Fish Response to Multiple Anthropogenic Stressors in Mediterranean Coastal Lagoons: A Comparative Study of the Role of Different Management Strategies

Transitional waters are among the most productive ecosystems of the world and their biotic communities show high diversity and complex mechanisms of self-regulation that provide valuable ecosystem services and societal goods and benefits. In this work a comparison of the fish assemblages of three non-tidal Mediterranean coastal lagoons is carried out in order to evaluate the impacts of alternative management strategies. The anthropogenic pressures acting on the lagoons were quantified by means of categorical indicators, while the characteristics of the fish assemblages were summarized in multi-metric indices (MMIs). Two MMIs were developed using data collected with a beach seine net and with fyke nets, following an empirical approach that selects, from a pool of 73 metrics, the combination that maximizes the MMI/pressure relationship. The two MMIs include four metrics each, most of which are based on feeding mode functional guilds and habitat use functional guilds, and they are sensitive to anthropogenic pressures. The human activities directly or indirectly affecting water quality are the ones that most influence the fish assemblage, while the presence of artisanal fisheries, a typical and relevant resource use in these lagoons, seems to play a beneficial role. Lagoon fisheries management relies on the maintenance of infrastructures that guarantee the hydraulic functioning of the lagoon, thus ensuring exchanges with the adjacent coastal sea, and therefore indirectly contributing to the habitat quality

Population structure and dynamics of the invasive Procambarus clarkii (Girard, 1852) in a Tiber river Ramsar site, Central Italy

Procambarus clarkii is a native species of Central America, but strongly invasive in many regions of the world. An investigation on the red swamp crayfish was carried out to obtain more information about its population dynamics in the Tiber River, in Central Italy. A total of 900 individuals, both males and females, were sampled within two different campaigns (2017 and 2019) aimed at collecting biometric data. A strong fishing effort was deployed (more than 100 nets set), to guarantee a large and randomized number of samples. The crayfish populations were grouped into seven different cohorts, according to Bhattacharya's method. The population showed a balanced sex ratio, the average cephalothorax length was 42.52 mm, with the most represented size class between 40-50 mm. K and L∞, as well as the growth parameter index (í˜), the mortality rate (Z), and longevity value (tmax), were calculated. K and í˜ values resulted very high, showing an impressive growth rate in the study area; tmax ranged from 4 to 5 years, L∞ values were lower compared with other studies (58.0-59.0 mm), while Z was very high for this population (4.2-4.5 year). The results revealed that crayfish population dynamics can be complex and vary depending on habitat type, available trophic resource and competition

Fishery-Induced Selection for Slow Somatic Growth in European Eel

Both theoretical and experimental studies have shown that fishing mortality can induce adaptive responses in body growth rates of fishes in the opposite direction of natural selection. We compared body growth rates in European eel (Anguilla anguilla) from three Mediterranean stocks subject to different fishing pressure. Results are consistent with the hypotheses that i) fast-growing individuals are more likely to survive until sexual maturity than slow-growing ones under natural conditions (no fishing) and ii) fishing can select for slow-growing individuals by removing fast-growing ones. Although the possibility of human-induced evolution seems remote for a panmictic species like such as the European eel, further research is desirable to assess the implications of the intensive exploitation on this critically endangered fish

Biological features of eel (Anguilla anguilla, L. 1758) local stocks in the Mediterranean Area, as a function of different ecological conditions

Memoria de tesis doctoral presentada por Fabrizio Capoccioni para optar al grado de Doctor por la Università degli studi di Roma "Tor Vergata", realizada bajo la dirección del Dr. Jacopo Aguzzi del Institut de Ciències del Mar (ICM-CSIC)Peer reviewe

Otolith growth allometry measurements in the european EEL

Martech 2009 Third Marine Technology Workshop, november 19th - 20th 2009, Vilanova i la Geltrú, Barcelona.-- 2 pagesPeer reviewe

EEL SILVERING STAGE BASED ON PLS CLASSIFICATION

To discriminate European eel (Anguilla anguilla, Linnaeus 1758) developmental stages on the basis of body colour, we observed the pigmentation pattern of skin and several biological characteristics of eels collected in the low course of River Tiber (Rome, Italy). A total of 454 individuals have been assigned to a determined stage (Yellow, Intermediate and Silver) and examined to measure five external parameters (total length, weight, pectoral fin length, vertical and horizontal eye diameter). A subsample of 229 eels has been sacrificed in order to collect liver and gut weight and to determine age from otholit observation. A supervised regression technique, Partial Least Squares (PLS) analysis, has been used to develop a model explaining the co-variation between measured parameters, and the three developmental stages. A good discriminant model was obtained for both datasets: the first PLS analysis, using five variables, yields a correct classification of 78 % of the individuals, the second, with eight input variables, yields a correct classification of 79,4 % of the individuals. Yellow and Silver eels are well discriminated by the model, while Intermediate eels don’t constitute an outlined group. The method of staging European eels on the basis of skin colour appeared to be reliable and easy to adopt during field surveys

Skin Pigmentation in Gilthead Seabream (Sparus aurata L.) Fed Conventional and Novel Protein Sources in Diets Deprived of Fish Meal

The pattern of yellowish pigmentation of the skin was assessed in gilthead seabream (Sparus aurata) fed for 12 weeks iso-proteic (45%) and iso-lipidic (20%) diets deprived of fish meal and containing either a blend of vegetable protein-rich ingredients or where graded levels of the vegetable protein blend were replaced by insect (Hermetia illucens—10%, 20% or 40%) pupae meal, poultry by-product meal (20%, 30% or 40%), red swamp crayfish meal (10%) and marine microalgae (Tisochrysis lutea and Tetraselmis suecica—10%) dried biomass. Digital images of fish fed diets differing in protein sources were analyzed by means of an automatic and non-invasive image analysis tool, in order to determine the number of yellow pixels and their dispersion on the frontal and lateral sides of the fish. The relationship between the total carotenoid concentration in the diet and the number of yellow pixels was investigated. Test diets differently affected gilthead seabream skin pigmentation both in the forefront and the operculum, due to their carotenoid content. The highest yellow pixels’ number was observed with the diet containing microalgae. Fish fed poultry by-product meal were characterized by the lowest yellow pixels’ number, diets containing insect meal had an intermediate coloring capacity. The vegetable control, the microalgae mix diet and the crayfish diet had significantly higher values of yellow pixels at both inspected skin sites

Ontogenetic and environmental effects on otolith shape variability in three Mediterranean European eel (Anguilla anguilla, L.) local stocks

7 pages, 4 figures, 3 tablesOtolith morphology is an efficient tool for the discrimination of fish stocks, populations and species when comparative genetic data are not available. Currently, the relationship between environmental factors and otolith shape is poorly characterized for the European eel (Anguilla anguilla), a highly migratory catadromous species constituting a single, randomly mating stock. The present study analyses the differences in otolith morphology between three Mediterranean eel local stocks from different environmental contexts (i.e. two brackish lagoons and one river). The relationship between otolith shape and otolith size was studied by means of Elliptic Fourier analysis and multivariate statistics. Otolith profile was digitally acquired and Cartesian coordinates were extracted. Partial Least Square (PLS) analysis pointed to continuous allometric growth in size and shape in otoliths from all three sites. In the three environments, shape variations occurred during growth as indicated by the presence of a significant and positive relationship between otolith size and the first PLS latent vector (i.e. which bears most of the information regarding otolith outline). Differences between smaller and larger sized otoliths were investigated using PLS Discriminant Analysis (PLSDA) and cluster analysis. Results indicate that otolith shape is highly uniform at smaller than at larger sizes. These shape differences apparently overlap the initial differentiation of the small otolith outlines acquired by eels during the growing phase as elvers in the marine environment. Data were discussed considering that the physical and chemical habitat variability in brackish lagoons and river could underlie a marked change in otolith shape during the animals' growthThe present work was funded by a grant from the Ministry of Research and University to EC within the PRIN 2006 Project “An Integrated Approach to the Conservation and Management of the European Eel in the Mediterranean Region” (Coordinator Prof. G. De Leo University of Parma); themorphological approach was developed within the framework of the project HIGHVISION (DM 19177/7303/03) to PM. The authors wish to thank the fishermen's associations of the river Tiber, Caprolace and Lesina for their help during samplings. Aguzzi J. is a Postdoctoral Fellow within the Ramon y Cajal Program (MICINN, España)Peer reviewe