g. extinctions), when they were invited to estimate total catches, a clear decreasing pattern emerged; this being a notable finding taking into account the steep escalation of fishing efficiency during the past century. The overall deteriorating status of stocks in most Mediterranean regions calls for responsible management and design of rebuilding plans. This should include historical information accounting for past exploitation patterns that could help defining a baseline of fish abundance prior to heavy industrial fisheries exploitation.

Catch composition and damage incurred to crabs discarded from the eastern Ligurian Sea “rapido” trawl fishery

Catch composition and damage incurred to the populations of three crabs (Liocarcinus depurator, Medorippe lanata and Goneplax rhomboides), discarded by the “rapido” trawl fishery of Viareggio (eastern Ligurian Sea), was investigated. Data were collected on a monthly basis (January–December 2001) through embarks on board of a commercial fishing vessel, so as to reflect commercial fishing practice. The three species represented from 7 to 31% of the discarded biomass, varying with season. Density and biomass indices were characterised by a clear seasonality, each species showing a peak in a different period of the year. A six level scale, based on macroscopic external injuries was used to assess the damage sustained by each species after fishing and sorting operations. For the three species, very similar percentages (56–58%) of individuals were macroscopically intact, while inspection of damaged individuals revealed some differences in the distribution of injuries. G. rhomboides showed the highest proportion of serious damage, followed by L. depurator and M. lanata. The severity and frequency of damage was mainly correlated with interspecific and intraspecific (sexual dimorphism) morphological and behavioural characteristics. For example, specimens with longer and thin appendages, like males of G. rhomboides, seemed to be particularly vulnerable to the fishing and sorting operations; this could also explain the positive correlation between damage level and size found in this species. In M. lanata, small individuals proved to be more vulnerable, while for L. depurator no significant correlation was found between damage and size. Although these estimations did not take other injury typologies into account (e.g. internal and physiological damage), these results can be seen as a first indirect estimation of discard mortality for these species and can represent an important term of reference both for similar studies performed in other areas and for the monitoring of this fishery.

Evidence of subtle genetic structure in the sympatric species Mullus barbatus and Mullus surmuletus (Linnaeus, 1758) in the Mediterranean Sea

Using thirteen microsatellite loci for Mullus barbatus and Mullus surmuletus collected in the Mediterranean Sea, the biogeographic boundaries, genetic distribution among and within basins and the impact of prolonged exploitation in both species were investigated as a basis for understanding their population dynamics and for improving Mullus spp. stock management. Different level of diversity indices among these co-occurring species were obtained, with M. barbatus showing higher allele richness and higher mean observed and expected heterozygosity than M. surmuletus. Reduced contemporary effective population size (Ne) and M-ratio values found in both species likely reflects recent demographic changes, due to a combination of high fishing pressures, habitat fragmentation and naturally occurring fluctuations in population size. Different patterns of genetic connectivity among populations sampled within the Mediterranean were observed for both species. Higher genetic structure was found for M. barbatus as opposed to a more homogenous pattern observed in M. surmuletus samples. Adriatic populations, previously considered panmictic and isolated from other Mediterranean regions, showed geographical partitioning within the basin but also population connectivity with the northern Ionian and Tyrrhenian Seas. Our results highlight the need for temporal sampling in understanding the complex pattern of population connectivity in the Mediterranean, particularly for management purposes.

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.