Tommaso Russo

The footprint of bottom trawling in European waters: distribution, intensity, and seabed integrity

Mapping trawling pressure on the benthic habitats is needed as background to support an ecosystem approach to fisheries management (EAFM). The extent and intensity of bottom trawling on the European continental shelf (0–1000 m) was analyzed from logbook statistics and VMS data for 2010, 2011 and 2012 at a resolution of 1×1 minutes longitude and latitude. Trawling intensity profiles with seabed impact at the surface and subsurface level are presented for 14 management areas in the North-east Atlantic, Baltic Sea and Mediterranean Sea. The footprint (proportion of the seabed trawled 1 or more times every ten years) ranged between 40–90% across EUNIS habitats with largest footprints observed in sandy (A5.2) and muddy (A5.3) habitats. The footprint of the management areas ranged between 52-99% and 5-94% for the depth zone from 0–200 m (Shallow) and from 201–1000 m (Deep), respectively. The footprint was estimated as the total area of all grid cells that were trawled fully or partially. Excluding these untrawled proportions reduced the footprint estimates to 28-85% and 2-77%. Mean trawling intensity ranged between 0.5 and almost 8.5 times per year, but was less in the Deep zone with a maximum intensity of 6.4 times per year. Highest intensities were recorded in the Skagerrak–Kattegat and Adriatic Sea. Largest footprints per unit landings were observed in the Mediterranean Sea. Bottom trawling was highly aggregated. The seabed area where 90% of the effort occurred comprised between 11% and 65% (median 44%) of the total area trawled. Using the longevity distribution of the untrawled infaunal community, the seabed integrity was estimated as the proportion of the biomass of benthic taxa where the trawling interval at the subsurface level exceeds their life span. Seabed integrity was low (<0.1) in large parts of the European continental shelfs, although smaller pockets of seabed with higher integrity values occur. The methods developed here integrate official fishing effort statistics and industry-based gear information to provide high-resolution pressure maps and indicators, which greatly improve the basis for assessing and managing benthic pressure from bottom trawling. Further they provide quantitative estimates of trawling impact on a continuous scale by which managers can steer.

SMART: a spatially explicit bio-economic model for assessing and managing demersal fisheries, with an application to italian trawlers in the strait of sicily.

Management of catches, effort and exploitation pattern are considered the most effective measures to control fishing mortality and ultimately ensure productivity and sustainability of fisheries. Despite the growing concerns about the spatial dimension of fisheries, the distribution of resources and fishing effort in space is seldom considered in assessment and management processes. Here we propose SMART (Spatial MAnagement of demersal Resources for Trawl fisheries), a tool for assessing bio-economic feedback in different management scenarios. SMART combines information from different tasks gathered within the European Data Collection Framework on fisheries and is composed of: 1) spatial models of fishing effort, environmental characteristics and distribution of demersal resources; 2) an Artificial Neural Network which captures the relationships among these aspects in a spatially explicit way and uses them to predict resources abundances; 3) a deterministic module which analyzes the size structure of catches and the associated revenues, according to different spatially-based management scenarios. SMART is applied to demersal fishery in the Strait of Sicily, one of the most productive fisheries of the Mediterranean Sea. Three of the main target species are used as proxies for the whole range exploited by trawlers. After training, SMART is used to evaluate different management scenarios, including spatial closures, using a simulation approach that mimics the recent exploitation patterns. Results evidence good model performance, with a noteworthy coherence and reliability of outputs for the different components. Among others, the main finding is that a partial improvement in resource conditions can be achieved by means of nursery closures, even if the overall fishing effort in the area remains stable. Accordingly, a series of strategically designed areas of trawling closures could significantly improve the resource conditions of demersal fisheries in the Strait of Sicily, also supporting sustainable economic returns for fishermen if not applied simultaneously for different species.

VMSbase: An R-Package for VMS and Logbook Data Management and Analysis in Fisheries Ecology

VMSbase is an R package devised to manage, process and visualize information about fishing vessels activity (provided by the vessel monitoring system - VMS) and catches/landings (as reported in the logbooks). VMSbase is primarily conceived to be user-friendly; to this end, a suite of state-of-the-art analyses is accessible via a graphical interface. In addition, the package uses a database platform allowing large datasets to be stored, managed and processed vey efficiently. Methodologies include data cleaning, that is removal of redundant or evidently erroneous records, and data enhancing, that is interpolation and merging with external data sources. In particular, VMSbase is able to estimate sea bottom depth for single VMS pings using an on-line connection to the National Oceanic and Atmospheric Administration (NOAA) database. It also allows VMS pings to be assigned to whatever geographic partitioning has been selected by users. Standard analyses comprise: 1) métier identification (using a modified CLARA clustering approach on Logbook data or Artificial Neural Networks on VMS data); 2) linkage between VMS and Logbook records, with the former organized into fishing trips; 3) discrimination between steaming and fishing points; 4) computation of spatial effort with respect to user-selected grids; 5) calculation of standard fishing effort indicators within Data Collection Framework; 6) a variety of mapping tools, including an interface for Google viewer; 7) estimation of trawled area. Here we report a sample workflow for the accessory sample datasets (available with the package) in order to explore the potentialities of VMSbase. In addition, the results of some performance tests on two large datasets (1×105 and 1×106 VMS signals, respectively) are reported to inform about the time required for the analyses. The results, although merely illustrative, indicate that VMSbase can represent a step forward in extracting and enhancing information from VMS/logbook data for fisheries studies.

Domestication shapes morphology in rainbow trout Oncorhynchus mykiss.

In this study, clonal lines from North American resident and migratory populations of rainbow trout Oncorhynchus mykiss adapted to different geographical conditions and with different domestication histories were characterized morphologically. Lines reared in a common-garden experiment were characterized for external shape and meristic values, searching for a general pattern of morphological variation due to exposure to captive conditions. A sharp distinction was identified between wild and captive lines. The body profile was deeper in captive lines, with longer dorsal and anal fins and shorter and deeper caudal peduncles. Highly significant differences were also identified in meristic values among the lines but no consistent relation between meristic values and domestication status was detected. This morphological characterization will facilitate the selection of lines with divergent phenotypes for subsequent quantitative trait loci analysis, aimed at identifying genome regions linked with morphological adaptive response to captive conditions.

Shape and size variation: Growth and development of the dusky grouper (Epinephelus marginatus Lowe, 1834)

Demersal fishes have complex life cycles that involve an ontogenetic change in morphology, physiology, and behavior, as their pelagic larval stages colonize benthic habitats. The developmental transition between larvae and juveniles leads to very complex processes of morphogenesis and differentiation. These processes primarily determine changes in external morphology, which is shaped by selective pressures to optimize performance for basic activities such as swimming, escape from predators, and feeding. Fishes have provided fertile grounds for ecomorphological investigations throughout ontogeny, as the role of changing morphology in inducing ontogenetic niche shifts is not always clear. In this framework, some studies have demonstrated that certain species undergo gradual changes, whereas other species experience threshold effects in their ecomorphological relationships during ontogeny. In this study, the intraspecific allometry of the dusky grouper was examined. Geometric morphometric tools were used to quantify shape changes through the development, and a modular approach was also applied to analyze the pattern of covariation between three distinct blocks (head, trunk, and tail). For this purpose, a two‐block Partial Least Square was computed. This method reveals that the pattern of changes in the overall body shape is the result of the modularized changes of these blocks. J. Morphol., 2009.

Testing Species Delimitations in Four Italian Sympatric Leuciscine Fishes in the Tiber River: A Combined Morphological and Molecular Approach

Leuciscine fishes represent an important component of freshwater ichthyofauna endemic to northern Mediterranean areas. This lineage shows high intra-specific morphological variability and exhibits high levels of hybridization, two characteristics that contribute to systematic uncertainties, misclassification of taxa and, potentially, the mismanagement of biodiversity. This study focused on brook chub, Squalius lucumonis, an endemic taxon of Central Italy. The taxonomic status of this species has long been questioned, and a hybrid origin from sympatric leusciscines (S. squalus x Rutilus rubilio, or S. squalus x Telestes muticellus) has been hypothesised. A phenotypic (evaluating shape and meristic counts) and genetic (using mitochondrial and nuclear markers) investigation of these four taxa was conducted to test species delimitation in sympatric areas and to evaluate the taxonomic status of S. lucumonis. One hundred and forty-five individuals of all four taxa were collected within streams of the lowest portion of the Tiber River basin and analysed; this region encompasses a large portion of the S. lucumonis distribution. The different morphological and genetic approaches were individually examined, compared, and then combined in a quantitative model to both investigate the limits of each approach and to identify cases of misclassification. The results obtained confirm the cladogenetic non-hybrid origin of S. lucumonis, highlight the need for immediate conservation actions and emphasise the value of an integrated approach in the study of leuciscines evolution.

Skeletal Anomaly Monitoring in Rainbow Trout (Oncorhynchus mykiss, Walbaum 1792) Reared under Different Conditions

The incidence of skeletal anomalies could be used as an indicator of the “quality” of rearing conditions as these anomalies are thought to result from the inability of homeostatic mechanisms to compensate for environmentally-induced stress and/or altered genetic factors. Identification of rearing conditions that lower the rate of anomalies can be an important step toward profitable aquaculture as malformed market-size fish have to be discarded, thus reducing fish farmers’ profits. In this study, the occurrence of skeletal anomalies in adult rainbow trout grown under intensive and organic conditions was monitored. As organic aquaculture animal production is in its early stages, organic broodstock is not available in sufficient quantities. Non-organic juveniles could, therefore, be used for on-growing purposes in organic aquaculture production cycle. Thus, the adult fish analysed in this study experienced intensive conditions during juvenile rearing. Significant differences in the pattern of anomalies were detected between organically and intensively-ongrown specimens, although the occurrence of severe, commercially important anomalies, affecting 2–12.5% of individuals, was comparable in the two systems. Thus, organic aquaculture needs to be improved in order to significantly reduce the incidence of severe anomalies in rainbow trout.

Applications of self-organizing maps for ecomorphological investigations through early ontogeny of fish.

We propose a new graphical approach to the analysis of multi-temporal morphological and ecological data concerning the life history of fish, which can typically serves models in ecomorphological investigations because they often undergo significant ontogenetic changes. These changes can be very complex and difficult to describe, so that visualization, abstraction and interpretation of the underlying relationships are often impeded. Therefore, classic ecomorphological analyses of covariation between morphology and ecology, performed by means of multivariate techniques, may result in non-exhaustive models. The Self Organizing map (SOM) is a new, effective approach for pursuing this aim. In this paper, lateral outlines of larval stages of gilthead sea bream (Sparus aurata) and dusky grouper (Epinephelus marginatus) were recorded and broken down using by means of Elliptic Fourier Analysis (EFA). Gut contents of the same specimens were also collected and analyzed. Then, shape and trophic habits data were examined by SOM, which allows both a powerful visualization of shape changes and an easy comparison with trophic habit data, via their superimposition onto the trained SOM. Thus, the SOM provides a direct visual approach for matching morphological and ecological changes during fish ontogenesis. This method could be used as a tool to extract and investigate relationships between shape and other sinecological or environmental variables, which cannot be taken into account simultaneously using conventional statistical methods.

“Right” or “wrong”? insights into the ecology of sidedness in european flounder, Platichthys flesus

Sidedness polymorphism in flatfish has been linked to ecological selection between morphs. However, the alternate hypothesis that morphological differences between right‐ and left‐sided forms may be due to errors during development, as a consequence of disturbed homeostasis, which still remains largely unexplored. Here, we examined the case of Platichthys flesus (flounder), a polymorphic flatfish exhibiting large and clinal variation in the frequency of the left‐sided morph, which is the reversed condition in this generally right‐sided species. An integrated approach consisting of the analyses of shape variation, stomach contents, and skeletal anomalies was used. Morphological differences were observed between morphs, which are in agreement with previous findings in a congeneric species (Platichthys stellatus). In parallel, significant differences in feeding choices were detected, suggesting a coherent association between subtle morphological differences between morphs and their use of trophic resources. Skeletal anomalies and meristic counts did not corroborate the hypothesis that morphometric divergence in reversed individuals may be caused or reinforced by developmental instability. J. Morphol. 2012.

A Holistic Approach to Fishery Management: Evidence and Insights from a Central Mediterranean Case Study (Western Ionian Sea)

The new Common Fisheries Policy (CFP) is designed to represent an appropriate response to the uncertainties and challenges facing the fisheries sector. It also adopts a holistic approach to fisheries management, considering all factors driving fishers’ behavior, and ultimately, the long-term maintenance of living resources. The most reliable way to pursue these aims could be represented by a change in the exploitation pattern, in order to guarantee the sustainability of fisheries without compromising their socioeconomic viability. In this paper, the demersal fisheries of the Ionian Sea (Geographic Sub-area [GSA] 19) were analyzed with respect to their spatial, temporal, economic, and biological characteristics in terms of four key species for fisheries, namely European hake, red mullet, giant red shrimp, and deep-water rose shrimp. Specifically, 1) a quantitative procedure was applied to break down the whole system (including small-scale fleet components) into a series of fishing grounds using input data about fishing efforts; 2) the different fleet segments were defined as a combination of main gear and fishing grounds; 3) the effort and production by fleet segment were derived according to biological samplings of commercial data (Data Collection Framework for the collection and management of fisheries data, DCF), information on localization of nursery and spawning grounds, and expert knowledge; and 4) all this information was used to feed a bioeconomic modelling tool (BEMTOOL), and to explore alternative exploitation patterns. A series of scenarios including the status quo were defined, starting from the actual management approach based on temporal fishing closure. The results showed that significant improvements in the exploitation pattern could be achieved by setting up spatial and/or temporal gear-specific bans of the fishing activity. More specifically, scenarios based on a 3-month fishing ban for trawlers are expected to provide high rebuilding of the spawning stock biomass (SSB) for all target stocks, and at the same time, result in a remarkable reduction of discards. When combined with a seasonal fishing ban for small-scale fleets equipped with nets and longlines, this approach could lead to a significant improvement in all indicators, but especially the SSB of the exploited species.